研究者業績

堂谷 忠靖

ドウタニ タダヤス  (Tadayasu Dotani)

基本情報

所属
国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 宇宙物理学研究系 教授
総合研究大学院大学 先端学術院 宇宙科学コース 教授
東京工業大学 理学院物理学系物理学コース 特定教授
関西学院大学 大学院理工学研究科 客員教授
学位
理学博士(東京大学)

J-GLOBAL ID
200901025041369206
researchmap会員ID
1000144439

専門はX線天文学。特に、中性子星やブラックホールを含むX線連星の観測的研究および衛星搭載X線CCDカメラの開発研究。


受賞

 1

論文

 215
  • Midori Ozaiwa, Hideki Uchiyama, Hiroshi Nakajima, Hideyuki Mori, Hironori MatsuMoto, Takeshi Go Tsuru, Katsuji Koyama, Masahiro Uchino, Kiyoshi Hayashida, Hiroshi Tsunemi, Hiroshi Murakami, Tadayasu Dotani, Gregory Prigozliin, Steve Kissel, Eric Miller, Beverly LaMarr, Marshall Bautz
    SPACE TELESCOPES AND INSTRUMENTATION 2008: ULTRAVIOLET TO GAMMA RAY, PTS 1 AND 2 7011 2008年  査読有り
    The X-ray Imaging Spectrometer (XIS) on board the Suzaku satellite is an X-ray CCD camera system that has features of a low background, high quantum efficiency, and good energy resolution in the 0.2-12 keV band. Because of the radiation damage, however, the energy resolution of the XIS has been degraded since Suzaku was launched (July 2005). In order to improve the energy resolution, one of the major advantages of the XIS over the other X-ray CCDs in orbit is the provision of a precision charge injection (CI) capability. We applied this Cl in two ways. First, in order to measure the precise charge transfer inefficiency (CTI), we applied the checker-flag Cl, and measured the CTI of each CCD column. Furthermore, we obtained the pulse height dependency of the CTI. Our precise CTI correction using these results improved the energy resolution from 193 eV to 173 eV in FWHM at 5.9 keV in July 2006 (one year after the launch). Second, the energy resolution can be improved also by reducing the CTI. For this purpose, we applied the spaced-row charge injection (SCI); periodically injected artificial charges work as if they compensate radiation-induced traps and prevent electrons produced by X-rays from being captured by the charge traps. Using this method, the energy resolution improved from 210 eV to 150 eV in FWHM at 5.9 keV in September 2006, which is close to the resolution just after the launch (140 eV). We report the current in-orbit calibration status of the XIS data using these two techniques. We present the time history of the gain and energy resolution determined from onboard calibration sources (Fe-55) and observed calibration objects like E0102-72.
  • S. Naik, T. Dotani, Y. Terada, M. Nakajima, T. Mihara, M. Suzuki, K. Makishima, K. Sudoh, S. Kitamoto, F. Nagase, T. Enoto, H. Takahashi
    ASTROPHYSICAL JOURNAL 672(1) 516-523 2008年1月  査読有り
    The transient X-ray binary pulsar A0535+262 was observed with Suzaku on 2005 September 14 when the source was in the declining phase of the August-September minor outburst. The similar to 103 s X-ray pulse profile was strongly energy dependent, with a double-peaked profile in the soft X-ray energy band (< 3 keV) and a single-peaked smooth profile in hard X-rays. The width of the primary dip is found to increase with energy. The broadband energy spectrum of the pulsar is well described with a negative and positive power law with exponential (NPEX) continuum model, along with a blackbody component for soft excess. A weak iron K alpha emission line with an equivalent width similar to 25 eV was detected in the source spectrum. The blackbody component is found to be pulsating over the pulse phase, implying that the accretion column and/or the inner edge of the accretion disk may be the possible emission site of the soft excess in A0535+262. The higher value of the column density is believed to be the cause of the secondary dip in the soft X-ray energy band. The iron line equivalent width is found to be constant (within errors) over the pulse phase. However, a sinusoidal type of flux variation of the iron emission line, in phase with the hard X-ray flux, suggests that the inner accretion disk is the possible emission region of the iron fluorescence line.
  • Y. Terada, M. Ishida, K. Mukai, T. Dotani, K. Makishima, S. Naik, T. Hayashi, S. Okada, R. Nakamura, T. Enoto
    ADVANCES IN SPACE RESEARCH 41(3) 512-517 2008年  査読有り
    Although rotating neutron stars (NSs) have been regarded as being textbook examples of astrophysical particle acceleration sites for decades, details of the acceleration mechanism remain a mystery; for example, we cannot yet observationally distinguish "polar cap" models from "outer gap" models. To solve the model degeneracy, it is useful to study similar systems with much different physical parameters. Strongly magnetized white dwarfs (WDs) are ideal for this purpose, because they have essentially the same system geometry as NSs, but differ largely from NSs in the system parameters, including the size, magnetic field, and the rotation velocity, with the induced electric field expected to reach 10(13)-10(14) eV. Based on this idea, the best candidate among WDs, AE Aquarii, was observed with the fifth Japaneses X-ray satellite, Suzaku. The hard X-ray detector (HXD) on-board Suzaku has the highest sensitivity in the hard X-ray band over 10 keV. A marginal detection in the hard X-ray band was achieved with the HXD, and was separated from the thermal emission. The flux corresponds to about 0.02% of its spin-down energy. If the signal is real, this observation must be a first case of the detection of non-thermal emission from WDs. (C) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.
  • Masanobu Ozaki, Naohisa Anabuki, Daisuke Matsuura, Hiroshi Nakajma, En-Ii Miyata, Kiyoshi Hayashida, Hiroshi Tsunemi, Tsuru G. Takeshi, Hironori Matsumoto, Aya Bamba, Takahisa Fujinaga, Tadayasu Dotani, Takeshi Takashima, Tadayuki Takahashi, Hiroshi Tomida, Junko Hiraga, Hiroshi Murakami, Takayoshi Kohmura, Kazunori Masukawa, Masahiro Kato, Atsushi Nakajima, Yo Watanabe
    SPACE TELESCOPES AND INSTRUMENTATION 2008: ULTRAVIOLET TO GAMMA RAY, PTS 1 AND 2 7011 2008年  査読有り
    The Soft X-ray Imager (SXI) is the X-ray CCD detector system on board the NeXT mission that is to be launched around 2013. The system consists of a camera, an SXI-specific data processing unit (SXI-E) and a CPU unit commonly used throughout the NeXT satellite. All the analog signal handling is restricted within the camera unit, and all the I/O of the unit are digital. The camera unit and SXI-E are connected by multiple LVDS lines, and SXI-E and the CPU unit will be connected by a SpaceWire (SpW) network. The network can connect SXI-E to multiple CPU units (the formal SXI CPU and neighbors) and all the CPU units in the network have connections to multiple neighbors: with this configuration, the SXI system can work even in the case that one SpW connection or the formal SXI CPU is down. The main tasks of SXI-E are to generate the CCD driving pattern, the acquisition of the image data stream and HK data supplied by the camera and transfer them to the CPU unit with the Remote Memory Access Protocol (RMAP) over SpW. In addition to them, SXI-E also detects the pixels whose values are higher than the event threshold and both adjacent pixels in the same line, and send their coordinates to the CPU unit. The CPU unit can reduce its load significantly with this information because it gets rid of the necessity to scan whole the image to detect X-ray events.
  • Takayasu Anada, Tadayasu Dotani, Masanobu Ozaki, Hiroshi Murakami
    SPACE TELESCOPES AND INSTRUMENTATION 2008: ULTRAVIOLET TO GAMMA RAY, PTS 1 AND 2 7011 2008年  査読有り
    We studied how the configuration parameters of a CCD (pixel size and depletion layer thickness) affect the instrumental background of an X-ray CCD camera in the space environment through the Monte-Carlo simulation. X-ray detectors are in general sensitive not only to X-rays but also to charged particles. The latter produce pseudo-signal indistinguish able from that of X-rays, which is called instrumental background. It is essential to reduce the instrumental background for the observations of dim and diffuse X-ray sources, but the low background was not considered as a, design goal of an X-ray CCD camera so far. We utilized the Monte-Carlo simulator, which could successfully reproduce the Suzaku XIS background, for the current analysis. We found that thicker depletion layer tends to increase the background except for the >5 keV band of the backside-illuminated CCD. On the other hand, pixel-size dependence was different between the frontside and backside illuminated CCDs. These results are interpreted in terms Of the interaction of cosmic/X-rays with the CCD.
  • Takahashi H, Fukazawa Y, Mizuno T, Hirasawa A, Kitamoto S, Sudoh K, Ogita T, Kubota A, Makishima K, Itoh T, Parmar A.N, Ebisawa K, Naik S, Dotani T, Kokubun M, Ohnuki K, Takahashi T, Yaqoob T, Angelini L, Ueda Y, Yamaoka K, Kotani T, Kawai N, Namlki M, Kohmura T, Negoro H
    Publications of the Astronomical Society of Japan 60(SPEC. ISS. 1) S69-S83 2008年  査読有り
  • Terada Y, Enoto T, Miyawaki R, Ishisaki Y, Dotani T, Ebisawa K, Ozaki M, Ueda Y, Kuiper L, Endo M, Fukazawa Y, Kamae T, Kawaharada M, Kokubun M, Kuroda Y, Makishima K, Masukawa K, Mizuno T, Murakami T, Nakazawa K, Nakajima A, Nomach M, Shibayama N, Takahashi T, Takahashi H, Tashiro M.S, Tamagawa T, Watanabe S, Yamaguchi M, Yamaoka K, Yonetoku D
    Publications of the Astronomical Society of Japan 60(SPEC. ISS. 1) 2008年  査読有り
  • Hayashida Kiyoshi, Torii Ken'ichi, Namiki Masaaki, Naohisa ANABUKI, Satoru KATSUDA, Noriaki TAWA, Tomofumi MIYAUCHI, Kazuto HASUIKE, Masaaki NAGAI, Hiroshi TSUNEMI, Hironori MATSUMOTO, Takeshi G. TSURU, Hideyuki MORI, Hiroshi NAKAJIMA, Hiroya YAMAGUCHI, Yoshiaki HYODO, Tatsuya INUI, Hideki UCHIYAMA, Midori OZAWA, Katsuji KOYAMA, Eric D. MILLER, Mark W. BAUTZ, Beverly LAMARR, Steve E. KISSEL, Tadayasu DOTANI, Hiroshi MURAKAMI, Masanobu OZAKI, Takayasu ANADA, Aya BAMBA, Junko HIRAGA, Atsushi SENDA, Dai TAKEI, Shunji KITAMOTO, Koji MORI, Shouta MAENO, Department of Earth, Space Science, Osaka University, Department of Earth, Space Science, Osaka University, Department of Earth, Space Science, Osaka University, Department of Earth, Space Science, Osaka University, Department of Earth, Space Science, Osaka University, Department of Earth, Space Science, Osaka University, Department of Earth, Space Science, Osaka University, Department of Earth, Space Science, Osaka University, Department of Earth, Space Science, Osaka University, Department of Earth, Space Science, Osaka University, Department of, Physics Kyoto University, Department of, Physics Kyoto University, Department of, Physics Kyoto University, Department of, Physics Kyoto University, Department of, Physics Kyoto University, Department of, Physics Kyoto University, Department of, Physics Kyoto University, Department of, Physics Kyoto University, Department of, Physics Kyoto University, Department of Physics Kyoto University, Kavli Institute for Astrophysics, Space Research, Kavli Institute for Astrophysics, Space Research, Kavli Institute for Astrophysics, Space Research, Kavli Institute for Astrophysics, Space Research, Institute of Space, Astronautical Science JAXA, Institute of Space, Astronautical Science JAXA, Institute of Space, Astronautical Science JAXA, Institute of Space, Astronautical Science JAXA, The Institute of Physical, Chemical Research, RIKEN, The Institute of Physical, Chemical Research, RIKEN, The Institute of Physical, Chemical Research (RIKEN, Department of, Physics Rikkyo University, Department of, Physics Rikkyo University, Department of Applied, Physics Miyazaki University, Department of Applied, Physics Miyazaki University
    Progress of theoretical physics. Supplement 169 316-321 2007年12月19日  
    Orbital calibrations of the XIS, in terms of the energy scale, energy resolution, and quantum efficiency, are needed not only to confirm the calibrations on the ground but also to examine inevitable performance change in orbit. Fundamentals of the XIS calibration issues have been established and are implemented the softwares and the data base for general observers. We overview the current status of the XIS calibration in orbit.
  • Y. Terada, M. Ishida, K. Mukai, K. Makishima, T. Dotani, L. Gallo, S. Naik, T. Hayashi, S. Okada, R. Nakamura, T. Enoto
    6TH INTEGRAL WORKSHOP: THE OBSCURED UNIVERSE 622 521-+ 2007年  査読有り
    As system similar to a rotating neutron star, a strongly magnetized white dwarf (WD) may be a moderate particle acceleration site. At the best case, the induced electric field is expected to reach 10(13) to 10(14) eV. A trial to detect non-thermal emission from a best candidate among WDs, AE Aquarii, was performed with the hard X-ray detector (HXD) on-board the fifth Japaneses X-ray satellite, Suzaku. Although the HXD has a non-imaging capability, the sensitivity in the 10 - 70 keV band reaches about the 5 x 10(-6) - 10(-5) photons/sec/cm(2)/keV level with only 100 ksec exposure. Marginal detection has been achieved with the HXD, which was separated from the thermal emission. If this is real, it must be the first case of a detection of non-thermal emission from ArDs.
  • T. Dotani, K. Mitsuda, M. Bautz, H. Inoue, R. L. Kelley, K. Koyama, H. Kunieda, K. Makishima, Y. Ogawara, R. Petre, T. Takahashi, H. Tsunemi, N. E. White, N. Anabuki, L. Angelini, K. Arnaud, H. Awaki, A. Bamba, K. Boyce, G. V. Brown, K. -W. Chan, J. Cottam, J. Doty, K. Ebisawa, Y. Ezoe, A. C. Fabian, E. Figueroa, R. Fujimoto, Y. Fukazawa, T. Furusho, A. Furuzawa, K. Gendreau, R. E. Griffiths, Y. Haba, K. Hamaguchi, l. Harrus, G. Hasinger, I. Hatsukade, K. Hayashida, P. J. Henry, J. S. Hiraga, S. S. Holt, A. Hornschemeier, J. P. Hughes, U. Hwang, M. Ishida, Y. Ishisaki, N. Isobe, M. Itoh, N. Iyomoto, S. M. Kahn, T. Kamae, H. Katagiri, J. Kataoka, H. Katayama, N. Kawai, M. Kawaharada, C. Kilbourne, K. Kinugasa, S. Kissel, S. Kitamoto, M. Kohama, T. Kohmura, M. Kokubun, T. Kotani, J. Kotoku, A. Kubota, G. M. Madejski, Y. Maeda, F. Makino, A. Markowitz, C. Matsumoto, H. Matsumoto, M. Matsuoka, K. Matsushita, D. McCammon, T. Mihara, K. Misaki, E. Miyata, T. Mizuno, K. Mori, H. Mori, M. Morii, H. Moseley, K. Mukai, H. Murakami, T. Murakami, R. Mushotzky, F. Nagase, M. Namiki, H. Negoro, K. Nakazawa, J. A. Nousek, T. Okajima, Y. Ogasaka, T. Ohashi, T. Oshima, N. Ota, M. Ozaki, H. Ozawa, A. N. Parmar, W. D. Pence, F. Scott Porter, J. N. Reeves, G. R. Ricker, L. Sakurai, W. T. Sanders, A. Senda, P. Serlemitsos, R. Shibata, K. Shinozaki, Y. Soong, R. Smith, M. Suzuki, A. E. Szymkowiak, H. Takahashi, Y. Takei, T. Tamagawa, K. Tamura, T. Tamura, Y. Tanaka, M. Tashiro, Y. Tawara, Y. Terada, Y. Terashima, H. Tomida, K. Torii, Y. Tsuboi, Y. Tsujimoto, T. Tsuru, M. J. L. Turner, Y. Uchiyama, Y. Ueda, S. Ueno, M. Ueno, S. Uno, Y. Urata, S. Watanabe, N. Yamamoto, K. Yamaoka, N. Y. Yamasaki, K. Yamashita, M. Yamauchi, S. Yajmauchi, T. Yaqoob, D. Yonetoku, A. Yoshida
    2007 IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD, VOLS 1-11 2526-+ 2007年  査読有り
    We report in-flight status of the X-ray detectors on board the Suzaku observatory, the 5th X-ray astronomy satellite of Japan launched on July 10, 2005. Suzaku is equipped with two types of instruments: one is the X-ray Imaging Spectrometers (XISs) and the other is Hard X-ray Detector (HXD). XIS utilizes the X-ray CCD camera in combination with the grazing-incidence X-ray telescope. HXD is a non-imaging, hybrid detector utilizing Si PIN diodes and GSO/BGO phoswich counters. Suzaku takes a low-earth, circular orbit with an altitude of 560 km and an inclination of 31 deg. This means that Suzaku goes through the south atlantic anomaly about 1/3 of its revolutions. This has a large impact on the in-flight performance of XIS and HXD, which is reported in detail in the present paper.
  • Kubota Aya, Dotani Tadayasu, Cottam Jean, KOTANI Taro, DONE Chris, UEDA Yoshihiro, FABIAN Andy C., YASUDA Tomonori, TAKAHASHI Hiromitsu, FUKAZAWA Yasushi, YAMAOKA Kazutaka, MAKISHIMA Kazuo, YAMADA Shinya, KOHMURA Takayoshi, ANGELINI Lorella
    Progress of theoretical physics. Supplement (169) 225-228 2007年  
    We present the results of six Suzaku observations of the recurrent black hole transient 4U 1630-472 during its decline from its most recent outburst in 2006. All observations show the typical high/soft state spectral shape in the 2-50keV band, roughly described by an optically thick disk spectrum in the soft energy band plus a weak power-law tail. The disk temperature decreases from 1.4keV to 1.2keV as the flux decreases by a factor 2, consistent with a constant radius as expected for disk-dominated spectra. All the observations reveal significant absorption lines from highly ionized (H-like and He-like) iron Ka at 7.0keV and 6.7keV. The energies of these absorption lines suggest a blue shift with an outflow velocity of~1000km s^<-1>. The H-like iron Kα equivalent width remains approximately constant at~30eV over all the observations, while that of the He-like Kα line increases from 7eV to 20eV. Thus the ionization state of the material decreases, as expected from the decline in flux. The data constrain the velocity dispersion of the absorber to 200-2000km s^<-1>, and the size of the plasma as~10^<10> cm assuming a source distance of 10kpc.
  • M. W. Bautz, B. J. LaMarr, E. D. Miller, S. E. Kissel, G. Y. Prigozhin, B. E. Burke, J. A. Gregory, H. Uchiyama, Y. Hyodo, H. Yamaguchi, H. Mori, T. Tsuru, H. Matsumoto, K. Koyama, K. Torii, S. Katsuda, K. Hasuike, H. Nakajima, K. Hayashida, H. Tsunemi, H. Murakami, M. Ozaki, T. Dotani
    UV, X-RAY, AND GAMMA-RAY SPACE INSTRUMENTATION FOR ASTRONOMY XV 6686 2007年  査読有り
    The CCD detectors in the X-ray Imaging Spectrometers (XIS) aboard Suzaku have been equipped with a precision charge injection capability. The purposes of this capability are to measure and reduce the detector degradation caused by charged particle radiation encountered on-orbit. Here we report the first results from routine operation of the XIS charge injection function. After 12 months' exposure of the XIS to the on-orbit charged particle environment, charge injection already provided measurable improvements in detector performance: the observed width of the 5.9 keV line from the onboard calibration source was reduced from 205 eV to less than 145 eV. The rate of degradation is also significantly smaller with charge injection, so its benefit will increase as the mission progresses. Measured at 5.9 keV, the radiation-induced rate of gain degradation is reduced by a factor of 4.3 +/- 0.1 in the front-illuminated sensors when injecting charge greater than 6 keV equivalent per pixel. The corresponding rate of degradation in spectral resolution is reduced by a factor 6.5 +/- 0.3. Injection of a smaller quantity of injected charge in the back-illuminated XIS sensor produces commensurately smaller improvement factors. Excellent uniformity of the injected charge pattern is essential to the effectiveness of charge injection in the XIS.
  • Tadayasu Dotani
    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT (169) 208-213 2007年  査読有り
    We summarize the presentations in this session from a point of view of particle acceleration in the vicinity of a magnetized neutron star and a white dwarf. We take the radio and hard X-ray emission as a clue for the particle acceleration, and summarize the results of the past observations in the literature. Efficient particle acceleration seems to be working only in the isolated, highly magnetized neutron stars. In the mass-accreting, highly magnetized objects, particle acceleration and even the production of hot, thin thermal plasma seem to be suppressed.
  • Kiyoshi Hayashida, Ken'ichi Torrii, Masaaki Namiki, Naohisa Anabuki, Satoru Katsuda, Noriaki Tawa, Tomofumi Miyauchi, Kazuto Hasuike, Masaaki Nagai, Hiroshi Tsunemi, Hironori Matsumoto, Takeshi G. Tsuru, Hideyuki Mori, Hiroshi Nakajtma, Hiroya Yamaguchi, Yoshiaki Hyodo, Tatsuya Inui, Hideki Uchiyama, Midori Ozawa, Katsuji Koyama, Eric D. Miller, Mark W. Bautz, Beverly LaMarr, Steve E. Kissel, Tadayasu Dotani, Hiroshi Murakami, Masanobu Ozaki, Takayasu Anada, Aya Bamba, Junko Hiraga, Atsushi Senda, Dai Takei, Shunji Kitamoto, Koji Mori, Shouta Maeno
    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT (169) 316-321 2007年  査読有り
    Orbital calibrations of the XIS, in terms of the energy scale, energy resolution, and quantum efficiency, are needed not only to confirm the calibrations on the ground but also to examine inevitable performance change in orbit. Fundamentals of the XIS calibration issues have been established and are implemented the softwares and the data base for general observers. We overview the current status of the XIS calibration in orbit.
  • Hideki Uchiyama, Yoshiaki Hyodo, Hiroya Yamaguchi, Hiroshi Nakajima, Hideyuki Mori, Takeshi Go Tsuru, Hironori Matsumoto, Katsuji Koyama, Ken'ichi Torii, Satoru Katsuda, Kazuto Hasuike, Kiyoshi Hayashida, Hiroshi Tsunemi, Hiroshi Murakami, Tadayasu Dotani, Gregory Prigozhin, Steve Kissel, Eric Miller, Beverly LaMarr, Marshall Bautz
    UV, X-RAY, AND GAMMA-RAY SPACE INSTRUMENTATION FOR ASTRONOMY XV 6686 id.66860P 2007年  
    The energy resolution of the X-ray CCDs onboard the Suzaku satellite (X-ray Imaging Spectrometer: XIS) has been degraded since the launch due to radiation damage. To recover from this, we have applied a spaced-row charge injection (SCI) technique to the Suzaku XIS in orbit. By injecting charge into CCD rows periodically; the energy resolution 14 months after launch is improved from 210 eV to 150 eV at 5.9 keV, which is close to the resolution just after the launch (140 eV). Additional information on these results is given in a companion paper by the XIS team. In this paper, we report the details of CCD charge transfer inefficiency (CTI) in the SCI mode, the correction method, and the implementation of it in ground analysis software for XIS data. In the SCI mode; CTI depends on the distance of a charge packet from the nearest charge-injected row, and the gain shows a periodic non-uniformity. Using flight data obtained with the onboard calibration sources; as well as a cosmic source (the Perseus cluster of galaxies), we studied the non-uniformity in detail. We developed a method to correct for the non-uniformity that will be valuable as the radiation damage progresses in future.
  • Terada Y, Mihara T, Nagase F, Angelini L, Dotani T, Enoto T, Kitamoto S, Kohmura T, Kokubun M, Kotani T, Makishima K, Naik S, Nakajima M, Sugita S, Sudoh K, Suzuki M, Takahashi H, Yonetoku D, Yoshida A
    Advances in Space Research 40(10) 1485-1490 2007年  査読有り
  • Dotani T, Mitsuda K, Bautz M, Inoue H, Kelley R.L, Koyama K, Kunieda H, Makishima K, Ogawara Y, Petre R, Takahashi T, Tsunemi H, White N.E, Anabuki N, Angelini L, Arnaud K, Awaki H, Bamba A, Boyce K, Brown G.V, Chan K.-W, Cottam J, Doty J, Ebisawa K, Ezoe Y, Fabian A.C, Figueroa E, Fujimoto R, Fukazawa Y, Furusho T, Furuzawa A, Gendreau K, Griffiths R.E, Haba Y, Hamaguchi K, Harrus I, Hasinger G, Hatsukade I, Hayashida K, Henry P.J, Hiraga J.S, Holt S.S, Hornschemeier A, Hughes J.P, Hwang U, Ishida M, Ishisaki Y, Isobe N, Itoh M, Iyomoto N, Kahn S.M, Kamae T, Katagiri H, Kataoka J, Katayama H, Kawai N, Kawaharada M, Kilbourne C, Kinugasa K, Kissel S, Kitamoto S, Kohama M, Kohmura T, Kokubun M, Kotani T, Kotoku J, Kubota A, Madejski G.M, Maeda Y, Makino F, Markowitz A, Matsumoto C, Matsumoto H, Matsuoka M, Matsushita K, McCammon D, Mihara T, Misaki K, Miyata E, Mizuno T, Mori K, Mori H, Morii M, Moseley H, Mukai K, Murakami H, Murakami T, Mushotzky R, Nagase F, Namiki M, Negoro H, Nakazawa K, Nousek J.A, Okajima T, Ogasaka Y, Ohashi T, Oshima T, Ota N, Ozaki M, Ozawa H, Parmar A.N, Pence W.D, Porter F.S, Reeves J.N, Ricker G.R, Sakurai I, Sanders W.T, Senda A, Serlemitsos P, Shibata R, Shinozaki K, Soong Y, Smith R, Suzuki M, Szymkowiak A.E, Takahashi H, Takei Y, Tamagawa T, Tamura K, Tamura T, Tanaka Y, Tashiro M, Tawara Y, Terada Y, Terashima Y, Tomida H, Torii K, Tsuboi Y, Tsujimoto Y, Tsuru T, Turner M.J.L, Uchiyama Y, Ueda Y, Ueno S, Ueno M, Uno S, Urata Y, Watanabe S, Yamamoto N, Yamaoka K, Yamasaki N.Y, Yamashita K, Yamauchi M, Yamauchi S, Yaqoob T, Yonetoku D, Yoshida A
    IEEE Nuclear Science Symposium Conference Record 4 2526-2531 2007年  査読有り
  • Maeda K, Tohma T, Saitoh T, Hara Y, Mitsuda K, Dotani T, Maeda Y, Ishida M, Kokubun M, Kunieda H, Hashimoto T, Sakai S
    Proceedings of the SICE Annual Conference 3019-3024 2007年  査読有り
  • Aya Kubota, Tadayasu Dotani, Jean Cottam, Taro Kotani, Chris Done, Yoshihiro Ueda, Andy C. Fabian, Tomonori Yasuda, Hiromitsu Takahashi, Yasushi Fukazawa, Kazutaka Yamaoka, Kazuo Makishima, Shinya Yamada, Takayoshi Kohmura, Lorella Angelini
    Proceedings of the International Astronomical Union 2(238) 23-28 2006年8月  査読有り
    We present the results of six Suzaku observations of the recurrent black hole transient 4U 1630472 during its decline from its most recent outburst in 2006. All observations show the typical high/soft state spectral shape in the 250 keV band, roughly described by an optically thick disk spectrum in the soft energy band plus a weak power-law tail. The disk temperature decreases from 1.4 keV to 1.2 keV as the flux decreases by a factor 2, consistent with a constant radius as expected for disk-dominated spectra. All the observations reveal significant absorption lines from highly ionized (H-like and He-like) iron K at 7.0 keV and 6.7 keV. The energies of these absorption lines suggest a blue shift with an outflow velocity of 1000 km s 1. The Hlike iron K equivalent width remains approximately constant at 30 eV over all the observations, while that of the Helike K line increases from 7 eV to 20 eV. Thus the ionization state of the material decreases, as expected from the decline in flux. The data constrain the velocity dispersion of the absorber to 2002000 km s 1, and the size of the plasma as 10 10 cm assuming a source distance of 10 kpc. © 2007 International Astronomical Union.
  • Kazumi Asai, Tadayasu Dotani
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 58(3) 587-594 2006年6月  査読有り
    We analyzed an effect of the photo-ionization on the continuum spectra using the XMM-Newton archive data of the low-mass X-ray binary EXO 0748-676. We found that the ionization degree of the circumstellar plasma, which modifies the soft X-ray spectrum through absorption, changes largely in association with the X-ray bursts and the dips. The burst light curve below similar to 1 keV is found to have a major contribution from the persistent emission, which temporary increased during the burst due to a reduction of the opacity of the absorber. We utilized a correlation diagram of the count rates (0.5-1.0 keV vs. 2.0-4.0 keV) to study the effect of photo-ionization during the dips. We found that the correlation can be much better reproduced if we take into account the photo-ionization of the absorber. No partial covering absorption was required, except for the residual flux in the deepest dips.
  • Tadayasu Dotani, Kazumi Asai
    Advances in Space Research 38(12) 2752-2755 2006年  
    We report on the analysis of XMM-Newton archival data of EXO 0748-676. We studied changes of the continuum spectra due to the presence of photo-ionized plasma on the line of sight. We show that the ionization degree of the plasma could change largely during the X-ray bursts and the dips. These changes can significantly modify the soft-band spectrum, which was in fact observed from EXO 0748-676. We discuss the effect of the photo-ionized plasma on the continuum spectra in comparison with a frequently used model such as partial covering absorption. © 2006 COSPAR.
  • T. G. Tsuru, S. Takagi, H. Matsumoto, T. Inui, M. Ozawa, K. Koyama, H. Tsunemi, K. Hayashida, E. Miyata, H. Ozawa, M. Touhiguchi, D. Matsuura, T. Dotani, M. Ozaki, H. Murakami, T. Kohmura, S. Kitamoto, H. Awaki
    European Space Agency, (Special Publication) ESA SP 2(604) 975-976 2006年  査読有り
    We give overview and the current status of the development of the Soft X-ray Imager (SXI) onboard the NeXT satellite. SXI is a back-illuminated supportless CCD (a combination of "back-illuminated CCD" and "supportless CCD") whose imaging area and the supportless region are 42 × 42mm2 and 30mmφ respectively. The goal of the thickness of the depletion layer is 300μm, which enables us to cover the energy range of 0.3 - 25 keV. The evaluation model 'CCD-NeXT1' with the size of 24 × 48mm2 shows no performance change due to the thinning process. The test model of P-channel CCD was confirmed to have high quantum efficiency above 10 keV with an equivalent depletion layer of 300m.
  • Takahashi H, Fukazawa Y, Mizuno T, Hirasawa A, Kitamoto S, Sudoh K, Ogita T, Kubota A, Makishima K, Kokubun M, Itoh T, Parmar A.N, Dotani T, Ebisawa K, Naik S, Takahashi T, Ohnuki K, Yaqoob T, Angelini L, Ueda Y, Yamaoka K, Kotani T, Kawai N, Namiki M, Kohmura T, Negoro H
    European Space Agency, (Special Publication) ESA SP 622(622 SP) 325-332 2006年  査読有り
  • Hiroshi Murakami, Masaki Kitsunezuka, Masanobu Ozaki, Tadayasu Dotani, Takayasu Anada
    Space Telescopes and Instrumentation II: Ultraviolet to Gamma Ray, Pts 1 and 2 6266 Y2662-Y2662 2006年  査読有り
    We report on the origin of the instrumental background of the X-ray CCD camera in space obtained from the Monte Carlo simulation with GEANT4. In the space environment, CCD detects many non-X-ray events, which are produced by the interactions of high-energy particles with the materials surrounding CCD. Most of these events are rejected through the analysis of the charge split pattern, but some are remained to be background. Such instrumental background need to be reduced to achieve higher sensitivity especially above several keV. We simulated the interactions of the cosmic-rays with the CCD housing, and extracted the background events which escaped from the screening process by the charge split pattern. We could reproduce the observed spectral shape of the instrumental background of Suzaku XIS on orbit with the Monte Carlo simulation. This means that the simulation succeeded to duplicate the background production process in space. From the simulation, we found that the major components of the background in the front-side illuminated CCD are the recoil electrons produced by the Compton-scattering of the hard X-ray photons in the CCD. On the other hand, for the backside illuminated CCD, contribution from the low energy electrons becomes dominant, which are produced by the interactions of cosmic-ray protons or hard X-rays with the housing. These results may be important to design the X-ray CCD camera for the future missions, such as NeXT.
  • Hironori Matsumoto, Hiroshi Nakajima, Hiroya Yamaguchi, Takeshi G. Tsuru, Katsuji Koyama, Kiyoshi Hayashida, Ken'ichi Torii, Masaaki Namiki, Hiroshi Tsunemi, Hiroshi Murakami, Masanobu Ozaki, Tadayasu Dotani, Beverly LaMarr, Steven E. Kissel, Mark W. Bautz
    Space Telescopes and Instrumentation II: Ultraviolet to Gamma Ray, Pts 1 and 2 6266 26641-26641 2006年  査読有り
    The X-ray Imaging Spectrometer on the Suzaku satellite consists three front-illuminated (FI) and one backilluminated (BI) CCD cameras. Using ground calibration data taken at Kyoto University and Osaka University, we obtained the energy response of the XIS, which consists of at least six components: 1. a main peak, 2. a sub peak, 3. a triangle component, 4. a Si escape, 5. a Si line, and 6. a constant component. The relation between the energy and the pulse height was also estimated, which is called as a gain. The relation cannot be represented with a single linear function. Then we divided the gain into two parts at the Si edge (1.839 keV) and each part can be described with a single linear function. Thus there is a discontinuity at 1.839 keV in the XIS gain. We have monitored the variation of the gain and energy resolution in orbit by observing the calibration source of Fe-55 illuminating two corners of each CCD.
  • Takeshi Go Tsuru, Shin-Ichiro Takagi, Hironori Matsumoto, Tatsuya Inui, Midori Ozawa, Katsuji Koyama, Hiroshi Tsunemi, Kiyoshi Hayashida, Emi Miyata, Hideki Ozawa, Masakuni Touhiguchi, Daisuke Matsuura, Tadayasu Dotani, Masanobu Ozaki, Hiroshi Murakami, Takayoshi Kohmura, Shunji Kitamoto, Hisamitsu Awaki
    SPACE TELESCOPES AND INSTRUMENTATION II: ULTRAVIOLET TO GAMMA RAY, PTS 1 AND 2 6266 id. 62662I 2006年  
    We give overview and the current status of the development of the Soft X-ray Imager (SXI) onboard the NeXT satellite. SXI is an X-ray CCD camera placed at the focal plane detector of the Soft X-ray Telescopes for Imaging (SXT-I) onboard NeXT. The pixel size and the format of the CCD is 24 x 24 mu m (IA) and 2048 x 2048 x 2 (IA+FS). Currently, we have been developing two types of CCD as candidates for SXI, in parallel. The one is front illumination type CCD with moderate thickness of the depletion layer (70 similar to 100 mu m) as a baseline plan. The other one is the goal plan, in which we develop back illumination type CCD with a thick depletion layer (200 similar to 300 mu m). For the baseline plan, we successfully developed the proto model 'CCD-NeXT1' with the pixel size of 12 mu m x 12 mu m and the CCD size of 24mm. x 48mm. The depletion layer of the CCD has reached 75 similar to 85 mu m. The goal plan is realized by introduction of a new type of CCD T-channel CCD', which collects holes in stead of electrons in the common 'N-channel CCD'. By processing a test model of P-channel CCD we have confirmed high quantum efficiency above 10 keV with an equivalent depletion layer of 300 mu m. A back illumination type of P-channel CCD with a depletion layer of 200 mu m with aluminum coating for optical blocking has been also successfully developed. We have been also developing a thermo-electric cooler (TEC) with the function of the mechanically support of the CCD wafer without standoff insulators, for the purpose of the reduction of thermal input to the CCD through the standoff insulators. We have been considering the sensor housing and the onboard electronics for the CCD clocking, readout and digital processing of the frame date.
  • Terada Y, Mihara T, Nakajima M, Suzuki M, Isobe N, Makishima K, Takahashi H, Enoto T, Kokubun M, Kitaguchi T, Naik S, Dotani T, Nagase F, Tanaka T, Watanabe S, Kitamoto S, Sudoh K, Yoshida A, Nakagawa Y, Sugita S, Kohmura T, Kotani T, Yonetoku D, Angelini L, Cottam J, Mukai K, Kelley R, Soong Y, Bautz M, Kissel S, Doty J
    Astrophysical Journal 648(2 II) 2006年  査読有り
  • H Matsumoto, K Koyama, TG Tsuru, H Nakajima, H Yamaguchi, H Tsunemi, K Hayashida, E Miyata, K Torii, M Namiki, T Dotani, M Ozaki, H Murakami, N Anabuki, S Kitamoto, H Awaki, T Kohmura, H Katayama, A Bamba, MW Bautz, JP Doty, GR Ricker, RF Foster, GY Prigozhin, SE Kissel, BE Burke, AD Pillsbury, B LaMarr
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 541(1-2) 357-364 2005年4月  査読有り
    Astro-E2 is the fifth Japanese X-ray astronomical satellite and will be launched in 2005. The Astro-E2 X-ray Imaging Spectrometers (XISs) consist of four sets of X-ray CCD cameras. Each CCD camera has an imaging area of 1024 x 1024 pixels and covers a region of 18' x 18' on the sky combined with an X-ray Telescope. One XIS will utilize backside illuminated (BI) CCDs, and the other three will be equipped with front-side illuminated (171) CCDs. The BI CCD has a higher quantum efficiency than the FI CCD below 2 keV, while the FI CCD is more sensitive to X-rays above 5 keV than the BI CCD. Both types of the CCDs have nearly the same energy resolution (full-width at half-maximum (FWHM) =similar to 130 eV at 6 keV). All four cameras have a charge injection capability and Fe-55 calibration sources, and we can correct the change of the gain and recover the degradation of the energy resolution due to radiation damage caused by cosmic rays. The sensors are cooled to -90 degrees C to minimize thermal noise in orbit. The low temperature is also helpful to reduce the influence of the radiation damage. (c) 2005 Elsevier B.V. All rights reserved.
  • TG Tsuru, S Takagi, H Matsumoto, T Inui, K Koyama, H Tsunemi, K Hayashida, E Miyata, T Dotani, M Ozaki, H Awaki, S Kitamoto, T Kohmura
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 541(1-2) 392-397 2005年4月  査読有り
    We give an overview, the current status and future plan of the development of the Soft X-ray Imager (SXI) onboard the NeXT (Non-thermal Energy eXploration Telescope) satellite proposed to be launched around 2010. The SXI is a back-illuminated supportless CCD (a combination of "back-illuminated CCD" and "supportless CCD") whose imaging area size and the supportless region are 42 mm x 42 mm and 30 mm phi, respectively. The goal of the depletion layer of the CCD is 300 mu m, which enable us to cover the X-ray energy range of 0.5-20 keV. The first test model of the supportless CCD shows no performance change due to the thinning process of the CCD. We have already started processing the evaluation model 'CCD-NeXT1', which will be completed at the end of 2004. We are also studying the camera system, the focal plane assembly including thermal electric cooler (TEC) and electronics as well as the CCD chip. (c) 2005 Published by Elsevier B.V.
  • Y Ueda, H Murakami, K Yamaoka, T Dotani, K Ebisawa
    ASTROPHYSICAL JOURNAL 609(1) 325-334 2004年7月  査読有り
    We present the results of high-resolution spectroscopy of absorption-line features of highly ionized ions in the X-ray spectra of GX 13+1 with the Chandra HETGS. We have resolved Kalpha absorption lines of hydrogen-like Fe, Mn, Cr, Ca, Ar, S, Si, and Mg ions and helium-like Fe ions. Applying the Voigt profile to these spectral features, we find that the plasma responsible for the absorption lines has a significant blueshift of 460 +/- 70 km s(-1), indicating an outflow velocity of approximate to 400 km s(-1) corrected for the proper motion, with a line-of-sight velocity dispersion of 490(-140)(+110) km s(-1). The plasma is photoionized with an ionization parameter of log xi similar or equal to 4.1-4.7. The inferred mass outflow rate is 0.7 x 10(18) g s(-1) or higher, comparable to the mass accretion rate ( 10(18) g s(-1)) estimated from the continuum spectrum. This indicates that the mass outflow plays a significant role to determine the whole dynamics of the accretion disk. We consider a simplified radiation-driven disk wind model for the origin of the outflow. Our observations are explained by the wind originating from radii of similar to 10(10) - 10(11) cm with a density greater than or similar to10(13) cm(-3).
  • M Takahashi, S Shibata, K Torii, Y Saito, N Kawai, M Hirayama, T Dotani, S Gunji, H Sakurai, IH Stairs, RN Manchester
    ASTROPHYSICAL JOURNAL 554(1) 316-321 2001年6月  査読有り
    We have detected pulsed X-ray emission from the fastest millisecond pulsar known, PSR B1937+21 (P = 1.558 ms), with ASCA. The pulsar is detected as a point source above similar to 1.7 keV, with no indication of nebulosity. The source flux in the 2-10 keV band is found to be f= (3.7 +/- 0.6) x 10(-13) ergs s(-1) cm(-2) which implies an isotropic luminosity of L-X = 4 piD(2)f similar to (5.7 +/- 1.0) x 10(32)(D3.6 kpc)(2) ergs s(-1), cm where D is the distance, and an X-ray efficiency of similar to5 x 10(-4) relative to the spin-down power of the pulsar. The pulsation is found at the period predicted by th radio ephemeris with a very narrow primary peak, the width of which is about 1/16 phase (similar to mus), near the time resolution limit (61 mus) of the observation. The instantaneous flux in the primary peak (1/16 phase interval) is found to be (4.0 +/- 0.8) x 10(-12) ergs s(-1) cm(-2). Although there is an indication for the secondary peak, we consider its statistical significance too low to claim a definite detection. The narrow pulse profile and the detection in the 2-10 keV band imply that the X-ray emission is caused by the magnetospheric particle acceleration. Comparison of X-ray and radio arrival times of pulses indicates, within the timing errors, that the X-ray pulse is coincident with the radio interpulse.
  • K Ebisawa, K Mukai, T Kotani, K Asai, T Dotani, F Nagase, HW Hartmann, J Heise, P Kahabka, A Van Teeseling
    ASTROPHYSICAL JOURNAL 550(2) 1007-1022 2001年4月  査読有り
    We report observation results of the supersoft X-ray sources CAL 87 and RX J0925.7-4758 with the X-ray CCD cameras (Solid-State Imaging Spectrometers [SISs]) on board ASCA. Because of the superior energy resolution of the SIS (DeltaE/E similar to 10% at 1 keV) relative to previous instruments, we could study detailed X-ray spectral structures of these sources for the first time. We have applied theoretical spectral models to CAL 87 and constrained the white dwarf mass and intrinsic luminosity as 0.8-1.2 M. and 4 x 10(37)-1.2 x 10(38) ergs s(-1), respectively. However, we have found the observed luminosity is an order of magnitude smaller than the theoretical estimate, which indicates that the white dwarf is permanently blocked by the accretion disk, and we are observing a scattering emission by a fully ionized accretion disk corona (ADC) whose column density is similar to1.5 x 10(23) cm(-2). Through simulation we have shown that the orbital eclipse can be explained by the ADC model, such that a part of the extended X-ray emission from the ADC is blocked by the companion star filling its Roche lobe. We have found that very high surface gravity and temperature, similar to 10(10) cm s(-2) and similar to 100 eV, respectively, as well as a strong absorption edge at similar to1.02 keV, are required to explain the X-ray energy spectrum of RX J0925.7-4758. These values are only possible for an extremely heavy white dwarf near the Chandrasekhar limit. Although the supersoft source luminosity should be similar to 10(38) ergs s(-1) at the Chandrasekhar limit, the observed luminosity of RX J0925.7-4758 is nearly 2 orders of magnitude smaller, even assuming an extreme distance of similar to 10 kpc. To explain the luminosity discrepancy, we propose a model in which very thick matter that was previously ejected from the system, as a form of jets, intervenes the line of sight and reduces the luminosity significantly because of Thomson scattering.
  • DW Fox, WHG Lewin, RE Rutledge, EH Morgan, R Guerriero, L Bildsten, M van der Klis, J van Paradijs, CB Moore, T Dotani, K Asai
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 321(4) 776-782 2001年3月  査読有り
    We have searched the rising portion of type I X-ray bursts observed from the Rapid Burster with the Rossi X-ray Timing Explorer for the presence of periodicities. The 95 per cent confidence upper limit on the average rms variation of near coherent pulsations with a width of less than or similar to1 Hz (in 60-2048 Hz) during the first second of the bursts is &lt;8.8 per cent. We find a possible detection (&gt; 98 per cent significance) at 306.5 Hz.
  • K Asai, A Yamagishi, A Yamashita, M Watanabe, T Dotani, K Mitsuda, F Nagase, K Ebisawa, S Yamauchi, A Yoshida, S Kitamoto, Hatsukade, I
    NEW CENTURY OF X-RAY ASTRONOMY 251 514-515 2001年  査読有り
    We report on the development of the ISAS Ginga archive. At ISAS, all the Ginga archive and analysis software were originally developed on the main-frame computers. We are installing them to the UNIX environment with minor modification so that all the analysis will become possible in the modern network computing environment. The archive will be made public from ISAS PLAIN Center (Center for Planning and information systems) in near future.
  • P Mahasena, T Dotani, K Mitsuda, H Inoue
    NEW CENTURY OF X-RAY ASTRONOMY 251 382-383 2001年  査読有り
    Absorption lines at similar to4.1 keV have been detected in the type I burst spectra of three sources, including X1608-52. If these lines are interpreted as redshifted resonance line of He-like iron ions, a large gravitational redshift (1 + z similar to 1.7) is required. This imposes a constraint on the neutron star structure. We have observed X1608-52 with ASCA for similar to 10 d in Feb. 2000. We report our systematic search for these lines in the 11 burst spectra obtained with the SIS in FAST mode. Our nondetection of any clear line feature from either one of the 11 bursts leads us to conclude that the absorption line, if it has an equivalent width like that detected by Tenma (120 eV), is intrinsically broad (W-eq greater than or equal to 100 eV), or none of the 11 bursts exhibit the significant absorption features.
  • H Ozawa, F Nagase, Y Ueda, T Dotani, M Ishida
    FROM DARKNESS TO LIGHT: ORIGIN AND EVOLUTION OF YOUNG STELLAR CLUSTERS 243 561-570 2001年  査読有り
    To investigate X-ray emission from protostars and T Tauri stars, we observed two star forming regions, L1630 in Orion and IC348 in Perceus with the X-ray observatory ASCA. From the observation of L1630, we detected X-ray emission from the region where two Class I protostars SSV63E and SSV63W are located (hereafter SSV63E+W). The spectrum of SSV63E+W is well explained by an optically thin thermal plasma model with a high temperature of kT = 5.0 (3.3-7.9) keV and a heavy at sorption of N-H = 1.5 (1.2-1.8) x 10(23) cm(-2), suggesting that it is enbedded deep in the: surrounding dusts. A significantly large X-ray flare was detected from SSV63E+W during the present ASCA observation with the heal: flux of about 9 times that of the quiescent flux. The 0.5-10 keV luminosity of SSV63E+W was about 1 x 10(32) erg s(-1) in the quiescent state. We detected 20 X-ray sources from IC348, 17 of which were identified with the ROSAT X-ray sources. We detected two X-ray flares from the center region of IC348. One of the flare exhibited an intersting feature that the hard X-ray flare in 2.0-7.0 keV band rose faster than the soft X-ray flare in 0.7-2.0 keV band. Combining the Hare light curves with the spectral evolution of the flare, we concluded that the temperature reached to the peak earlier than the emission measure along the progress of the flare. This time lag between the temperature peal: and the peak of emission measure was observed for the first time from T Tauri stars, while such time lags are often observed in solar flares.
  • B Paul, M Kawasaki, T Dotani, F Nagase
    ASTROPHYSICAL JOURNAL 537(1) 319-326 2000年7月  査読有り
    We present new observations of two anomalous X-ray pulsars (AXPs), 4U 0142+61 and 1E 1048.1-5937, made in 1998 with ASCA. The energy spectrum of each of these two AXPs is found to consist of two components, a power-law and a blackbody emission from the neutron star surface. These observations, when compared with earlier ASCA observations in 1994, show remarkable stability in the intensities, spectral shapes, and pulse profiles. However, we find that the spin-down rate in 1E 1048.1-5937 is not constant. In this source, we have clearly identified three epochs with spin-down rates different from each other and from the average value. This has very strong implications for the magnetar hypothesis for AXPs. We also note that the spin-down rate and its variations in 1E 1048.1-5937 are much larger than can normally be produced by an accretion disk with a very low mass accretion rate corresponding to its low X-ray luminosity.
  • K Hayashida, S Kitamoto, E Miyata, H Tsunemi, E Yoshita, T Kohmura, K Mori, K Katayama, H Katayama, M Shouho, M Ohta, T Dotani, M Ozaki, K Koyama, H Awaki, TG Tsuru, G Ricker, MW Bautz, R Foster, S Kissel
    X-RAY OPTICS, INSTRUMENTS, AND MISSIONS III 4012 123-136 2000年  査読有り
    Soft X-ray response of X-ray Imaging Spectrometers (XIS) for the Astro-E satellite is measured with a grating spectrometer system at Osaka. First, relation between incident X-ray energy and output pulse height peak (E-PH relation) is examined with an SX grating. It is found that jump in the E-PH relation around Si-K edge is at most 2.7 eV. Second, quantum efficiency (QE) of the XIS in 0.4-2.2 keV range is measured relatively to the reference CCD of which absolute QE was calibrated with a gas proportional counter. The QE is-fitted with a model in which CCD gate structures are considered. Systematic error on the QE results is estimated by referring an independent measurement. Third, tuning and improvement of the response function is performed. We employ six components to reproduce the response profile of the XIS. In this paper, improvement of one component which is originated in the events absorbed in the channel-stop is presented. Neverthless, Astro-E was lost due to the launch failure. We overview the XIS project in its flight model phase, modified points of the design, problems and solutions etc., in order to be utilized in a possible recovery of the satellite.
  • A. Kubota, Y. Tanaka, K. Makishima, Y. Ueda, H. Inoue, K. Yamaoka, T. Dotani
    Advances in Space Research 25(3-4) 449-452 2000年  査読有り
    We report on the result of the X-ray observation of X-ray Nova Velorum 1993 (GRS 1009-45), made with ASCA on November 10-11, 1993. The energy spectrum was extremely soft and accompanied by a hard tail, characteristics of the Galactic black-hole binaries in the soft state. It is well represented by a two component model consisting of a multicolor disk model or a general relativistic accretion disk model, both describing emission from an optically-thick accretion disk, and a power-law component with a photon index of ∼ 2.5. Spectral analysis of the soft component allows estimation of the mass of the central object. For the optically-estimated distance (&gt 1 kpc) and inclination (&gt 37°), the mass is estimated to be &gt 3.1 M⊙. These results strongly support that the compact object is a black hole. © 2000 COSPAR. Published by Elsevier Science Ltd.
  • M Takahashi, S Shibata, K Torii, Y Saito, N Kawai, M Hirayama, T Dotani, S Gunji, H Sakurai
    PULSAR ASTRONOMY - 2000 AND BEYOND: IAU COLLOQUIUM 177 202 353-354 2000年  査読有り
    We report the first detection of the pulsed X-ray emission from the fastest millisecond pulsar known PSR B1937+21 (P =1.558msec) with ASCA. The pulsar is detected as a point source above similar to 1.7keV, with no nebulosity indicated. The source flux in the energy band 2-10keV is found to be f = 4.3 x 10(-13)erg s(-1) cm(-2), which corresponds to the luminosity of L-x = 4 pi D(2)f approximate to 6.6 x 10(32)(D/3.6kpc)(2) erg s(-1), where D is the distance, and correspond to approximate to 6 x 10(-4) of the rotation power of the pulsar. The pulsation is found at the period predicted by the radio ephemerides with very narrow primary peaks, the width of which is about 1/16 phase approximate to 100 mu s near the time resolution limit (61 mu s) of the observation. The pulsed luminosity within the primary peak (1/16 phase interval) is found to be f(p) = 4.0 x 10(-12)erg s(-1) cm(-2) Although there may be a secondary peak, its statistical significance is too low to identify. Spectra of the whole source region and the primary peak are fitted by power law models to give photon indices of about unity for both.
  • Hayashida K, Kitamoto S, Miyata E, Tsunemi H, Yoshita K, Kohmura T, Mori K, Katayama K, Katayama H, Shouho M, Ohta M, Dotani T, Ozaki M, Koyama K, Awaki H
    Proceedings of SPIE - The International Society for Optical Engineering 4012 123-136 2000年  
    Soft X-ray response of X-ray Imaging Spectrometers (XIS) for the Astro-E satellite is measured with a grating spectrometer system at Osaka. First, relation between incident X-ray energy and output pulse height peak (E-PH relation) is examined with an SX grating. It is found that jump in the E-PH relation around Si-K edge is at most 2.7 eV. Second, quantum efficiency (QE) of the XIS in 0.4-2.2 kev range is measured relatively to the reference CCD of which absolute QE was calibrated with a gas proportional counter. The QE is fitted with a model in which CCD gate structures are considered. Systematic error on the QE results is estimated by referring an independent measurement. Third, tuning and improvement of the response function is performed. We employ six components to reproduce the response profile of the XIS. In this paper, improvement of one component which is originated in the events absorbed in the channel-stop is presented. Neverthless, Astro-E was lost due to the launch failure. We overview the XIS project in its flight model phase, modified points of the design, problems and solutions etc., in order to be utilized in a possible recovery of the satellite.
  • A. Yamashita, T. Dotani, H. Ezuka, M. Kawasaki, K. Takahashi
    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 436(1-2) 68-73 1999年10月21日  
    The performance of the charge coupled devices on-board the ASCA satellite has been traced for five years after the launch. We found the gradual increase of the dark current and the decrease of the charge transfer efficiency. These changes may be explained by charge traps due to the radiation damage. The nature of the radiation damage is investigated in detail using various methods.
  • H. Ozawa, F. Nagase, Y. Ueda, T. Dotani, M. Ishida
    Astrophysical Journal 523(1) L81-L84 1999年9月20日  
    We observed the HH 24-26 region in the L1630 Orion molecular cloud complex with the X-ray observatory ASCA in the 0.5-10 keV band. X-ray emission was detected from the T Tauri star SSV 61 and from the region in which the class I protostars SSV 63E and SSV 63W (hereafter SSV 63E+W) are located. The spectra of both SSV 63E+W and SSV 61 are well explained by an optically thin thermal plasma model. The spectrum of the T Tauri star SSV 61 has a low temperature of kT = 0.9 (0 7-1.2) keV and a moderate absorption of NH = 1.3 (0.9-1.7) x 1022 cm-2, while that of the protostar SSV 63E+W has a high temperature of kT = 5.0 (3.3-7.9) keV and a heavy absorption of NH = 1.5 (1.2-1.8) x 1023 cm-2. The X-ray light curve of SSV 63E+W showed a flare during the observation. The peak flux reached about 9 times the intensity of the quiescent flux. The temperature and the absorption column density do not change conspicuously during the flare. The 0.5-10 keV luminosity of SSV 63E+W was about l x 1032 ergs s-' in the quiescent state. The present detection of hard X-rays from SSV 63E+W is remarkable, since this is the first X-ray detection of a protostar in Orion.
  • Torii K, Tsunemi H, Dotani T, Mitsuda K, Kawai N, Kinugasa K, Saito Y, Shibata S
    ASTROPHYSICAL JOURNAL 523(1) L69-L72 1999年9月20日  査読有り
  • A. Kubota, F. Marshall, K. Makishima, T. Dotani, Y. Ueda, H. Negoro
    Astronomische Nachrichten 320(4-5) 353 1999年  査読有り
  • M. Nishiuchi, K. Koyama, H. Awaki, T. Tsuru, M. Sakano, K. Hamaguchi, H. Murakami, H. Tsunemi, K. Hayashida, S. Kitamoto, E. Miyata, T. Dotani, M. Ozaki, M. Bautz, J. Doty, S. Kissel, R. Foster, G. Ricker
    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 436(1-2) 79-84 1999年  査読有り
  • CS Choi, T Dotani
    ASTRONOMISCHE NACHRICHTEN 320(4-5) 348-348 1999年  査読有り
  • T Dotani
    ASTRONOMISCHE NACHRICHTEN 320(4-5) 215-216 1999年  査読有り
    X-ray properties of the Galactic jet sources are studied using the ASCA data. Two different types are found in the jet sources. One type, represented by the superluminal jet sources GRO J1655-40 and GRS1915+105, includes a rapidly rotating compact star (a black hole or a neutron star) receiving super-critical mass accretion. On the other hand, relatively dim sources, such as GX339-4, 1E1740.7-2942 and GRS 1758-258, may constitute of the other type, which can produce jets at luminosities much lower than the Eddington limit.
  • M Takahashi, S Shibata, S Gunji, H Sakurai, K Torii, Y Saito, N Kawai, T Dotani, M Hirayama
    ASTRONOMISCHE NACHRICHTEN 320(4-5) 340-340 1999年  査読有り
  • Torii K, Tsunemi H, Dotani T, Mitsuda K, Kawai N, Kinugasa K, Saito Y, Shibata S
    ASTRONOMISCHE NACHRICHTEN 320(4-5) 343 1999年  査読有り

MISC

 200
  • 堂谷忠靖, 他LiteBIRD Joint Study Group
    日本天文学会2024年春季年会 V130a 2024年3月  筆頭著者
  • 宮城生成, 堂谷忠靖
    日本天文学会2024年春季年会 W32a 2024年3月  
  • 中嶋大, 森浩二, 冨田洋, 野田博文, 鈴木寛大, 小林翔悟, 萩野浩一, 内田裕之, 米山友景, 田中孝明, 村上弘志, 信川正順, 信川久実子, 内山秀樹, 幸村孝由, 鶴剛, 松本浩典, 小高裕和, 山内誠, 廿日出勇, 山岡和貴, 吉田鉄生, 金丸善朗, 水野恒史, 宮崎啓太郎, 楠康平, 大塚芳徳, 横須晴彦, 米丸若菜, 市川雄大, 中野瑛子, 福田将大, 朝倉一統, 善本真梨那, 大出優一, 佐藤淳矢, 袴田知宏, 青柳美緒, 青木悠馬, 伊藤耶馬斗, 青木大輝, 藤澤海斗, 清水康行, 樋口茉由, 東竜一, 寺農夏樹, 阪本菜月, OKAJIMA Takashi, 石田学, 前田良知, 平賀純子, 尾崎正伸, 堂谷忠靖, 常深博, 林田清
    日本天文学会年会講演予稿集 2024 2024年  
  • 信川久美子, 森浩二, 森浩二, 冨田洋, 中嶋大, 中嶋大, 野田博文, 林田清, 鈴木寛大, 小林翔悟, 内田裕之, 萩野浩一, 青木悠馬, 伊藤耶馬斗, 金丸善朗, 宮崎啓太郎, 楠康平, 大塚芳徳, 横須晴彦, 米丸若菜, 市川雄大, 中野瑛子, 中村彰太郎, 亀井貴光, 朝倉一統, 善本真梨那, 大出優一, 佐藤淳矢, 袴田知宏, 青柳美緒, 角町駿, 土居俊輝, 青木大輝, 藤澤海斗, 清水康行, 畠中大介, 田中孝明, 村上弘志, 信川正順, 内山秀樹, 吉田鉄生, 米山友景, 幸村孝由, 鶴剛, 松本浩典, OKAJIMA Takashi, 石田学, 前田良知, 山内誠, 廿日出勇, 平賀純子, 山岡和貴, 尾崎正伸, 堂谷忠靖, 常深博
    日本天文学会年会講演予稿集 2023 2023年  
  • 野田博文, 森浩二, 森浩二, 冨田洋, 中嶋大, 中嶋大, 林田清, 鈴木寛大, 小林翔悟, 内田裕之, 萩野浩一, 金丸善朗, 宮崎啓太郎, 楠康平, 大塚芳徳, 横須晴彦, 米丸若菜, 市川雄大, 中野瑛子, 中村彰太郎, 亀井貴光, 朝倉一統, 善本真梨那, 大出優一, 佐藤淳矢, 袴田知宏, 青柳美緒, 青木悠馬, 伊藤耶馬斗, 角町駿, 土居俊輝, 青木大輝, 藤澤海斗, 清水康行, 畠中大介, 田中孝明, 村上弘志, 信川正順, 信川久実子, 内山秀樹, 吉田鉄生, 米山友景, 幸村孝由, 鶴剛, 松本浩典, OKAJIMA Takashi, 石田学, 前田良知, 山内誠, 廿日出勇, 平賀純子, 山岡和貴, 尾崎正伸, 堂谷忠靖, 常深博
    日本物理学会講演概要集(CD-ROM) 78(1) 2023年  

共同研究・競争的資金等の研究課題

 15

● 指導学生等の数

 1
  • 年度
    2021年度(FY2021)
    修士課程学生数
    2
    連携大学院制度による学生数
    2
    学術特別研究員数
    1

● 専任大学名

 1
  • 専任大学名
    総合研究大学院大学(SOKENDAI)