Curriculum Vitaes
Profile Information
- Affiliation
- Professor, Graduate School of Science and Engineering, Saitama UniversitySpecially Appointed Professor, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
- Degree
- Master (Science)(the University of Tokyo)Dr. (Science)(the University of Tokyo)
- J-GLOBAL ID
- 200901083726265608
- researchmap Member ID
- 1000161587
- External link
Research Interests
14Research History
4-
Apr, 2007 - Present
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Sep, 2000 - Mar, 2007
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Apr, 1993 - Aug, 2000
Education
3-
Apr, 1990 - Mar, 1993
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Apr, 1987 - Mar, 1990
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- Mar, 1988
Committee Memberships
2-
Nov, 2020 - Present
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Jan, 2009 - May, 2013
Awards
2-
2007
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1999
Papers
193-
Publications of the Astronomical Society of Japan, Sep 30, 2025
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Publications of the Astronomical Society of Japan, Apr 11, 2025 Peer-reviewedLead authorCorresponding authorAbstract 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, Feb 12, 2025 Peer-reviewed
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Publications of the Astronomical Society of Japan, 77(1) L1-L8, Dec 26, 2024 Peer-reviewedAbstract 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, 2024 Peer-reviewedAbstract 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.
289Presentations
101-
MAXI 15 Year Workshop for the Time Domain Astronomy, Dec 10, 2024 Invited
Teaching Experience
67Professional Memberships
2-
1987 - Present
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1987 - Present
Research Projects
16-
Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Jul, 2020 - Mar, 2023
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Apr, 2015 - Mar, 2018
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Apr, 2010 - Mar, 2015
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科学研究費助成事業, 日本学術振興会, 2008 - 2008
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, 2006 - 2008
