Curriculum Vitaes
Profile Information
- Affiliation
- Professor, Institute of Space and Astronautical Science, High Energy Astrophysics, Japan Aerospace Exploration AgencyProfessor, Graduate Institute for Advanced Studies, Space and Astronautical Science program, The Graduate University for Advanced Studies, SOKENDAIVisiting Professor, School of Science, Institute of Science TokyoVisiting professor, Graduate School of Science and Technology, Kwansei Gakuin University
- Degree
- PhD(The University of Tokyo)
- J-GLOBAL ID
- 200901025041369206
- researchmap Member ID
- 1000144439
My research field is X-ray astronomy, especially observational studies of X-ray binaries including neutron stars or black holes, and development of X-ray CCD cameras for X-ray astronomy satellites.
Research Interests
6Research Areas
2Awards
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1996
Papers
231-
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, 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.
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Publications of the Astronomical Society of Japan, Oct 10, 2024Abstract 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.
Misc.
201-
Publications of the Astronomical Society of Japan, 70(2), Mar 1, 2018
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J. Astron. Telesc. Instrum. Syst. 4(1), 011211 (2018), 4(1), Jan 22, 2018
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Proceedings of SPIE - The International Society for Optical Engineering, 10699, Jan 1, 2018
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110(8) 513-521, Aug, 2017
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Publications of the Astronomical Society of Japan, 70(2), Jul 1, 2017The Crab nebula originated from a core-collapse supernova (SN) explosion<br /> observed in 1054 A.D. When viewed as a supernova remnant (SNR), it has an<br /> anomalously low observed ejecta mass and kinetic energy for an Fe-core collapse<br /> SN. Intensive searches were made for a massive shell that solves this<br /> discrepancy, but none has been detected. An alternative idea is that the SN1054<br /> is an electron-capture (EC) explosion with a lower explosion energy by an order<br /> of magnitude than Fe-core collapse SNe. In the X-rays, imaging searches were<br /> performed for the plasma emission from the shell in the Crab outskirts to set a<br /> stringent upper limit to the X-ray emitting mass. However, the extreme<br /> brightness of the source hampers access to its vicinity. We thus employed<br /> spectroscopic technique using the X-ray micro-calorimeter onboard the Hitomi<br /> satellite. By exploiting its superb energy resolution, we set an upper limit<br /> for emission or absorption features from yet undetected thermal plasma in the<br /> 2-12 keV range. We also re-evaluated the existing Chandra and XMM-Newton data.<br /> By assembling these results, a new upper limit was obtained for the X-ray<br /> plasma mass of <~ 1Mo for a wide range of assumed shell radius, size, and<br /> plasma temperature both in and out of the collisional equilibrium. To compare<br /> with the observation, we further performed hydrodynamic simulations of the Crab<br /> SNR for two SN models (Fe-core versus EC) under two SN environments (uniform<br /> ISM versus progenitor wind). We found that the observed mass limit can be<br /> compatible with both SN models if the SN environment has a low density of <~<br /> 0.03 cm-3 (Fe core) or <~ 0.1 cm-3 (EC) for the uniform density, or a<br /> progenitor wind density somewhat less than that provided by a mass loss rate of<br /> 10-5 Mo yr-1 at 20 km s-1 for the wind environment.
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ASTROPHYSICAL JOURNAL LETTERS, 837(1), Mar, 2017
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Meeting Abstracts of the Physical Society of Japan, 71 503-503, 2016
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SPACE TELESCOPES AND INSTRUMENTATION 2016: OPTICAL, INFRARED, AND MILLIMETER WAVE, 9904, 2016 Peer-reviewed
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Meeting abstracts of the Physical Society of Japan, 69(2) 37-37, Aug 22, 2014
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Meeting abstracts of the Physical Society of Japan, 69(1) 129-129, Mar 5, 2014
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Meeting abstracts of the Physical Society of Japan, 68(2) 111-111, Aug 26, 2013
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Meeting abstracts of the Physical Society of Japan, 68(1) 134-134, Mar 26, 2013
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Publications of the Astronomical Society of Japan, 64(5) "112-1"-"112-11", Oct 25, 2012
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Technical report of IEICE. SANE, 112(229) 17-22, Oct 3, 2012Japan Aerospace Exploration Agency (JAXA) has been developing an X-ray astronomy satellite named "ASTRO-H", which will be launched in 2014. This paper provides a summary of the design overview and development status of an electrical power subsystem for ASTRO-H. The subsystem consists of rigid solar array paddles that generate approximately 3500W at the end of life of the system, a power control unit that delivers an unregulated 50V bus power supply, shunt dissipators, battery charge control units, two 100-Ah Li-ion batteries, and a non-explosive actuator controller. Currently, manufacturing and verification tests for the satellite system have been implemented for the launch.
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Meeting abstracts of the Physical Society of Japan, 67(2) 119-119, Aug 24, 2012
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Meeting abstracts of the Physical Society of Japan, 67(2) 119-119, Aug 24, 2012
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Meeting abstracts of the Physical Society of Japan, 67(2) 182-182, Aug 24, 2012
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Astrophysical Journal, 753(2), Jul 10, 2012
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Publications of the Astronomical Society of Japan, 64(3) "53-1"-"53-12", Jun 25, 2012
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Meeting abstracts of the Physical Society of Japan, 67(1) 139-139, Mar 5, 2012
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SUZAKU 2011: Exploring the X-ray Universe: Suzaku and Beyond. AIP Conference Proceedings, 1427 247-248, Mar, 2012
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SUZAKU 2011: EXPLORING THE X-RAY UNIVERSE: SUZAKU AND BEYOND, 1427 253-254, 2012 Peer-reviewed
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Astrophysical Journal, 746(2), 2012 Peer-reviewed
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Meeting abstracts of the Physical Society of Japan, 66(2) 112-112, Aug 24, 2011
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Meeting abstracts of the Physical Society of Japan, 66(1) 110-110, Mar 3, 2011
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Meeting abstracts of the Physical Society of Japan, 65(2) 83-83, Aug 18, 2010
Professional Memberships
4-
Jan, 2000 - Present
Research Projects
15-
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Japan Society for the Promotion of Science, Apr, 2019 - Mar, 2023
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Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), Japan Society for the Promotion of Science, Jun, 2012 - Mar, 2017
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Apr, 2012 - Mar, 2015
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Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Japan Society for the Promotion of Science, Apr, 2010 - Mar, 2013
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科学研究費助成事業 特別研究員奨励費, 日本学術振興会, 2005 - 2007
● 指導学生等の数
1-
Fiscal Year2021年度(FY2021)Master’s program3Students under Cooperative Graduate School System3JSPS Research Fellowship (Young Scientists)1
● 専任大学名
1-
Affiliation (university)総合研究大学院大学（SOKENDAI)
