Profile Information
- Affiliation
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
- Degree
- 博士(理学)(Mar, 2008, 京都大学)
- Researcher number
- 00513467
- J-GLOBAL ID
- 201801007525282778
- researchmap Member ID
- B000340695
- External link
主な研究テーマ・プロジェクト業務
宇宙プラズマ現象、Ia型超新星、超新星残骸、銀河団、Ｘ線連星、実験室宇宙物理学
XRISM 副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。
Research Interests
5Research Areas
2Research History
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Apr, 2023 - Present
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Apr, 2019 - Present
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Sep, 2018 - Present
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Jul, 2017 - Aug, 2018
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Aug, 2013 - Aug, 2018
Education
3-
Apr, 2003 - Mar, 2008
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Apr, 1999 - Mar, 2003
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Apr, 1996 - Mar, 1999
Committee Memberships
8-
Apr, 2023 - Present
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Apr, 2022 - Present
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Jun, 2021 - Present
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May, 2021 - Present
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Oct, 2020 - Present
Awards
9Papers
56-
The Astrophysical Journal, 982(2) 190-190, Mar 28, 2025Abstract Measuring shock velocities is crucial for understanding the energy transfer processes at the shock fronts of supernova remnants (SNRs), including acceleration of cosmic rays. Here we present shock velocity measurements on the SNR N132D, based on the thermal properties of the shock-heated interstellar medium. We apply a self-consistent model developed in our previous work to X-ray data from deep Chandra observations with an effective exposure of ∼900 ks. In our model, both temperature and ionization relaxation processes in postshock plasmas are simultaneously calculated, so that we can trace back to the initial condition of the shock-heated plasma to constrain the shock velocity. We reveal that the shock velocity ranges from 800 to 1500 km s−1 with moderate azimuthal dependence. Although our measurement is consistent with the velocity determined by independent proper motion measurements in the south rim regions, a large discrepancy between the two measurements (up to a factor of 4) is found in the north rim regions. This implies that a substantial amount of the kinetic energy has been transferred to the nonthermal component through highly efficient particle acceleration. Our results are qualitatively consistent with the gamma-ray observations of this SNR.
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The Astrophysical Journal Letters, 982(1) L5-L5, Mar 12, 2025Abstract We present XRISM Resolve observations of the core of the hot, relaxed galaxy cluster Abell 2029 (A2029). We find that the line-of-sight bulk velocity of the intracluster medium (ICM) within the central 180 kpc is at rest with respect to the brightest cluster galaxy, with a 3σ upper limit of ∣v bulk∣ < 100 km s−1. We robustly measure the field-integrated ICM velocity dispersion to be σ v = 169 ± 10 km s−1, obtaining similar results for both single-temperature and two-temperature plasma models to account for the cluster cool core. This result, if ascribed to isotropic turbulence, implies a subsonic ICM with Mach number and a nonthermal pressure fraction of 2.6 ± 0.3%. The turbulent velocity is similar to what was measured in the core of the Perseus cluster by Hitomi, but here in a more massive cluster with an ICM temperature of 7 keV, the limit on the nonthermal pressure fraction is even more stringent. Our result is consistent with expectations from simulations of relaxed clusters, but it is on the low end of the predicted distribution, indicating that A2029 is an exceptionally relaxed cluster with no significant impacts from either a recent minor merger or active galactic nucleus activity.
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Nature, 638(8050) 365-369, Feb 12, 2025
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Publications of the Astronomical Society of Japan, 77(1) L1-L8, Dec 26, 2024Abstract 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, Dec 11, 2024Abstract 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.
Misc.
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NASA/GSFC press release, Apr, 2015
Books and Other Publications
1Presentations
37Teaching Experience
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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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Advanced Plasma Physics (The University of Tokyo)
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Advanced Space Physics and Astronomy (The University of Tokyo)
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JAXA宇宙科学技術講義 (立教大学)
Professional Memberships
2Research Projects
4-
Grants-in-Aid for Scientific Research (A), Japan Society for the Promotion of Science, Apr, 2022 - Mar, 2025
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科研費 基盤研究(A), 日本学術振興会, Apr, 2020 - Mar, 2023
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科研費 基盤研究(A), 日本学術振興会, Apr, 2019 - Mar, 2022
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NIFS General Collaboration Project, National Institute for Fusion Science, Apr, 2019 - Mar, 2020
● 指導学生の顕著な論文
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Student nameYuken OhshiroStudent affiliation東京大学Author(s), journal, volume number, pagination (year of publication)Ohshiro et al., ApJL 913, L34, 7 (2021)TitleDiscovery of a Highly Neutronized Ejecta Clump in the Type Ia Supernova Remnant 3C 397DOIhttps://doi.org/10.3847/2041-8213/abff5b
● 専任大学名
1-
Affiliation (university)東京大学（University of Tokyo)
