研究者業績
基本情報
- 所属
- 埼玉大学大学院 理工学研究科 教授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 特任教授
- 学位
- 修士(理学)(東京大学)博士(理学)(東京大学)
- J-GLOBAL ID
- 200901083726265608
- researchmap会員ID
- 1000161587
- 外部リンク
研究キーワード
14経歴
4-
2007年4月 - 現在
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2017年4月 - 2025年3月
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2000年9月 - 2007年3月
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1993年4月 - 2000年8月
学歴
3-
1990年4月 - 1993年3月
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1987年4月 - 1990年3月
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- 1988年3月
委員歴
2-
2020年11月 - 現在
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2009年1月 - 2013年5月
受賞
2-
2007年
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1999年
論文
193-
Publications of the Astronomical Society of Japan 2025年9月30日
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Publications of the Astronomical Society of Japan 2025年4月11日 査読有り筆頭著者責任著者Abstract The X-Ray Imaging and Spectroscopy Mission (XRISM) is a joint mission between the Japan Aerospace Exploration Agency (JAXA) and the National Aeronautics and Space Administration (NASA) in collaboration with the European Space Agency (ESA). In addition to the three space agencies, universities and research institutes from Japan, North America, and Europe have joined to contribute to developing satellite and onboard instruments, data-processing software, and the scientific observation program. XRISM is the successor to the ASTRO-H (Hitomi) mission, which ended prematurely in 2016. Its primary science goal is to examine astrophysical problems with precise, high-resolution X-ray spectroscopy. XRISM promises to discover new horizons in X-ray astronomy. It carries a 6 × 6 pixelized X-ray microcalorimeter on the focal plane of an X-ray mirror assembly (Resolve) and a co-aligned X-ray CCD camera (Xtend) that covers the same energy band over a large field of view. XRISM utilizes the Hitomi heritage, but all designs were reviewed. The attitude and orbit control system was improved in hardware and software. The spacecraft was launched from the JAXA Tanegashima Space Center on 2023 September 6 (UTC). During the in-orbit commissioning phase, the onboard components were activated. Although the gate valve protecting the Resolve sensor with a thin beryllium X-ray entrance window was not yet opened, scientific observation started in 2024 February with the planned performance verification observation program. The nominal observation program commenced with the following guest observation program beginning in 2024 September.
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Nature 638(8050) 365-369 2025年2月12日 査読有り
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Publications of the Astronomical Society of Japan 77(1) L1-L8 2024年12月26日 査読有りAbstract Sagittarius A East is a supernova remnant with a unique surrounding environment, as it is located in the immediate vicinity of the supermassive black hole at the Galactic center, Sagittarius A$^{*}$. The X-ray emission of the remnant is suspected to show features of overionized plasma, which would require peculiar evolutionary paths. We report on the first observation of Sagittarius A East with the X-Ray Imaging and Spectroscopy Mission (XRISM). Equipped with a combination of a high-resolution microcalorimeter spectrometer and a large field-of-view CCD imager, we for the first time resolved the Fe xxv K-shell lines into fine structure lines and measured the forbidden-to-resonance intensity ratio to be $1.39 \pm 0.12$, which strongly suggests the presence of overionized plasma. We obtained a reliable constraint on the ionization temperature just before the transition into the overionization state, of $\gt\! 4\:$keV. The recombination timescale was constrained to be $\lt\! 8 \times 10^{11} \:$cm$^{-3}\:$s. The small velocity dispersion of $109 \pm 6\:$km$\:$s$^{-1}$ indicates a low Fe ion temperature $\lt\! 8\:$keV and a small expansion velocity $\lt\! 200\:$km$\:$s$^{-1}$. The high initial ionization temperature and small recombination timescale suggest that either rapid cooling of the plasma via adiabatic expansion from dense circumstellar material or intense photoionization by Sagittarius A$^{*}$ in the past may have triggered the overionization.
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The Astrophysical Journal Letters 977(2) L34-L34 2024年12月11日 査読有りAbstract The X-ray binary system Cygnus X-3 (4U 2030+40, V1521 Cyg) is luminous but enigmatic owing to the high intervening absorption. High-resolution X-ray spectroscopy uniquely probes the dynamics of the photoionized gas in the system. In this Letter, we report on an observation of Cyg X-3 with the XRISM/Resolve spectrometer, which provides unprecedented spectral resolution and sensitivity in the 2–10 keV band. We detect multiple kinematic and ionization components in absorption and emission whose superposition leads to complex line profiles, including strong P Cygni profiles on resonance lines. The prominent Fe xxv Heα and Fe xxvi Lyα emission complexes are clearly resolved into their characteristic fine-structure transitions. Self-consistent photoionization modeling allows us to disentangle the absorption and emission components and measure the Doppler velocity of these components as a function of binary orbital phase. We find a significantly higher velocity amplitude for the emission lines than for the absorption lines. The absorption lines generally appear blueshifted by ∼−500–600 km s−1. We show that the wind decomposes naturally into a relatively smooth and large-scale component, perhaps associated with the background wind itself, plus a turbulent, denser structure located close to the compact object in its orbit.
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Geophysical Research Letters 51(20) 2024年10月26日 査読有りAbstract We present X‐ray observations of the upper atmospheric density disturbance caused by the explosive eruption of the Hunga Tonga‐Hunga Ha'apai (HTHH) volcano on 15 January 2022. From 14 January to 16 January, the Chinese X‐ray astronomy satellite, Insight‐HXMT, was observing the supernova remnant Cassiopeia A. The X‐ray data obtained during Earth's atmospheric occultations allowed us to measure neutral densities in the altitude range of 90–150 km. The density profiles above 110 km altitude obtained before the major eruption are in reasonable agreement with expectations by both GAIA and NRLMSIS 2.0 models. In contrast, after the HTHH eruption, a severe density depletion was found up to 1,000 km away from the epicenter, and a relatively weak depletion extending up to km for over 8 hr after the eruption. In addition, density profiles showed wavy structures with a typical length scale of either 20 km (vertical) or 1,000 km (horizontal). This may be caused by Lamb waves or gravity waves triggered by the volcanic eruption.
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Publications of the Astronomical Society of Japan 76(6) 1186-1201 2024年10月10日 査読有りAbstract We present an initial analysis of the X-Ray Imaging and Spectroscopy Mission (XRISM) first-light observation of the supernova remnant (SNR) N 132D in the Large Magellanic Cloud. The Resolve microcalorimeter has obtained the first high-resolution spectrum in the 1.6–10 keV band, which contains K-shell emission lines of Si, S, Ar, Ca, and Fe. We find that the Si and S lines are relatively narrow, with a broadening represented by a Gaussian-like velocity dispersion of $\sigma _v \sim 450$ km s$^{-1}$. However, the Fe He$\alpha$ lines are substantially broadened with $\sigma _v \sim 1670$ km s$^{-1}$. This broadening can be explained by a combination of the thermal Doppler effect due to the high ion temperature and the kinematic Doppler effect due to the SNR expansion. Assuming that the Fe He$\alpha$ emission originates predominantly from the supernova ejecta, we estimate the reverse shock velocity at the time when the bulk of the Fe ejecta were shock heated to be $-1000 \lesssim V_{\rm rs}$ (km s$^{-1}$) $\lesssim 3300$ (in the observer frame). We also find that Fe Ly$\alpha$ emission is redshifted with a bulk velocity of $\sim 890$ km s$^{-1}$, substantially larger than the radial velocity of the local interstellar medium surrounding N 132D. These results demonstrate that high-resolution X-ray spectroscopy is capable of providing constraints on the evolutionary stage, geometry, and velocity distribution of SNRs.
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Astrophysical Journal Letters 973(1) 2024年9月1日 査読有り
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray 224-224 2024年8月21日
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray 235-235 2024年8月21日
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray 61-61 2024年8月21日
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray 60-60 2024年8月21日
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray 52-52 2024年8月21日 筆頭著者責任著者
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The Astrophysical Journal 2023年8月1日 査読有り
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Journal of Geophysical Research: Space Physics 128(2) 2023年2月21日 査読有り
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Nature Astronomy 6(12) 1364-1375 2022年12月12日 査読有り
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Nature Astronomy 7(1) 80-87 2022年12月8日 査読有り
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Journal of Low Temperature Physics 209(5-6) 1088-1096 2022年9月19日 査読有り
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Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray 2022年8月31日 査読有り
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Publications of the Astronomical Society of Japan 2022年6月2日 査読有り
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Monthly Notices of the Royal Astronomical Society 512(4) 5995-6006 2022年4月19日 査読有りAbstract The far infrared counterpart of hot spot D, the terminal hot spot of the eastern jet hosted by the radio galaxy Cygnus A, is detected with Herschel Aperture photometery of the source performed in 5 photometric bands covering the wavelength range of 70–350 μm. After removing the contamination from another nearby hot spot, E, the far-infrared intensity of hot spot D is derived as 83 ± 13 and 269 ± 66 mJy at 160 and 350 μm, respectively. Since the far-infrared spectrum of the object smoothly connects to the radio one, the far-infrared emission is attributed to the synchrotron radiation from the radio-emitting electron population. The radio-to-near-infrared spectrum is confirmed to exhibit a far-infrared break feature at the frequency of $\nu _\mathrm{br}=2.0^{+1.2}_{-0.8} \times 10^{12}$ Hz. The change in energy index at the break (Δα = 0.5) is interpreted as the impact of radiative cooling on an electron distribution sustained by continuous injection from diffusive shock acceleration. By ascribing the derived break to this cooling break, the magnetic field, B, in the hot spot is determined as a function of its radius, R within a uniform one-zone model combined with the strong relativistic shock condition. An independent B-R constraint is obtained by assuming the X-ray spectrum is wholly due to synchrotron-self-Compton emission. By combining these conditions, the two parameters are tightly determined as B = 120–150 μG and R = 1.3–1.6 kpc. A further investigation into the two conditions indicates the observed X-ray flux is highly dominated by the synchrotron-self-Compton emission.
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International Journal of Modern Physics D, 31(2) id 2230001 2022年1月 査読有り招待有り筆頭著者
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Journal of Astronomical Telescopes, Instruments, and Systems 7(03) 2021年7月1日 査読有り
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Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray 2020年12月13日
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Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray 2020年12月13日 筆頭著者責任著者
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Journal of Geophysical Research: Space Physics 126(4) 2020年11月24日 査読有り
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The Astrophysical Journal 899(1) 17-17 2020年8月1日 査読有り
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The Astrophysical Journal 891(2) 126-126 2020年3月10日 査読有り
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The Astrophysical Journal 889(2) 2020年2月1日
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Proceedings of the International Astronomical Union 29-36 2020年
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Proceedings of SPIE - The International Society for Optical Engineering 11444 2020年
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Proceedings of SPIE - The International Society for Optical Engineering 11444 2020年
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The Astrophysical Journal 884(2) L58-L58 2019年10月21日 査読有り
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Publications of the Astronomical Society of Japan 71(4) 2019年8月1日
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Journal of Low Temperature Physics 1-7 2018年3月8日 査読有り
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Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 2018年1月1日
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Publications of the Astronomical Society of Japan 70(2) 2018年 査読有り
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Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 011218 2018年1月1日 査読有り
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JOURNAL OF ASTRONOMICAL TELESCOPES INSTRUMENTS AND SYSTEMS 4(1) 2018年1月 査読有り
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Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 2018年1月1日 査読有り
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Journal of Astronomical Telescopes, Instruments, and Systems 4(2) 2018年 査読有り
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Journal of Astronomical Telescopes, Instruments, and Systems vol.4 011217 2018年1月 査読有り
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The Astrophysical Journal 850(2) 193-193 2017年12月1日 査読有り
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 69(3) 2017年6月 査読有り
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Monthly Notices of the Royal Astronomical Society 466(4) 4558-4567 2017年5月1日
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ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 229(2) 2017年4月 査読有り
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JOURNAL OF LOW TEMPERATURE PHYSICS 184(1-2) 498-504 2016年7月 査読有り
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 68 2016年6月 査読有りWe report on the T-90 and T-50 duration distributions and their relations with spectral hardness using 1464 gamma-ray bursts (GRBs), which were observed by the Suzaku Wide-band All-sky Monitor (WAM) from 2005 August 4 to 2010 December 29. The duration distribution is clearly bimodal in three energy ranges (50-120, 120-250, and 250-550 keV), but is unclear in the 550-5000 keV range, probably because of the limited sample size. The WAM durations decrease with energy according to a power-law index of -0.058(-0.034, +0.033). The hardness-duration relation reveals the presence of short-hard and long-soft GRBs. The short: long event ratio tends to be higher with increasing energy. We compared the WAM distribution with ones measured by eight other GRB instruments. The WAM T-90 distribution is very similar to those of INTEGRAL/SPI-ACS and Granat/PHEBUS, and least likely to match the Swift/BAT distribution. The WAM short: long event ratio (0.25:0.75) is much different from Swift/BAT (0.08:0.92), but is almost the same as CGRO/BATSE (0.25:0.75). To explain this difference for BAT, we examined three effects: BAT trigger types, energy dependence of the duration, and detection sensitivity diffe
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Publications of the Astronomical Society of Japan 68(SP1) S10-S10 2016年6月 査読有り
MISC
289講演・口頭発表等
101担当経験のある科目(授業)
67共同研究・競争的資金等の研究課題
16-
日本学術振興会 科学研究費助成事業 2020年7月 - 2023年3月
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日本学術振興会 科学研究費助成事業 2015年4月 - 2018年3月
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日本学術振興会 科学研究費助成事業 2010年4月 - 2015年3月
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日本学術振興会 科学研究費助成事業 2008年 - 2008年
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日本学術振興会 科学研究費助成事業 2006年 - 2008年