Updated on 2024/05/26

写真a

 
NAKAGAWA, Yujin
 
Affiliation
Research Council (Research Organization), Research Organization for Nano & Life Innovation
Job title
Researcher(Associate Professor)
Degree
博士(理学) ( 青山学院大学 )

Research Experience

  • 2024.04
    -
    Now

    Waseda University   Research Organization for Nano & Life Innovation, Integrated Institute for Regulatory Science   Resercher   Associate Professor

  • 2020.08
    -
    2024.03

    Japan Agency for Marine-Earth Science and Technology

  • 2020.04
    -
    2020.07

    Japan Agency for Marine-Earth Science and Technology

  • 2018.04
    -
    2020.03

    Japan Agency for Marine-Earth Science and Technology

  • 2016.06
    -
    2018.03

    Japan Agency for Marine-Earth Science and Technology

  • 2016.04
    -
    2016.05

    Japan Aerospace Exploration Agency

  • 2015.07
    -
    2016.03

    Japan Aerospace Exploration Agency

  • 2015.04
    -
    2015.06

    Japan Aerospace Exploration Agency

  • 2013.04
    -
    2015.03

    Japan Aerospace Exploration Agency

  • 2011.04
    -
    2013.03

    Waseda University, Faculty of Science and Engineering   Assistant Professor

  • 2010.04
    -
    2011.03

    RIKEN

  • 2008.04
    -
    2010.03

    RIKEN

  • 2007.04
    -
    2008.01

    日本学術振興会(青山学院大学)   特別研究員PD

  • 2005.04
    -
    2007.03

    日本学術振興会(青山学院大学)   特別研究員DC1

  • 2004.04
    -
    2005.03

    Aoyama Gakuin University   Graduate School of Science and Engineering

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Education Background

  • 2005.04
    -
    2007.03

    Aoyama Gakuin University   Graduate School of Science and Engineering   Department of Science and Engineering  

  • 2002.04
    -
    2004.03

    Aoyama Gakuin University   Graduate School of Science and Engineering  

  • 1998.04
    -
    2002.03

    Aoyama Gakuin University   College of Science and Engineering  

Professional Memberships

  • 2022.11
    -
    2024.03

    Advanced Marine Science and Technology

  • 2002.06
    -
    2022.03

    The Astronomical Society of Japan

  • 2002.10
    -
    2021.12

    The Physical Society of Japan

  • 2017.01
    -
    2019.12

    American Geophysical Union

  • 2006.02
    -
    2017.03

    High Energy AstroPhysics Association in Japan

Research Areas

  • Atmospheric and hydrospheric sciences / Astronomy / Experimental studies related to particle-, nuclear-, cosmic ray and astro-physics / Marine engineering   掘削 / Marine engineering   水中音響学 / Database

Research Interests

  • 音源分離

  • 機械学習

  • 掘削

  • 水中音響

  • データアーカイブ

  • 気候変動

  • ガンマ線バースト

  • 超強磁場中性子星

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Papers

  • Evaluating Profitability of Hybrid Approach for Early Stuck-Sign Detection: Analyzing False Alarms and Quantifying Reduction in Nonproductive Time

    Tatsuya Kaneko, Tomoya Inoue, Nakagawa, Yujin, Ryota Wada, Shungo Abe, Gota Yasutake, Kazuhiro Fujita

    Proceedings for 2024 IADC/SPE International Drilling Conference and Exhibition   SPE-217697-MS  2024.03  [International journal]

  • Hybrid Approach Using Physical Insights and Data Science for Stuck-Pipe Prediction

    Tatsuya Kaneko, Tomoya Inoue, Yujin Nakagawa, Ryota Wada, Shungo Abe, Gota Yasutake, Kazuhiro Fujita

    SPE Journal    2024.02  [Refereed]

    DOI

  • Hybrid Approach Using Physical Insights and Data Science for Early Stuck Detection

    Tatsuya Kaneko, Tomoya Inoue, Yujin Nakagawa, Ryota Wada, Keisuke Miyoshi, Shungo Abe, Kouhei Kuroda, Kazuhiro Fujita

    Proceedings for Offshore Technology Conference   OTC-32532-MS  2023.05  [International journal]

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  • Early stuck detection using supervised and unsupervised machine learning approaches

    Tomoya Inoue, Yujin Nakagawa, Ryota Wada, Keisuke Miyoshi, Shungo Abe, Kouhei Kuroda, Masatoshi Nishi, Hakan Bilen, Konda Reddy Mopuri

    Offshore Technology Conference Asia   OTC-31376-MS  2022.03  [International journal]

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  • Approach for real-time prediction of pipe stuck risk using a long short-term memory autoencoder architecture

    Yujin Nakagawa, Tomoya Inoue, Hakan Bilen, Konda R. Mopuri, Keisuke Miyoshi, Shungo Abe, Ryota Wada, Kouhei Kuroda, Masatoshi Nishi, Hiroyasu Ogasawara

    Proceedings for 2021 Abu Dhabi International Petroleum Exhibition & Conference   SPE-207805-MS  2021.11  [International journal]

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  • An unsupervised learning model for pipe stuck predictions using a long short-term memory autoencoder architecture

    Yujin Nakagawa, Tomoya Inoue, Hakan Bilen, Konda R. Mopuri, Keisuke Miyoshi, Shungo Abe, Ryota Wada, Kouhei Kuroda, Hitoshi Tamamura

    Proceedings for SPE/IATMI Asia Pacific Oil & Gas Conference and Exhibition   SPE-205677-MS  2021.10  [International journal]

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  • High-z gamma-ray bursts unraveling the dark ages and extreme space-time mission: HiZ-GUNDAM

    Daisuke Yonetoku, Tatehiro Mihara, Akihiro Doi, Takanori Sakamoto, Kohji Tsumura, Kunihito Ioka, Yusuke Amaya, Makoto Arimoto, Teruaki Enoto, Takeru Fujii, Hatsune Goto, Shuichi Gunji, Junko Hiraga, Hirokazu Ikeda, Nobuyuki Kawai, Shunsuke Kurosawa, Jin Li, Yoshitomo Maeda, Ikuyuki Mitsuishi, Toshio Murakami, Yujin Nakagawa, Naoki Ogino, Masanori Ohno, Tatsuya Sawano, Kensho Sei, Motoko Serino, Satoshi Sugita, Toru Tamagawa, Keisuke Tamura, Takaaki Tanaka, Toru Tanimori, Makoto S. Tashiro, Hiroshi Tomida, Hyeongsoon Wang, Tomohiro Yamaguchi, Ayumi Yamamoto, Kazutaka Yamaoka, Makoto Yamauchi, Yoichi Yatsu, Atsumasa Yoshida, Daito Yuhi, Hiroshi Akitaya, Akihiko Fukui, Yoshifusa Ita, Hidehiro Kaneda, Koji Kawabata, Yoshikatsu Kawata, Miku Kurimata, Toshio Matsumoto, Shuji Matsuura, Akihiro Miyasaka, Kentaro Motohara, Norio Narita, Hirofumi Noda, Akisato Ohashi, Hirofumi Okita, Kei Sano, Masaomi Tanaka, Yuji Urata, Takehiko Wada, Hikaru Yamaguchi, Kenshi Yanagisawa, Michitoshi Yoshida, Katsuaki Asano, Kohei Inayoshi, Susumu Inoue, Hirotaka Ito, Hideyuki Izumiura, Norita Kawanaka, Tomoya Kinugawa, Shota Kisaka, Kenta Kiuchi, Jin Matsumoto, Akira Mizuta, Kohta Murase, Hiroki Nagakura, Shigehiro Nagataki, Yoshikazu Nakada, Takashi Nakamura, Yuu Niino, Yudai Suwa, Keitaro Takahashi, Takahiro Tanaka, Kenji Toma, Tomonori Totani, Ryo Yamazaki, Jun'ichi Yokoyama

    Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray   11444  2020.12

     View Summary

    HiZ-GUNDAM is a future satellite mission which will lead the time-domain astronomy and the multi-messenger astronomy through observations of high-energy transient phenomena. A mission concept of HiZ-GUNDAM was approved by ISAS/JAXA, and it is one of the future satellite candidates of JAXA's medium-class mission. We are in pre-phase A (before pre-project) and elaborating the mission concept, mission/system requirements for the launch in the late 2020s. The main themes of HiZ-GUNDAM mission are (1) exploration of the early universe with high-redshift gamma-ray bursts, and (2) contribution to the multi-messenger astronomy. HiZ-GUNDAM has two kinds of mission payload. The wide field X-ray monitors consist of Lobster Eye optics array and focal imaging sensor, and monitor similar to 1 steradian field of view in 0.5 - 4 keV energy range. The near infrared telescope has an aperture size 30 cm in diameter, and simultaneously observes four wavelength bands between 0.5 - 2.5 mu m. In this paper, we introduce the mission overview of HiZ-GUNDAM.

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  • Development of a system for efficient content-based retrieval to analyze large volumes of climate data

    Yujin Nakagawa, Yosuke Onoue, Shitnaro Kawahara, Fumiaki Araki, Koji Koyamada, Daisuke Matsuoka, Yoichi Ishikawa, Mikiko Fujita, Shiori Sugimoto, Yasuko Okada, Sho Kawazoe, Shingo Watanabe, Masayoshi Ishii, Ryo Mizuta, Akihiko Murata, Hiroaki Kawase

    Progress in Earth and Planetary Science   7 ( 1 )  2020.12  [Refereed]

    DOI

  • Spectral properties of gamma-ray bursts observed by the Suzaku wide-band all-sky monitor

    Norisuke Ohmori, Kazutaka Yamaoka, Makoto Yamauchi, Yuji Urata, Masanori Ohno, Satoshi Sugita, Kevin Hurley, Makoto S Tashiro, Yasushi Fukazawa, Wataru Iwakiri, Daisuke Katsukura, Motohide Kokubun, Kazuo Makishima, Souta Murakami, Yujin E Nakagawa, Kazuhiro Nakazawa, Katsuya Odaka, Kaito Takahashi, Tadayuki Takahashi, Yukikatsu Terada

    Publications of the Astronomical Society of Japan    2019.08  [Refereed]

     View Summary

    <jats:title>Abstract</jats:title>
    <jats:p>We have systematically studied the spectral properties of 302 localized gamma-ray bursts (GRBs) observed by the Suzaku wide-band all-sky monitor (WAM) from 2005 August to 2010 December. The energy spectra in the 100–5000 keV range integrated over the entire emission and the 1 s peak were fitted by three models: a single power law, a power law with an exponential cutoff (CPL), and the GRB Band function (GRB). Most of the burst spectra were well fitted by a single power law. The average photon index α was −2.11 and −1.73 for long and short bursts, respectively. For the CPL and GRB models, the low-energy and high-energy photon indices (α and β) for the entire emission spectra were consistent with previous measurements. The averages of the α and β were −0.90 and −2.65 for long-duration GRBs, while the average α was −0.55 and the β was not well constrained for short-duration GRBs. However, the average peak energy Epeak was 645 and 1286 keV for long- and short-duration GRBs respectively, which are higher than previous Fermi/GBM measurements (285 keV and 736 keV). The α and Epeak of the 1 s peak spectra were larger, i.e., the spectra were harder, than the total fluence spectra. Spectral simulations based on Fermi-GBM results suggest that the higher Epeaks measured by the Suzaku WAM could be due to detector selection bias, mainly caused by the limited energy range above 100 keV.</jats:p>

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  • Automatic Detection of Stationary Fronts around Japan Using a Deep Convolutional Neural Network

    Daisuke Matsuoka, Shiori Sugimoto, Yujin Nakagawa, Shintaro Kawahara, Fumiaki Araki, Yosuke Onoue, Masaaki Iiyama, Koji Koyamada

    SOLA    2019  [Refereed]

    DOI

  • FLOOD FREQUENCY ANALYSIS AND IMPACT ASSESSMENT FOR CLIMATE CHANGE IN THE NAGARA RIVER BASIN

    Morihiro HARADA, Yasuyuki MARUYA, Toshiharu KOJIMA, Daisuke MATSUOKA, Yujin NAKAGAWA, Shintaro KAWAHARA, Fumiaki ARAKI

    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering)    2018  [Refereed]

    DOI

  • Detection of the thermal component in GRB 160107A

    Yuta Kawakubo, Takanori Sakamoto, Satoshi Nakahira, Kazutaka Yamaoka, Motoko Serino, Yoichi Asaoka, Michael L Cherry, Shohei Matsukawa, Masaki Mori, Yujin Nakagawa, Shunsuke Ozawa, Ana V Penacchioni, Sergio B Ricciarini, Akira Tezuka, Shoji Torii, Yusuke Yamada, Atsumasa Yoshida

    Publications of the Astronomical Society of Japan    2018.01  [Refereed]

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  • Energy Dependent Intensity Variation of the Persistent X-ray Emission of the Magnetars Observed with Suzaku

    Yujin Nakagawa, Ken Ebisawa, Teruaki Enoto

    Publication of the Astronomical Society of Japan   70 ( 2 ) 32 (1-10)  2018  [Refereed]

     View Summary

    The emission mechanism of magnetars is still controversial even though various observational and theoretical studies have been made. In order to investigate mechanisms of both the persistent X-ray emission and the burst emission of the magnetars, we propose a model in which the persistent X-ray emission consists of numerous micro-bursts of various sizes. If this model is correct, root mean square (rms) intensity variations of the persistent emission would exceed the values expected from the Poisson distribution. Using Suzaku archive data of 11 magnetars (22 observations), the rms intensity variations were calculated from 0.2 keV to 70 keV. As a result, we found significant excess rms intensity variations from all 11 magnetars. We suppose that numerous micro-bursts constituting the persistent X-ray emission cause the observed variations, suggesting that the persistent X-ray emission and the burst emission have identical emission mechanisms. In addition, we found that the rms intensity variations clearly increase toward higher energy bands for four magnetars (six observations). The energy-dependent rms intensity variations imply that the soft thermal component and the hard X-ray component are emitted from different regions far apart from each other.

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  • Suzaku Wide-band All-sky Monitor (WAM) observations of GRBs and SGRs

    Kazutaka Yamaoka, Masanori Ohno, Makoto S. Tashiro, Kevin Hurley, Hans A. Krimm, Amy Y. Lien, Norisuke Ohmori, Satoshi Sugita, Yuji Urata, Tetsuya Yasuda, Junichi Enomoto, Takeshi Fujinuma, Yasushi Fukazawa, Yoshitaka Hanabata, Wataru Iwakiri, Takafumi Kawano, Ryuuji Kinoshita, Motohide Kokubun, Kazuo Makishima, Shunsuke Matsuoka, Tsutomu Nagayoshi, Yujin Nakagawa, Souhei Nakaya, Kazuhiro Nakazawa, Yusuke Nishioka, Takanori Sakamoto, Tadayuki Takahashi, Sawako Takeda, Yukikatsu Terada, Seiya Yabe, Makoto Yamauchi, Hiraku Yoshida

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   69 ( 3 ) 2  2017.06  [Refereed]

     View Summary

    We will review results for gamma-ray bursts (GRBs) and soft gamma repeaters (SGRs), obtained from the Suzaku Wide-band All-sky Monitor (WAM) which operated for about 10 years from 2005 to 2015. The WAM is a BGO (bismuth germanate: Bi4Ge3O12) lateral shield for the Hard X-ray Detector (HXD),used mainly for rejecting its detector background, but it also works as an all-sky monitor for soft gamma-ray transients in the 50-5000 keV range thanks to its large effective area (similar to 600 cm(2) at 1MeV for one detector) and wide field of view (about half of the entire sky). The WAM actually detected more than 1400 GRBs and 300 bursts from SGRs, and this detection number is comparable to that of other GRB-specific instruments. Based on the 10 years of operation, we describe timing and spectral performance for short GRBs, weak GRBs with high redshifts, and time-resolved pulses with good statistics.

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  • Energy calibration of CALET onboard the International Space Station

    Y. Asaoka, Y. Akaike, Y. Komiya, R. Miyata, S. Torii, O. Adriani, K. Asano, M.G. Bagliesi, G. Bigongiari, W.R. Binns, S. Bonechi, M. Bongi, P. Brogi, J.H. Buckley, N. Cannady, G. Castellini, C. Checchia, M.L. Cherry, G. Collazuol, V. Di Felice, K. Ebisawa, H. Fuke, T.G. Guzik, T. Hams, M. Hareyama, N. Hasebe, K. Hibino, M. Ichimura, K. Ioka, W. Ishizaki, M.H. Israel, A. Javaid, K. Kasahara, J. Kataoka, R. Kataoka, Y. Katayose, C. Kato, N. Kawanaka, Y. Kawakubo, H. Kitamura, H.S. Krawczynski, J.F. Krizmanic, S. Kuramata, T. Lomtadze, P. Maestro, P.S. Marrocchesi, A.M. Messineo, J.W. Mitchell, S. Miyake, K. Mizutani, A.A. Moiseev

    Astroparticle Physics    2017.05  [Refereed]

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  • Suzaku/WAM Hard X-ray Observations of Solar Flares - from 2005 to 2014

    Seiya Yabe, M. S. Tashiro, Y. Terada, T. Yasuda, K. Yamaoka, K. Makishima, W. Iwakiri, M. Yamauchi, N. Ohmori, S. Sugita, Y. Fukazawa, M. Ohno, T. Kawano, T. Takahashi, M. Kokubun, Y. Nakagawa, Y. Urata, K. Nakazawa, Suzaku/WAM Team

    7 years of MAXI: monitoring X-ray Transients    2017.01  [International journal]

  • Suzaku Wide-band All-sky Monitor view of soft gamma-ray transient

    Masanori Ohno, Kazutaka Yamaoka, Makoto S. Tashiro, Kevin Hurley, Hans A. Krimm, Amy Y. Lien, Norisuke Ohmori, Satoshi Sugita, Yuji Urata, Tetsuya Yasuda, Ryuuji Kinoshita, Yusuke Nishioka, Yoshitaka Hanabata, Jun'ichi Enomoto, Takeshi Fujinuma, Yasushi Fukazawa, Wataru Iwakiri, Takafumi Kawano, Motohide Kokubun, Kazuo Makishima, Shunsuke Matsuoka, Tsutomu Nagayoshi, Yujin Nakagawa, Souhei Nakaya, Kazuhiro Nakazawa, Takanori Sakamoto, Tadayuki Takahashi, Sawako Takeda, Yukikatsu Terada, Seiya Yabe, Makoto Yamauchi

    7 years of MAXI: monitoring X-ray Transients     185  2017.01  [International journal]  [International coauthorship]

  • MAXI Data Archive Plan

    K. Ebisawa, S. Nahahira, Y. Sugawara, S. Ueno, H. Tomida, T. Furusho, T. Mihara, M. Sugizaki, M. Shidatsu, M. Serino, H. Negoro, Y. Nakagawa, L. Angelini

    7 years of MAXI: monitoring X-ray Transients     269  2017.01  [International journal]  [International coauthorship]

  • Large X-ray flares on stars detected with MAXI/GSC: A universal correlation between the duration of a flare and its X-ray luminosity

    Yohko Tsuboi, Kyohei Yamazaki, Yasuharu Sugawara, Atsushi Kawagoe, Soichiro Kaneto, Ryo Iizuka, Takanori Matsumura, Satoshi Nakahira, Masaya Higa, Masaru Matsuoka, Mutsumi Sugizaki, Yoshihiro Ueda, Nobuyuki Kawai, Mikio Morii, Motoko Serino, Tatehiro Mihara, Hiroshi Tomida, Shiro Ueno, Hitoshi Negoro, Arata Daikyuji, Ken Ebisawa, Satoshi Eguchi, Kazuo Hiroi, Masaki Ishikawa, Naoki Isobe, Kazuyoshi Kawasaki, Masashi Kimura, Hiroki Kitayama, Mitsuhiro Kohama, Taro Kotani, Yujin E. Nakagawa, Motoki Nakajima, Hiroshi Ozawa, Megumi Shidatsu, Tetsuya Sootome, Kousuke Sugimori, Fumitoshi Suwa, Hiroshi Tsunemi, Ryuichi Usui, Takayuki Yamamoto, Kazutaka Yamaoka, Atsumasa Yoshida

    Publications of the Astronomical Society of Japan    2016.10  [Refereed]

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  • CALET UPPER LIMITS ON X-RAY AND GAMMA-RAY COUNTERPARTS OF GW151226

    O. Adriani, Y. Akaike, K. Asano, Y. Asaoka, M. G. Bagliesi, G. Bigongiari, W. R. Binns, S. Bonechi, M. Bongi, P. Brogi, J. H. Buckley, N. Cannady, G. Castellini, C. Checchia, M. L. Cherry, G. Collazuol, V. Di Felice, K. Ebisawa, H. Fuke, T. G. Guzik, T. Hams, M. Hareyama, N. Hasebe, K. Hibino, M. Ichimura, K. Ioka, W. Ishizaki, M. H. Israel, A. Javaid, K. Kasahara, J. Kataoka, R. Kataoka, Y. Katayose, C. Kato, N. Kawanaka, Y. Kawakubo, H. Kitamura, H. S. Krawczynski, J. F. Krizmanic, S. Kuramata, T. Lomtadze, P. Maestro, P. S. Marrocchesi, A. M. Messineo, J. W. Mitchell, S. Miyake, K. Mizutani, A. A. Moiseev, K. Mori, M. Mori, N. Mori

    The Astrophysical Journal    2016.09  [Refereed]

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  • The MAXI/GSC Nova-Alert System and results of its first 68 months

    Hitoshi Negoro, Mitsuhiro Kohama, Motoko Serino, Hiroki Saito, Tomonori Takahashi, Sho Miyoshi, Hiroshi Ozawa, Fumitoshi Suwa, Masato Asada, Kosuke Fukushima, Satoshi Eguchi, Nobuyuki Kawai, Jamie Kennea, Tatehiro Mihara, Mikio Morii, Satoshi Nakahira, Yuji Ogawa, Aya Sugawara, Hiroshi Tomida, Shiro Ueno, Masaki Ishikawa, Naoki Isobe, Taiki Kawamuro, Masashi Kimura, Takahiro Masumitsu, Yujin E. Nakagawa, Motoki Nakajima, Takanori Sakamoto, Megumi Shidatsu, Mutsumi Sugizaki, Juri Sugimoto, Kazuhiko Suzuki, Toshihiro Takagi, Kazuki Tanaka, Yohko Tsuboi, Hiroshi Tsunemi, Yoshihiro Ueda, Kazutaka Yamaoka, Makoto Yamauchi, Atsumasa Yoshida, Masaru Matsuoka

    Publications of the Astronomical Society of Japan    2016.06  [Refereed]

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  • Suzaku Wide-band All-sky Monitor measurements of duration distributions of gamma-ray bursts

    Norisuke Ohmori, Kazutaka Yamaoka, Masanori Ohno, Satoshi Sugita, Ryuuji Kinoshita, Yusuke Nishioka, Kevin Hurley, Yoshitaka Hanabata, Makoto S. Tashiro, Junichi Enomoto, Takeshi Fujinuma, Yasushi Fukazawa, Wataru Iwakiri, Takafumi Kawano, Motohide Kokubun, Kazuo Makishima, Shunsuke Matsuoka, Tsutomu Nagayoshi, Yujin E. Nakagawa, Souhei Nakaya, Kazuhiro Nakazawa, Tadayuki Takahashi, Sawako Takeda, Yukikatsu Terada, Yuji Urata, Seiya Yabe, Tetsuya Yasuda, Makoto Yamauchi

    Publications of the Astronomical Society of Japan    2016.06  [Refereed]

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  • 全天 X 線監視装置「MAXI」のデータアーカイブの開発

    中川 友進, 海老沢 研, 中平 聡志, 上野 史郎, 冨田 洋, 木村 公, 杉崎 睦, 芹野 素子, 三原 建弘, 根來 均

    宇宙科学情報解析論文誌   ( 第5号 ) 71 - 79  2016  [Refereed]

  • Developments of the MAXI Data Archive

    Y. E. Nakagawa, K. Ebisawa, S. Nakahira, M. Sugizaki, H. Tomida, S. Ueno, M. Serino, H. Negoro, M. Kimura, T. Mihara

    Astronomical Data Analysis Software an Systems XXIV (ADASS XXIV)   495   499  2015.09  [International journal]

  • The CALorimetric Electron Telescope (CALET) for high-energy astroparticle physics on the International Space Station

    O. Adriani, Y. Akaike, K. Asano, Y. Asaoka, M. G. Bagliesi, G. Bigongiari, W. R. Binns, S. Bonechi, M. Bongi, J. H. Buckley, G. Castellini, M. L. Cherry, G. Collazuol, K. Ebisawa, V. Di Felice, H. Fuke, T. G. Guzik, T. Hams, M. Hareyama, N. Hasebe, K. Hibino, M. Ichimura, K. Ioka, M. H. Israel, A. Javaid, E. Kamioka, K. Kasahara, J. Kataoka, R. Kataoka, Y. Katayose, N. Kawanaka, H. Kitamura, T. Kotani, H. S. Krawczynski, J. F. Krizmanic, A. Kubota, S. Kuramata, T. Lomtadze, P. Maestro, L. Marcelli, P. S. Marrocchesi, J. W. Mitchell, S. Miyake, K. Mizutani, A. A. Moiseev, K. Mori, M. Mori, N. Mori, H. M. Motz, K. Munakata, H. Murakami, Y. E. Nakagawa, S. Nakahira, J. Nishimura, S. Okuno, J. F. Ormes, S. Ozawa, F. Palma, P. Papini, B. F. Rauch, S. B. Ricciarini, T. Sakamoto, M. Sasaki, M. Shibata, Y. Shimizu, A. Shiomi, R. Sparvoli, P. Spillantini, I. Takahashi, M. Takayanagi, M. Takita, T. Tamura, N. Tateyama, T. Terasawa, H. Tomida, S. Torii, Y. Tunesada, Y. Uchihori, S. Ueno, E. Vannuccini, J. P. Wefel, K. Yamaoka, S. Yanagita, A. Yoshida, K. Yoshida, T. Yuda

    Journal of Physics: Conference Series   632 ( 1 )  2015.08  [Refereed]

     View Summary

    The CALorimetric Electron Telescope (CALET) is a space experiment, currently under development by Japan in collaboration with Italy and the United States, which will measure the flux of cosmic-ray electrons (and positrons) up to 20 TeV energy, of gamma rays up to 10 TeV, of nuclei with Z from 1 to 40 up to 1 PeV energy, and will detect gamma-ray bursts in the 7 keV to 20 MeV energy range during a 5 year mission. These measurements are essential to investigate possible nearby astrophysical sources of high energy electrons, study the details of galactic particle propagation and search for dark matter signatures. The main detector of CALET, the Calorimeter, consists of a module to identify the particle charge, followed by a thin imaging calorimeter (3 radiation lengths) with tungsten plates interleaving scintillating fibre planes, and a thick energy measuring calorimeter (27 radiation lengths) composed of lead tungstate logs. The Calorimeter has the depth, imaging capabilities and energy resolution necessary for excellent separation between hadrons, electrons and gamma rays. The instrument is currently being prepared for launch (expected in 2015) to the International Space Station ISS, for installation on the Japanese Experiment Module - Exposure Facility (JEM-EF).

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  • Sub-MeV band observation of a hard burst from AXP 1E 1547.0-5408 with the Suzaku Wide-band All-sky Monitor

    Tetsuya Yasuda, Wataru B. Iwakiri, Makoto S. Tashiro, Yukikatsu Terada, Tomomi Kouzu, Teruaki Enoto, Yujin E. Nakagawa, Aya Bamba, Yuji Urata, Kazutaka Yamaoka, Masanori Ohno, Shinpei Shibata, Kazuo Makishima

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   67 ( 3 )  2015.06  [Refereed]

     View Summary

    The 2.1-s anomalous X-ray pulsar 1E 1547.0-5408 exhibited an X-ray outburst on 2009 January 22, emitting a large number of short bursts. The wide-band all-sky monitor (WAM) on-board Suzaku detected at least 254 bursts in the 160 keV-6.2MeV band over the period of January 22 00: 57-17: 02 UT from the direction of 1E 1547.0-5408. One of these bursts, which occurred at 06: 45: 13, produced the brightest fluence in the 0.5-6.2 MeV range, with an averaged 0.16-6.2 MeV flux and extrapolated 25 keV-2 MeV fluence of about 1x10(-5) erg cm(-2) s(-1) and about 3x10(-4) erg cm(-2), respectively. After pile-up corrections, the time-resolved WAM spectra of this burst were well-fitted in the 0.16-6.2 MeV range by two-component models; specifically, a blackbody plus an optically thin thermal bremsstrahlung or a combination of a blackbody and a power-law component with an exponential cut-off. These results are compared with previous works reporting the persistent emission and weaker short bursts followed by the same outburst.

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  • Energy Dependent Intensity Variations of Persistent X-ray Emission of Magnetars

    Y. Nakagawa, K. Ebisawa

    Proceedings of Swift: 10 Years of Discovery (SWIFT 10)     150 - 150  2014.12  [Refereed]  [International journal]

  • Status and performance of the CALorimetric Electron Telescope (CALET) on the international space station

    O. Adriani, Y. Akaike, Y. Asaoka, K. Asano, M. G. Bagliesi, G. Bigongiari, W. R. Binns, M. Bongi, J. H. Buckley, A. Cassese, G. Castellini, M. L. Cherry, G. Collazuol, K. Ebisawa, V. di Felice, H. Fuke, T. G. Guzik, T. Hamsa, N. Hasebe, M. Hareyama, K. Hibino, M. Ichimura, K. Ioka, M. H. Israel, A. Javaid, E. Kamioka, K. Kasahara, Y. Katayose, J. Kataoka, R. Kataoka, N. Kawanaka, H. Kitamura, T. Kotani, H. S. Krawczynski, J. F. Krizmanic, A. Kubota, S. Kuramata, T. Lomtadze, P. Maestro, L. Marcelli, P. S. Marrocchesi, J. W. Mitchell, S. Miyake, K. Mizutani, H. M. Motz, A. A. Moiseev, K. Mori, M. Mori, N. Mori, K. Munakata, H. Murakami, Y. E. Nakagawa, S. Nakahira, J. Nishimura, S. Okuno, J. F. Ormes, S. Ozawa, F. Palma, P. Papini, B. F. Rauch, S. Ricciarini, T. Sakamoto, M. Sasaki, M. Shibata, Y. Shimizu, A. Shiomi, R. Sparvoli, P. Spillantini, I. Takahashi, M. Takayanagi, M. Takita, T. Tamura, N. Tateyama, T. Terasawa, H. Tomida, S. Torii, Y. Tunesada, Y. Uchihori, S. Ueno, E. Vannuccini, J. P. Wefel, K. Yamaoka, S. Yanagita, A. Yoshida, K. Yoshida, T. Yuda

    Nuclear Physics B - Proceedings Supplements   256-257   225 - 232  2014.12  [Refereed]

     View Summary

    The CALorimetric Electron Telescope (CALET) space experiment, currently under development by Japan in collaboration with Italy and the United States, will measure the flux of cosmic-ray electrons (including positrons) to 20 TeV, gamma rays to 10 TeV and nuclei with Z=1 to 40 up to 1,000 TeV during a two-year mission on the International Space Station (ISS), extendable to five years. These measurements are essential to search for dark matter signatures, investigate the mechanism of cosmic-ray acceleration and propagation in the Galaxy and discover possible astrophysical sources of high-energy electrons nearby the Earth. The instrument consists of two layers of segmented plastic scintillators for the cosmic-ray charge identification (CHD), a 3 radiation length thick tungsten-scintillating fiber imaging calorimeter (IMC) and a 27 radiation length thick lead-tungstate calorimeter (TASC). CALET has sufficient depth, imaging capabilities and excellent energy resolution to allow for a clear separation between hadrons and electrons and between charged particles and gamma rays. The instrument will be launched to the ISS within 2014 Japanese Fiscal Year (by the end of March 2015) and installed on the Japanese Experiment Module-Exposed Facility (JEM-EF). In this paper, we will review the status and main science goals of the mission and describe the instrument configuration and performance.

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  • MAXI observations of gamma-ray bursts

    Motoko Serino, Takanori Sakamoto, Nobuyuki Kawai, Atsumasa Yoshida, Masanori Ohno, Yuji Ogawa, Yasunori Nishimura, Kosuke Fukushima, Masaya Higa, Kazuto Ishikawa, Masaki Ishikawa, Taiki Kawamuro, Masashi Kimura, Masaru Matsuoka, Tatehiro Mihara, Mikio Morii, Yujin E. Nakagawa, Satoshi Nakahira, Motoki Nakajima, Yuki Nakano, Hitoshi Negoro, Takuya Onodera, Masayuki Sasaki, Megumi Shidatsu, Juri Sugimoto, Mutsumi Sugizaki, Fumitoshi Suwa, Kazuhiko Suzuki, Yutaro Tachibana, Toshihiro Takagi, Takahiro Toizumi, Hiroshi Tomida, Yohko Tsuboi, Hiroshi Tsunemi, Yoshihiro Ueda, Shiro Ueno, Ryuichi Usui, Hisaki Yamada, Takayuki Yamamoto, Kazutaka Yamaoka, Makoto Yamauchi, Koshiro Yoshidome, Taketoshi Yoshii

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   66 ( 5 )  2014.10  [Refereed]

     View Summary

    The Monitor of All-sky X-ray Image (MAXI) Gas Slit Camera (GSC) detects gamma-ray bursts (GRBs), including bursts with soft spectra, such as X-ray flashes (XRFs). MAXI/GSC is sensitive to the energy range from 2 to 30 keV. This energy range is lower than other currently operating instruments which are capable of detecting GRBs. Since the beginning of the MAXI operation on 2009 August 15, GSC observed 35 GRBs up to the middle of 2013. One third of them were also observed by other satellites. The rest of them show a trend to have soft spectra and low fluxes. Because of the contribution of those XRFs, the MAXI GRB rate is about three times higher than those expected from the BATSE logN-log P distribution. When we compare it to the observational results of the Wide-field X-ray Monitor on the High Energy Transient Explorer 2, which covers the the same energy range as that of MAXI/GSC, we find the possibility that many of the MAXI bursts are XRFs with E-peak lower than 20 keV. We discuss the source of soft GRBs observed only by MAXI. The MAXI logN-log S distribution suggests that the MAXI XRFs are distributed over a closer distance than hard GRBs. Since the distributions of the hardness of galactic stellar flares and X-ray bursts overlap with those of MAXI GRBs, we discuss the possibility of confusion of such galactic transients with the MAXI GRB samples.

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  • Short-term X-ray variability study using MAXI/GSC data

    Kazuhiko Suzuki, Hitoshi Negoro, Hiroki Sakakibara, Takuya Onodera, Kosuke Fukushima, Yujin Nakagawa, MAXI Team

    Suzaku-MAXI 2014: Expanding the Frontiers of the X-ray Universe     230  2014.09  [International journal]

  • Suzaku Discovery of Energy Dependent Intensity Variations in Persistent X-ray Emission of Magnetars

    Yujin E. Nakagawa, Ken Ebisawa

    Suzaku-MAXI 2014: Expanding the Frontiers of the X-ray Universe     190  2014.09  [International journal]

  • Spectral calculation through outflows around compact objects and its hydrodynamic simulation

    Tessei Yoshida, Ken Ebisawa, Masahiro Tsujimoto, Ken Ohsuga, Yujin Nakagawa, Mariko Nomura

    40th COSPAR Scientific Assembly   40  2014.01  [International journal]

  • VizieR Online Data Catalog: 2nd MAXI/GSC catalog in high galactic- latitude sky (Hiroi+, 2013)

    K. Hiroi, Y. Ueda, M. Hayashida, M. Shidatsu, R. Sato, T. Kawamuro, M. Sugizaki, S. Nakahira, M. Serino, N. Kawai, M. Matsuoka, T. Mihara, M. Morii, M. Nakajima, H. Negoro, T. Sakamoto, H. Tomida, Y. Tsuboi, H. Tsunemi, S. Ueno, K. Yamaoka, A. Yoshida, M. Asada, S. Eguchi, T. Hanayama, M. Higa, K. Ishikawa, M. Ishikawa, N. Isobe, M. Kohama, M. Kimura, K. Morihana, Y. E. Nakagawa, Y. Nakano, Y. Nishimura, Y. Ogawa, M. Sasaki, J. Sugimoto, T. Takagi, R. Usui, T. Yamamoto, M. Yamauchi, K. Yoshidome

    VizieR Online Data Catalog     J/ApJS/207/36  2013.09  [International journal]

  • THE 37 MONTH MAXI/GSC SOURCE CATALOG OF THE HIGH GALACTIC-LATITUDE SKY

    Kazuo Hiroi, Yoshihiro Ueda, Masaaki Hayashida, Megumi Shidatsu, Ryosuke Sato, Taiki Kawamuro, Mutsumi Sugizaki, Satoshi Nakahira, Motoko Serino, Nobuyuki Kawai, Masaru Matsuoka, Tatehiro Mihara, Mikio Morii, Motoki Nakajima, Hitoshi Negoro, Takanori Sakamoto, Hiroshi Tomida, Yohko Tsuboi, Hiroshi Tsunemi, Shiro Ueno, Kazutaka Yamaoka, Atsumasa Yoshida, Masato Asada, Satoshi Eguchi, Takanori Hanayama, Masaya Higa, Kazuto Ishikawa, Masaki Ishikawa, Naoki Isobe, Mitsuhiro Kohama, Masashi Kimura, Kumiko Morihana, Yujin E. Nakagawa, Yuki Nakano, Yasunori Nishimura, Yuji Ogawa, Masayuki Sasaki, Juri Sugimoto, Toshihiro Takagi, Ryuichi Usui, Takayuki Yamamoto, Makoto Yamauchi, Koshiro Yoshidome

    The Astrophysical Journal Supplement Series    2013.08  [Refereed]

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  • Spectral evolution of a New X-Ray transient MAXIJ0556-332 observed by MAXI, swift, and RXTE

    Mutsumi Sugizaki, Kazutaka Yamaoka, Masaru Matsuoka, Jamie A. Kennea, Tatehiro Mihara, Kazuo Hiroi, Masaki Ishikawa, Naoki Isobe, Nobuyuki Kawai, Masashi Kimura, Hiroki Kitayama, Mitsuhiro Kohama, Takanori Matsumura, Mikio Morii, Yujin E. Nakagawa, Satoshi Nakahira, Motoki Nakajima, Hitoshi Negoro, Motoko Serino, Megumi Shidatsu, Tetsuya Sootome, Kousuke Sugimori, Fumitoshi Suwa, Takahiro Toizumi, Hiroshi Tomida, Yoko Tsuboi, Hiroshi Tsunemi, Yoshihiro Ueda, Shiro Ueno, Ryuichi Usui, Takayuki Yamamoto, Makoto Yamauchi, Kyohei Yamazaki, Atsumasa Yoshida

    Publications of the Astronomical Society of Japan   65 ( 3 ) 58  2013.06  [Refereed]

     View Summary

    We report on the spectral evolution of a new X-ray transient, MAXIJ0556-332, observed by MAXI, Swift, and RXTE. The source was discovered on 2011 January 11 (MJD = 55572) by the MAXI Gas Slit Camera allsky survey at (l , b) = (238.i9, -25.i2), relatively away from the Galactic plane. Swift/XRT follow-up observations identified it with a previously uncatalogued bright X-ray source, which led to optical identification. For more than one year since its appearance, MAXIJ0556-332 has been X-ray active, with a 2-10 keV intensity above 30 mCrab. The MAXI/GSC data revealed rapid X-ray brightening in the first five days, and a hard-to-soft transition in the meantime. For the following ×70 days, the 0.5-30 keV spectra, obtained by the Swift/XRT and the RXTE/PCA on an almost daily basis, show a gradual hardening, with large flux variability. These spectra are approximated by a cutoff power-law with a photon index of 0.4-1 and a high-energy exponential cutoff at 1.5-5 keV, throughout the initial 10 months where the spectral evolution is mainly represented by a change of the cutoff energy. To be more physical, the spectra are consistently explained by thermal emission from an accretion disk plus Comptonized emission from a boundary layer around a neutron star. This supports the source identification as being a neutron-star X-ray binary. The obtained spectral parameters agree with those of neutron-star X-ray binaries in the soft state, whose luminosity is higher than 1.8 × 1037 erg s-1. This suggests a source distance of >17 kpc. © 2013. Astronomical Society of Japan.

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  • Suzaku View of Recent Magnetar and Magnetar-related Objects

    T. Enoto, K. Makishima, S. Shibata, Y. Nakagawa, T. Sakamoto

    The Fast and the Furious: Energetic Phenomena in Isolated Neutron Stars, Pulsar Wind Nebulae and Supernova Remnants     54  2013.05  [International journal]

  • All-sky observations by Suzaku wide-band all-sky monitor

    M. Ohno, Y. Hanabata, T. Kawano, K. Takaki, R. Nakamura, Y. Tanaka, Y. Fukazawa, H. Ueno, M. Tashiro, Y. Terada, W. Iwakiri, T. Yasuda, M. Asahina, S. Kobayashi, A. Sakamoto, Y. Ishida, S. Sugimoto, M. Akiyama, N. Ohmori, M. Yamauchi, Y. E. Nakagawa, S. Sugita, K. Yamaoka, M. Kokubun, T. Takahashi, Y. Urata, P. Tssai, K. Nakazawa, K. Makishima, the Suzaku-WAM Team

    Memorie della Societa Astronomica Italiana   84   735  2013.01  [International journal]

  • Wide-band spectra of magnetar burst and persistent emission

    Y. E. Nakagawa, K. Makishima, T. Enoto, T. Sakamoto, T. Mihara, M. Sugizaki, K. Yamaoka, K. Hurley, A. Yoshida, P. Gandhi, M. Tashiro, M. Morii

    Memorie della Societa Astronomica Italiana   84   560  2013.01  [International journal]  [International coauthorship]

  • Spectral comparison of weak short bursts to the persistent X-rays from the magnetar 1E 1547.0-5408 in its 2009 outburst

    T. Enoto, Y. E. Nakagawa, T. Sakamoto, K. Makishima

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   427 ( 4 ) 2824 - 2840  2012.12  [Refereed]

     View Summary

    In 2009 January, the 2.1-s anomalous X-ray pulsar 1E 1547.0-5408 evoked intense burst activity. A follow-up Suzaku observation on January 28 recorded enhanced persistent emission in both soft and hard X-rays. Through a reanalysis of the same Suzaku data, 18 short bursts were identified in the X-ray events recorded by the Hard X-ray Detector (HXD) and the X-ray Imaging Spectrometer (XIS). Their spectral peaks appear in the HXD-PIN band, and their 10-70 keV X-ray fluences range from similar to 2 x 10(-9) to 10(-7) erg cm(-2). Thus, the 18 events define a significantly weaker burst sample than has ever been obtained previously, similar to 10(-8)-10(-4) erg cm(-2). In the similar to 0.8 to similar to 300 keV band, the spectra of the three brightest bursts can be represented successfully by a two-blackbody model, or a few alternative models. A spectrum that is constructed by stacking 13 weaker short bursts with fluences in the range (0.2-2) x 10(-8) erg s(-1) is less curved, and its ratio to the persistent emission spectrum becomes constant at similar to 170 above similar to 8 keV. As a result, the two-blackbody model was able to reproduce the stacked weaker-burst spectrum only after adding a power-law model, for which the photon index is fixed at 1.54 as measured by the persistent spectrum. These results imply that there is a possibility that the spectrum composition that employs an optically thick component and a hard power-law component can describe the wide-band spectra of both the persistent and weak-burst emissions, despite the fact that their fluxes differ by two orders of magnitude. Based on the spectral similarity, we discuss a possible connection between the unresolved short bursts and the persistent emission.

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  • The six year results of Suzaku wide-band all-sky monitor

    M. Ohno, Y. Hanabata, T. Uehara, T. Takahashi, M. Mizuno, Y. Fukazawa, K. Yamaoka, S. Sugita, N. Ohmori, M. Akiyama, M. Yamauchi, T. Yasuda, Y. Terada, W. Iwakiri, K. Takahara, M. Asahina, S. Kobayashi, M. Tashiro, M. Kokubun, Y. E. Nakagawa, Y. Urata, P. Tsai, C. J. Chuang, K. Nakazawa, K. Makishima, T. Murakami, H. Tajima

    AIP Conference Proceedings   1427   115 - 122  2012

     View Summary

    All-sky observations from hard X-ray to soft gamma-ray band is very important to study non-thermal processes for many bright astronomical objects such as Gamma-ray Bursts (GRBs), soft gamma-ray repeaters (SGRs), and solar flares. The Wide-band All-sky Monitor (WAM) onboard Suzaku enables unique observations utilizing its wide energy coverage between 50 keV to 5000 keV with very large effective area of 400 cm2 even at 1 MeV. After six year observations, the WAM has detected more than 850 GRBs. Thanks to its largest effective area above 300 keV among all all-sky instruments, many data with good photon statistics is available even for both timeresolved spectroscopy and short duration GRBs and some implications for emission mechanism and physical condition of emission region of GRBs have been suggested. The WAM also observed many solar flares and SGRs. We summarized the observational results from 105 solar flares and their characteristics and addressed discussion on particle acceleration and heating process in solar flares. In addition to above transient objects, many bright gamma-ray sources such as Crab, Cyg X-1, GRB 1915-105, and NGC 4541 are monitored by the WAM using earth occultation technique. © 2012 American Institute of Physics.

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  • Recent Suzaku Studies of the X-ray Emission from Magnetars

    Teruaki Enoto, Yujin E. Nakagawa, Toshio Nakano, Hiroyuki Nishioka, Tetsuya Yasuda, Yukikatsu Terada, Takanori Sakamoto, Kazuo Makishima

    SUZAKU 2011: EXPLORING THE X-RAY UNIVERSE: SUZAKU AND BEYOND   1427  2012  [Refereed]

     View Summary

    Magnetars are a fascinating subclass of neutrons stars, mainly emerging in the X-ray frequency, with evidence of ultra-strong magnetic field exceeding the critical value, B-c = 4.4 x 10(13) G. So far, soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are believed to be magnetars, based on their slow rotations, high spin-down rates, and burst activities. From its launch, Suzaku has been observed 11 magnetars, and also performed some successful ToO observations of transient sources. Becoming new promising targets in the Suzaku era, the AO-4 Magnetar Key Project has been performed since 2009. Using a best combination of the XIS and the HXD, the hard X-ray tail above 10 keV was clearly detected from 7 of them, including at least two activated sources, together with the soft thermal component from all of them. These Suzaku investigations revealed that a broad-band (0.8-70 keV) spectra of known magnetars systematically change depending on their characteristic age and/or magnetic field. The hard X-rays of magnetars become weaker but harder for older and weak-field objects. In addition, we have been monitoring broad-band persistent X-ray spectra of transient magnetars, together with spectral diagnostics of their weak short bursts. Here we summarize latest Suzaku results on magnetars. Although the emission mechanism of the hard X-rays has not yet been explained by conventional interpretations, the future ASTRO-H mission is expected to provide a more unified understanding of magnetars.

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  • A Large X-Ray Flare from a Single Weak-Lined T Tauri Star TWA-7 Detected with MAXI GSC

    Akiko Uzawa, Yohko Tsuboi, Mikio Morii, Kyohei Yamazaki, Nobuyuki Kawai, Masaru Matsuoka, Satoshi Nakahira, Motoko Serino, Takanori Matsumura, Tatehiro Mihara, Hiroshi Tomida, Yoshihiro Ueda, Mutsumi Sugizaki, Shiro Ueno, Arata Daikyuji, Ken Ebisawa, Satoshi Eguchi, Kazuo Hiroi, Masaki Ishikawa, Naoki Isobe, Kazuyoshi Kawasaki, Masashi Kimura, Hiroki Kitayama, Mitsuhiro Kohama, Taro Kotani, Yujin E. Nakagawa, Motoki Nakajima, Hitoshi Negoro, Hiroshi Ozawa, Megumi Shidatsu, Tetsuya Sootome, Kousuke Sugimori, Fumitoshi Suwa, Hiroshi Tsunemi, Ryuichi Usui, Takayuki Yamamoto, Kazutaka Yamaoka, Atsumasa Yoshida

    Publications of the Astronomical Society of Japan    2011.11  [Refereed]

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  • The First MAXI/GSC Catalog in the High Galactic-Latitude Sky

    Kazuo Hiroi, Yoshihiro Ueda, Naoki Isobe, Masaaki Hayashida, Satoshi Eguchi, Mutsumi Sugizaki, Nobuyuki Kawai, Hiroshi Tsunemi, Masaru Matsuoka, Tatehiro Mihara, Kazutaka Yamaoka, Masaki Ishikawa, Masashi Kimura, Hiroki Kitayama, Mitsuhiro Kohama, Takanori Matsumura, Mikio Morii, Yujin E. Nakagawa, Satoshi Nakahira, Motoki Nakajima, Hitoshi Negoro, Motoko Serino, Megumi Shidatsu, Tetsuya Sootome, Kousuke Sugimori, Fumitoshi Suwa, Takahiro Toizumi, Hiroshi Tomida, Yohko Tsuboi, Shiro Ueno, Ryuichi Usui, Takayuki Yamamoto, Kyohei Yamazaki, Atsumasa Yoshida

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   63   S677 - S689  2011.11  [Refereed]

     View Summary

    We present the first unbiased source catalog of the Monitor of All-sky X-ray Image (MAXI) mission at high Galactic latitudes (vertical bar b vertical bar > 10 degrees), produced from the first 7-month data (2009 September 1 to 2010 March 31) of the Gas Slit Camera in the 4-10 keV band. We have developed an analysis procedure to detect faint sources from the MAXI data, utilizing a maximum likelihood image fitting method, where the image response, background, and detailed observational conditions are taken into account. The catalog consists of 143 X-ray sources above the 7 sigma significance level with a limiting sensitivity of similar to 1.5 x 10(-11) erg cm(-2)s(-1) (1.2 mCrab) in the 4-10 keV band. Among them, we have identified 38 Galactic/LMC/SMC objects, 48 galaxy clusters, 39 Seyfert galaxies, 12 blazars, and 1 galaxy. Four other sources are confused with multiple objects, and one remains unidentified. The log N-log S relation of extragalactic objects is in good agreement with the HEAO-1 A-2 result, although the list of the brightest AGNs in the entire sky has significantly changed since that produced 30 yr ago.

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  • MAXI GSC Monitoring of the Crab Nebula and Pulsar during the GeV Gamma-Ray Flare in 2010 September

    Mikio Morii, Mutsumi Sugizaki, Nobuyuki Kawai, Motoko Serino, Takayuki Yamamoto, Ryuichi Usui, Arata Daikyuji, Ken Ebisawa, Satoshi Eguchi, Kazuo Hiroi, Masaki Ishikawa, Naoki Isobe, Kazuyoshi Kawasaki, Masashi Kimura, Hiroki Kitayama, Mitsuhiro Kohama, Takanori Matsumura, Masaru Matsuoka, Tatehiro Mihara, Yujin E. Nakagawa, Satoshi Nakahira, Motoki Nakajima, Hitoshi Negoro, Hiroshi Ozawa, Megumi Shidatsu, Tetsuya Sootome, Kousuke Sugimori, Fumitoshi Suwa, Hiroshi Tomida, Yohko Tsuboi, Hiroshi Tsunemi, Yoshihiro Ueda, Shiro Ueno, Akiko Uzawa, Kazutaka Yamaoka, Kyohei Yamazaki, Atsumasa Yoshida

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   63   S821 - S825  2011.11  [Refereed]

     View Summary

    We report on the MAXI GSC X-ray monitoring of the Crab nebula and pulsar during the GeV gamma-ray flare for the period of 2010 September 18-24 (MJD 55457-55463), detected by AGILE and Fermi-LAT. There were no significant variations on the pulse phase averaged and pulsed fluxes during the gamma-ray flare on time scales from 0.5 to 5 days. The pulse profile also showed no significant change during this period. The upper limits on the variations of the pulse phase averaged and pulsed fluxes for the period MJD 55457.5-55462.5 in the 4-10 keV band were derived to be 1% and 19%, respectively, at the 90% confidence limit of the statistical uncertainty. The lack of variations in the pulsed component over the multi-wavelength range (radio, X-ray, hard X-ray, and gamma-ray) supports not a pulsar, but a nebular origin for the gamma-ray flare.

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  • Peculiarly Narrow SED of GRB 090926B with MAXI and Fermi/GBM

    Motoko Serino, Atsumasa Yoshida, Nobuyuki Kawai, Yujin E. Nakagawa, Tatehiro Mihara, Yoshihiro Ueda, Satoshi Nakahira, Satoshi Eguchi, Kazuo Hiroi, Masaki Ishikawa, Naoki Isobe, Masashi Kimura, Hiroki Kitayama, Mitsuhiro Kohama, Takanori Matsumura, Masaru Matsuoka, Mikio Morii, Motoki Nakajima, Hitoshi Negoro, Megumi Shidatsu, Tetsuya Sootome, Kousuke Sugimori, Mutsumi Sugizaki, Fumitoshi Suwa, Takahiro Toizumi, Hiroshi Tomida, Yohko Tsuboi, Hiroshi Tsunemi, Shiro Ueno, Ryuichi Usui, Takayuki Yamamoto, Kazutaka Yamaoka, Makoto Yamauchi, Kyohei Yamazaki

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   63   S1035 - S1040  2011.11  [Refereed]

     View Summary

    The monitor of the all-sky X-ray image (MAXI) Gas Slit Camera (GSC) on the International Space Station (ISS) detected a gamma-ray burst (GRB) on 2009, September 26, GRB 090926B. This GRB had extremely hard spectra in the X-ray energy range. Joint spectral fitting with the Gamma-ray Burst Monitor on the Fermi Gamma-ray Space Telescope shows that this burst had a peculiarly narrow spectral energy distribution, which can be represented by a Comptonized blackbody model. This spectrum can be interpreted as photospheric emission from a low baryon-load GRB fireball. Calculating the parameter of the fireball, we found the size of the base of the flow to be r(0) = (4.3 +/- 0.9) x 10(9) Y'(-3/2) cm, the Lorentz factor of the plasma is Gamma = (110 +/- 10) Y'(1/4), where Y' is a ratio between the total fireball energy and the energy in the blackbody component of the gamma-ray emission. This r(0) is a factor of a few times larger, and the Lorentz factor of 110 is smaller by also factor of a few than other bursts that have blackbody components in the spectra.

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  • Long-Term Monitoring of the Black Hole Binary GX 339-4 in the High/Soft State during the 2010 Outburst with MAXI/GSC

    Megumi Shidatsu, Yoshihiro Ueda, Satoshi Nakahira, Hitoshi Negoro, Kazutaka Yamaoka, Mutsumi Sugizaki, Kazuo Hiroi, Nobuyuki Kawai, Tatehiro Mihara, Masaru Matsuoka, Masashi Kimura, Masaki Ishikawa, Naoki Isobe, Hiroki Kitayama, Mitsuhiro Kohama, Takanori Matsumura, Mikio Morii, Yujin E. Nakagawa, Motoki Nakajima, Motoko Serino, Tetsuya Sootome, Kousuke Sugimori, Fumitoshi Suwa, Takahiro Toizumi, Hiroshi Tomida, Yohko Tsuboi, Hiroshi Tsunemi, Shiro Ueno, Ryuichi Usui, Takayuki Yamamoto, Kyohei Yamazaki, Atsumasa Yoshida

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   63   S803 - S811  2011.11  [Refereed]

     View Summary

    We present the results of monitoring the galactic black hole candidate GX 339-4 with the Monitor of All-sky X-ray Image (MAXI)/Gas Slit Camera in the high/soft state during an outburst in 2010. All of the spectra throughout the 8-month period were well reproduced with a model consisting of multi-color disk emission and its Comptonization component, whose fraction is <= 25% in the total flux. In spite of the flux variability over a factor of 3, the innermost disk radius is constant at R-in = 61 +/- 2 km for an inclination angle of i = 46 degrees and a distance of d = 8 kpc. This R-in, value is consistent with those of past measurements with Tenma in the high/soft state. Assuming that the disk extends to the innermost stable circular orbit of a non-spinning black hole, we estimate the black hole mass to be M = 6.8 +/- 0.2 M-circle dot for i = 46 degrees and d = 8 kpc, which is consistent with that estimated from the Suzaku observation of the previous low/hard state. Further combined with the mass function, we obtained a mass constraint of 4.3 M-circle dot < M < 13.3 M-circle dot for the allowed range of d = 6-15 kpc and i < 60 degrees. We also discuss the spin parameter of the black hole in GX 339-4 by applying relativistic accretion disk models to the Swift/XRT data.

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  • Revisit of Local X-Ray Luminosity Function of Active Galactic Nuclei with the MAXI Extragalactic Survey

    Yoshihiro Ueda, Kazuo Hiroi, Naoki Isobe, Masaaki Hayashida, Satoshi Eguchi, Mutsumi Sugizaki, Nobuyuki Kawai, Hiroshi Tsunemi, Tatehiro Mihara, Masaru Matsuoka, Masaki Ishikawa, Masashi Kimura, Hiroki Kitayama, Mitsuhiro Kohama, Takanori Matsumura, Mikio Morii, Yujin E. Nakagawa, Satoshi Nakahira, Motoki Nakajima, Hitoshi Negoro, Motoko Serino, Megumi Shidatsu, Tetsuya Sootome, Kousuke Sugimori, Fumitoshi Suwa, Takahiro Toizumi, Hiroshi Tomida, Yohko Tsuboi, Shiro Ueno, Ryuichi Usui, Takayuki Yamamoto, Kazutaka Yamaoka, Kyohei Yamazaki, Atsumasa Yoshida

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   63   S937 - S945  2011.11  [Refereed]

     View Summary

    We constructed a new X-ray (2-10 keV) luminosity function of Compton-thin active galactic nuclei (AGNs) in the local universe, using the first MAXI/GSC source catalog surveyed in the 4-10 keV band. The sample consists of 37 non-blazar AGNs at z = 0.002-0.2, whose identification is highly (>97%) complete. We confirmed the trend that the fraction of absorbed AGNs with N-H > 10(22) cm(-2) rapidly decreases against the luminosity (L-X), from 0.73 +/- 0.10 at L-X = 10(42-43.5) erg s(-1) to 0.12 +/- 0.08 at L-X = 10(43.5-45.5) erg s(-1). The obtained luminosity function was well-fitted with a smoothly connected double power-law model whose indices are gamma(1) = 0.84 (fixed) and gamma(2) = 2.0 +/- 0.2 below and above the break luminosity, L-* = 10(43.3 +/- 10-4) erg s(-1), respectively. While the result of the MAXI/GSC agrees well with that of HEAO-1 at L-X greater than or similar to 10(43.5) erg s(-1), it gives a larger number density at the lower luminosity range. A comparison between our luminosity function in the 2-10 keV band and that in the 14-195 keV band obtained from the Swift/BAT survey indicates that the averaged broad-band spectra in the 2-200 keV band should depend on the luminosity, approximated by Gamma similar to 1.7 for L-X less than or similar to 10(44) erg s(-1), while Gamma - 2.0 for L-X greater than or similar to 1044 erg s(-1). This trend was confirmed by the correlation between the luminosities in the 2-10 keV and 14-195 keV bands in our sample. We argue that there is no contradiction in the luminosity functions between above and below 10 keV once this effect is taken into account.

    DOI

  • The Suzaku Discovery of A Hard Power-Law Component in the Spectra of Short Bursts from SGR 0501+4516

    Yujin E. Nakagawa, Kazuo Makishima, Teruaki Enoto

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   63 ( SP3 ) S813 - S820  2011.11  [Refereed]

     View Summary

    Using data with the Suzaku XIS and HXD, spectral studies of short bursts from the soft gamma repeater SGR 0501+4516 were performed. In total, 32 bursts were detected during the similar to 60 ks of observation conducted in the 2008 August activity. Excluding the strongest one, the remaining 31 bursts showed an average 2-40 keV fluence of (1.0(-0.5)(+0.3)) x 10(-9) erg cm(-2). A 1-40 keV spectrum summed over them leaves significant positive residuals in the HXD-PIN band with chi(2)/d.o.f. = 74/50, when fitted with a two-blackbody function. By adding a power-law model, the fit became acceptable with chi(2)/d.o.f. = 56/48, yielding a photon index of Gamma = 1.0(-0.3)(+0.4). This photon index is comparable to Gamma = 1.33(-0.16)(+0.23) (Enoto et al. 2010, ApJ, 715, 665) for the persistent emission of the same object obtained with Suzaku. The two-blackbody components showed very similar ratios, both in the temperature and the emission radii, to those comprising the persistent emission. However, the power-law to two-blackbody flux ratio was possibly higher than that of the persistent emission at the 2.6 sigma level. Based on these measurements, average wide-band properties of these relatively weak bursts are compared with those of the persistent emission.

    DOI

  • Long-term spectral and timing properties of the soft gamma-ray repeater SGR 1833-0832 and detection of extended X-ray emission around the radio pulsar PSR B1830-08

    P. Esposito, G. L. Israel, R. Turolla, F. Mattana, A. Tiengo, A. Possenti, S. Zane, N. Rea, M. Burgay, D. Goetz, S. Mereghetti, L. Stella, M. H. Wieringa, J. M. Sarkissian, T. Enoto, P. Romano, T. Sakamoto, Y. E. Nakagawa, K. Makishima, K. Nakazawa, H. Nishioka, C. Francois-Martin

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   416 ( 1 ) 205 - 215  2011.09  [Refereed]

     View Summary

    SGR 1833-0832 was discovered on 2010 March 19, thanks to the Swift detection of a short hard X-ray burst and follow-up X-ray observations. Since then, it was repeatedly observed with Swift, Rossi X-ray Timing Explorer and XMM-Newton. Using these data, which span about 225 d, we studied the long-term spectral and timing characteristics of SGR 1833-0832. We found evidence for diffuse emission surrounding SGR 1833-0832, which is most likely a halo produced by the scattering of the point-source X-ray radiation by dust along the line of sight, and we show that the source X-ray spectrum is well described by an absorbed blackbody, with temperature kT similar to 1.2 keV and absorbing column N-H = (10.4 +/- 0.2) x 10(22) cm(-2), while different or more complex models are disfavoured. The source persistent X-ray emission remained fairly constant at similar to 3.7 x 10(-12) erg cm(-2) s(-1) for the first similar to 20 d after the onset of the bursting episode, then it faded by a factor of similar to 40 in the subsequent similar to 140 d, following a power-law trend with index alpha similar or equal to -0.5. We obtained a phase-coherent timing solution with the longest baseline (similar to 225 d) to date for this source which, besides period P = 7.565 4084(4) s and period derivative. P = 3.5(3) x 10(-12) s s(-1), includes higher order period derivatives. We also report on our search of the counterpart to the soft gamma-ray repeater (SGR) at radio frequencies using the Australia Telescope Compact Array and the Parkes Radio Telescope. No evidence for radio emission was found, down to flux densities of 0.9 mJy (at 1.5 GHz) and 0.09 mJy (at 1.4 GHz) for the continuum and pulsed emissions, respectively, consistently with other observations at different epochs. Finally, the analysis of the field of PSR B1830-08 (J1833-0827), which was serendipitously imaged by the XMM-Newton observations, led to the discovery of the X-ray pulsar wind nebula generated by this 85-ms radio pulsar. We discuss its possible association with the unidentified TeV source HESS J1834-087.

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  • The calet gamma-ray burst monitor (CGBM)

    Kazutaka Yamaoka, Atsumasa Yoshida, Yuki Nonaka, Yoko Sakauchi, Takumi Hara, Tatsuma Yamamoto, Kunishiro Mori, Satoshi Nakahira, Taro Kotani, Yujin E. Nakagawa, Hiroshi Tomida, Shiro Ueno, Tadahisa Tamura, Shoji Torii

    Proceedings of the 32nd International Cosmic Ray Conference, ICRC 2011   9   111 - 114  2011.08  [Refereed]  [International journal]

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  • Wide-band X-ray studies of magnetars with Suzaku

    Teruaki Enoto, Kazuo Makishima, Nanda Rea, Yujin E. Nakagawa, Kazuhiro Nakazawa, Takanori Sakamoto

    Astrophysics and Space Science Proceedings   ( 202589 ) 275 - 278  2011  [Refereed]

     View Summary

    From its launch in 2005, the Suzaku satellite has been observed 10 magnetars including 7 persistent objects and 3 activated ones. The hard-tail component was successfully detected from 7 of them, including two activated sources (SGR 0501+4516 and 1E 1547.0-5408), together with the soft component from all of them. Unified spectral studies over the 0.8–70 keV range revealed a clear wide-band spectral evolution, in which the hard-tail component become weaker and harder towards sources with older characteristic age. Specifically, a tight correlation was found between the characteristic age and the hardness ratio between the two components. In addition, the photon index of the hard emission, ranging from∼1.7 to∼0.4, is negatively correlated to the characteristic age.

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  • Suzaku detection of hard X-ray emission in SGR 0501+4516 short burst spectrum

    Yujin E. Nakagawa, Teruaki Enoto, Kazuo Makishima, Atsumasa Yoshida, Kazutaka Yamaoka, Takanori Sakamoto, Nanda Rea, Kevin Hurley

    Astrophysics and Space Science Proceedings   ( 202589 ) 323 - 327  2011  [Refereed]

     View Summary

    Spectral studies of bursts from SGR 0501+4516 are presented using Suzaku data. We discovered hard X-ray emission in a summed spectrum of short bursts with low fluences, which has been found only in quiescent emission spectra so far. This result supports our idea that there are common emission mechanisms between the quiescent emission and the bursts of soft gamma repeaters and anomalous X-ray pulsars. The quiescent emission could consist of numerous micro-bursts. If this is the case, total released energy of small fluence (&lt
    10−8 erg cm−2, 2-100 keV) bursts of a cumulative number-intensity distribution can be comparable to the energy released in the quiescent emission. We found that the total released energy can easily maintain the quiescent emission energy.

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  • Discovery of MeV emission from a Magnetar, AXP 1E1547.0- 5408, with Suzaku / Wide-band All-sky Monitor

    T. Yasuda, W. Iwakiri, Y. Terada, M. S. Tashiro, T. Enoto, A. Bamba, S. Shibata, Y. E. Nakagawa, K. Makishima, Suzaku-Wam Team

    The First Year of MAXI: Monitoring Variable X-ray Sources     31  2010.12  [International journal]

  • A giant flare from a weak-lined T Tauri Star TWA-7 detected with MAXI/GSC

    A. Uzawa, Y. Tsuboi, M. Morii, M. Matsuoka, S. Nakahira, T. Matsumara, K. Yamazaki, R. Satoh, K. Kawasaki, S. Ueno, H. Tomida, Y. Adachi, Y. Itamoto, M. Kohama, T. Mihara, M. Sugizaki, M. Serino, Y. Nakagawa, M. Kimura, H. Kitayama, N. Kawai, K. Sugimori, R. Usui, A. Yoshida, K. Yamaoka, T. Kotani, Kotani, T. Hirose, H. Negoro, M. Nakajima, H. Ozawa, A. Sugawara, F. Suwa, Y. Ueda, N. Isobe, S. Eguchi, K. Hiroi, M. Yamauchi, A. Daikyuji, Maxi Team

    The First Year of MAXI: Monitoring Variable X-ray Sources     34  2010.12  [International journal]

  • All-sky Observations with Suzaku Wide-band All-sky Monitor and MAXI

    M. Ohno, M. Kokubun, T. Takahashi, K. Yamaoka, M. Serino, Y. E. Nakagawa, T. Tamagawa, Y. Fukazawa, T. Uehara, Y. Hanabata, T. Takahashi, S. Sugita, N. Vasquez, Y. Terada, M. Tashiro, W. Iwakiri, K. Takahara, T. Yasuda, N. Ohmori, A. Daikyuji, Y. Nishioka, M. Yamauchi, Y. Urata, P. Tsai, K. Nakazawa, S. Makishima, K. Hong

    The First Year of MAXI: Monitoring Variable X-ray Sources     53  2010.12  [International journal]

  • Magnetars, X-ray Pulsars, and Related Objects

    K. Makishima, M. Sasano, K. Nakajima, T. Nakano, H. Nishioka, T. Yuasa, K. S. Yamada, Nakazawa, J. S. Hiraga, T. Enoto, Y. E. Nakagawa, T. Mihara, A. Bamba, T. Sato, Y. Terada, T. Kohzu, T. Yasuda

    The First Year of MAXI: Monitoring Variable X-ray Sources     28  2010.12  [International journal]

  • The observation result of Galactic X-ray sources by MAXI

    M. Ishikawa, K. Kawasaki, S. Ueno, H. Tomida, M. Kohama, T. Mihara, Y. E. Nakagawa, M. Sugizaki, M. Serino, T. Yamamoto, T. Sootome, M. Matsuoka, N. Kawai, M. Morii, K. Sugimori, R. Usui, A. Yoshida, K. Yamaoka, S. Nakahira, H. Tsunemi, M. Kimura, H. Negoro, S. Nakahira, H. Tsunemi, M. Kimura, H. Negoro, M. Nakajima, H. Ozawa, F. Suwa, Y. Ueda, N. Isobe, S. Eguchi, K. Hiroi, A. Daikyuji, Uzawa, T. Matsumura, K. Yamazaki, MAXI Team

    The First Year of MAXI: Monitoring Variable X-ray Sources     10  2010.12  [International journal]

  • The First MAXI/GSC View of Galactic Magnetars

    Yujin E. Nakagawa, Tatehiro Mihara, Mutsumi Sugizaki, Mitsuhiro Kohama, Takayuki Yamamoto, Motoko Suzuki, Masaru Matsuoka, Nobuyuki Kawai, Mikio Morii, Ryuichi Usui, Kohsuke Sugimori, Satoshi Nakahira, Hitoshi Negoro, Motoki Nakajima, Naoki Isobe, MAXI Team

    The First Year of MAXI: Monitoring Variable X-ray Sources     29  2010.12  [International journal]

  • Bright X-Ray Flares from the BL Lac Object Markarian 421, Detected with MAXI in 2010 January and February

    Naoki Isobe, Kousuke Sugimori, Nobuyuki Kawai, Yoshihiro Ueda, Hitoshi Negoro, Mutsumi Sugizaki, Masaru Matsuoka, Arata Daikyuji, Satoshi Eguchi, Kazuo Hiroi, Masaki Ishikawa, Ryoji Ishiwata, Kazuyoshi Kawasaki, Masashi Kimura, Mitsuhiro Kohama, Tatehiro Mihara, Sho Miyoshi, Mikio Morii, Yujin E. Nakagawa, Satoshi Nakahira, Motoki Nakajima, Hiroshi Ozawa, Tetsuya Sootome, Motoko Suzuki, Hiroshi Tomida, Hiroshi Tsunemi, Shiro Ueno, Takayuki Yamamoto, Kazutaka Yamaoka, Atsumasa Yoshida

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   62 ( 6 ) L55 - L60  2010.12  [Refereed]

     View Summary

    Strong X-ray flares from the blazar Mrk 421 were detected in 2010 January and February through 7-month monitoring with the MAXI GSC. The maximum 2-10 keV flux in the January and February flares was measured to be 120 +/- 10 mCrab and 164 +/- 17 mCrab, respectively; the latter is the highest among those reported from the object. A comparison of the MAXI and Swift BAT data suggests a convex X-ray spectrum with an approximated photon index of Gamma greater than or similar to 2. This spectrum is consistent with a picture that MAXI is observing near the synchrotron peak frequency. The source exhibited a spectral variation during these flares, slightly different from those in previous observations, in which the positive correlation between the flux and hardness was widely reported. By equating the halving decay timescale in the January flare, t(d) similar to 2.5 x 10(4)s, to the synchrotron cooling time, the magnetic field was evaluated to be B similar to 4.5 x 10(-2)G (delta/10)(-1/3), where delta is the jet beaming factor. Assuming that the light crossing time of the emission region is shorter than the doubling rise time, t(r) less than or similar to 2 x 10(4)s, the region size was roughly estimated as R < 6 x 10(15)cm (delta/10). These results are consistent with values previously reported. For the February flare, the rise time, t(r) < 1.3 x 10(5)s, gives a loose upper limit on the size as R < 4 x 10(16)cm (delta/10), although the longer decay time, t(d) similar to 1.4 x 10(5)s, indicates B similar to 1.5 x 10(-2)G (delta/10)(-1/3), which is weaker than the previous results. This could be reconciled by invoking a scenario that this flare is a superposition of unresolved events with a shorter timescale.

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  • Timing Analysis of Unusual GRB 090709A Observed by Suzaku Wide-band All sky Monitor

    W. Iwakiri, M. Ohno, T. Kamae, Y. E. Nakagawa, Y. Terada, M. S. Tashiro, A. Yoshida, K. Yamaoka, and K. Makishima

    American Institute of Physics Conference Series   1279   89 - 92  2010.10  [International journal]

  • MAXI GSC Observations of a Spectral State Transition in the Black Hole Candidate XTE J1752-223

    Satoshi Nakahira, Kazutaka Yamaoka, Mutsumi Sugizaki, Yoshihiro Ueda, Hitoshi Negoro, Ken Ebisawa, Nobuyuki Kawai, Masaru Maisuoka, Hiroshi Tsunemi, Arata Daikyuji, Satoshi Eguchi, Kazuo Hiroi, Masaki Ishikawa, Ryoji Ishiwata, Naoki Isobe, Kazuyoshi Kawasaki, Masashi Kimura, Mitsuhiro Kohama, Tatehiro Mihara, Sho Miyoshi, Mikio Morii, Yujin E. Nakagawa, Motoki Nakajima, Hiroshi Ozawa, Tetsuya Sootome, Kousuke Sugimori, Motoko Suzuki, Hiroshi Tomida, Shiro Ueno, Takayuki Yamamoto, Atsumasa Yoshida

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   62 ( 5 ) L27 - L32  2010.10  [Refereed]

     View Summary

    We present the first results on the black-hole candidate XTE J1752-223 from the Gas Slit Camera (GSC) aboard the Monitor of All-sky X-ray Image (MAXI) on the International Space Station. Including the onset of an outburst reported by the Proportional Counter Array aboard the Rossi X-ray Timing Explorer on 2009 October 23, MAXI / GSC has been monitoring this source approximately 10 times per day with high sensitivity in the 2-20 keV band. XTE J1752-223 was initially in a low/hard state during the first 3 months. An anti-correlated behavior between the 2-4 keV and 4-20 keV bands was observed around 2010 January 20, indicating that the source exhibited a spectral transition to the high / soft state. A transient radio jet may have been ejected when the source was in the intermediate state where the spectrum was roughly explained by a power-law with a photon index of 2.5-3.0. The unusually long period in the initial low/hard state implies a slow variation in the mass-accretion rate, and a dramatic soft X-ray increase may be explained by a sudden appearance of the accretion disk component with a relatively low innermost temperature (0.4-0.7 keV). Such a low temperature might suggest that the maximum accretion rate was just above the critical gas-evaporation rate required for the state transition.

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  • MAXI Nova Alert System and the Latest Scientific Results

    H. Negoro, S. Miyoshi, H. Ozawa, R. Ishiwata, N. Nakajima, M. Matsuoka, K. Kawasaki, S. Ueno, H. Tomida, M. Suzuki, M. Ishikawa, T. Mihara, M. Kohama, M. Sugizaki, Y. Nakagawa, H. Tsunemi, N. Kawai, M. Morii, A. Yoshida, K. Yamaoka, Y. Ueda, N. Isobe, S. Eguchi

    X-ray Astronomy 2009; Present Status, Multi-Wavelength Approach and Future Perspectives   1248   589 - 590  2010.07  [International journal]

  • The First Light from MAXI onboard JEM (Kibo)-EF on ISS

    M. Matsuoka, M. Suzuki, K. Kawasaki, S. Ueno, H. Tomida, Y. Adachi, M. Ishikawa, Y. Itamoto, D. Takahashi, H. Katayama, K. Ebisawa, T. Mihara, M. Kohama, M. Sugizaki, Y. Nakagawa, T. Yamamoto, H. Tsunemi, M. Kimura, N. Kawai, M. Morii, K. Sugimori, A. Yoshida, K. Yamaoka, S. Nakahira, I. Taka- hashi, H. Negoro, M. Nakajima, R. Ishiwata, S. Miyoshi, H. Ozawa, Y. Ueda, N. Isobe, S. Eguchi, K. Hiroi, M. Yamauchi, A. Daikuuji

    X-ray Astronomy 2009; Present Status, Multi-Wavelength Approach and Future Perspectives   1248   531 - 536  2010.07  [International journal]

  • The ASTRO-H Mission

    Tadayuki Takahashi, Kazuhisa Mitsuda, Richard Kelley, Felix Aharonian, Fumie Akimoto, Steve Allen, Naohisa Anabuki, Lorella Angelini, Keith Arnaud, Hisamitsu Awaki, Aya Bamba, Nobutaka Bando, Mark Bautz, Roger Blandford, Kevin Boyce, Greg Brown, Mara Chernyakova, Paolo Coppi, Elisa Costantini, Jean Cottam, John Crow, Jelle de Plaa, Cor de Vries, Jan-Willem den Herder, Michael Dipirro, Chris Done, Tadayasu Dotani, Ken Ebisawa, Teruaki Enoto, Yuichiro Ezoe, Andrew Fabian, Ryuichi Fujimoto, Yasushi Fukazawa, Stefan Funk, Akihiro Furuzawa, Massimiliano Galeazzi, Poshak Gandhi, Keith Gendreau, Kirk Gilmore, Yoshito Haba, Kenji Hamaguchi, Isamu Hatsukade, Kiyoshi Hayashida, Junko Hiraga, Kazuyuki Hirose, Ann Hornschemeier, John Hughes, Una Hwang, Ryo Iizuka, Kazunori Ishibashi, Manabu Ishida, Kosei Ishimura, Yoshitaka Ishisaki, Naoki Isobe, Masayuki Ito, Naoko Iwata, Jelle Kaastra, Tim Kallman, Tuneyoshi Kamae, Hideaki Katagiri, Jun Kataoka, Satoru Katsuda, Madoka Kawaharada, Nobuyuki Kawai, Shigeo Kawasaki, Dmitry Khangaluyan, Caroline Kilbourne, Kenzo Kinugasa, Shunji Kitamoto, Tetsu Kitayama, Takayoshi Kohmura, Motohide Kokubun, Tatsuro Kosaka, Taro Kotani, Katsuji Koyama, Aya Kubota, Hideyo Kunieda, Philippe Laurent, Francois Lebrun, Olivier Limousin, Michael Loewenstein, Knox Long, Grzegorz Madejski, Yoshitomo Maeda, Kazuo Makishima, Maxim Markevitch, Hironori Matsumoto, Kyoko Matsushita, Dan McCammon, Jon Miller, Shin Mineshige, Kenji Minesugi, Takuya Miyazawa, Tsunefumi Mizuno, Koji Mori, Hideyuki Mori, Koji Mukai, Hiroshi Murakami, Toshio Murakami, Richard Mushotzky, Yujin Nakagawa, Takao Nakagawa, Hiroshi Nakajima, Takeshi Nakamori, Kazuhiro Nakazawa, Yoshiharu Namba, Masaharu Nomachi, Stephen O’Dell, Hiroyuki Ogawa, Mina Ogawa, Keiji Ogi, Takaya Ohashi, Masanori Ohno, Masayuki Ohta, Takashi Okajima, Naomi Ota, Masanobu Ozaki, Frederik Paerels, Stéphane Paltani, Arvind Parmar, Robert Petre, Martin Pohl, S. Porter, Brian Ramsey, Christopher Reynolds, Shin-Ichiro Sakai, Rita Sambruna, Goro Sato, Yoichi Sato, Peter Serlemitsos, Maki Shida, Takanobu Shimada, Keisuke Shinozaki, Peter Shirron, Randall Smith, Gary Sneiderman, Yang Soong, Lukasz Stawarz, Hiroyuki Sugita, Andrew Szymkowiak, Hiroyasu Tajima, Hiromitsu Takahashi, Yoh Takei, Tohru Tamagawa, Takayuki Tamura, Keisuke Tamura, Takaaki Tanaka, Yasayuki Tanaka, Yasuo Tanaka, Makoto Tashiro, Yuzuru Tawara, Yukikatsu Terada, Yuichi Terashima, Francesco Tombesi, Hiroshi Tomida, Miyako Tozuka, Yohko Tsuboi, Masahiro Tsujimoto, Hiroshi Tsunemi, Takeshi Tsuru, Hiroyuki Uchida, Yasunobu Uchiyama, Hideki Uchiyama, Yoshihiro Ueda, Shinichiro Uno, Meg Urry, Shin Watanabe, Nicholas White, Takahiro Yamada, Hiroya Yamaguchi, Kazutaka Yamaoka, Noriko Yamasaki, Makoto Yamauchi, Shigeo Yamauchi, Yoichi Yatsu, Daisuke Yonetoku, Atsumasa Yoshida

    Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray   7732   77320Z  2010.07  [International journal]  [International coauthorship]

  • Time-Resolved Spectral Variability of the Prompt Emission from GRB 070125 Observed with Suzaku/WAM

    Kaori Onda, Makoto S. Tashiro, Yujin E. Nakagawa, Kazutaka Yamaoka, Yukikatsu Terada, Masanori Ohno, Satoshi Sugita, Takanori Sakamoto, Kenji Toma, Poshak Gandhi, Natsuki Kodaka, Wataru Iwakiri, Yuji Urata, Makoto Yamauchi, Yasushi Fukazawa

    Publications of the Astronomical Society of Japan   62 ( 3 ) 547 - 556  2010.06  [Refereed]

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  • WIDE-BAND SUZAKU ANALYSIS OF THE PERSISTENT EMISSION FROM SGR 0501+4516 DURING THE 2008 OUTBURST

    T. Enoto, N. Rea, Y. E. Nakagawa, K. Makishima, T. Sakamoto, P. Esposito, D. Goetz, K. Hurley, G. L. Israel, M. Kokubun, S. Mereghetti, H. Murakami, K. Nakazawa, L. Stella, A. Tiengo, R. Turolla, S. Yamada, K. Yamaoka, A. Yoshida, S. Zane

    ASTROPHYSICAL JOURNAL   715 ( 1 ) 665 - 670  2010.05  [Refereed]

     View Summary

    We observed the soft gamma repeater SGR 0501+4516 with Suzaku for similar to 51 ks on 2008 August 26-27, about 4 days after its discovery. Following the first paper, which reported on the persistent soft X-ray emission and the wide-band spectrum of an intense short burst, this paper presents an analysis of the persistent broadband (1-70 keV) spectra of this source in outburst, taken with the X-ray Imaging Spectrometer (XIS) and the Hard X-ray Detector (HXD). Pulse-phase folding in the 12-35 keV HXD-PIN data on an ephemeris based on multi-satellite timing measurements at soft X-rays revealed the pulsed signals at greater than or similar to 99% confidence in the hard X-ray band. The wide-band spectrum clearly consists of a soft component and a separate hard component, crossing over at similar to 7 keV. When the soft component is modeled by a blackbody plus a Comptonized blackbody, the hard component exhibits a 20-100 keV flux of 4.8(-0.6)(+0.8) (stat.)(-0.4)(+ 0.8) (sys.) x 10(-11) erg s(-1) cm(-2) and a photon index of Gamma = 0.79(-0.18)(+ 0.01) (sys.). The hard X-ray data are compared with those obtained by INTEGRAL about 1 day later. Combining the present results with those on other magnetars, we discuss a possible correlation between the spectral hardness of magnetars and their characteristic age and magnetic field strengths.

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  • Suzaku Discovery of a Hard X-Ray Tail in the Persistent Spectra from the Magnetar 1E 1547.0$-$5408 during its 2009 Activity

    Teruaki Enoto, Kazuhiro Nakazawa, Kazuo Makishima, Yujin E. Nakagawa, Takanori Sakamoto, Masanori Ohno, Tadayuki Takahashi, Yukikatsu Terada, Kazutaka Yamaoka, Toshio Murakami, Hiromitsu Takahashi

    Publications of the Astronomical Society of Japan   62 ( 2 ) 475 - 485  2010.04  [Refereed]

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  • Spectral-Lag Relations in GRB Pulses Detected with HETE-2

    Makoto Arimoto, Nobuyuki Kawai, Katsuaki Asano, Kevin Hurley, Motoko Suzuki, Yujin E. Nakagawa, Takashi Shimokawabe, Nicolas Vasquez Pazmino, Rie Sato, Masaru Matsuoka, Atsumasa Yoshida, Toru Tamagawa, Yuji Shirasaki, Satoshi Sugita, Ichiro Takahashi, Jean-Luc Atteia, Alexandre Pelangeon, Roland Vanderspek, Carlo Graziani, Gregory Prigozhin, Joel Villasenor, J. Garrett Jernigan, Geoffrey B. Crew, Takanori Sakamoto, George R. Ricker, Stanford E. Woosley, Nat Butler, Alan Levine, John P. Doty, Timothy Q. Donaghy, Donald Q. Lamb, Edward Fenimore, Mark Galassi, Michel Boer, Jean-Pascal Dezalay, Jean-Francois Olive, Joao Braga, Ravi Manchanda, Graziella Pizzichini

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   62 ( 2 ) 487 - 499  2010.04  [Refereed]

     View Summary

    Using a pulse-tit method, we investigated the spectral lags between the traditional gamma-ray band (50-400 keV) and the X-ray band (6-25 keV) for 8 GRBs with known redshifts (GRB 010921, GRB 020124, GRB 020127, ORB 021211, GRB 030528, GRB 040924, GRB 041006, and GRB 050408), detected with the WXM and FREGATE instruments aboard the HETE-2 satellite. We found several relations for individual ORB pulses between the spectral lag and other observables, such as the luminosity, pulse duration, and peak energy, E-peak. The obtained results are consistent with those for BATSE, indicating that the BATSE correlations are still valid at lower energies (6-25 keV). Furthermore, we found that the photon energy dependence for the spectral lags can be reconciled with the simple curvature effect model. We discuss the implications of these results from various points of view.

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  • A new analysis of the short-duration, hard-spectrum GRB 051103, a possible extragalactic soft gamma repeater giant flare

    K. Hurley, A. Rowlinson, E. Bellm, D. Perley, I. G. Mitrofanov, D. V. Golovin, A. S. Kozyrev, M. L. Litvak, A. B. Sanin, W. Boynton, C. Fellows, K. Harshmann, M. Ohno, K. Yamaoka, Y. E. Nakagawa, D. M. Smith, T. Cline, N. R. Tanvir, P. T. O'Brien, K. Wiersema, E. Rol, A. Levan, J. Rhoads, A. Fruchter, D. Bersier, J. J. Kavelaars, N. Gehrels, H. Krimm, D. M. Palmer, R. C. Duncan, C. Wigger, W. Hajdas, J.-L. Atteia, G. Ricker, R. Vanderspek, A. Rau, A. von Kienlin

    Monthly Notices of the Royal Astronomical Society   403 ( 1 ) 342 - 352  2010.03  [Refereed]

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  • The MAXI Experiment: Monitor of All-sky X-ray Image installed on the International Space Station

    Shiro Ueno, Masaru Matsuoka, Kazuyoshi Kawasaki, Hiroshi Tomida, Mitsuhiro Kohama, Motoko Suzuki, Masaki Ishikawa, Yasuki Adachi, Tatehiro Mihara, Mutsumi Sugizaki, Yujin E. Nakagawa, Takayuki Yamamoto, Hiroshi Tsunemi, Masashi Kimura, Nobuyuki Kawai, Mikio Morii, Kousuke Sugimori, Atsumasa Yoshida, Kazutaka Yamaoka, Satoshi Nakahira, Hitoshi Negoro, Ryoji Ishiwata, Sho Miyoshi, Motoki Nakajima, Yoshihiro Ueda, Naoki Isobe, Satoshi Eguchi, Kazuo Hiroi, Haruyoshi Katayama, Ken Ebisawa, MAXI Team

    The Energetic Cosmos: from Suzaku to ASTRO-H     400 - 403  2010.02  [International journal]

  • The absorption structures in spectra of 1E1207.4-5409 seen by Suzaku

    Ichiro Takahashi, Atsumasa Yoshida, Satoshi Sugita, Toru Kojima, Kazutaka Yamaoka, Yujin E. Nakagawa

    The Energetic Cosmos: from Suzaku to ASTRO-H     216 - 217  2010.02  [International journal]

  • Suzaku Studies of the Extremely Hard Emission Components of Magnetars

    Teruaki Enoto, N. Rea, Yujin E. Nakagawa, Kazuhiro Nakazawa, T. Sakamoto, Kazuo Makishima, Suzaku Magnetar Team

    The Energetic Cosmos: from Suzaku to ASTRO-H     186 - 189  2010.02  [International journal]  [International coauthorship]

  • Uniting Burst and Quiescent Emission Mechanisms of Magnetars

    Yujin E. Nakagawa, Atsumasa Yoshida, Kevin Hurley, Kazutaka Yamaoka, Noriaki Shibazaki, Teruaki Enoto, Takanori Sakamoto, Kazuo Makishima, HETE-2 Team, Suzaku SGR/AXP ToO Team

    The Energetic Cosmos: from Suzaku to ASTRO-H     220 - 221  2010.02  [International journal]  [International coauthorship]

  • AROMA (AGU Robotic Optical Monitor for Astrophysical Objects)

    Ichiro Takahashi, Kosuke Tsunashima, Takayuki Shiraki, Toru Kojima, Atsumasa Yoshida, Yujin E. Nakagawa

    Advances in Astronomy   2010   1 - 5  2010  [Refereed]

     View Summary

    We are developing and operating the automatic telescopeAoyama Gakuin University Robotic Optical Monitor for Astrophysical objects(AROMA) in the Sagamihara Campus of Aoyama Gakuin University. AROMA is composed of two observational equipments, AROMA-N and AROMA-W. AROMA-N is a 30-cm aperture telescope system for rapid follow-up observations of the optical afterglow of gamma-ray bursts. Automatic analysis pipeline for AROMA-N has been developed and is working. The other observational equipment AROMA-W is a wide-field observation system using multiple digital single-lens reflex cameras. It covers a large FOV of about . AROMAW provides photometric data in four bands with a limiting V magnitude of about 12-13 mag. Software to analyze massive image data automatically is being developed. We plan to monitor the luminosities of all the stars in the FOV of AROMA-W, detect optical transients, and trigger a follow-up observation with AROMA-N. We report on the development status and observational results of AROMA.

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  • Early Results of MAXI (Monitor of all-sky X-ray image) on ISS

    M. Matsuoka, T. Mihara, M. Sugizaki, M. Suzuki, Y. E. Nakagawa, T. Yamamoto, T. Sootome, K. Kawasaki, S. Ueno, H. Tomida, M. Kohama, M. Ishikawa, Y. Adachi, Y. Itamoto, Y. Kobayashi, H. Katayama, N. Kawai, M. Morii, K. Sugimori, H. Tsunemi, M. Kimura, A. Yoshida, K. Yamaoka, S. Nakahira, H. Negoro, H. Ozawa, F. Suwa, M. Nakajima, Y. Ueda, N. Isobe, S. Eguchi, K. Hiroi, K. Ebisawa, A. Daikyuji, M. Yamauchi, A. Uzawa, T. Matsumura, K. Yamazaki, Y. Tsuboi

    Proceedings of SPIE - The International Society for Optical Engineering   7732  2010  [Refereed]

     View Summary

    MAXI, the first astronomical payload on JEM-EF of ISS, began operation on August 3, 2009 for monitoring all-sky X-ray images every ISS orbit (92 min). All instruments as well as two main X-ray slit cameras, the GSC and SSC, worked well as expected for one month test operation. The MAXI has been operated since August, 2009 and monitored more than 300 X-ray sources, which include Galactic black holes and black hole candidates (BH/BHC), transient X-ray pulsars, X-ray novae, X-ray bursts, CVns, a considerable number of AGNs and so on. Automatic nova-alert and rapid report system is starting up, while we have published more than 30 results publicly on GCN and ATel with manual analysis. We are also releasing daily data more than 200 targets publicly. Now MAXI has continued steady operation since the beginning of 2010 although capability of a part of X-ray detectors is going down from initial ability. We have obtained some remarkable results concerning BH/BHC, X-ray pulsars and AGNs. As one of the results XTE J1752-223, an X-ray nova accompanying a black hole candidate, has revealed an evolution of accretion disc and high energy plasma from the data for seven-month observations. In this paper we report the operation status of MAXI on the ISS as well as early several astronomical results. © 2010 SPIE.

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  • The MAXI Mission on the ISS: Science and Instruments for Monitoring All-Sky X-Ray Images

    Masaru Matsuoka, Kazuyoshi Kawasaki, Shiro Ueno, Hiroshi Tomida, Mitsuhiro Kohama, Motoko Suzuki, Yasuki Adachi, Masaki Ishikawa, Tatehiro Mihara, Mutsumi Sugizaki, Naoki Isobe, Yujin Nakagawa, Hiroshi Tsunemi, Emi Miyata, Nobuyuki Kawai, Jun Kataoka, Mikio Morii, Atsumasa Yoshida, Hitoshi Negoro, Motoki Nakajima, Yoshihiro Ueda, Hirotaka Chujo, Kazutaka Yamaoka, Osamu Yamazaki, Satoshi Nakahira, Tetsuya You, Ryoji Ishiwata, Sho Miyoshi, Satoshi Eguchi, Kazuo Hiroi, Haruyoshi Katayama, Ken Ebisawa

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   61 ( 5 ) 999 - 1010  2009.10  [Refereed]

     View Summary

    The Monitor of All-sky X-ray Image (MAXI) mission is the first astronomical payload to be installed on the Japanese Experiment Module - Exposed Facility (JEM-EF or Kibo-EF) on the International Space Station. It has two types of X-ray slit cameras with wide FOVs and two kinds of X-ray detectors consisting of gas proportional counters covering the energy range of 2 to 30keV and X-ray CCDs covering the energy range of 0.5 to 12keV. MAXI will be more powerful than any previous X-ray All Sky Monitor payloads, being able to monitor hundreds of Active Galactic Nuclei. A realistic simulation under optimal observation conditions suggests that MAXI will provide all-sky images of X-ray sources of similar to 20 mCrab (similar to 7 x 10(-10) erg cm(-2) s(-1) in the energy band of 2-30 keV) from observations during one ISS orbit (90 min), similar to 4.5 mCrab for one day, and similar to 2 mCrab for one week. The final detectability of MAXI could be similar to 0.2 mCrab for two years, which is comparable to the source confusion limit of the MAXI field of view (FOV). The MAXI objectives are: (1) to alert the community to X-ray novae and transient X-ray sources, (2) to monitor long-term variabilities of X-ray sources, (3) to stimulate multi-wavelength observations of variable objects, (4) to create unbiased X-ray source cataloges, and (5) to observe diffuse cosmic X-ray emissions, especially with better energy resolution for soft X-rays down to 0.5 keV.

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  • Suzaku-WAM, Konus-Wind, and Swift-BAT Observations of Prompt Emission of the High-Redshift GRB 050904

    Satoshi Sugita, Kazutaka Yamaoka, Masanori Ohno, Makoto S. Tashiro, Yujin E. Nakagawa, Yuji Urata, Valentin Pal’shin, Sergei Golenetskii, Takanori Sakamoto, Jay Cummings, Hans Krimm, Michael Stamatikos, Ann Parsons, Scott Barthelmy, Neil Gehrels

    Publications of the Astronomical Society of Japan   61 ( 3 ) 521 - 527  2009.06  [Refereed]

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  • Development of the GRB Monitor for the CALET Experiment

    Kazutaka Yamaoka, Atsumasa Yoshida, Taro Kotani, Satoshi Nakahira, Kei Suzuki, Takuya Ohyama, Takaaki Doshida, Tohru Kojima, Takayuki Shiraki, Tomoki Kataoka, Yujin E. Nakagawa, Hiroshi Tomida, Shoji Torii

    American Institute of Physics Conference Series   1133   88 - 90  2009.05  [International journal]

  • New probes of GRB prompt emission properties using wide-band spectroscopy by Suzaku Wide-band All-sky Monitor

    M. Ohno, K. Ioka, M. Kokubun, M. Suzuki, T. Takahashi, T. Uehara, T. Takahashi, Y. Fukazawa, C. Kira, Y. Hanabata, K. Yamaoka, S. Sugita, Y. Terada, Y. Urata, K. Onda, N. Kodaka, A. Endo, K. Morigami, T. Sugasahara, W. Iwakiri, M. S. Tashiro, Y. E. Nakagawa, T. Tamagawa, T. Enoto, K. Nakazawa, K. Makishima, E. Sonoda, M. Yamauchi, H. Tanaka, R. Hara, N. Ohmori, K. Kono, H. Hayasi, S. Hong

    American Institute of Physics Conference Series   1133   338 - 343  2009.05  [International journal]

  • Time-Evolution of Peak Energy and Luminosity Relation within Pulses for GRB 061007: Probing Fireball Dynamics

    Masanori Ohno, Kunihito Ioka, Kazutaka Yamaoka, Makoto Tashiro, Yasushi Fukazawa, Yujin E. Nakagawa

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   61 ( 2 ) 201 - 211  2009.04  [Refereed]

     View Summary

    We performed a time-resolved spectral analysis of a bright, long gamma-ray burst GRB 061007 using Suzaku/WAM and Swift/BAT. Because of the large effective area of the WAM, we can investigate the time evolution of the spectral peak energy E-peak(t) and the luminosity L-iso(t) with 1-s time resolution, and we find that the time-resolved pulses also satisfy the E-peak-L-iso relation, which was found for the time-averaged spectra of other bursts, suggesting the same physical conditions in each pulse. Furthermore, the initial rising phase of each pulse could be an outlier of this relation with higher E-peak(t) Value by a factor of 2. This difference could Suggest that the fireball radius expands by a factor of 2-4 and / or bulk Lorentz factor of the fireball is decelerated by a factor of similar to 4 during the initial phase, providing a new probe of fireball dynamics in real time.

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  • New Magnetar Frontiers with MAXI Survey

    Y. E. Nakagawa, A. Yoshida, K. Yamaoka

    Astrophysics with All-Sky X-Ray Observations     120  2009.03  [International journal]

  • SUZAKU OBSERVATION OF THE NEW SOFT GAMMA REPEATER SGR 0501+4516 IN OUTBURST

    T. Enoto, Y. E. Nakagawa, N. Rea, P. Esposito, D. Goetz, K. Hurley, G. L. Israel, M. Kokubun, K. Makishima, S. Mereghetti, H. Murakami, K. Nakazawa, T. Sakamoto, L. Stella, A. Tiengo, R. Turolla, S. Yamada, K. Yamaoka, A. Yoshida, S. Zane

    ASTROPHYSICAL JOURNAL LETTERS   693 ( 2 ) L122 - L126  2009.03  [Refereed]

     View Summary

    We present the first Suzaku observation of the new Soft Gamma Repeater, SGR 0501+4516, performed on 2008 August 26, four days after the onset of bursting activity of this new member of the magnetar family. The soft X-ray persistent emission was detected with the X-ray Imaging Spectrometer (XIS) at a 0.5-10 keV flux of 3.8 x 10-(11) erg s(-1) cm(-2), with a spectrum well fitted by an absorbed blackbody plus power-law model. The source pulsation was confirmed at a period of 5.762072 +/- 0.000002 s, and 32 X-ray bursts were detected by the XIS, four of which were also detected at higher energies by the Hard X-ray Detector (HXD). The strongest burst, which occurred at 03:16:16.9 (UTC), was so bright that it caused instrumental saturation, but its precursor phase, lasting for about 200 ms, was detected successfully over the 0.5-200 keV range, with a fluence of similar to 2.1 x 10(-7) erg cm-2 and a peak intensity of about 89 crab. The entire burst fluence is estimated to be similar to 50 times higher. The precursor spectrum was very hard, and well modeled by a combination of two blackbodies. We discuss the bursting activity and X/gamma-ray properties of this newly discovered Soft Gamma Repeater in comparison with other members of the class.

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  • Uniting the Quiescent Emission and Burst Spectra of Magnetar Candidates

    Yujin E. Nakagawa, Atsumasa Yoshida, Kazutaka Yamaoka, Noriaki Shibazaki

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   61 ( 1 ) 109 - 122  2009.02  [Refereed]

     View Summary

    Spectral studies of quiescent emission and bursts of magnetar candidates based on XMM-Newton, Chandra, and Swift data are presented. Spectra of both the quiescent emission and the burst for most magnetar candidates are reproduced by a photoelectrically absorbed two-blackbody function (21313). There is a strong correlation between the lower and higher temperatures of 2BB (kT(LT) and kT(HT)) for the magnetar candidates of which the spectra are well reproduced by 2BB. In addition, a square of radius for kT(LT) (R-LT(2)) is well correlated with a square of radius for kT(HT) (R-HT(2)). The ratio kT(LT)/kT(HT) approximate to 0.4 is nearly constant irrespective of the objects and/or emission types (i.e., the quiescent emission and the burst). This would imply that an emission mechanism is common among the magnetar candidates. The relation between the quiescent emission and the burst might be analogous to a relation between the solar microflare and the solar flare. Three anomalous X-ray pulsars (AXPs) (4U 0142+614, IRXSJ170849.0-400910, and IE2259+586) seem to have an excess above similar to 7keV, which well agrees with a nonthermal hard component discovered by the International Gamma-Ray Astrophysics Laboratory (INTEGRAL).

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  • The First Light from MAXI

    S. Ueno, M. Matsuoka, K. Kawasaki, H. Tomida, M. Suzuki, M. Ishikawa, Y. Adachi, Y. Itamoto, T. Mihara, M. Kohama, M. Sugizaki, Y. E. Nakagawa, T. Yamamoto, H. Tsunemi, M. Kimura, N. Kawai, M. Morii, K. Sugimori, A. Yoshida, K. Yamaoka, S. Nakahira, H. Negoro, R. Ishiwata, S. Miyoshi, H. Ozawa, M. Nakajima, Y. Ueda, N. Isobe, S. Eguchi, K. Hiroi, H. Katayaymai, K. Ebisawa

    The Extreme Sky: Sampling the Universe above 10 keV     11  2009.01  [International journal]

  • HETE-2 highlights

    Y. E. Nakagawa, Hete-2 Collaboration

    Frontier Objects in Astrophysics and Particle Physics     315  2009.01  [International journal]

  • Current Status of the Suzaku Wide-band All-sky Monitor (WAM)

    Kazutaka Yamaoka, Satoshi Sugita, Makoto Tashiro, Yukikatsu Terada, Yuji Urata, Akira Endo, Kaori Onda, Kouichi Morigami, Natsuki Kodaka, Takako Sugasawara, Wataru Iwakiri, Yasushi Fukazawa, Takeshi Uehara, Chie Kira, Yoshitaka Hanabata, Makoto Yamauchi, Eri Sonoda, Hiroki Tanaka, Ryuji Hara, Norisuke Ohmori, Hidenori Hayashi, Kenta Kono, Soojing Hong, Kazuo Makishima, Kazuhiro Nakazawa, Teruaki Enoto, Hiroyasu Tajima, Tadayuki Takahashi, Motohide Kokubun, Masanori Ohno, Yujin E. Nakagawa, Tohru Tamagawa, Toshio Murakami, Kevin Hurley

    GAMMA-RAY BUSTS   1133   91 - 93  2009  [Refereed]

     View Summary

    The Suzaku Wide-band All-sky Monitor (WAM) consists of 20 BGO anti-coincidence scintillators for the Hard X-ray Detector (HXD), The WAM has a wide field of view (FOV), about half of the whole sky, a large collecting area, 800 cm(2), and broad-band energy coverage from 50 to 5000 keV. Thus it has been designed to work as a gamma-ray burst detector. For the three years since Suzaku launch in July 2005, the WAM has been working very well. About 500 GRBs have been detected through the end of 2008, corresponding to a detection rate of similar to 140 GRBs per year. The current status of the WAM is presented in this paper.

  • Design and In-Orbit Performance of the Suzaku Wide-Band All-Sky Monitor

    Kazutaka Yamaoka, Akira Endo, Teruaki Enoto, Yasushi Fukazawa, Ryuji Hara, Yoshitaka Hanabata, Soojing Hong, Tsuneyoshi Kamae, Chie Kira, Natsuki Kodaka, Motohide Kokubun, Shouta Maeno, Kazuo Makishima, Ryohei Miyawaki, Kouichi Morigami, Toshio Murakami, Yujin E. Nakagawa, Kazuhiro Nakazawa, Norisuke Ohmori, Masanori Ohno, Kaori Onda, Goro Sato, Eri Sonoda, Satoshi Sugita, Masanobu Suzuki, Motoko Suzuki, Hiroyasu Tajima, Tadayuki Takahashi, Takuya Takahashi, Hiroki Tanaka, Tohru Tamagawa, Makoto S. Tashiro, Yukikatsu Terada, Takeshi Uehara, Yuji Urata, Makoto Yamauchi, Atsumasa Yoshida, Kevin Hurley, Valentin PaL'Shin, Takanori Sakamoto, Jay Cummings

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   61   S35 - S53  2009.01  [Refereed]

     View Summary

    The Suzaku Wide-band All-sky Monitor (WAM) consists of thick BGO anti-coincidence shields of the Hard X-ray Detectors (HXD). It views about half of the sky and has a geometrical area of 800 cm(2) per side and an effective area of 400 cm(2), even at 1 MeV. Hence, the WAM can provide unique opportunities to detect high-energy emission from GRBs and solar flares in the sub-MeV to MeV range. The WAM has detected more than 400 GRBs and 100 solar flares since its launch. This paper describes the in-flight performance of the HXD/WAM during the initial two years of operations, including the in-flight energy response, spectral and timing capabilities, and in-orbit background.

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  • Suzaku Observations of SGR 1900+14 and SGR 1806-20

    Yujin E. Nakagawa, Tatehiro Mihara, Atsumasa Yoshida, Kazutaka Yamaoka, Satoshi Sugita, Toshio Murakami, Daisuke Yonetoku, Motoko Suzuki, Motoki Nakajima, Makoto S. Tashiro, Kazuhiro Nakazawa

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   61 ( SP1 ) S387 - S393  2009.01  [Refereed]

     View Summary

    Spectral and timing studies of Suzaku ToO observations of two SGRs, 1900+14 and 1806-20, are presented. The X-ray quiescent emission spectra were well fitted by a two blackbody function, or a blackbody plus a power-law model. The non-thermal hard component discovered by INTEGRAL was detected by PIN diodes and its spectrum was reproduced by the power-law model reported by INTEGRAL. The XIS detected a periodicity of P = 5.1998 +/- 0.0002s for SGR 1900+14 and P = 7.6022 +/- 0.0007s for SGR 1806-20. The pulsed fraction was related to the burst activity for SGR 1900+14.

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  • Observations of the Prompt Gamma‐Ray Emission of GRB 070125

    Eric C. Bellm, Kevin Hurley, Valentin Pal’shin, Kazutaka Yamaoka, Mark S. Bandstra, Steven E. Boggs, Soojing Hong, Natsuki Kodaka, A. S. Kozyrev, M. L. Litvak, I. G. Mitrofanov, Yujin E. Nakagawa, Masanori Ohno, Kaori Onda, A. B. Sanin, Satoshi Sugita, Makoto Tashiro, V. I. Tretyakov, Yuji Urata, Claudia Wigger

    The Astrophysical Journal   688 ( 1 ) 491 - 498  2008.11  [Refereed]

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  • Intrinsic properties of a complete sample ofHETE-2 gamma-ray bursts

    A. Pélangeon, J.-L. Atteia, Y. E. Nakagawa, K. Hurley, A. Yoshida, R. Vanderspek, M. Suzuki, N. Kawai, G. Pizzichini, M. Boër, J. Braga, G. Crew, T. Q. Donaghy, J. P. Dezalay, J. Doty, E. E. Fenimore, M. Galassi, C. Graziani, J. G. Jernigan, D. Q. Lamb, A. Levine, J. Manchanda, F. Martel, M. Matsuoka, J.-F. Olive, G. Prigozhin, G. R. Ricker, T. Sakamoto, Y. Shirasaki, S. Sugita, K. Takagishi, T. Tamagawa, J. Villasenor, S. E. Woosley, M. Yamauchi

    Astronomy &amp; Astrophysics   491 ( 1 ) 157 - 171  2008.11  [Refereed]

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  • Multiple-Component Analysis of the Time-Resolved Spectra of GRB 041006: A Clue to the Nature of the Underlying Soft Component of GRBs

    Yuji Shirasaki, Atsumasa Yoshida, Nobuyuki Kawai, Toru Tamagawa, Takanori Sakamoto, Motoko Suzuki, Yujin Nakagawa, Akina Kobayashi, Satoshi Sugita, Ichiro Takahashi, Makoto Arimoto, Takashi Shimokawabe, Nicolas Vasquez Pazmino, Takuto Ishimura, Rie Sato, Masaru Matsuoka, Edward E. Fenimore, Mark Galassi, Donald Q. Lamb, Carlo Graziani, Timothy Q. Donaghy, Jean-Luc Atteia, Alexandre Pelangeon, Roland Vanderspek, Geoffrey B. Crew, John P. Doty, Joel Villasenor, Gregory Prigozhin, Nat Butler, George R. Ricker, Kevin Hurley, Stanford E. Woosley, Graziella Pizzichini

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   60 ( 4 ) 919 - 931  2008.08  [Refereed]

     View Summary

    GRB 041006 was detected by HETE-2 on 2004 October 06. The light curves in four different energy bands display different features. At higher energy bands several peaks are seen in the light curve, while at lower energy bands a single broader bump dominates. It is expected that these different features are the result of a mixture of several components, each of which has different energetics and variability. We analyzed the time-resolved spectra, which were resolved into several components. These components can be classified into two distinct classes. One is a component that has an exponential decay of E-p with a characteristic timescale shorter than similar to 30 s; its spectrum is well represented by a broken power-law function, which is frequently observed in many prompt GRB emissions, so it should have an internal-shock origin. Another is a component whose E-p is almost unchanged with a characteristic timescale longer than similar to 60 s, and shows a very soft emission and slower variability. The spectrum is characterized by either a broken power law or a black-body spectrum. By assuming that the soft component is a thermal emission, the radiation radius is initially 4.4 x 10(6) km, which is a typical radius of a blue supergiant, and its expansion velocity is 2.4 x 10(5) km s(-1) in the source frame.

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  • The swift discovery of X-ray afterglows accompanying short bursts from SGR 1900+14

    Y. E. Nakagawa, T. Sakamoto, G. Sato, N. Gehrels, K. Hurley, D. M. Palmer

    ASTROPHYSICAL JOURNAL LETTERS   681 ( 2 ) L89 - L92  2008.07  [Refereed]

     View Summary

    The discovery of X-ray afterglows accompanying two short bursts from SGR 1900+ 14 is presented. The afterglow luminosities at the end of each observation are lower by 30%-50% than their initial luminosities, and decay with power-law indices p similar to 0.2-0.4. Their initial bolometric luminosities are L similar to 10(34)-10(35) erg s(-1). We discuss analogies and differences between the X-ray afterglows of SGR short bursts and short gamma-ray bursts.

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  • Suzaku and Swift observations for X-ray afterglows; Investigation into the electron acceleration in the internal/external shocks

    Daisuke Yonetoku, Sachiko Tanabe, Toshio Murakami, N. Emura, Y. Aoyama, T. Kidamura, H. Kodaira, Y. Kodama, R. Kozaka, T. Nashimoto, S. Okuno, S. Yokota, S. Yoshinari, K. Abe, K. Onda, M. S. Tashiro, Y. Urata, Y. E. Nakagawa, S. Sugita, K. Yamaoka, A. Yoshida, T. Ishimura, N. Kawai, T. Shimokawabe, K. Kinugasa, T. Kohmura, K. Kubota, K. Sugiyasu, Y. Ueda, K. Masui, K. Nakazawa, T. Takahashi, S. Maeno, E. Sonoda, M. Yamauchi, M. Kuwahara, T. Tamagawa, D. Matsuura, M. Suzuki, N. Gehrels, J. Nousek

    American Institute of Physics Conference Series   1000   603 - 606  2008.05  [International journal]  [International coauthorship]

  • Status of GRB Observations with the Suzaku Wideband All-sky Monitor

    M. S. Tashiro, Y. Terada, Y. Urata, K. Onda, N. Kodaka, A. Endo, M. Suzuki, K. Morigami, K. Yamaoka, Y. E. Nakagawa, S. Sugita, Y. Fukazawa, M. Ohno, T. Takahashi, C. Kira, T. Uehara, T. Tamagawa, T. Enoto, R. Miyawaki, K. Nakazawa, K. Makishima, E. Sonoda, M. Yamauchi, S. Maeno, H. Tanaka, R. Hara, M. Suzuki, M. Kokubun, T. Takahashi, S. J. Hong, T. Murakami, H. Tajima, HXD Team

    American Institute of Physics Conference Series   1000   162 - 165  2008.05  [International journal]

  • The spectral properties of the GRB prompt gamma-ray emission observed by the Suzaku Wide-band All-sky Monitor

    M. Ohno, T. Uehara, T. Takahashi, Y. Fukazawa, C. Kira, Y. Hanabata, K. Yamaoka, Y. E. Nakagawa, S. Sugita, T. Tamagawa, Y. Terada, Y. Urata, K. Onda, N. Kodaka, A. Endo, M. Suzuki, K. Morigami, M. S. Tashiro, T. Enoto, R. Miyawamki, K. Nakazawa, K. Makishima, E. Sonoda, M. Yamauchi, S. Maeno, H. Tanaka, R. Hara, M. Kokubun, M. Suzuki, T. Takahashi, S. Hong, T. Murakami, H. Tajima

    American Institute of Physics Conference Series   1000   101 - 104  2008.05  [International journal]

  • Suzaku observation of the anomalous X-ray pulsar CXOU J164710.2-455216

    Sachindra Naik, Tadayasu Dotani, Nobuyuki Kawai, Motohide Kokubun, Takayasu Anada, Mikio Morii, Tatehiro Mihara, Teruaki Enoto, Madoka Kawaharada, Toshio Murakami, Yujin E. Nakagawa, Hiromitsu Takahashi, Yukikatsu Terada, Atsumasa Yoshida

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   60 ( 2 ) 237 - 244  2008.04  [Refereed]

     View Summary

    A Suzaku TOO observation of CXOU J164710.2-455216 was performed on 2006 September 23-24 for a net exposure of 38.8 ks. Pulsations were clearly detected in the XIS light curves with a pulse period of 10.61063(2) s. The XIS pulse profile is found to be highly non-sinusoidal. It shows 3 peaks of different amplitudes with an RMS fractional amplitude of similar to 11% in the 0.2-6.0 keV energy band. The 1 -10 keV XIS spectra were well fitted by two different models consisting of a power-law and a blackbody component and two blackbody components, respectively. Although both the models are statistically acceptable, a difference in the pulse profiles at soft (0.2-6.0 keV) and hard (6-12keV) X-rays favors the model consisting of two blackbody components. The temperatures of two blackbody components are found to be 0.61 +/- 0.01 keV and 1.22 +/- 0.06 keV, and the value of the absorption column density is 1.73 +/- 0.03 x 10(22) atoms cm(-2). Pulse phase resolved spectroscopy shows that the flux of the soft blackbody component consists of three narrow peaks, whereas the flux of the other component shows a single peak over the pulse period of the AXP. The blackbody radii change between 2.2-2.7 km and 0.28-0.38 km (assuming the source distance to be 5 kpc) over the pulse phases for the soft and hard components, respectively. The details of the results obtained from the timing and spectral analyses are presented.

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  • Swift captures the spectrally evolving prompt emission of GRB 070616★

    R. L. C. Starling, P. T. O'Brien, R. Willingale, K. L. Page, J. P. Osborne, M. De Pasquale, Y. E. Nakagawa, N. P. M. Kuin, K. Onda, J. P. Norris, T. N. Ukwatta, N. Kodaka, D. N. Burrows, J. A. Kennea, M. J. Page, M. Perri, C. B. Markwardt

    Monthly Notices of the Royal Astronomical Society   384 ( 2 ) 504 - 514  2008.02  [Refereed]

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  • Spectral evolution of GRB 060904A observed with swift and Suzaku - Possibility of inefficient electron acceleration

    Daisuke Yonetoku, Sachiko Tanabe, Toshio Murakami, Naomi Emura, Yuka Aoyama, Takashi Kidamura, Hironobu Kodaira, Yoshiki Kodama, Ryota Kozaka, Takuro Nashimoto, Shinya Okuno, Satoshi Yokota, Satoru Yoshinari, Keiichi Abe, Kaori Onda, Makoto S. Tashiro, Yuji Urata, Yujin E. Nakagawa, Satoshi Sugita, Kazutaka Yamaoka, Atsumasa Yoshida, Takuto Ishimura, Nobuyuki Kawai, Takashi Shimokawabe, Kenzo Kinugasa, Takayoshi Kohmura, Kaori Kubota, Kei Sugiyasu, Yoshihiro Ueda, Kensuke Masui, Kazuhiro Nakazawa, Tadayuki Takahashi, Shouta Maeno, Eri Sonoda, Makoto Yamauchi, Makoto Kuwahara, Toru Tamagawa, Daisuke Matsuura, Motoko Suzuki, Scott Barthelmy, Neil Gehrels, John Nousek

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   60 ( No. ) S351 - S360  2008.02  [Refereed]

     View Summary

    We observed an X-ray afterglow of GRB 060904A with the Swift and Suzaku satellites. We found rapid spectral softening during both the prompt tail phase and the decline phase of an X-ray flare in the Swift/BAT and Swift/XRT +004 data. The observed spectra were fit by power-law photon indices which rapidly changed from Gamma = (+1.51)(-0.03) to Gamma = 5.30(-0.59)(+0.69) within a few hundred seconds. This is one of the steepest X-ray spectra ever observed, making it quite difficult to explain by simple electron-acceleration and synchrotron -radiation processes. We then applied an alternative broken power-law with exponential cutoff (BPEC) model. It is valid to consider the exponential shape is equivalent to a synchrotron cutoff. Since the spectral cutoff appears in the soft X-ray band, we conclude that the electron acceleration must be inefficient in the internal shocks of GRB 060904A. These cutoff spectra suddenly disappeared at the end of the prompt tail. After that, typical afterglow spectra with F = 2.0 have been continuously and preciously monitored by both Swift/XRT and Suzaku/XIS. We could successfully trace the temporal history of two characteristic break energies that have a time dependence of (proportional to t(-3)-t(-4), while the following afterglow spectra are quite stable. This fact indicates that the emitting material of the prompt tail is due to completely different dynamics from the shallow decay component. Therefore, the emission sites of two distinct phenomena obviously differ from each other.

    DOI

  • Observations of short bursts from soft gamma repeaters detected by HETE-2

    Yujin E. Nakagawa

    Astronomical Herald   101   7 - 17  2008.01  [International journal]

  • Suzaku Wide-band All-sky Monitor Observations of Gamma-Ray Burst

    K. Yamaoka, A. Endo, T. Enoto, Y. Fukazawa, R. Hara, S. Hong, C. Kira, N. Kodaka, M. Kokubun, S. Maeno, K. Makishima, R. Miyawaki, K. Morigami, T. Murakami, Y. Nakagawa, K. Nakazawa, M. Ohno, K. Onda, E. Sonoda, S. Sugita, M. Suzuki, M. Suzuki, H Tajima, T. Takahashi, T. Takahashi, Y. Tanaka, T. Tamagawa, M. Tashiro, Y. Terada, T. Uehara, Y. Urata, M. Yamauchi, the Suzaku WAM Team

    International Cosmic Ray Conference   3   1151 - 1154  2008.01  [Refereed]  [International journal]

  • Development of a new background reduction method for WXM/HETE-2 and its application for bright GRB spectra

    I. Takahashi, Y. E. Nakagawa, S. Sugita, T. Tamagawa, M. Kuwahara, N. Kawai, M. Arimoto, T. Shimokawabe, T. Ishimura, N. Vasquez, M. Suzuki, R. Sato, Y. Shirasaki, George R. Ricker

    GAMMA-RAY BURSTS 2007   1000   174 - +  2008

     View Summary

    HETE-2 detected gamma-ray bursts (GRBs) since its launch on 9 October 2000. For spectral analyses using data of WXM on-board HETE-2, background spectra are conventionally obtained with time regions before and/or after prompt emission. In some cases, the background spectra change during the prompt ernission and/or the downlink trouble causes a loss of data around the prompt emission. If this is the case, the problem seems to lie in the fact that the conventional method cannot obtain correct background spectra. To make more appropriate background spectra, we develop a new analysis method using mask patterns of the WXM. The background spectra are estimated with shaded regions by the WXM mask pattern using the prompt emission data. Our new method might obtain a reliable result for a spectrum of GRB 030329. In this paper, we introduce our new analysis method and show a preliminary spectral result.

  • Spectrum feature of the underlying soft component of GRB041006

    Y. Shirasaki, A. Yoshida, N. Kawai, Y. Nakagawa, T. Tamagawa, M. Suzuki, S. Sugita, I. Takahashi, M. Arimoto, T. Shimokawabe, N. Vasquez, T. Ishimura, R. Sato, T. Sakamoto, M. Kuwahara, M. Matsuoka

    GAMMA-RAY BURSTS 2007   1000   158 - +  2008

     View Summary

    GRB 041006 was detected by HETE-2 at 12:19:08 UT on 06 October 2004. The GRB shows a soft X-ray emission, a precursor before the onset of the main GRB, and also shows a soft X-ray tail after the end of the main peak. The light curves within four different energy bands show different features; At higher energy bands several peaks are seen in the light curve, while at lower energy band a single broader bump is dominated. It is expected that these different features are the result of mixture of several components each of which has different energetics and variability. To reveal the nature of each component we analysed the time resolved spectra and they are successfully resolved into several components.

  • Substructure spectral analysis of HETE-2 burst GRB060115

    N. Vasquez, N. Kawai, M. Arimoto, T. Shimokawabe, T. Ishimura, M. Suzuki, R. Sato, A. Yoshida, Y. Nakagawa, S. Sugita, T. Tamagawa, M. Kuwahara, T. Sakamoto, Y. Shirasaki, G. R. Ricker

    GAMMA-RAY BURSTS 2007   1000   150 - 153  2008

     View Summary

    GRB060115 is a long, hard GRB detected with High Energy Transient Explorer 2 (HETE-2). It presents substantial substructures in its light curve. With the spectral analysis of the whole burst and its substructures in. the wide energy range of HETE-2 (2-400 keV), we find in the time history of the emission process a hard-to-soft trend first followed by a soft-to-hard evolution. This evolution is not common in GRBs, which generally exhibit only a hard-to-soft evolution. The evolution of the prompt emission of GRB060115 is discussed in this framework.

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  • HETE-2 observation of the evidence of a long acting engine in the extremely soft XRF 040916

    Makoto Arimoto, Nobuyuki Kawai, Motoko Suzuki, Rie Sato, Nicolas Vasquez Pazmino, Takashi Shimokawabe, Takuto Ishimura, Yujin E. Nakagawa, Alexandre Pelangeon, Jean-Luc Atteia, Kevin Hurley, Graziella Pizzichini, Donald Q. Lamb

    GAMMA-RAY BURSTS 2007   1000   331 - +  2008

     View Summary

    A long and extremely soft X-ray flash was detected and localized by the instruments aboard the HETE-2 at 00:03:30 UT on 2004 Sep. 16. This burst consists of two peaks separated by similar to 200 s, with durations of about 110 s and 60 s. We have analyzed the energy spectra of the 1st and 2nd peaks observed with the Wide Field X-Ray Monitor (WXM) and the French Gamma Telescope (FREGATE). We discuss the origin of the 2nd peak in terms of flux variabilities and timescales. We find that it is most likely part of the prompt emission, and is explained by the long-acting engine model.

  • Design and development of Gamma-ray Burst Monitor for the CALET Mission

    S. Nakahira, K. Yamaoka, A. Yoshida, T. Doshida, K. Suzuki, S. Sugita, T. Oyama, Y. E. Nakagawa, H. Tomida, S. Torii

    AIP Conference Proceedings   1000   616 - 619  2008  [Refereed]

     View Summary

    We propose to provide a gamma-ray burst monitor (GBM) for the CALET mission to monitor gamma-ray bursts (GRBs) together with the CALET Imaging Calorimeter detector. The major purpose is to derive a wide-band energy spectrum of GRBs over an unprecedented 9 decades of energy (from a few keV to a few TeV) in combination with the CALET tower detector. Hence it is desirable to have the CALET-GBM covering an energy range from a few keV to about 20 MeV to avoid a gap in the observational energy bands. The design of GBM is underway to fulfill this requirement. The current detector candidate is BGO, and a LaBr (Ce) scintillator which has a superior energy resolution to that of NaI(Tl). In this paper, design and expected performance of the CALET-GBM is shown. © 2008 American Institute of Physics.

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  • HETE-2 observations of the X-ray flash XRF 040916

    Makoto Arimoto, Nobuyuki Kawai, Motoko Suzuki, Rie Sato, Nicolas Vasquez Pazmino, Takashi Shimokawabe, Takuto Ishimura, Jun'ichi Kotoku, Atsumasa Yoshida, Toru Tamagawa, Yuji Shirasaki, Masaru Matsuoka, Yujin Nakagawa, Nobuyuki Ishikawa, Akina Kobayashi, Satoshi Sugita, Ichiro Takahashi, Makoto Kuwahara, Makoto Yamauchi, Kunio Takagishi, Isamu Hatsukade, Jean-Luc Atteia, Alexandre Pelangeon, Roland Vanderspek, Carlo Graziani, Gregory Prigozhin, Joel Villasenor, J. Garrett Jernigan, Geoffrey B. Crew, Kevin Hurley, Takanori Sakamoto, George R. Ricker, Stanford E. Woosley, Nat Butler, Al Levine, John P. Doty, Timothy Q. Donaghy, Donald Q. Lamb, Edward E. Fenimore, Mark Galassi, Michel Boer, Jean-Pascal Dezalay, Jean-Francois Olive, Joao Braga, Ravi Manchanda, Graziella Pizzichini

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   59 ( 3 ) 695 - 702  2007.06  [Refereed]

     View Summary

    A long X-ray flash was detected and localized by instruments aboard the High Energy Transient Explorer II (HETE-2) at 00:03:30 UT on 2004 September 16. The position was reported to the GRB Coordinates Network (GCN) approximately 2 hours after the burst. This burst consisted of two peaks separated by similar to 200 s, with durations of about 110 s and 60 s. We analyzed the energy spectra of the 1st and 2nd peaks observed with the Wide Field X-Ray Monitor (WXM) and the French Gamma Telescope (FREGATE). We discuss the origin of the 2nd peak in terms of the flux variabilities and timescales. We find that it is most likely to be part of prompt emission, and is explained by a long-acting engine model. This feature is similar to some bright X-ray flares detected in the early afterglow phase of bursts observed by the Swift satellite.

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  • A comprehensive study of short bursts from SGR 1806-20 and SGR 1900+14 detected by HETE-2

    Yujin E. Nakagawa, Atsumasa Yoshida, Kevin Hurley, Jean-Luc Atteia, Miki Maetou, Toru Tamagawa, Motoko Suzuki, Tohru Yamazaki, Kaoru Tanaka, Nobuyuki Kawai, Yuji Shirasaki, Alexandre Pelangeon, Masaru Matsuoka, Roland Vanderspek, Geoff B. Crew, Joel S. Villasenor, Rie Sato, Satoshi Sugita, Jun'ichi Kotoku, Makoto Arimoto, Graziella Pizzichini, John P. Doty, George R. Ricker

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   59 ( 3 ) 653 - 678  2007.06  [Refereed]

     View Summary

    Temporal and spectral studies of short bursts (less than or similar to a few hundred milliseconds) are presented for the soft gamma repeaters (SGRs) 1806-20 and 1900+14 using the HETE-2 samples. In five years from 2001 to 2005, HETE-2 localized 50 bursts from SGR 1806-20 and 5 bursts from SGR 1900+14. The cumulative number-intensity distribution of SGR 1806-20 in the active year 2004 is well described by a power-law model with an index of -1.1 +/- 0.6. It is consistent with previous studies, but burst data taken in other years clearly give a steeper distribution. This may suggest that more energetic bursts could occur more frequently in periods of greater activity. From the data, the spectral evolution during bursts with a time scale of greater than or similar to 20 ms does not seem to be common in the HETE-2 sample. The spectra of all short bursts are well reproduced by a two blackbody function with temperatures of similar to 4 and similar to 11 keV. From a timing analysis to the SGR 1806-20 data, a time lag of 2.2 +/- 0.4 ms is found between the 30-100 keV and 2-10 keV radiation bands. This may imply (1) a very rapid spectral softening and energy reinjection, (2) diffused (elongated) emission plasma along the magnetic field lines in pseudo-equilibrium with multi-temperatures, or (3) a separate (located at less than or similar to 700 km) emission region of a softer component (say, similar to 4 keV), which could be reprocessed X-rays by higher energy (greater than or similar to 11 keV) photons from an emission region near the stellar surface.

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  • Discovery of a New X-Ray Burst/Millisecond Accreting Pulsar, HETE J1900.1-2455

    Motoko Suzuki, Nobuyuki Kawai, Toru Tamagawa, Atsumasa Yoshida, Yujin E. Nakagawa, Kaoru Tanaka, Yuji Shirasaki, Masaru Matsuoka, George R. Ricker, Roland Vanderspek, Nat Butler, Donald Q. Lamb, Carlo Graziani, Graziella Pizzichini, Rie Sato, Makoto Arimoto, Jun’ichi Kotoku, Miki Maetou, Makoto Yamauchi

    Publications of the Astronomical Society of Japan   59   263 - 268  2007.02  [Refereed]

     View Summary

    A class of low-mass X-ray binary sources is known to be both X-ray burst sources and millisecond pulsars at the same time. A new source of this class was discovered by High Energy Transient Explorer 2 (HETE-2) on 2005 June 14 as a source of type-I X-ray bursts, which was named HETE J1900.1-2455. Five X-ray bursts from HETE J1900.1-2455 were observed during the summer of 2005. A time-resolved spectral analysis of these bursts has revealed that their spectra are consistent with the blackbody radiation throughout the bursts. The bursts show an indication of radius expansion. The bolometric flux remained almost constant during the photospheric radius expansion, while blackbody temperature dropped during the same period. Assuming that the flux reached the Eddington limit on a standard 1.4 solar-mass neutron star with a helium atmosphere, we estimate the distance to the source to be ∼ 4 kpc. © 2007. Astronomical Society of Japan.

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  • Wide-Band Study of X-Ray Pulsars with Suzaku

    T. Enoto, R. Miyawaki, M. Kokubun, K. Makishima, Y. Terada, T. Mihara, M. Nakajima, M. Suzuki, A. Bamba, A. Senda, K. Makishima, Y. Ishisaki, H. Takahashi, K. Tamura, S. Naik, K. Ebisawa, F. Nagase, S. Kitamoto, K. Sudoh, A. Yoshida, Y. Nakagawa, S. Sugita, T. Kohmura, T. Kotani, N. Kawai, D. Yonetoku, K. Mori

    The Obscured Universe. Proceedings of the VI INTEGRAL Workshop   622   453  2007.01  [International journal]

  • A Comprehensive Study for Short Bursts from SGRs Detected by HETE-2

    Y. E. Nakagawa, A. Yoshida, K. Hurley, J. L. Atteia, T. Tamagawa, M. Suzuki, T. Yamazaki, K. Tanaka, N. Kawai, Y. Shirasaki, A. Pelangeon, M. Matsuoka, R. Vanderspek, G. B. Crew, J. S. Villasenor, R. Sato, S. Sugita, J. Kotoku, M. Arimoto, G. Pizzichini, J. P. Doty, G. R. Ricker, HETE-2 Science Team

    Proceedings of International Conference on Cosmic-Rays and High Energy Universe    2007  [International journal]  [International coauthorship]

  • Two Components Model for SGR Short Flares - Detailed Timing and Spectral Studies on HETE-2 Samples -

    Y. E. Nakagawa, A. Yoshida, K. Hurley, J.-L. Atteia, M. Maetou, T. Tamagawa, M. Suzuki, T. Yamazaki, K. Tanaka, N. Kawai, Y. Shirasaki, A. Pelangeon, M. Matsuoka, R. Vanderspek, G. B. Crew, J. S. Villasenor, R. Sato, S. Sugita, J. Kotoku, M. Arimoto, G. Pizzichini, J. P. Doty, G. R. Ricker, HETE-2 Science Team

    Proceedings of International Conference on The Extreme Universe in the Suzaku Era    2007  [International journal]  [International coauthorship]

  • Strategy of the Suzaku gamma-ray burst observations

    M.S. Tashiro, K. Abe, L. Angelini, Y. Endo, T. Enoto, Y. Fukazawa, S. Hong, N. Ishikawa, L.J. Kaluzienski, N. Kawai, R.L. Kelley, K. Kinugasa, H. Kodaira, T. Kohmura, M. Kokubun, K. Kubota, S. Maeno, K. Makishima, R. Miyawaki, T. Murakami, Y.E. Nakagawa, K. Nakazawa, J.A. Nousek, M. Ohno, S. Okuno, K. Onda, J.N. Reeves, G. Ricker, G. Sato, E. Sonoda, S. Sugita, M. Suzuki, T. Takahashi, T. Takahashi, T. Tamagawa, Y. Terada, K. Torii, Y. Ueda, Y. Urata, K. Yamaoka, M. Yamauchi, A. Yoshida, S. Yoshinari, D. Yonetoku

    Advances in Space Research   40 ( 8 ) 1255 - 1258  2007.01  [Refereed]

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  • The Suzaku-Swift joint observation of the early X-ray afterglow of GRB060105

    Makoto S. Tashiro, Keiichi Abe, Lorella Angelini, Scott Barthelmy, Neil Gehrels, Nobuyuki Ishikawa, Louis J. Kaluzienski, Nobuyuki Kawai, Richard L. Kelley, Kenzo Kinugasa, Hironobu Kodaira, Takayoshi Kohmura, Kaori Kubota, Yoshitomo Maeda, Shouta Maeno, Hiroshi Murakami, Toshio Murakami, Yujin E. Nakagawa, Kazuhiro Nakazawa, John Nousek, Shin'ya Okuno, Kaori Onda, James N. Reeves, George Ricker, Goro Sato, Eri Sonoda, Motoko Suzuki, Tadayuki Takahashi, Toru Tamagawa, Ken'ichi Torii, Yoshihiro Ueda, Yuji Urata, Kazutaka Yamaoka, Makoto Yamauchi, Daisuke Yonetoku, Atsumasa Yoshida, Satoru Yoshinari

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT   ( 169 ) 3 - 6  2007

     View Summary

    Results are presented of a Suzaku and Swift joint observation for an early X-ray afterglow of GRB 060105. The bright, long gamma-ray burst GRB 060105 triggered the Swift Burst Alert Telescope (BAT) at 06:49:28 on 5 January 2006 (To). The Suzaku team commenced a pre-planned target of opportunity observation at 12:10 and continued till 12:00 on January 6. The X-ray flux faded during the observations from 6.8 x 10(-9) erg s(-1)cm(-2) to 1.5 x 10(-13) erg s(-1)cm(-2) in the 2-10 keV energy band. Following the prompt emission and successive "very steep decay", a "shallow decay" was observed from T-0 + 187 s to T-0 + 1287 s. After an observation gap during T-0 + (1.5 - 3) ks, an extremely early steep decay was observed in To + (4 - 30) ks. The steep decay exhibited decay indices of 2.3 - 2.4. This very early break, if it is a jet break, is the earliest case among X-ray afterglow observations, suggesting a very narrow jet whose opening angle is well below 1 degrees.

  • Swift and Suzaku observations of the X-ray afterglow from the GRB 060105

    Makoto S. Tashiro, Keiichi Abe, Lorella Angelini, Scott Barthelmy, Neil Gehrels, Nobuyuki Ishikawa, Louis J. Kaluzienski, Nobuyuki Kawai, Richard L. Kelley, Kenzo Kinugasa, Hironobu Kodaira, Takayoshi Kohmura, Kaori Kubota, Yoshitomo Maeda, Shouta Maeno, Hiroshi Murakami, Toshio Murakami, Yujin E. Nakagawa, Kazuhiro Nakazawa, John Nousek, Shin'ya Okuno, Kaori Onda, James N. Reeves, George Ricker, Goro Sato, Eri Sonoda, Motoko Suzuki, Tadayuki Takahashi, Toru Tamagawa, Ken'ichi Torii, Yoshihiro Ueda, Yuji Urata, Kazutaka Yamaoka, Makoto Yamauchi, Daisuke Yonetoku, Atsumasa Yoshida, Satoru Yoshinari

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   59 ( No. ) S361 - S367  2007.01  [Refereed]

     View Summary

    Results are presented of early X-ray afterglow observations of GRB 060105 by Swift and Suzaku. The bright, long gamma-ray burst GRB; 060105 triggered the Swift Burst Alert Telescope at 06:49:28 on 2006 January 5 (T-0). The Suzaku team commenced a pre-planned target of opportunity observation at 19 ks (5.3 hr) after the Swift trigger. The X-ray flux faded during observations from 6.8 x 10(-9) ergs(-1) cm(-2) (at T-0 + 87 s with the Swift/XRT) to 1.5 x 10(-13) erg s(-1) cm(-2) [at T-0 + 94-101 ks with the Suzaku X-ray Imaging Spectrometer (XIS)] in the 2-10 keV energy band. Following prompt emission and successive very steep decay, a shallow decay was observed from To + 187 s to T-0 + 1287 s. After an observation gap during T-0 + (1.5-3) ks, an extremely early steep decay was observed in T-0 + (4-30) ks. The lightcurve flattened again at T-0 + 30ks, and another steep decay followed from T-0 + 50ks to the end of observations. Both steep decays exhibited decay indices of 2.3-2.4. This very early break, if it is a jet break, is the earliest case among X-ray afterglow observations, suggesting a very narrow jet whose opening angle is well below 1 degrees. The unique Suzaku/XIS data allow us to set very tight upper limits on line emission or absorption in this GRB. For the reported pseudo-redshift of z = 4.0 +/- 1.3 the upper limit on the iron line equivalent width is 50 eV.

    DOI

  • Gamma-ray burst monitor for the CALET mission

    K. Yamaoka, A. Yoshida, Y. E. Nakagawa, S. Sugita, S. Nakahira, H. Tomida, S. Torii

    Proceedings of the 30th International Cosmic Ray Conference, ICRC 2007   3 ( OG PART 2 ) 1465 - 1468  2007  [Refereed]

     View Summary

    We propose to provide a gamma-ray burst monitor (GBM) for the CALET mission to monitor gamma-ray bursts (GRBs) simultaneously with the CALET main detector. The major purpose is to derive a wide-band energy spectrum of GRB over an unprecedented 9 decades of energy (from a few keV to a few TeV) in combination with the CALET tower detector. Hence it is desirable to have the CALET-GBM covering an energy range from a few keV to about 20 MeV to avoid a gap in observational energy band. The design of GBM is underway to fulfill this requirement. The current detector candidate is LaBr3(Ce) scintillator which has a superior energy resolution to that of NaI(Tl). The design and expected performance of the CALET-GBM will be presented in this paper.

  • Observation of GRB 051022 detected by HETE-2

    Y. E. Nakagawa, A. Yoshida, S. Sugita, K. Tanaka, N. Ishikawa, T. Tamagawa, M. Suzuki, Y. Shirasaki, N. Kawai, M. Matsuoka, J. L. Atteia, A. Pelangeon, R. Vanderspek, G. B. Crew, J. S. Villasenor, N. Butler, J. Doty, G. R. Ricker, G. Pizzichini, T. Q. Donaghy, D. Q. Lamb, C. Graziani, J. G. Jernigan, T. Sakamoto, J. F. Olive, M. Boër, E. E. Fenimore, M. Galassi, S. E. Woosley, M. Yamauchi, K. Takagishi, I. Hatsukade, HETE-2 Science Team

    Nuovo Cimento B Serie   121   1535 - 1537  2006.12  [Refereed]  [International journal]  [International coauthorship]

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  • Detailed analyses of GRB 060105 X-ray afterglow observed by Suzaku

    Y. E. Nakagawa, M. Tashiro, K. Abe, A. Yoshida, K. Yamaoka, K. Nakazawa, T. Murakami, D. Yonetoku, N. Kawai, J. Nousek, N. Ishikawa, Y. Urata, K. Onda, T. Tamagawa, M. Suzuki, M. Kuwahara, T. Takahashi, M. Yamauchi, E. Sonoda, S. Maeno, K. Kinugasa, T. Kohmura, K. Torii, Y. Ueda, K. Kubota, K. Sugiyasu, H. Kodaira, S. Okuno, S. Yoshinari, T. Shimokawabe, T. Ishimura, G. R. Ricker, J. N. Reeves, L. Angelini, L. J. Kaluzienski, R. L. Kelley

    Nuovo Cimento della Societa Italiana di Fisica B   121 ( 12 ) 1531 - 1533  2006.12  [Refereed]

     View Summary

    GRB 060105 was detected with the BAT instrument on-board Swift. The Suzaku follow-up observation started just 5.3 hours after the trigger with the XIS and HXD instruments. The XIS detected an uncatalogued fading source and its position was consistent with that previously reported by Swift XRT. We performed the spectral analyses using the data derived from Suzaku XIS and Swift XRT, and found that the spectrum of X-ray afterglow was well reproduced by the absorbed power law model. The best-fit spectral index and absorption are β = 2.15 ± 0.03 and NH = (3.74 ± 0.03) × 1021 cm-2, respectively. The observed decay curve by Suzaku XIS is fully consistent with the Swift XRT result. The Suzaku and Swift observations imply the possibility of the jet break at t = 3500 s, and the brightening of afterglow around t = 40000 s likely due to the refreshed shock. We see neither significant spectral evolution during the decay, nor evidence of emission line feature. © Società Italiana di Fisica.

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  • X-ray bursts observed by HETE-2

    M. Suzuki, M. Arimoto, N. Ishikawa, A. Kobayashi, J. Kotoku, M. Maetou, Y. Nakagawa, T. Sakamoto, R. Sato, T. Shimokawabe, Y. Shirasaki, S. Sugita, T. Tamagawa, K. Tanaka, N. Kawai, A. Yoshida, M. Matsuoka, N. Butler, G. B. Crew, R. Vanderspek, C. Graziani, T. Q. Donaghy, J. Doty, E. E. Fenimore, M. Galassi

    NUOVO CIMENTO DELLA SOCIETA ITALIANA DI FISICA B-GENERAL PHYSICS RELATIVITY ASTRONOMY AND MATHEMATICAL PHYSICS AND METHODS   121 ( 12 ) 1593 - 1594  2006.12  [Refereed]

     View Summary

    The High Energy Transient Explorer II (HETE-2) observed more than 500 X-Ray Bursts (XRBs) since its launch. Most of them are from similar to 20 known X-ray sources. We investigated the observation coverage for each source and studied the frequency of the bursts from each source from 2001 to 2005.

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  • X-ray flashes or soft gamma-ray bursts? The case of the likely distant XRF 040912

    G. Stratta, S. Basa, N. Butler, J. L. Atteia, B. Gendre, A. Pélangeon, F. Malacrino, Y. Mellier, D. A. Kann, S. Klose, A. Zeh, N. Masetti, E. Palazzi, J. Gorosabel, A. J. Castro-Tirado, A. de Ugarte Postigo, M. Jelinek, J. Cepa, H. Castañeda, D. Martínez-Delgado, M. Boër, J. Braga, G. Crew, T. Q. Donaghy, J.-P. Dezalay, J. Doty, E. E. Fenimore, M. Galassi, C. Graziani, J. G. Jernigan, N. Kawai, D. Q. Lamb, A. Levine, R. K. Manchanda, F. Martel, M. Matsuoka, Y. Nakagawa, J.-F. Olive, G. Pizzichini, G. Prigozhin, G. Ricker, T. Sakamoto, Y. Shirasaki, S. Sugita, M. Suzuki, K. Takagishi, T. Tamagawa, R. Vanderspek, J. Villasenor, S. E. Woosley, M. Yamauchi, A. Yoshida

    Astronomy &amp; Astrophysics   461 ( 2 ) 485 - 492  2006.10  [Refereed]

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  • Generalized relationship between Ep and brightness for multi-spike GRBs

    A. Yoshida, Y. E. Nakagawa, S. Sugita, M. Suzuki, K. Tanaka, T. Tamagawa, N. Ishikawa, I. Takahashi, N. Kawai, Y. Shirasaki, HETE-2 Science Team

    Nuovo Cimento B Serie   121   1267 - 1272  2006.10  [Refereed]  [International journal]

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  • Suzaku observation of X-ray afterglow: Spectral and temporal behaviors

    D. Yonetoku, T. Murakami, H. Kodaira, S. Okuno, S. Yoshinari, K. Abe, L. Angelini, S. Barthelmy, N. Gehrels, N. Ishikawa, L. J. Kaluzienski, N. Kawai, R. L. Kelley, K. Kinugasa, T. Kohmura, K. Kubota, Y. Maeda, S. Maeno, H. Murakami, Y. E. Nakagawa, K. Nakazawa, J. Nousek, K. Onda, J. N. Reeves, G. Ricker, G. Sato, E. Sonoda, M. Suzuki, T. Takahashi, T. Tamagawa, M. S. Tashiro, K. Torii, Y. Ueda, Y. Urata, K. Yamaoka, M. Yamauchi, A. Yoshida

    Nuovo Cimento B Serie   121   1253 - 1256  2006.10  [Refereed]  [International journal]  [International coauthorship]

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  • GRB 060121: Implications of a Short-/Intermediate-Duration γ-Ray Burst at High Redshift

    A. de Ugarte Postigo, A. J. Castro-Tirado, S. Guziy, J. Gorosabel, G. Jóhannesson, M. A. Aloy, S. McBreen, D. Q. Lamb, N. Benitez, M. Jelínek, S. B. Pandey, D. Coe, M. D. Pérez-Ramírez, F. J. Aceituno, M. Alises, J. A. Acosta-Pulido, G. Gómez, R. López, T. Q. Donaghy, Y. E. Nakagawa, T. Sakamoto, G. R. Ricker, F. R. Hearty, M. Bayliss, G. Gyuk, D. G. York

    The Astrophysical Journal   648 ( 2 ) L83 - L87  2006.08  [Refereed]

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  • Cyclotron Resonance Energies at a Low X-Ray Luminosity: A0535+262 Observed with Suzaku

    Y. Terada, T. Mihara, M. Nakajima, M. Suzuki, N. Isobe, K. Makishima, H. Takahashi, T. Enoto, M. Kokubun, T. Kitaguchi, S. Naik, T. Dotani, F. Nagase, T. Tanaka, S. Watanabe, S. Kitamoto, K. Sudoh, A. Yoshida, Y. Nakagawa, S. Sugita, T. Kohmura, T. Kotani, D. Yonetoku, L. Angelini, J. Cottam, K. Mukai, R. Kelley, Y. Soong, M. Bautz, S. Kissel, J. Doty

    The Astrophysical Journal   648 ( 2 ) L139 - L142  2006.08  [Refereed]

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  • An optically dark GRB observed by HETE-2: GRB 051022

    Yujin E. Nakagawa, Atsumasa Yoshida, Satoshi Sugita, Kaoru Tanaka, Nobuyuki Ishikawa, Toru Tamagawa, Motoko Suzuki, Yuji Shirasaki, Nobuyuki Kawai, Masaru Matsuoka, Jean-Luc Atteia, Alexandre Pelangeon, Roland Vanderspek, Geoffrey B. Crew, Joel S. Villasenor, Nat Butler, John P. Doty, George R. Ricker, Graziella Pizzichini, Timothy Q. Donaghy, Donald Q. Lamb, Carlo Graziani, Rie Sato, Miki Maetou, Makoto Arimoto, Jun'ichi Kotoku, J. Garrett Jernigan, Takanori Sakamoto, Jean-Francois Olive, Michel Boer, Edward E. Fenimore, Mark Galassi, Stanford E. Woosley, Makoto Yamauchi, Kunio Takagishi, Isamu Hatsukade

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   58 ( 4 ) L35 - L39  2006.08  [Refereed]

     View Summary

    GRB 051022 was detected at 13:07:58 on 2005 October 22 UT by HETE-2. The location of GRB 051022 was determined immediately by the fight localization system. This burst contained multiple pulses, and had a rather long duration of about 190 s. The detections of candidate X-ray and radio afterglows were reported, whereas no optical afterglow was found. Optical spectroscopic observations of the host galaxy revealed a redshift of z = 0.8. Using data derived by a HETE-2 observation of the prompt emission, we found absorption of N-H = (8.8(-2.9)(+3.1)) x 10(22) cm(-2) and visual extinction of A(V) = 49(-16)(+17) mag in the host galaxy. If this is the case, no detection of any optical transient would be quite reasonable. The absorption derived by Swift XRT observations of the afterglow is fully consistent with those obtained from an early HETE-2 observation of the prompt emission. Our analysis implies an interpretation that the absorbing medium may be outside the external shock at R similar to 10(16) cm, which could be a dusty molecular cloud.

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  • HETE-2 Localizations and Observations of Four Short Gamma-Ray Bursts: GRBs 010326B, 040802, 051211 and 060121

    T. Q. Donaghy, D. Q. Lamb, T. Sakamoto, J. P. Norris, Y. Nakagawa, J. Villasenor, J. -L. Atteia, R. Vanderspek, C. Graziani, N. Kawai, G. R. Ricker, G. B. Crew, J. Doty, G. Prigozhin, J. G. Jernigan, Y. Shirasaki, M. Suzuki, N. Butler, K. Hurley, T. Tamagawa, A. Yoshida, M. Matsuoka, E. E. Fenimore, M. Galassi, M. Boer, J. -P. Dezalay, J. -F. Olive, A. Levine, F. Martel, E. Morgan, R. Sato, S. E. Woosley, J. Braga, R. Manchanda, G. Pizzichini, K. Takagishi, M. Yamauchi

       2006

     View Summary

    Here we report the localizations and properties of four short-duration GRBs localized by the High Energy Transient Explorer 2 satellite (HETE-2): GRBs 010326B, 040802, 051211 and 060121, all of which were detected by the French Gamma Telescope (Fregate) and localized with the Wide-field X-ray Monitor (WXM) and/or Soft X-ray Camera (SXC) instruments. We discuss eight possible criteria for determining whether these GRBs are "short population bursts" (SPBs) or "long population bursts" (LPBs). These criteria are (1) duration, (2) pulse widths, (3) spectral hardness, (4) spectral lag, (5) energy Egamma radiated in gamma rays (or equivalently, the kinetic energy E_KE of the GRB jet), (6) existence of a long, soft bump following the burst, (7) location of the burst in the host galaxy, and (8) type of host galaxy. In particular, we have developed a likelihood method for determining the probability that a burst is an SPB or a LPB on the basis of its T90 duration alone. A striking feature of the resulting probability distribution is that the T90 duration at which a burst has an equal probability of being a SPB or a LPB is T90 = 5 s, not T90 = 2 s, as is often used. All four short-duration bursts discussed in detail in this paper have T90 durations in the Fregate 30-400 keV energy band of 1.90, 2.31, 4.25, and 1.97 sec, respectively, yielding probabilities P(S|T90) = 0.97, 0.91, 0.60, and 0.95 that these bursts are SPBs on the basis of their T90 durations alone. All four bursts also have spectral lags consistent with zero. These results provide strong evidence that all four GRBs are SPBs (abstract continues).

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  • Properties of multi pulsed GRBs seen by HETE-2

    Y. E. Nakagawa, A. Yoshida, N. Ishikawa, K. Tanaka, T. Tamagawa, M. Suzuki, N. Kawai, M. Matsuoka, Y. Shirasaki, R. Vanderspek, E. E. Fenimore, M. Galassi, J. -L. Atteia, G. R. Ricker

    GAMMA-RAY BURSTS IN THE SWIFT ERA   836 ( No. ) 177 - +  2006

     View Summary

    It is claimed by many authors that there are tight correlations between the spectral peak energy E-p, and the "brightness" such as isotropic energy E-rad, collimation-corrected energy E-gamma, or peak luminosity L-p. In many long GRBs, their light curves consist of several pulses or humps, and each pulse has a different spectrum. Using data of multi pulsed GRBs observed by HETE-2, we investigated these relations for each pulse and found it looked to have some correlations. This may imply that each pulse could behave as a single burst. Considering that the GRB rate follow the star formation rate of the Universe, we should have already detected a number of distant GRBs. Some methods are proposed to estimate a redshift by applying the above mentioned correlations. Extending the previous studies, we apply the redshill estimations using E-p-E-rad correlation for an individual pulse.

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  • Temporal and spectral analyses of SGRs observed by HETE-2

    Y. E. Nakagawa, A. Yoshida, M. Maetou, M. Suzuki, T. Tamagawa, T. Sakamoto, N. Kawai, Y. Shirasaki, K. Tanaka, M. Matsuoka, E. E. Fenimore, M. Galassi, J. -L. Atteia, K. Hurley, G. R. Ricker

    GAMMA-RAY BURSTS IN THE SWIFT ERA   836 ( No. ) 173 - +  2006

     View Summary

    HETE-2 localized 63 flares from SGR1806-20 and 6 flares from SGR1900+14 in the summer periods from June 18 2001 through August 7 2005. We report on the temporal and spectral analyses of short flares from those SGRs. The estimation of T-90 durations in 2-30 keV and 30-100 keV revealed that there is no difference between them with a few exceptions. For these exceptional short flares, there seems softening or possibly hardening during flares, but these spectral evolution are not common. We also found a good linear correlation between the rise and decay time, and they do not depend on a peak flux. We also found that the spectra are well reproduced by a sum of two blackbody models for all short flares. The temperatures are lying around 4 keV and I I keV which are consistent with previous studies. T'hey are not depend on either the magnitude of flare, the event morphology or the source.

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  • New concept of small satellite, HETE-2 and its scientific activity

    M. Matsuoka, N. Kawai, A. Yoshida, T. Tamagawa, Y. Shirasaki, M. Suzuki, Y. Nakagawa, T. Sakamoto, T. Sakamoto, R. Sato, G. Ricker, J. Doty, R. Vanderspek, G. Crew, J. Vilasenor, J. L. Atteia, E. E. Fenimore, M. Galassi, D. Q. Lamb, C. Graziani, K. Hurley, J. G. Jernigan, S. Woosley, F. Martel, G. Monnelly, G. Prigozhin, J. F. Olive, J. P. Dezalay, M. Boer, T. Cline, J. Braga, R. Manchanda, G. Pizzichini, A. Levine, E. Morgan, N. Butler, T. Kotani, J. Kotoku, K. Torii, Y. Urata, Y. Urata, M. Arimoto, N. Ishikawa, A. Kobayashi, M. Maeto, T. Shimokawabe, S. Sugita, K. Tanaka, M. Yamauchi

    International Astronautical Federation - 56th International Astronautical Congress 2005   3   2092 - 2098  2005.12  [Refereed]

     View Summary

    HETE-2 (High Energy Transient Explorer-2) has made remarkable observations of gamma-ray bursts (GRBs) since HETE-2 was launched in October, 2000. HETE-2 can perform the prompt notification of gamma-ray bursts with onboard computer and ground receiving system. The concept of data processing system of HETE-2 is contrived to follow a short bursting astronomical objects such as gamma-ray bursts. HETE-2 is the first small satellite which has achieved a prompt alert system of gamma-ray burst locations calculated by onboard computer. Thus researchers of gamma-ray bursts can access the accurate location of bursts observed with HETE-2 through internet. HETE-2 has observed many gamma-ray bursts alerted their locations; i.e., a few to several bursts every month. Thus, optical, radio and X-ray observatories have made follow-up observations promptly. As a result a considerable number of optical transients are discovered and then their detailed observations are made. In this paper we report a unique concept of HETE-2, a gamma-ray observation satellite and some remarkable results obtained by HETE-2.

  • Multiple Pulsed Gamma-Ray Bursts Observed by HETE-2

    Y. Nakagawa, A. Yoshida, HETE Team

    American Astronomical Society Meeting Abstracts     75.09  2005.12  [International journal]

  • Discovery of the short gamma-ray burst GRB 050709

    JS Villasenor, DQ Lamb, GR Ricker, JL Atteia, N Kawai, N Butler, Y Nakagawa, JG Jernigan, M Boer, GB Crew, TQ Donaghy, J Doty, EE Fenimore, M Galassi, C Graziani, K Hurley, A Levine, F Martel, M Matsuoka, JF Olive, G Prigozhin, T Sakamoto, Y Shirasaki, M Suzuki, T Tamagawa, R Vanderspek, SE Woosley, A Yoshida, J Braga, R Manchanda, G Pizzichini, K Takagishi, M Yamauchi

    NATURE   437 ( 7060 ) 855 - 858  2005.10  [Refereed]

     View Summary

    Gamma-ray bursts (GRBs) fall into two classes: short-hard and long-soft bursts(1-3). The latter are now known to have X-ray(4) and optical(5) afterglows, to occur at cosmological distances(6) in star-forming galaxies(7), and to be associated with the explosion of massive stars(8,9). In contrast, the distance scale, the energy scale and the progenitors of the short bursts have remained a mystery. Here we report the discovery of a short-hard burst whose accurate localization has led to follow-up observations that have identified the X-ray afterglow(10) and ( for the first time) the optical afterglow(10,11) of a short-hard burst; this in turn led to the identification of the host galaxy of the burst as a late-type galaxy at z = 0.16 (ref. 10). These results show that at least some short-hard bursts occur at cosmological distances in the outskirts of galaxies, and are likely to be caused by the merging of compact binaries.

    DOI PubMed

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  • In-flight calibration and detector response matrices for WXM/HETE-2

    Y. E. Nakagawa, T. Yamazaki, T. Sakamoto, A. Yoshida, N. Kawai, T. Tamagawa, Y. Shirasaki, K. Torii, M. Suzuki, M. Matsuoka, E. E. Fenimore, M. Galassi, HETE-2 WXM Team

    Nuovo Cimento C Geophysics Space Physics C   28   849 - 852  2005.07  [Refereed]  [International journal]  [International coauthorship]

    DOI

  • Bursts from Soft Gamma-Ray Repeaters triggered by HETE-2

    Y. E. Nakagawa, M. Maetou, A. Yoshida, T. Sakamoto, M. Suzuki, Y. Yamamoto, T. Tamagawa, Y. Shirasaki, T. Yamazaki, N. Kawai, M. Matsuoka, E. E. Fenimore, M. Galassi, J. L. Atteia, K. Hurley, G. Ricker

    Nuovo Cimento C Geophysics Space Physics C   28   625 - 628  2005.07  [Refereed]  [International journal]  [International coauthorship]

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  • HETE‐2Observation of Two Gamma‐Ray Bursts atz&gt; 3

    J.‐L. Atteia, N. Kawai, R. Vanderspek, G. Pizzichini, G. R. Ricker, C. Barraud, M. Boer, J. Braga, N. Butler, T. Cline, G. B. Crew, J.‐P. Dezalay, T. Q. Donaghy, J. Doty, E. E. Fenimore, M. Galassi, C. Graziani, K. Hurley, J. G. Jernigan, D. Q. Lamb, A. Levine, R. Manchanda, F. Martel, M. Matsuoka, E. Morgan, Y. Nakagawa, J.‐F. Olive, G. Prigozhin, T. Sakamoto, R. Sato, Y. Shirasaki, M. Suzuki, K. Takagishi, T. Tamagawa, K. Torii, J. Villasenor, S. E. Woosley, M. Yamauchi, A. Yoshida

    The Astrophysical Journal   626 ( 1 ) 292 - 297  2005.06  [Refereed]

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  • HETE-2 localization and observation of the gamma-ray burst GRB 020813

    R. Sato, T. Sakamoto, N. Kawai, A. Yoshida, M. Matsuoka Y. Shirasaki, T. Tamagawa, M. Suzuki, Y. Nakagawa, G. R. Ricker D. Q. Lamb, J. L. Atteia, C. Graziani, R. Vanderspek, G. B. Crew J. Villasenor, E. E. Fenimore, HETE-2 Science Team

    Nuovo Cimento C Geophysics Space Physics C   28   343 - 346  2005.05  [Refereed]  [International journal]  [International coauthorship]

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  • Global characteristics of X-ray flashes and X-ray rich GRBs observed by HETE-2

    T. Sakamoto, D. Q. Lamb, N. Kawai, A. Yoshida, C. Fenimore, Graziani E. E., T. Q. Donaghy, M. Matsuoka, M. Ricker, Suzuki G., J. L. Atteia, Y. Shirasaki, T. Torii, Tamagawa K., Y. Nakagawa, M. Galassi, J. Doty, R. Crew, Vanderspek G. B., J. Villasenor, N. Butler, J. G. Barraud, Jernigan C., M. Boër, J. P. Dezalay, J. F. Olive, K. Woosley, Hurley S. E., G. Pizzichini, HETE-2 Science Team

    Nuovo Cimento C Geophysics Space Physics C   28   339 - 342  2005.05  [Refereed]  [International journal]  [International coauthorship]

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  • HETE-2 localization and observations of the gamma-ray burst GRB 020813

    Rie Sato, Takanori Sakamoto, Jun Kataoka, Atsumasa Yoshida, Motoko Suzuki, Junichi Kotoku, Yuji Urata, Yoshihisa Yamamoto, Makoto Arimoto, Toru Tamagawa, Yuji Shirasaki, Ken'ichi Torii, Masaru Matsuoka, Yujin Nakagawa, Toru Yamazaki, Kaoru Tanaka, Miki Maetou, Makoto Yamauchi, Kunio Takagishi, Donald Q. Lamb, Jean Luc Atteia, Roland Vanderspek, Carlo Graziani, Gregory Prigozhin, Joel Villasenor, J. Garrett Jernigan, Geoffrey B. Crew, Kevin Hurley, George R. Ricker, Stanford E. Woosley, Nat Butler, Al Levine, John P. Doty, Timothy Q. Donaghy, Edward E. Fenimore, Mark Galassi, Michel Boer, Jean Pascal Dezalay, Jean François Olive, Joao Braga, Ravi Manchanda, Graziella Pizzichini, Nobuyuki Kawai

    Publications of the Astronomical Society of Japan   57 ( 6 ) 1031 - 1039  2005  [Refereed]

     View Summary

    A bright, long gamma-ray burst (GRB) was detected and localized by the instruments on board the High Energy Transient Explorer 2 satellite (HETE-2) at 02:44:19.17 UTC (9859.17 s UT) on 2002 August 13. The location was reported to the GRB Coordinates Network (GCN) about 4 min after the burst. In the prompt emission, the burst had a duration of approximately 125 s, and more than four peaks. We analyzed the time-resolved 2-400 keV energy spectra of the prompt emission of GRB 020813 using the Wide Field X-Ray Monitor (WXM) and the French Gamma Telescope (FREGATE) in detail. We found that the early part of the burst (17-52 s after the burst trigger) shows a depletion of low-energy photons below about 50 keV. It is difficult to explain the depletion by either synchrotron self-absorption or Comptonization. One possibility is that the low-energy depletion may be understood as a mixture of "jitter" radiation with the usual synchrotron radiation component. © 2005. Astronomical Society of Japan.

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  • Current Status of HETE-2 Operations

    R. Vanderspek, N. Butler, G. B. Crew, A. Dullighan, G. Prigozhin, J. P. Doty, J. N. Villasenor, G. R. Ricker, T. Tamagawa, K. Torii, N. Kawai, T. Sakamoto, R. Sato, M. Suzuki, Y. Urata, Y. Yamamoto, A. Yoshida, Y. E. Nakagawa, T. Yamazaki, Y. Shirasaki, C. Graziani, T. Donaghy, D. Q. Lamb, J. G. Jernigan, K. Hurley, J. L. Atteia, E. E. Fenimore, M. Galassi

    Gamma-Ray Bursts: 30 Years of Discovery   727   630 - 636  2004.09  [International journal]  [International coauthorship]

  • In-flight Calibration of the HETE-2 WXM Detector Response

    T. Sakamoto, Y. Nakagawa, K. Torii, Y. Shirasaki, T. Tamagawa, N. Kawai, A. Yoshida, M. Matsuoka, E. E. Fenimore, M. Galassi, D. Q. Lamb, C. Graziani, T. Q. Donaghy, J. L. Atteia, C. Barraud, M. Boer, J. P. Dezalay, HETE-2 Team

    Gamma-Ray Bursts: 30 Years of Discovery   727   618 - 621  2004.09  [International journal]  [International coauthorship]

  • HETE-2 Observation of the Extremely Soft X-Ray Flashes, XRF010213 and XRF020903

    T. Sakamoto, M. Suzuki, N. Kawai, Y. Nakagawa, A. Yoshida, Y. Shirasaki, T. Tamagawa, K. Torii, M. Matsuoka, E. E. Fenimore, M. Galassi, D. Q. Lamb, C. Graziani, T. Q. Donaghy, J. L. Atteia, C. Bar- raud, M. Boer, J. P. Dezalay, J. F. Olive, G. Ricker, J. Doty, R. Vanderspek, G. B. Crew, J. Villasenor, N. Butler, J. G. Jernigan, K. Hurley, S. E. Woosley, HETE-2 Science Team

    Gamma-Ray Bursts: 30 Years of Discovery   727   106 - 110  2004.09  [International journal]  [International coauthorship]

  • Broad-band (2-400 keV) Spectra of Gamma-Ray Bursts and X-Ray Flashes based on HETE-2 Observations

    N. Kawai, T. Sakamoto, M. Suzuki, M. Matsuoka, A. Yoshida, Y. Shirasaki, T. Tamagawa, Y. Nakagawa, Y. Yamazaki, R. Sato, K. Torii, E. E. Fenimore, M. Galassi, D. Q. Lamb, C. Graziani, T. Q. Donaghy, G. Ricker, J. Doty, R. Vanderspek, G. B. Crew, J. Villasenor, N. Butler, J. L. Atteia, C. Barraud, M. Boer, J. P. Dezalay, J. F. Olive, J. G. Jernigan, K. Hurley, S. E. Woosley, HETE-2 Science Team

    Gamma-Ray Bursts: 30 Years of Discovery   727   192 - 197  2004.09  [International journal]  [International coauthorship]

  • Observations of X-ray Bursts by HETE-2

    Y. E. Nakagawa, T. Yamazaki, M. Suzuki, A. Yoshida, N. Kawai, D. Takahashi, M. Matsuoka, Y. Shirasaki, T. Tamagawa, K. Torii, T. Sakamoto, Y. Urata, R. Sato, Y. Yamamoto, E. E. Fenimore, M. Galassi, D. Q. Lamb, C. Graziani, G. Ricker

    Gamma-Ray Bursts: 30 Years of Discovery   727   566 - 569  2004.09  [International journal]  [International coauthorship]

  • In-orbit calibration and performance of the HETE-2 WXM

    Y. Shirasaki, N. Kawai, A. Yoshida, M. Matsuoka, T. Tamagawa, K. Torii, T. Sakamoto, M. Suzuki, Y. Urata, R. Sato, Y. Nakagawa, D. Takahashi, E. Fenimore, M. Galassi, D. Lamb, C. Graziani, T. Donaghy, R. Vanderspek

    Gamma-Ray Bursts in the Afterglow Era   312   543  2004.06  [International journal]  [International coauthorship]

  • The Gamma-Ray Burst Alert System and the Results of HETE-2

    Yujin Nakagawa

    Baltic Astronomy   13   201 - 206  2004.01  [Refereed]

  • HETE-2 Observations of Gamma-Ray Bursts and Their Follow-Ups(Session 9 : Gamma-Ray Bursts : Afterglows and Acceleration) :

    KAWAI Nobuyuki, MATSUOKA Masaru, YOSHIDA Atsumasa, SHIRASAKI Yuji, RICKER G., DOTY J., VANDERSPEK R., CREW G., VILLASENOR J., ATTEIA J-L., FENIMORE E. E., GALASSI M., LAMB D. Q., GRAZIANI C., HURLEY K., JERNIGAN J. G., WOOSLEY S., MARTEL F., MONNELLY G., PRIGOZHIN G., OLIVE J.-F., DEZALAY J.-P., BOER M., PIZZICHINI G., CLINE T., LEVINE A., MORGAN E., TAMAGAWA Toru, BUTLER N., SAKAMOTO Takanori, TORII Ken'ichi, BARRAUD C., DONAGHY T., SUZUKI Motoko, NAKAGAWA Yujin, TAKAHASHI Daiki, TAVENNER T., SATO Rie, URATA Yuji, MANCHANDA R., AZZIBROUCK G., BRAGA J., TAKAGISHI Kunio, YAMAUCHI Makoto, HATSUKADE Isamu

    Progress of theoretical physics. Supplement   ( 155 ) 279 - 286  2004

    DOI CiNii

    Scopus

    1
    Citation
    (Scopus)
  • Design and Performance of the Wide-Field X-Ray Monitor on Board the High-Energy Transient Explorer 2

    Yuji Shirasaki, Nobuyuki Kawai, Atsumasa Yoshida, Masaru Matsuoka, Toru Tamagawa, Ken’ichi Torii, Takanori Sakamoto, Motoko Suzuki, Yuji Urata, Rie Sato, Yujin Nakagawa, Daiki Takahashi, Edward E. Fenimore, Mark Galassi, Donald Q. Lamb, Carlo Graziani, Timothy Q. Donaghy, Roland Vanderspek, Makoto Yamauchi, Kunio Takagishi, Isamu Hatsukade

    Publications of the Astronomical Society of Japan   55 ( 5 ) 1033 - 1049  2003.10  [Refereed]

    DOI

    Scopus

    35
    Citation
    (Scopus)
  • Spectral Properties of "Classical" GRBs Seen by HETE-2 Satellite

    A. Yoshida, Y. Nakagawa, T. Yamazaki, D. Takahashi, N. Kawai, T. Sakamot, M. Suzuki, R. Sato, Y. Urata, Y. Shirasaki, T. Tamagawa, K. Torii, M. Matsuoka, E. Fenimore, M. Galassi, D. Q. Lamb, C. Graziani, T. Donaghy, J-L Atteia, C. Barraud, J-F Olive, J-P Dezalay, M. Boer, K. Hurley, J. G. Jernigan, G. Ricker, J. Doty, J. Villaseno, Vanderspek, G. Crew, G. Prigozhin, G. Monnelly, N. Butler, S. Woosley, HETE-2 Science Team

    International Cosmic Ray Conference   7   2693 - 2696  2003.07  [Refereed]  [International journal]  [International coauthorship]

  • Prompt Gamma-Ray Burst Alert System of the HETE-2 Spacecraft

    T. Tamagawa, N. Kawai, A. Yoshida, Y. Shirasaki, K. Torii, T. Sakamoto, M. Suzuki, Y. Urata, Y. Nakagawa, D. Takahashi, R. Sato, M. Matsuoka, R. Vanderspek, G. B. Crew, J. P. Doty, G. Y. Villasenor, Prigozhin, N. Butler, G. R. Ricker, D. Q. Lamb, C. Graziani, T. Donaghy, E. Fenimore, M. Galassi, M. Yamauchi, K. Takagishi, I. Hatsukade

    International Cosmic Ray Conference   7   2741 - 2744  2003.07  [Refereed]  [International journal]  [International coauthorship]

  • Timing Properties of GRBs Detected by HETE-2

    M. Suzuki, N. Kawai, T. Sakamoto, R. Sato, Y. Urata, A. Yoshida, Y. Nakagawa, D. Takahashi, Y. Shirasaki, T. Tamagawa, K. Torii, M. Matsuoka, E. Fenimore, M. Galassi, D. Q. Lamb, C. Graziani, T. Donaghy, J-L. Atteia, C. Barraud, J-F. Olive, J-P. Dezalay, M. Boër, K. Hurley, G. Ricker, J. Doty, J. Villasenor, R. Vanderspek, G. Crew, G. Monnelly, N. Butler, HETE-2 Science Team

    International Cosmic Ray Conference   7   2697 - 2700  2003.07  [Refereed]  [International journal]  [International coauthorship]

  • In-Orbit Calibration and Performance of the HETE-2 WXM

    Y. Shirasaki, N. Kawai, T. Sakamoto, M. Suzuki, R. Sato, Y. Urata, A. Yoshida, Y. Nakagawa, D. Takahashi, T. Tamagawa, K. Torii, M. Matsuoka, M. Yamauchi, K. Takagishi, I. Hatsukade, E. E. Fenimore, M. Galassi, D. Q. Lamb, C. Graziani, T. Donaghy, R. Vanderspek, G. R. Ricker, HETE-2 Science Team

    International Cosmic Ray Conference   7   2745 - 2748  2003.07  [Refereed]  [International journal]  [International coauthorship]

  • Observations of Gamma-Ray Bursts by HETE-2

    N. Kawai, M. Matsuoka, A. Yoshida, Y. Shirasaki, G. Ricker, J. Doty, R. Vanderspek, G. Crew, J. Villasenor, J. L. Atteia, E. E. Fenimore, M. Galassi, D. Q. Lamb, C. Graziani, K. Hurley, J. G. Jernigan, S. Woosley, F. Martel, G. Monnelly, G. Prigozhin, J. F. Olive, J. P. Dezalay, M. Boër, G. Pizzichini, T. Cline, A. Levine, E. Morgan, T. Tamagawa, N. Butler, T. Sakamoto, K. Torii, C. Barraud, T. Donaghy, M. Suzuki, Y. Nakagawa, D. Takahashi, T. Tavenner, R. Satoh, Y. Urata, R. Manchanda, G. Azzibrouck, J. Braga, K. Takagishi, M. Yaumuchi, I. Hatsukade

    International Cosmic Ray Conference   7   2737 - 2740  2003.07  [Refereed]  [International journal]  [International coauthorship]

  • An Unusual Time-Variable High Radiation Region Seen by HETE-2 Satellite

    [Y. E. Nakagawa, Toru Tamagawa, Tsugunobu Nagai, Tohru Yamazaki, Atsumasa Yoshida, Nobuyuki Kawai, Ken'ichi Torii, Yugi Shiraski, Hiromasa Miyasaka, Takanori Sakamoto, Motoko Suzuki, Yuji Urata, Rie Sato, George Ricker, Kevin Hurley, Geoff Crew

    International Cosmic Ray Conference   7   4261 - 4264  2003.07  [Refereed]  [International journal]  [International coauthorship]

  • COOLING AND QUASI-STATIC CONTRACTION OF THE PRIMITIVE SOLAR NEBULA AFTER GAS ACCRETION

    S WATANABE, Y NAKAGAWA, K NAKAZAWA

    ASTROPHYSICAL JOURNAL   358 ( 1 ) 282 - 292  1990.07  [Refereed]

▼display all

Presentations

  • 機械学習による掘削地層の岩質予測

    中川 友進, 井上 朝哉, 勝井 辰博, 和田 良太, 鈴木 博善

    日本地球惑星科学連合2023年大会  日本地球惑星科学連合

    Presentation date: 2023.05

    Event date:
    2023.05
     
     
  • 機械学習による掘削地層の岩質予測

    中川 友進, 井上 朝哉, 勝井 辰博, 和田 良太, Hakan Bilen, 鈴木 博善

    海洋理工学会・令和4年度秋季大会  海洋理工学会

    Presentation date: 2022.11

    Event date:
    2022.11
     
     
  • Early stuck detection using supervised and unsupervised machine learning approaches

    Tomoya Inoue, Yujin Nakagawa, Ryota Wada, Keisuke Miyoshi, Shungo Abe, Kouhei Kuroda, Masatoshi Nishi, Hakan Bilen, Konda Reddy Mopuri

    Offshore Technology Conference Asia  Offshore Technology Conference Asia

    Presentation date: 2022.03

    Event date:
    2022.03
     
     
  • Approach for real-time prediction of pipe stuck risk using a long short-term memory autoencoder architecture

    Yujin Nakagawa, Tomoya Inoue, Hakan Bilen, Konda R. Mopuri, Keisuke Miyoshi, Shungo Abe, Ryota Wada, Kouhei Kuroda, Masatoshi Nishi, Hiroyasu Ogasawara

    2021 Abu Dhabi International Petroleum Exhibition & Conference  2021 Abu Dhabi International Petroleum Exhibition & Conference

    Presentation date: 2021.11

    Event date:
    2021.11
     
     
  • An unsupervised learning model for pipe stuck predictions using a long short-term memory autoencoder architecture

    Yujin Nakagawa, Tomoya Inoue, Hakan Bilen, Konda R. Mopuri, Keisuke Miyoshi, Shungo Abe, Ryota Wada, Kouhei Kuroda, Hitoshi Tamamura

    SPE/IATMI Asia Pacific Oil & Gas Conference and Exhibition  SPE/IATMI Asia Pacific Oil & Gas Conference and Exhibition

    Presentation date: 2021.10

    Event date:
    2021.10
     
     
  • 超強磁場中性子星「マグネター」のバーストの時間的な性質(4)

    中川 友進

    日本天文学会2021年秋季年会  日本天文学会

    Presentation date: 2021.09

    Event date:
    2021.09
     
     
  • 超強磁場中性子星「マグネター」のバーストの時間的な性質(2)

    中川 友進

    日本物理学会第75回年次大会  日本物理学会

    Presentation date: 2020.03

    Event date:
    2020.03
     
     
  • A content-based database system for large volume climate data

    Yujin Nakagawa, Yosuke Onoue, Shintaro Kawahara, Fumiaki Araki, Koji Koyamada, Daisuke Mat- suoka, Yoichi Ishikawa, Mikiko Fujita, Shiori Sugimoto, Yasuko Okada, Sho Kawazoe, Shingo Watanabe, Masayoshi Ishii, Ryo Mizuta, Akihiko Murata, Hioroaki Kawase

    AGU Fall Meeting 2019  American Geophysical Union

    Presentation date: 2019.12

    Event date:
    2019.12
     
     
  • A content-based database system for large volume of climate data

    Yujin Nakagawa, Yosuke Onoue, Shintaro Kawahara, Fumiaki Araki, Koji Koyamada, Daisuke Mat- suoka, Yoichi Ishikawa, Mikiko Fujita, Shiori Sugimoto, Yasuko Okada, Sho Kawazoe, Shingo Watanabe, Masayoshi Ishii, Ryo Mizuta, Akihiko Murata, Hioroaki Kawase.

    VizAfrica Botswana 2019  VizAfrica Botswana 2019

    Presentation date: 2019.11

    Event date:
    2019.11
     
     
  • 大規模アンサンブル気候データの効率的な解析に向けたコンテンツベース検索システム

    中川 友進, 尾上 洋介, 川原 慎太郎, 荒木 文明, 小山田 耕二, 松岡 大祐, 石川 洋一, 藤田 実季子, 杉本 志織, 岡田 靖子, 川添 祥, 渡辺 真吾, 石井 正好, 水田 亮, 村田 昌彦, 川瀬 宏明

    日本気象学会2019年度秋季大会  日本気象学会

    Presentation date: 2019.10

    Event date:
    2019.10
     
     
  • A content-based retrieval system for conventional and machine learning methods to analyze large volume climate data

    Yujin Nakagawa, Yosuke Onoue, Shintaro Kawahara, Fumiaki Araki, Koji Koyamada, Daisuke Mat- suoka, Yoichi Ishikawa, Mikiko Fujita, Shiori Sugimoto, Yasuko Okada, Sho Kawazoe, Shingo Watanabe, Masayoshi Ishii, Ryo Mizuta, Akihiko Murata, Hioroaki Kawase

    Climate Informatics 2019  Climate Informatics 2019

    Presentation date: 2019.10

    Event date:
    2019.10
     
     
  • 超強磁場中性子星「マグネター」のバーストの時間的な性質

    中川 友進

    日本物理学会2019年秋季大会  日本物理学会

    Presentation date: 2019.09

    Event date:
    2019.09
     
     
  • 超強磁場中性子星「マグネター」のバーストの時間的な性質

    中川 友進

    日本天文学会2019年秋季年会  日本天文学会

    Presentation date: 2019.09

    Event date:
    2019.09
     
     
  • Temporal behavior of magnetar bursts

    Yujin Nakagawa  [Invited]

    2nd Global Summit on Physics  Scientific Federation

    Presentation date: 2019.09

    Event date:
    2019.09
     
     
  • Suzaku observations of magnetars

    Yujin Nakagawa  [Invited]

    FRASCATI WORKSHOP 2019 on Multifrequency Behaviour of High Energy Cosmic Sources - XIII  FRASCATI WORKSHOP

    Presentation date: 2019.06

    Event date:
    2019.06
     
     
  • 大規模アンサンブル気候データの効率的な解析に向けたコンテン ツベース検索システム

    中川 友進, 川原 慎太郎, 荒木 文明, 松岡 大祐, 石川 洋一, 藤田 実季子, 杉本 志織, 岡田 靖子, 川添 祥, 渡辺 真吾, 石井 正好, 水田 亮, 村田 昌彦, 川瀬 宏明

    JpGU 2019  日本地球惑星科学連合

    Presentation date: 2019.05

    Event date:
    2019.05
     
     
  • A content-based database system for large ensemble future climate simulations

    Yujin Nakagawa, Shintaro Kawahara, Fumiaki Araki, Daisuke Matsuoka, Yoichi Ishikawa, Mikiko Fujita, Shiori Sugimoto, Yasuko Okada, Sho Kawazoe, Shingo Watanabe, Masayoshi Ishii, Ryo Mizuta, Akihiko Murata, Hioroaki Kawase

    AGU Fall Meeting 2018  American Geophysical Union

    Presentation date: 2018.12

    Event date:
    2018.12
     
     
  • SI-CAT気候実験データベースシステムの開発

    中川 友進, 川原 慎太郎, 荒木 文明, 松岡 大祐, 石川 洋一, 藤田 実季子, 杉本 志織, 岡田 靖子, 川添 祥, 渡辺 真吾, 石井 正好, 水田 亮, 村田 昌彦, 川瀬 宏明

    JpGU 2018  日本地球惑星科学連合

    Presentation date: 2018.05

    Event date:
    2018.05
     
     
  • SI-CAT気候実験データベースシステムの開発

    中川 友進, 川原 慎太郎, 荒木 文明, 松岡 大祐, 石川 洋一, 藤田 実季子, 杉本 志織, 岡田 靖子, 川添 祥, 渡辺 真吾, 石井 正好, 水田 亮, 村田 昭彦, 川瀬 宏明

    DIASコミュニティフォーラム2018  DIAS

    Presentation date: 2018.03

    Event date:
    2018.03
     
     
  • Development of a database system for near-future climate change projections under the japanese national project SI-CAT

    Yujin Nakagawa, Shintaro Kawahara, Fumiaki Araki, Daisuke Matsuoka, Yoichi Ishikawa, Mikiko Fujita, Shiori Sugimoto, Yasuko Okada, Sho Kawazoe, Shingo Watanabe, Masayoshi Ishii, Ryo Mizuta, Akihiko Murata, Hioroaki Kawase

    AGU Fall Meeting 2017  American Geophysical Union

    Presentation date: 2017.12

    Event date:
    2017.12
     
     
  • 近未来気候変動予測データベースシステムの開発

    中川 友進, 川原 慎太郎, 荒木 文明, 松岡 大祐, 石川 洋一, 渡辺 真吾

    日本気象学会2017年度秋季大会  日本気象学会

    Presentation date: 2017.10

    Event date:
    2017.10
     
     
  • 近未来気候変動予測データベースシステムの開発

    中川 友進, 川原 慎太郎, 荒木 文明, 松岡 大祐, 石川 洋一, 渡邉 真吾

    DIASシンポジウム2017  DIAS

    Presentation date: 2017.07

    Event date:
    2017.07
     
     
  • Development of a database system for near-future climate change predictions

    Yujin Nakagawa, Shintaro Kawahara, Fumiaki Araki, Daisuke Matsuoka, Yoichi Ishikawa, Shingo Watanabe

    JpGU-AGU Joint Meeting 2017  Japan Geoscience Union & American Geophysical Union

    Presentation date: 2017.05

    Event date:
    2017.05
     
     
  • User-Friendly Data Analsys Software and Archive for the Japanese X-ray All Sky Monitor MAXI on-board ISS

    Yujin E. Nakagawa, Ken Ebisawa, Satoshi Nakahiara, Mutsumi Sugizaki, Hiroshi Tomida, Shiro Ueno, Motoko Serino, Hitoshi Negoro, Masashi Kimura, Mihara Tatehiro

    Astronomical Data Analysis Software & Systems (ADASS) XXV  Astronomical Data Analysis Software & Systems

    Presentation date: 2015.10

    Event date:
    2015.10
     
     
  • 全天X線監視装置「MAXI」のデータアーカイブ開発(2)

    中川 友進

    2014年度宇宙情報解析シンポジウム 

    Presentation date: 2015.02

    Event date:
    2015.02
     
     
  • Energy Dependent Intensity Variations of Persistent X-ray Emission of Magnetars

    Yujin E. Nakagawa, Ken Ebisawa

    Swift 10 Years Discovery 

    Presentation date: 2014.12

    Event date:
    2014.12
     
     
  • Developments of the MAXI Data Archive

    Yujin E. Nakagawa, Ken Ebisawa, Satoshi Nakahiara, Mutsumi Sugizaki, Hiroshi Tomida, Shiro Ueno, Motoko Serino, Hitoshi Negoro, Masashi Kimura, Mihara Tatehiro

    Astronomical Data Analysis Software and System 2014  Astronomical Data Analysis Software & Systems

    Presentation date: 2014.10

    Event date:
    2014.10
     
     
  • 「すざく」衛星によるマグネターのX線定常放射のエネルギー依存性のある強度揺らぎの研究

    中川 友進, 海老沢 研

    日本天文学会2014年秋季年会  日本天文学会

    Presentation date: 2014.09

    Event date:
    2014.09
     
     
  • 「すざく」衛星を用いたマグネターのX線定常放射におけるエネルギー依存性のある強度揺らぎの研究

    中川 友進, 海老沢 研

    日本天文学会2014年春季年会  日本天文学会

    Presentation date: 2014.03

    Event date:
    2014.03
     
     
  • 全天X線監視装置「MAXI」のデータアーカイブ開発

    中川 友進

    2013年度宇宙情報解析シンポジウム 

    Presentation date: 2014.02

    Event date:
    2014.02
     
     
  • Suzaku Discovery of Energy Dependent Intensity Variations in Persistent X-ray Emission of Magnetars

    Yujin E. Nakagawa, Ken Ebisawa

    Suzaku-MAXI 2014 

    Presentation date: 2014.02

    Event date:
    2014.02
     
     
  • X-ray Emission in Magnetar Short Bursts

    Yujin E. Nakagawa

    Presentation date: 2013.12

    Event date:
    2013.12
     
     
  • 「すざく」によるマグネターのX線定常放射の強度揺らぎの研究

    中川 友進, 海老沢 研

    日本天文学会2013年秋季年会  日本天文学会

    Presentation date: 2013.09

    Event date:
    2013.09
     
     
  • Energy Dependent Intensity Variations in Persistent X-ray Emissions of Magnetars

    Yujin E. Nakagawa, Ken Ebisawa

    Explosive Transients: Lighthouses of the Universe 

    Presentation date: 2013.09

    Event date:
    2013.09
     
     
  • すざく衛星による活動期のAXP 4U 0142+614のX線観測

    中川 友進, 牧島 一夫, 榎戸 輝揚, 三原 建弘, 杉崎 睦, 吉田 篤正, 坂本 貴紀, 山岡 和貴, Poshak Gandhi, 田代 信, 森井 幹雄, Kevin Hurley

    日本天文学会2013年春季年会  日本天文学会

    Presentation date: 2013.03

    Event date:
    2013.03
     
     
  • Wide-Band Spectra of Magnetar Persistent and Burst Emission

    Yujin E. Nakagawa, Kazuo Makishima, Teruaki Enoto, Takanori Sakamoto, Tatehiro Mihara, Mutsumi Sugizaki, Kazutaka Yamaoka, Kevin Hurley, Atsumasa Yoshida, Poshak Gandhi, Makoto Tashiro, Morii Mikio

    X-ray Astronomy: towards the next 50 years! 

    Presentation date: 2012.10

    Event date:
    2012.10
     
     
  • 「すざく」衛星による活動期のAXP 4U 0142+614の観測的研究

    中川 友進, 山岡 和貴, 牧島 一夫, 榎戸 輝揚, 三原 建弘, 杉崎 睦, 坂本 貴紀, 吉田 篤正, Poshak Gandhi, 田代 信, 森井 幹雄, Kevin Hurley

    日本天文学会2012年秋季年会  日本天文学会

    Presentation date: 2012.09

    Event date:
    2012.09
     
     
  • 「すざく」衛星・HETE-2衛星によるマグネターのバースト/定常放射のX線スペクトルの研究

    中川 友進, 牧島 一夫, 榎戸 輝揚, 坂本 貴紀, 三原 建弘, 杉崎 睦, 山岡 和貴, 吉田 篤正, Poshak Gandhi, 田代 信, 森井 幹雄, Kevin Hurley, ほかHETE-2衛星チーム

    日本天文学会2012年春季年会  日本天文学会

    Presentation date: 2012.03

    Event date:
    2012.03
     
     
  • Wide-Band Spectra of Magnetar Burst Emission

    Yujin E. Nakagawa, Kazuo Makishima, Teruaki Enoto, Takanori Sakamoto, Tatehiro Mihara, Mutsumi Sugizaki, Kazutaka Yamaoka, Kevin Hurley, Atsumasa Yoshida, Poshak Gandhi, Makoto Tashiro, Morii Mikio

    Positrons in Astrophysics 

    Presentation date: 2012.03

    Event date:
    2012.03
     
     
  • Wide-Band Spectra of Magnetar Burst Emission

    Yujin E. Nakagawa, Kazuo Makishima, Teruaki Enoto, Takanori Sakamoto

    IAU Symposium 279 

    Presentation date: 2012.03

    Event date:
    2012.03
     
     
  • マグネターのバースト/定常放射のスペクトルの研究

    中川 友進, 牧島 一夫, 榎戸 輝揚

    日本天文学会2011年秋季年会  日本天文学会

    Presentation date: 2011.09

    Event date:
    2011.09
     
     
  • 全天X線監視装置MAXIによるマグネターの観測

    中川 友進, 三原 建弘, 杉崎 睦, 小浜 光洋, 山本 堂之, 鈴木 素子, 松岡 勝, 河合 誠之, 森井 幹雄, 薄井 竜一, 杉森 航介, 吉田 篤正, 山岡 和貴, 中平 聡志, 根来 均, 中島 基樹, 磯部 直樹, 他MAXIチーム

    日本天文学会2011年春季年会  日本天文学会

    Presentation date: 2011.03

    Event date:
    2011.03
     
     
  • マグネターのX線・γ線による観測的研究

    中川 友進  [Invited]

    超新星からのマルチメッセンジャー 

    Presentation date: 2011.03

    Event date:
    2011.03
     
     
  • マグネターのX線・γ線による観測的研究

    中川 友進  [Invited]

    コンパクト天体で探る極限物理 

    Presentation date: 2011.03

    Event date:
    2011.03
     
     
  • マグネターのバースト/X線定常放射の広帯域スペクトルの研究

    中川 友進, 榎戸 輝揚, 牧島 一夫, 中澤 知洋, 坂本 貴紀, 吉田 篤正, 山岡 和貴

    日本天文学会2010年秋季年会  日本天文学会

    Presentation date: 2010.09

    Event date:
    2010.09
     
     
  • Wide-Band Spectra of Magnetar Emission

    Yujin E. Nakagawa, Teruaki Enoto, Kazuo Makishima, Kazuhiro Nakazawa, Takanori Sakamoto, Atsumasa Yoshida, Kazutaka Yamaoka, Kevin Hurley, Nanda Rea

    8th INTEGRAL Workshop “The Restless Gamma-Ray Universe” 

    Presentation date: 2010.09

    Event date:
    2010.09
     
     
  • The First Results of Monitoring Galactic Magnetar Activities with MAXI/GSC

    Yujin E. Nakagawa, Tatehiro Mihara, Mutsumi Sugizaki, Mitsuhiro Kohama, Takayuki Yamamoto, Motoko Suzuki, Masaru Matsuoka, Nobuyuki Kawai, Mikio Morii, Kohsuke Sugimori, Atsumasa Yoshida, Kazutaka Yamaoka, Satoshi Nakahira, Hitoshi Negoro, Motoki Nakajima, Naoki Isobe, MAXI Team

    COSPAR 2010 

    Presentation date: 2010.07

    Event date:
    2010.07
     
     
  • Suzaku Detection of Hard X-ray Emission in SGR 0501+4516 Short Burst Spectrum

    Yujin E. Nakagawa, Teruaki Enoto, Kazuo Makishima, Atsumasa Yoshida, Kazutaka Yamaoka, Takanori Sakamoto, Nanda Rea, Kevin Hurley, Suzaku SGR 0501+4516 Team, HETE-2 Team

    ICREA Workshop on The High-Energy Emission from Pulsars and their Systems 

    Presentation date: 2010.04

    Event date:
    2010.04
     
     
  • Suzaku Observations of Long-Duration GRB 090709A X-ray Afterglow

    Yujin E. Nakagawa, Toru Tamagawa, Kazutaka Yamaoka, Satoshi Sugita, Atsumasa Yoshida, Rie Sato, Masanori Ohno, Kazuhiro Nakazawa, Makoto Tashiro, Takako Sugasahara, Wataru Iwakiri, Kaori Onda, Yuji Urata, Daisuke Yonetoku, Toshio Murakami, Nobuyuki Kawai, Ryuichi Usui, Hideyo Nakajima, Aki- nori Endo, Makoto Yamauchi, Eri Sonoda, Norisuke Ohmori, Kenta Kohno, Hidenori Hayashi, Arata Daikyuji, Kazuhiro Noda, Yusuke Nishioka, Motoko Suzuki, Fumie Tazaki, Satoshi Eguchi, Kaori Kubota, Yukiko Ishino, Kazuo Hiroi, Yoshihiro Ueda, Suzaku GRB ToO Team

    The GRB Conference in Kyoto 2010 

    Presentation date: 2010.04

    Event date:
    2010.04
     
     
  • 「すざく」衛星によるSGR 0501+4516のバーストに付随する硬X線放射の検出

    中川 友進, 牧島 一夫, 榎戸 輝揚, 山岡 和貴, 吉田 篤正, 坂本 貴紀, Kevin Hurley, Nanda Rea, 他SGR0501+4516観測チーム

    日本天文学会2010年春季年会  日本天文学会

    Presentation date: 2010.03

    Event date:
    2010.03
     
     
  • 全天X線監視装置MAXIによるマグネターの初期観測

    中川 友進, 三原 建弘, 杉崎 睦, 小浜 光洋, 山本 堂之, 鈴木 素子, 松岡 勝, 河合 誠之, 森井 幹雄, 杉森 航介, 吉田 篤正, 山岡 和貴, 中平 聡志, 根来 均, 中島 基樹, 磯部 直樹, 他MAXIチーム

    日本物理学会2010年第65回年次大会  日本物理学会

    Presentation date: 2010.03

    Event date:
    2010.03
     
     
  • 「すざく衛星によるマグネター研究の最新成果(2)

    中川 友進, 牧島 一夫, 榎戸 輝揚, 山岡 和貴, 吉田 篤正, 大野 雅功, 坂本 貴紀, すざく衛星チーム

    第10回宇宙科学シンポジウム 

    Presentation date: 2010.01

    Event date:
    2010.01
     
     
  • 「すざく」衛星による超強磁場中性子星SGR 0501+4516の小バーストの観測

    中川 友進, 榎戸 輝揚, 牧島 一夫, 吉田 篤正, 山岡 和貴, 坂本 貴紀, Nanda Rea, Kevin Hurley, 他SGR0501+4516観測チーム

    日本物理学会2009年秋季大会  日本物理学会

    Presentation date: 2009.09

    Event date:
    2009.09
     
     
  • Suzakuによる準周期的プロンプト放射を示したGRB090709AのX線残光観測

    中川 友進

    ガンマ線バーストで読み解く太古の宇宙・第三回領域シンポジウム 

    Presentation date: 2009.09

    Event date:
    2009.09
     
     
  • Suzaku Observations of Short Bursts from SGR0501+4516

    Yujin E. Nakagawa, Teruaki Enoto, Kazuo Makishima, Atsumasa Yoshida, Kazutaka Yamaoka, Takanori Sakamoto, Nanda Rea, Kevin Hurley, Suzaku SGR 0501+4516 Team, HETE-2 Team

    The Shocking Universe - Gamma Ray Bursts and High Energy Shock phenomena in the Universe 

    Presentation date: 2009.09

    Event date:
    2009.09
     
     
  • Uniting Burst and Quiescent Emission Mechanisms of Magnetars

    Yujin Nakagawa, Atsumasa Yoshida, Kevin Hurley, Kazutaka Yamaoka, Noriaki Shibazaki, Teruaki Enoto, Takanori Sakamoto, Kazuo Makishima, HETE-2 Team, Suzaku SGR/AXP ToO Team

    The Energetic Cosmos: from Suzaku to ASTRO-H 

    Presentation date: 2009.06

    Event date:
    2009.06
     
     
  • 「すざく」による軟ガンマ線リピーターSGR 0501+4516のToO観測(2)

    中川 友進, 榎戸 輝揚, 山田 真也, 中澤 知洋, 牧島 一夫, 山岡 和貴, 吉田 篤正, 村上 弘志, 坂本 貴紀, 国分 紀秀, Kevin Hurley, Nanda Rea, 他SGR0501+4516観測チーム

    日本天文学会2009年春季年会  日本天文学会

    Presentation date: 2009.03

    Event date:
    2009.03
     
     
  • MAXIで切り拓くマグネター研究〜全天マップ・活動モニタリング〜

    中川 友進, 三原 建弘, 森井 幹雄, 吉田 篤正, 山岡 和貴, 江口 智士, 河合 誠之, 鈴木 素子, 松岡 勝, 他MAXIチーム

    日本天文学会2009年春季年会  日本天文学会

    Presentation date: 2009.03

    Event date:
    2009.03
     
     
  • Uniting Quiescent and Burst Emission Mechanisms of Magnetar Candidates

    Y. E. Nakagawa, A. Yoshida, K. Yamaoka, S. Shibazaki

    Neutron Stars & Gamma Ray Bursts – Recent Developments & Future Directions 

    Presentation date: 2009.03

    Event date:
    2009.03
     
     
  • Studies on Quiescent and Burst Emission Spectra of Magnetar Candidates

    Yujin E. Nakagawa

    2009 Aspen Winter Conference on Astrophysics – Thirty Years of Magnetars: New Frontiers 

    Presentation date: 2009.02

    Event date:
    2009.02
     
     
  • すざく衛星を中心としたマグネター研究の最新成果(2)

    中川 友進, 吉田 篤正, Kevin Hurley, 山岡 和貴, 柴崎 徳明, 松岡 勝, 河合 誠之, 坂本 貴紀, George Ricker, HETE-2チーム, AO-1 SGR ToO チーム, Swift チーム

    第9回宇宙科学シンポジウム 

    Presentation date: 2009.01

    Event date:
    2009.01
     
     
  • X-ray Afterglows Accompanying SGR Short Bursts Discovered by Swift

    Yujin E. Nakagawa

    The Sixth Huntsville : Gamma-Ray Burst Symposium 2008 

    Presentation date: 2008.10

    Event date:
    2008.10
     
     
  • Studies on Time Resolved Spectral Properties using HETE-2 GRBs

    Yujin E. Nakagawa

    The Sixth Huntsville : Gamma-Ray Burst Symposium 2008 

    Presentation date: 2008.10

    Event date:
    2008.10
     
     
  • 「すざく」衛星による軟ガンマ線リピータSGR 1900+14/1806-20の観測

    中川 友進, 三原 建弘, 吉田 篤正, 山岡 和貴, 杉田 聡司, 鈴木 素子, 中島 基樹, 村上 敏夫, 米徳 大介, 田代 信, 中澤知洋

    日本天文学会2008年秋季年会  日本天文学会

    Presentation date: 2008.09

    Event date:
    2008.09
     
     
  • HETE-2 Highlights

    Y. E. Nakagawa  [Invited]

    Vulcano Workshop 2008 - Frontier Objects in Astrophysics and Particle Physics 

    Presentation date: 2008.05

    Event date:
    2008.05
     
     
  • Swift衛星による軟ガンマ線リピータの短いバーストに伴うX線残光の発見

    中川 友進, 坂本 貴紀, 佐藤 悟朗, Neil Gehrels, Kevin Hurley, David Palmer, Swift BAT Team

    日本天文学会2008年春季年会  日本天文学会

    Presentation date: 2008.03

    Event date:
    2008.03
     
     
  • A spectral unified scheme of magnetar candidates

    Yujin E. Nakagawa

    Accelerators in the Universe 

    Presentation date: 2008.03

    Event date:
    2008.03
     
     
  • Swift衛星が発見した軟ガンマ線リピータの短いバーストに伴うX線残光

    中川 友進

    ガンマ線バーストで読み解く太古の宇宙 

    Presentation date: 2008.01

    Event date:
    2008.01
     
     
  • Suzaku ToO observations of two SGRs 1806-20 and 1900+14

    Yujin E. Nakagawa

    The Suzaku X-ray Universe 

    Presentation date: 2007.12

    Event date:
    2007.12
     
     
  • Suzaku ToO observations of gamma-ray burst x-ray afterglow

    Yujin E. Nakagawa

    The Suzaku X-ray Universe 

    Presentation date: 2007.12

    Event date:
    2007.12
     
     
  • HETE-2 observations of soft gamma repeaters from 2001 to 2005

    Yujin E. Nakagawa

    Gamma-ray Bursts 2007 

    Presentation date: 2007.11

    Event date:
    2007.11
     
     
  • マグネター候補天体の定常X線スペクトルの系統的な研究

    中川 友進, 吉田 篤正, 山岡 和貴, 柴崎 徳明

    日本天文学会2007年秋季年会  日本天文学会

    Presentation date: 2007.09

    Event date:
    2007.09
     
     
  • HETE-2衛星による軟ガンマ線リピータからの短いバーストの観測

    中川 友進, 吉田 篤正, 杉田 聡司, Kevin Hurley, 玉川 徹, 鈴木 素子, 白崎 裕治, 河合 誠之, 佐藤 理江, 古徳 純一, 有元 誠, 松岡 勝, George R. Ricker, 他HETE-2チーム

    日本天文学会2007年春季年会  日本天文学会

    Presentation date: 2007.03

    Event date:
    2007.03
     
     
  • A comprehensive study for short bursts from sgrs detected by HETE-2

    Yujin E. Nakagawa

    The International Workshop on Cosmic-rays and High Energy Universe 

    Presentation date: 2007.03

    Event date:
    2007.03
     
     
  • Observational study of SGR short bursts detected by HETE-2

    Yujin E. Nakagawa

    High Energy Radiation from the Compact Object 

    Presentation date: 2007.03

    Event date:
    2007.03
     
     
  • Two components model for SGR short flares – detailed timing and spectral studies on HETE-2 samples –

    Y. E. Nakagawa, A. Yoshida, K. Hurley, T. Tamagawa, M. Suzuki, N. Kawai, M. Matsuoka, HETE-2 Science Team

    The Extreme Universe in the Suzaku Era 

    Presentation date: 2006.12

    Event date:
    2006.12
     
     
  • HETE-2衛星による可視光で暗いガンマ線バーストGRB 051022の観測

    中川 友進, 吉田 篤正, 杉田 聡司, 田中 薫, 石川 信行, 玉川 徹, 鈴木 素子, 白崎 裕治, 河合 誠之, 松岡 勝, 佐藤 理恵, 有本 誠, 古徳 純一, 小林 明菜, 下川辺 隆史, G. Ricker, 他HETE-2チーム

    日本物理学会2006年秋季大会  日本物理学会

    Presentation date: 2006.09

    Event date:
    2006.09
     
     
  • Observation of GRB 051022 detected by HETE-2

    Y. E. Nakagawa, A. Yoshida, N. Ishikawa, N. Kawai, T. Tamagawa, M. Suzuki, K. Tanaka, Y. Shirasaki, S. Sugita, M. Masaru, R. Vanderspek, E. E. Fenimore, M. Galassi, J.-L. Atteia, G. R. Ricker, HETE-2 Science Team

    Swift and GRBs: Unveiling the Relativistic Universe 

    Presentation date: 2006.06

    Event date:
    2006.06
     
     
  • Detailed analyses of GRB 060105 X-ray afterglow observed by Suzaku

    Y. E. Nakagawa, K. Nakazawa, K. Yamaoka, N. Ishikawa, A. Yoshida, D. Yonetoku, T. Murakami, M. Tashiro, K. Abe, K. Onda, T. Tamagawa, M. Suzuki, Y. Urata, T. Takahashi, M. Yamauchi, E. Sonoda, S. Maeno, K. Kinugasa, N. Kawai, T. Kohmura, K. Torii, Y. Ueda, K. Kubota, H. Kodaira, S. Okuno, S. Yoshinari, G. Ricker, J. N. Reeves, J. Nousek, L. Angelini, L. J. Kaluzienski, R. L. Kelley, Suzaku GRB ToO Members

    Swift and GRBs: Unveiling the Relativistic Universe 

    Presentation date: 2006.06

    Event date:
    2006.06
     
     
  • HETE-2衛星が捉えたGRB 051022のプロンプト放射〜残光に見られる吸収

    中川 友進, 吉田 篤正, 石川 信行, 河合 誠之, 玉川 徹, 鈴木 素子, 白崎 裕治, 田中 薫, 前當 未来, 杉田 聡司, 小林 明菜, 佐藤 理江, 古徳 純一, 有元 誠, 下川辺 隆史, 松岡 勝, G. Ricker, 他HETE-2チーム

    日本天文学会2006年春季年会  日本天文学会

    Presentation date: 2006.03

    Event date:
    2006.03
     
     
  • Multiple pulsed gamma-ray bursts observed by HETE-2

    Y. E. Nakagawa, A. Yoshida, HETE Team

    American Astronomical Society 207th Meeting 

    Presentation date: 2006.01

    Event date:
    2006.01
     
     
  • HETE-2衛星が捉えたGRB 051022のプロンプト放射〜残光に見られる吸収

    中川 友進

    ガンマ線バースト 2005 - HETE-2, Swift, Suzaku で築く GRB 観測 - 

    Presentation date: 2005.12

    Event date:
    2005.12
     
     
  • HETE-2衛星による軟ガンマ線リピータの観測(3)

    中川 友進, 前當 未来, 吉田 篤正, 河合 誠之, 坂本 貴紀, 玉川 徹, 鈴木 素子, 白崎 裕治, 田中 薫, 山本 佳久, 佐藤 理恵, 小谷 太郎, 古徳 純一, 有元 誠, 石川 信行, 小林 明菜, 下川辺 隆史, 杉田 聡司, 松岡 勝, G. Ricker, 他HETE-2チーム

    日本天文学会2005年秋季年会  日本天文学会

    Presentation date: 2005.10

    Event date:
    2005.10
     
     
  • HETE-2衛星が捉えた複数ピークを持つガンマ線バースト

    中川 友進, 吉田 篤正, 河合 誠之, 玉川 徹, 鈴木 素子, 白崎 裕治, 坂本 貴紀, 田中 薫, 前當 未来, 石川 信行, 小林 明菜, 杉田 聡司, 佐藤 理恵, 古徳 純一, 有元 誠, 下川辺 隆史, 松岡 勝, G. Ricker, 他HETE-2チーム

    日本天文学会2005年秋季年会  日本天文学会

    Presentation date: 2005.10

    Event date:
    2005.10
     
     
  • Temporal and spectral analyses of SGRs observed by HETE-2

    Y. E. Nakagawa, A. Yoshida, M. Maetou, M. Suzuki, T. Tamagawa, T. Sakamoto, N. Kawai, Y. Shirasaki, K. Tanaka, M. Matsuoka, E. E. Fenimore, M. Galassi, J.-L. Atteia, K. Hurley, G. R. Ricker

    Gamma-Ray Bursts in the Swift Era 

    Presentation date: 2005.10

    Event date:
    2005.10
     
     
  • Properties of multi pulsed GRBs seen by HETE-2

    Y. E. Nakagawa, A. Yoshida, N. Ishikkawa, K. Tanaka, T. Tamagawa, M. Suzuki, N.Kawai, M. Matsuoka, Y. Shirasaki, E. E. Fenimore, M. Galassi, HETE-2 team

    Gamma-Ray Bursts in the Swift Era 

    Presentation date: 2005.10

    Event date:
    2005.10
     
     
  • HETE-2衛星による軟ガンマ線リピータの観測(2)

    中川 友進, 前當 未来, 吉田 篤正, 河合 誠之, 玉川 徹, 鳥居 研一, 白崎 裕治, 坂本 貴紀, 松岡 勝, 田中 薫 山崎 徹, 鈴木 素子, 浦田 裕次, 佐藤 理江, 山本 佳久, 古徳 純一, 有元 誠, G.R.Ricker

    日本天文学会2005年春季年会  日本天文学会

    Presentation date: 2005.03

    Event date:
    2005.03
     
     
  • HETE-2衛星が捉えたガンマ線バーストのX線アクティビティ

    中川 友進, 吉田 篤正, 坂本 貴紀, 鈴木 素子, 河合 誠之, 玉川 徹, 白崎 裕治, 松岡 勝, 山崎 徹, 田中 薫, 前當 未来, 浦田 裕次, 佐藤 理江, 山本 佳久, 古徳 純一, 有元 誠, R. Vanderspek, G. R. Ricker

    日本天文学会2005年春季年会  日本天文学会

    Presentation date: 2005.03

    Event date:
    2005.03
     
     
  • HETE-2衛星が捉えたガンマ線バーストのX線アクティビティ

    中川 友進

    ガンマ線バースト研究会@京都 

    Presentation date: 2004.12

    Event date:
    2004.12
     
     
  • Bursts from soft gamma-ray repeaters triggered by HETE-2

    Y. E. Nakagawa, M. Maetou, A. Yoshida, T. Sakamoto, M. Suzuki, Y. Yamamoto, T. Tamagawa, Y. Shi- rasaki, T. Yamazaki, N. Kawai, M. Matsuoka, E. E. Fenimore, M. Galassi, J-L. Atteia, K. Hurley, G. Ricker, HETE-2 science team

    GRB in the Afterglow Era: 4th Workshop 

    Presentation date: 2004.10

    Event date:
    2004.10
     
     
  • HETE-2衛星による軟ガンマ線リピータの観測

    中川 友進, 前當 未来, 吉田 篤正, 河合 誠之, 玉川 徹, 鳥居 研一, 白崎 裕治, 坂本 貴紀, 松岡 勝, 山崎 徹, 田中 薫, 鈴木 素子, 浦田 裕次, 佐藤 理恵, 山本 佳久, G. Ricker, 他HETE-2チーム

    日本物理学会2004年秋季大会  日本物理学会

    Presentation date: 2004.09

    Event date:
    2004.09
     
     
  • HETE-2がとらえたエクアドル上空における粒子数異常(3)

    中川 友進, 玉川 徹, 長井 嗣信, 山崎 徹, 吉田 篤正, 河合 誠之, 松岡 勝, 鳥居 研一, 白崎 裕治, 宮坂 浩正, 坂本 貴紀, 鈴木 素子, 浦田 裕次, 佐藤 理江, 山本 佳久, G. Ricker, 他HETE-2チーム

    日本物理学会第59回年次大会  日本物理学会

    Presentation date: 2004.03

    Event date:
    2004.03
     
     
  • HETE-2衛星が捉えたエクアドル上空における粒子数異常増加現象

    中川 友進, 山崎 徹, 吉田 篤正, 玉川 徹, 長井 嗣信, 河合 誠之, 坂本 貴紀, 鈴木 素子, 浦田 裕次, 佐藤 理江, 山本 佳久, 小谷 太郎, 宮坂 浩正, 松岡 勝, 鳥居 研一, 白崎 裕治, G. Ricker, R. Vanderspek, G. Crew, K. Hurley, 他HETE-2チーム

    第4回宇宙科学シンポジウム 

    Presentation date: 2004.01

    Event date:
    2004.01
     
     
  • HETE-2衛星がとらえた赤道上空での粒子数異常増加現象(2)

    中川 友進, 玉川 徹, 長井 嗣信, 山崎 徹, 吉田 篤正, 河合 誠之, 松岡 勝, 鳥居 研一, 白崎 裕治, 宮坂 浩正, 坂本 孝紀, 鈴木 素子, 浦田 裕次, 佐藤 理江, 山本 佳久, G.Ricker, 他HETE-2チーム

    日本天文学会2003年秋季年会  日本天文学会

    Presentation date: 2003.09

    Event date:
    2003.09
     
     
  • Observations of the x-ray bursts by HETE-2

    Y. E. Nakagawa, T. Yamazaki, M. Suzuki, A. Yoshida, N. Kawai, D. Takahashi, M. Matsuoka, Y. Shirasaki, T. Tamagawa, K. Torii, T. Sakamoto, Y. Urata, R. Sato, Y. Yamamoto, E. E. Fenimore, M. Galassi, D. Q. Lamb, G. Graziani, G. Ricker, HETE-2 team

    Gamma Ray Burst Symposium 

    Presentation date: 2003.09

    Event date:
    2003.09
     
     
  • An unusual time-variable high radiation region seen by HETE-2 satellite

    Y. E. Nakagawa, T. Tamagawa, T. Nagai, T. Yamazaki, A. Yoshida, N. Kawai, K. Torii, Y. Shirasaki, H. Miyasaka, T. Sakamoto, M. Suzuki, Y. Urata, R. Sato, G. Ricker, K. Hurley, G. Crew, HETE-2 Team

    The 28th International Cosmic Ray Conference 

    Presentation date: 2003.07

    Event date:
    2003.07
     
     
  • HETE-2がとらえたエクアドル上空における粒子数異常(2)

    中川 友進, 吉田 篤正, 玉川 徹, 鳥居 研一, 河合 誠之, 高橋 大樹, 山崎 徹, 白崎 裕治, 坂本 貴紀, 鈴木 素子, 浦田 裕次, 佐藤 理江, G.Ricker, 他HETE-2チーム

    日本物理学会第58回年次大会  日本物理学会

    Presentation date: 2003.03

    Event date:
    2003.03
     
     
  • HETE-2衛星がとらえた赤道上空での粒子数異常増加現象

    中川 友進, 吉田 篤正, 高橋 大樹, 玉川 徹, 鳥居 研一, 河合 誠之, 西田 竜介, 山崎 徹, 白崎 裕治, 坂本 貴紀, 鈴木 素子, 浦田 裕次, 佐藤 理江, G. Ricker, 他HETE-2チーム

    日本天文学会2002年秋季年会  日本天文学会

    Presentation date: 2002.10

    Event date:
    2002.10
     
     

▼display all

Research Projects

  • 機械学習による音源分離に立脚したAUVの物体検知の高精度化の研究

    日本学術振興会  科学研究費助成事業

    Project Year :

    2024.04
    -
    2027.03
     

    中川 友進

  • 計測融合解析によるドリルビット挙動把握と機械学習による掘削状態識別への展開

    日本学術振興会  科学研究費助成事業

    Project Year :

    2020.04
    -
    2023.03
     

    井上 朝哉, 鈴木 博善, 和田 良太, 中川 友進, 勝井 辰博

     View Summary

    1.ドリルビット接地荷重変動解析において,ドリルパイプ縦振動数理モデルの構築を行い,過去に実施した科学掘削のドリルパイプ編成にて試解析を行った.大深度掘削においては、ドリルパイプ弾性影響により,船上掘削データにより推算・監視されているドリルビット接地荷重変動より大きな変動が生じることを示した.
    2.ドリルビット挙動解析において,掘削地層の摩擦特性とドリルビットの接地荷重が支配的なパラメータとなる.そこで,ドリルパイプ上端変動の下端への伝搬縦振動を加味したドリルビット回転挙動数理モデルの構築を行い,仮編成にて数値解析を実施し,縦振動伝搬の有無によるドリルビット挙動の影響の考察を進めた.
    3.計測融合解析に向けて,掘削データ取得システムの開発を開始した.掘削船の掘削システムに対応した,掘削データ取得装置のシステム概念検討,掘削データの取得インターフェイス規格やフォーマットの検討,掘削データの伝送プロトコルやフォーマットの検討,および、データ伝送受信インターフェイスの検討を行った上で,掘削データ取得を行う受信ソフトの開発を行った.
    4.機械学習においては,教師データとなる過去の科学掘削航海における取得可能な船上掘削データや地層サンプルに関する情報の収集を行い,一部のデータを取得し,教師データの作成を開始した.また,掘削データを教師データとした,掘削地層予測に関する多クラス分類機械学習プログラムの開発を行った.

  • X線観測と理論との比較によるコンパクト天体への質量降着とアウトフロー現象の研究

    独立行政法人日本学術支援機構  学術研究助成基金助成金 基盤研究(C)

    Project Year :

    2016.04
    -
    2019.03
     

    海老沢 研

  • マグネターの超強磁場におけるX線放射機構の研究

    独立行政法人日本学術支援機構  学術研究助成基金助成金 基盤研究(C)

    Project Year :

    2015.04
    -
    2018.03
     

    中川 友進

  • マグネターの観測に立脚した超強磁場でのX線放射の研究

    独立行政法人日本学術支援機構  学術研究助成基金助成金 基盤研究(C)

    Project Year :

    2012.04
    -
    2015.03
     

    中川 友進

  • ロケット実験によるX線偏光宇宙物理学の開拓

    独立行政法人日本学術支援機構  科学研究費補助金 基盤研究(A)

    Project Year :

    2010.04
    -
    2014.03
     

    玉川 徹

  • Revealing Magnetars Based on Studies on Proton Cyclotron Absorption Line in Super-Strong Magnetic Field

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2009.04
    -
    2012.03
     

    NAKAGAWA Yujin

     View Summary

    I performed observational studies of higly magnetized neutron stars with~10^<15> G "Magnetars" using Japanese X-ray satellite Suzaku. In order to detect proton cyclotron resonance featrures and directly measure a magnetic field strength, I performed observations and analyses of three magnetars in active phases. Although I did not find any features in X-ray spectra, I discovered hard X-ray components in the X-ray spectra of weak bursts. In addition, I found a possibility that X-ray spectra in active phases are hader than those in quiet phases.

  • 超強磁場での陽子サイクロトロン吸収線を手掛かりにマグネターの正体を暴く

    独立行政法人日本学術支援機構  科学研究費補助金 若手研究スタートアップ (2009年度廃止)

    Project Year :

    2008.10
    -
    2010.03
     

    中川 友進

     View Summary

    観測事実から我々の宇宙にはB〜10^<15>Gもの超強磁場を持つ中性子星「マグネター」が要求されている。ところが候補天体の発見から30年を経過しても直接的な証拠が無い。本研究の目的は日本のX線天文衛星「すざく」を用いたX線・γ線の観測的研究により、陽子サイクロトロン共鳴散乱による吸収線を発見し、マグネターの存在を直接的に証明する事である。これは世界初の大発見になるだけでなく、B>4.4×10^<13>Gでのみ可能な物理学の研究が現実となる「宇宙の超強磁場実験場」の開拓になる。
    2008年8月22日に新候補天体(SGR 0501+4516)が発見され、私は即座に「すざく」衛星を用いた緊急観測を行った。観測中にバーストを検出し、スペクトルの約28keVに吸収線構造を見出した。起源が陽子のサイクロトロン共鳴散乱の基本波ならB〜4.5×10^<15>Gとなる。成果は即座に論文誌に掲載した。さらに2009年1月22日に候補天体であるAXP 1E 1547.0-5408が活発なバースト活動を示した(一日で約260個のバースト)。「すざく」衛星による緊急観測を行い、解析は現在進行中である。
    さらなる研究を平成21年度に行うために二つの事前提案を行った。一つは活発なバースト活動期に行う観測であり、もう一つは静穏状態の系統的な観測である。これらの事前提案は現在審査中である。

  • γ線バーストのプロンプト放射および残光観測によるバースト中心天体の解明

    独立行政法人日本学術支援機構  科学研究費補助金 特別研究員奨励費

    Project Year :

    2005.04
    -
    2008.03
     

    中川 友進

     View Summary

    2007年度は、ガンマ線バースト(Gamma-Ray Burst; GRB)の第三の起源だと提案されている軟ガンマ線リピータ(Soft Gamma Repeater; SGR)の研究を中心に行った。SGRと異常なX線パルサー(Anomalous X-ray Pulsar; AXP)は、マグネター(B〜10^<15>G)の候補天体である。
    SGRは数十ミリ秒のバーストを繰り返し起こすことが知られているが、放射メカニズムは解明されていなかった。我々はHETE-2衛星が捉えた55個のバーストのデータを用いて系統的な研究を行った。その結果、1)軟X線と硬X線の放射には2.2±0.4ミリ秒の「時間の遅れ」が存在すること、2)エネルギースペクトルのモデルは二温度黒体放射(〜4keV、〜11keV)が尤もらしいこと、3)放射メカニズムは地震や太陽フレアと類似していることを明らかにした。成果はPASJ誌に掲載した。
    SGRとAXPは定常的にX線を放射しているが、放射メカニズムは解明されていない。SGRとAXPは磁気エネルギーの散逸によって、X線・ガンマ線のエネルギーを放出すると考えられている。もしこれが本当ならば、X線定常放射のエネルギースペクトルは、バーストで尤もらしかった二温度黒体放射でよく再現されるはずである。そこで我々は既知のSGRとAXPのX線定常放射についてエネルギースペクトル解析を行い、バーストと比較した。その結果、低温度と高温度の比はX線定常放射とバーストによらず0.4で一定であることを明らかにした。これは、X線定常放射とバーストが自己相似的な放射メカニズムを持つことを示唆する。本研究はPASJ誌で査読中である。
    「すざく」衛星を用いたGRB060904のX線残光の研究はPASJ誌、他研究機関との共同でのXRF040916の研究はPASJ誌、GRB070616の研究はMNRAS誌に成果を掲載した。

▼display all

Misc

  • 2020-2021 食品トレンド

    日本食糧新聞社

       2020.07

  • 日本シミュレーション学会・小特集「気候変動への適応にむけたデータセットの 開発とその活用」

    中川友進, 尾上洋介, 荒木文明, 小山田耕二

       2019

  • 天文月報(第101巻, 第1号)

    中川友進

       2008.12

  • 天文月報(第99巻, 第5号)

    田代信, 山岡和貴, 大野雅功, 村上敏夫, 中澤知洋, 中川友進, 河合誠之, 高橋忠幸, 寺田幸功

       2006.04

 

Social Activities

  • 未来を守る大作戦!学ぼう、気候変動!!

    三菱みなとみらい技術館  夏休み自由研究大集合 

    2019.07
     
     

  • 気候と二人三脚で歩く! 2018

    三菱みなとみらい技術館  自由研究ワークショップ 

    2018.08
     
     

  • 気候と二人三脚で歩く! 2017

    三菱みなとみらい技術館  自由研究ワークショップ 

    2017.07
     
     

  • 気候と二人三脚で歩く!

    三菱みなとみらい技術館  サイエンスフェスティバル 

    2016.07
     
     

  • 宇宙の監視員「MAXI」の 6 年間の軌跡

    JAXA相模原キャンパス特別公開2015  ミニ講演会 

    2015.07
     
     

  • 宇宙のあらゆる方向からやってくるエックス線を監視し続ける MAXI とは?

    JAXA相模原キャ ンパス特別公開2014 

    2014.07
     
     

  • MAXI が捉えたブラックホールへの燃料投下

    JAXA相模原キャンパス特別公開2013 

    2013.07
     
     

  • ガンマ線バースト~混沌の時代~

    埼玉大学  大学院特別講義 

    2007.07
     
     

  • ガンマ線バースト~星の死と誕生の瞬間を捉える~

    国立天文台  天塾・第 22 回 

    2005.01
     
     

▼display all

Internal Special Research Projects

  • マグネターの正体解明へ向けた超強磁場でのX線放射の観測的研究

    2011  

     View Summary

     観測的・理論的な研究により、我々の宇宙にはB~10^15 Gもの超強磁場を持つ中性子星である「マグネター」が提案されている。本研究の目的は日本のX線天文衛星「すざく」を用いたX線・ガンマ線の観測的研究により、陽子のサイクロトロン共鳴散乱による吸収線を発見し、マグネターの磁場強度を直接的に測定することである。これは世界初の大発見になるだけでなく、B>4.4×10^13 Gでのみ可能な物理学の研究が初めて現実となる「宇宙の超強磁場実験場」の開拓になる。 平成23年度は、マグネターが活発なバースト活動を示した際に行う「すざく」衛星による緊急観測の提案が評価Aで採択されており、実際に観測を実施した。アメリカのSwift衛星の観測チームにより、マグネターの1つであるAXP 4U 0142+614 が2011年7月29日にバースト活動を示し、少なくとも10個以上のバーストを起こしている事が報告された。その後、私はSwift衛星の観測チームと協力して定常放射のモニタリングを行ったところ、1ヵ月以上に渡って20-30%ほど明るい状態が続いている事が分かった。しかし、過去10年間において+/-10%ほどの変動しか報告されていない(Gonzalez et al. 2010, APJ 716, 1345)。そこで私はAXP 4U 0142+614が稀な活動期を示していると判断して、前述の「すざく」衛星による緊急観測を2011年9月7日に実施した。観測データを解析した結果、明確なバーストは検出できず、定常放射のエネルギースペクトルに明確な吸収線は見られなかったものの、静穏期と比べると定常放射が明るく、エネルギースペクトルが硬いことが分かった。これまでの研究では静穏期と活動期でのエネルギースペクトルの明確な違いは報告されておらず、重要な成果になると期待している。暗いバーストの探査、エネルギースペクトルの吸収線の探査など、より詳細な解析を進めている。