Ｘ線分光撮像衛星(XRISM)プロジェクトチーム
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 教授東京大学 大学院理学系研究科 物理学専攻 併任教授青山学院大学 理工学部 客員教授核融合科学研究所 プラズマ量子プロセスユニット 客員教授
- 学位
- 博士(理学)(2008年3月 京都大学)
- 連絡先
- yamaguchi.hiroya
jaxa.jp - 研究者番号
- 00513467
- J-GLOBAL ID
- 201801007525282778
- researchmap会員ID
- B000340695
- 外部リンク
主な研究テーマ・プロジェクト業務
宇宙プラズマ現象、Ｘ線連星、Ia型超新星、超新星残骸、銀河団、原子過程、実験室宇宙物理学
XRISM プロジェクトサイエンティスト
下記の業績リストは不完全です。「論文」は主要論文のみ、「講演・口頭発表等」は最近の招待講演のみリストしています。
座右の銘
努力して運を待て（仁科芳雄） 努力を続けていれば運が向いた時に見逃さないって意味だと思う。運は誰にでも同じ頻度で巡ってくる。それに気づき活かせるかは本人の努力次第。
疑行無名、疑事無功（『戦国策』） 後から迷走しないように達成目標と実施計画を明確にすべしって意味だと思う。目的意識もなく仕事に取り掛かるから、行き当たりばったりになり良い成果が挙がらない。
人、城を頼らば、城、人を捨せん（織田信長） プロジェクトがあれば何とかなると考えていたらプロジェクトが頓挫したときに自力で起き上がれないって意味だと思う。この懸念は2016年に現実のものとなった。
経歴
13-
2026年4月 - 現在
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2025年7月 - 現在
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2025年6月 - 現在
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2025年5月 - 現在
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2023年4月 - 2026年3月
学歴
3-
2003年4月 - 2008年3月
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1999年4月 - 2003年3月
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1996年4月 - 1999年3月
委員歴
9-
2026年4月 - 現在
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2023年4月 - 現在
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2022年4月 - 現在
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2021年5月 - 現在
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2018年10月 - 現在
受賞
9論文
71-
The Astrophysical Journal Letters 1006(2) L61-L61 2026年7月28日 査読有りAbstract Accretion disks in X-ray binaries regulate mass transfer onto compact objects and drive radiative and kinetic feedback to their surroundings. Here we report X-ray spectroscopy of the eclipsing neutron star low-mass X-ray binary AX J1745.6−2901 with XRISM/Resolve. The phase-averaged Fe xxvi Ly α absorption profile exhibits two absorption minima with relative depths that are inconsistent with the theoretical Ly α 1 /Ly α 2 doublet ratio expected from a single velocity component. We demonstrate that this profile is well described by two discrete velocity components: a blueshifted component at v ≃ −160 km s −1 and a redshifted component at v ≃ +590 km s −1 . The significance of the redshifted component is more than 3 σ based on a Monte–Carlo calculation. This velocity structure persists across orbital phases, disfavoring a localized origin such as a bulge or dip. The blueshifted component, well below the outer-disk escape velocity, is consistent with a slow outflow or disk atmosphere. The redshifted absorber can be explained either by infalling gas from a failed wind or by a gravitational redshift, and the present data cannot rule out either possibility. Regardless of its origin, the redshifted component is kinematically separate from the disk atmosphere and outflow. The absence of absorption at intermediate velocities further indicates a genuinely bimodal velocity distribution rather than the two ends of a single continuous flow, offering a new view of the absorbing-gas kinematics.
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Publications of the Astronomical Society of Japan 78(4) 1268-1283 2026年6月8日 査読有り最終著者Abstract We observed the dwarf nova SS Cyg with the X-ray microcalorimeter onboard XRISM both in quiescence and outburst. The quiescence spectrum is explained with a multi-temperature optically thin thermal plasma emission model, characterized by He$\alpha$ and Ly$\alpha$ emission lines of Fe and Ly$\alpha$ lines of Si and S. We discovered redshifts of the Fe He$\alpha$ and Ly$\alpha$ lines that are larger than Ly$\alpha$ lines from Si and S. This indicates that the boundary layer (BL) plasma accretes on to the white dwarf (WD) accompanied by radiative cooling. Its radial accretion velocity estimated from the Fe redshift is 210–280 km s$^{-1}$. Since a 6.4 keV Fe emission line is much narrower ($\sigma _v = 561$ km s$^{-1}$) than that expected from the inner accretion disk rotation, we believe that it is emitted from the surface of the WD. The outburst spectrum can also be explained with the multi-temperature optically thin thermal plasma emission model, but is much softer than in quiescence and is dominated by He$\alpha$ lines. The Fe He$\alpha$ and Ly$\alpha$ lines and the 6.4 keV line are much broader than in quiescence, with Gaussian sigma values of 2390 and 3040 km s$^{-1}$, respectively. This leads us to the idea that the hot plasma is a corona generated through magnetic activity in the optically thick BL that has strong differential rotation, and is anchored to the BL with the magnetic field. This picture is supported by the facts that the plasma follows the universal correlation between the temperature and the emission measure of the stellar flares, and the relation between the X-ray luminosity and the photospheric luminosity of low-mass stars. The fluorescent 6.4 keV line is emitted via fluorescence from the optically thick BL and/or from the equatorial accretion belt formed temporarily during the outburst.
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Publications of the Astronomical Society of Japan 78(3) 1141-1153 2026年5月4日 査読有りAbstract Cygnus X-3, hosting a Wolf–Rayet (WR) star whose dense wind produces various spectral lines due to photoionization by X-rays from a compact object, provides an ideal laboratory for studying wind dynamics and density structure. We measured the orbital modulations of the Fe, Ca, Ar, and S Ly$\alpha$ lines observed with the X-ray microcalorimeter (Resolve) onboard the XRISM, taking account of both emission and absorption lines of the Ly$\alpha$ complexes. The modulations of Doppler shifts of the Fe, Ca, Ar, and S Ly$\alpha$ lines showed amplitudes of $500$ km s$^{-1}$ and phase offsets of 0.04, 0.09, 0.11, and 0.17, respectively, in units of an orbital period ($4.8$ h) relative to the orbital motion of the compact object. This result indicated that H-like Fe most closely follows the compact object’s motion. The line widths ranged from 400 to $1000$ km s$^{-1}$. The intensities of both emission and absorption lines reached their minima around orbital phase 0.0 and their maxima around phase 0.5. The absorption peaks, however, did not align exactly with phase 0.5, suggesting inhomogeneous structures such as an accretion wake and/or a bow shock. We compared the observed modulations with calculations based on a stellar wind model, accelerated by ultraviolet radiation from the WR star. One of the calculations qualitatively reproduced the observed trend that H-like Fe ions were concentrated near the compact object, whereas H-like S was distributed across the binary system, with H-like Ca and Ar showing intermediate spatial distributions. From this comparison, we estimated that the mass-loss rate of the stellar wind was approximately $5 \times 10^{-6}$–$1 \times 10^{-5}\, M_{\odot }$ yr$^{-1}$.
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Nature 651(8107) 909-913 2026年3月25日 査読有り
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Publications of the Astronomical Society of Japan 78(2) 735-744 2026年3月6日 査読有りAbstract The Fe K$\alpha$ fluorescence line at 6.4 keV is a powerful probe of cold matter surrounding X-ray sources and has been widely used in various astrophysical contexts. The X-ray microcalorimeter spectrometer onboard XRISM can measure line shifts with unprecedented precision of ${\sim }$0.2 eV, equivalent to a line-of-sight velocity of ${\sim }$10 km s$^{-1}$. At this level of accuracy, however, several factors that influence the line energy must be carefully considered prior to astrophysical interpretation. One such important factor is the ionization degree, Fe$^{q+}$. The K$\alpha$ line shifts redward by ${\sim }$4 eV as q increases from 0 (neutral) to 8 (Ar-like). Additionally, the accompanying Fe K$\beta$ line at 7.06 keV shifts blueward by ${\sim }$30 eV from $q=0$ to 8. We demonstrate that this effect is actually observable in the XRISM data of the high-mass X-ray binary Centaurus X-3 (Cen X-3). We advocate that the differential energy shift between the K$\alpha$ and K$\beta$ line provides a robust estimate of q by decoupling from other effects that shift the two lines in the same direction. We derived $q \sim 5$ (Sc-like) for the fluorescing matter by comparing the observation with atomic structure calculations of our own and in the literature. By accounting for the derived charge state and the corresponding shift in the rest-frame line energy, we made corrections for this effect and reached a consistent residual shift among the K$\alpha$, K$\beta$, and the optical measurement attributable to the systemic velocity of the system. Consequently, we obtained a new constraint on the location of the cold matter. This ionization effect needs to be assessed in all use cases of the Fe K$\alpha$ line shift beyond Cen X-3, and the proposed metric is generally applicable to all of them.
MISC
9-
NASA/GSFC プレスリリース 2015年4月
書籍等出版物
2講演・口頭発表等
51-
The 16th Asian International Seminar on Atomic and Molecular Physics 2026年10月28日 招待有り
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2nd Plasma Astrophysics School and Workshop (PASW26) 2026年5月12日 招待有り
担当経験のある科目(授業)
5-
物理学ゼミナール (東京大学)
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高エネルギー天文学特論 (東京大学 天文学専攻)
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プラズマ物理学特論 (東京大学)
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宇宙物理学特論 (東京大学)
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JAXA宇宙科学技術講義 (立教大学)
共同研究・競争的資金等の研究課題
9-
日本学術振興会 科学研究費助成事業 2026年4月 - 2030年3月
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核融合科学研究所 所外施設利用共同研究 研究コア提案型共同研究 2025年4月 - 2028年3月
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自然科学研究機構 OPEN MIX LAB 2026年4月 - 2027年3月
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日本学術振興会 科学研究費助成事業 2023年4月 - 2027年3月
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自然科学研究機構 OPEN MIX LAB 2024年4月 - 2026年3月
● 指導学生等の数
1-
年度2026年度(FY2026)博士課程学生数3修士課程学生数5連携大学院制度による学生数4受託指導学生数4技術習得生の数3
● 指導学生の表彰・受賞
4-
指導学生名平田玲央所属大学東京大学受賞内容（タイトル、団体名等）高エネルギー加速器研究機構 測定器開発センター 第15回測定器開発優秀修士論文賞受賞年月日2025/9/17
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指導学生名平田玲央所属大学東京大学受賞内容（タイトル、団体名等）22nd International Conference on Atomic Processes in Plasmas Best Student Poster Award受賞年月日2025/7/24
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指導学生名三浦大貴所属大学東京大学受賞内容（タイトル、団体名等）XRISM Science Workshop for Young Researchers 2024 Best Poster Award受賞年月日2024/9/27
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指導学生名大城勇憲所属大学東京大学受賞内容（タイトル、団体名等）XRISM Science Workshop for Young Researchers 2024 Best Poster Award受賞年月日2024/9/27
● 指導学生の顕著な論文
2-
指導学生名大城勇憲所属大学東京大学著者名, ジャーナル名, 巻号ページ（出版年）Ohshiro et al., ApJL 913, L34, 7 (2021)論文タイトルDiscovery of a Highly Neutronized Ejecta Clump in the Type Ia Supernova Remnant 3C 397DOIhttps://doi.org/10.3847/2041-8213/abff5b
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指導学生名三浦大貴所属大学東京大学著者名, ジャーナル名, 巻号ページ（出版年）The Astrophysical Journal, 968, 95 (2024)論文タイトルPhase-dependent Spectral Shape Changes in the Ultraluminous X-Ray Pulsar NGC 5907 ULX1DOI10.3847/1538-4357/ad4451
● 専任大学名
1-
専任大学名東京大学（University of Tokyo)
