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
1-
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.
-
Nature, 638(8050) 365-369, Feb 12, 2025
-
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.
-
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.
-
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-
Meeting abstracts of the Physical Society of Japan, 65(1) 106-106, Mar 1, 2010
-
Meeting abstracts of the Physical Society of Japan, 65(1) 102-102, Mar 1, 2010
-
(9) 414-415, Feb 26, 2010The 3rd Suzaku international Conference "Energetic Cosmos : from Suzaku to ASTRO-H" (June 29-July 2, 2009. Grand Park Otaru Hotel), Otaru, Hokkaido JapanWe report the XIS calibration on the data taken with the 2 x 2 mode and window option and the current status of the XIS Non-X-ray Background (NXB) database. The 2 x 2 mode and window option are useful for bright source observations to avoid telemetry saturation and event pile-up. The NXB database provides the best-estimated NXB spectrum for any specific observations obtained with the standard mode (Normal-Clock with no Window or Burst and 5 x 5(sub -) (3 x 3(sub -) Editing mode). The data taken with the 2 x 2 mode in the "SCI-off" era are fully calibrated, and there is no practical difference from those taken with the standard mode. A calibration study for the data taken with the 2 x 2 mode in the "SCI-on" era is on-going. The calibration for the data taken with the window option was significantly improved in the HEASOFT 6.6.2 released at 2009 April 1st. In the comparison with the standard-mode data, the gain difference around 6 keV becomes less than 10 and 15 eV in XIS 0,3 and XIS 1, respectively. We have been updating the NXB database every half a year. There is no drastic change in the light curves, but steady approximately 4 % year(sup -1) level increase and decrease are found in those of XIS 0,3 and XIS 1, respectively.Meeting sponsors: The University of Tokyo, The Institute of Physical and Chemical Research, The Japan Society for the Promotion of ScienceNumber of authors: 25
-
Proceedings of SPIE - The International Society for Optical Engineering, 7732, 2010
-
Journal of the Korean Physical Society, 54(6,Pt.1) 2552-2565, 2009
-
Publications of the Astronomical Society of Japan, 61(SUPPL. 1), Oct 6, 2008
-
Publications of the Astronomical Society of Japan, 61(SUPPL. 1), Sep 22, 2008
-
Meeting abstracts of the Physical Society of Japan, 63(2) 89-89, Aug 25, 2008
-
Meeting abstracts of the Physical Society of Japan, 63(2) 89-89, Aug 25, 2008
-
Publ.Astron.Soc.Jap.60:S11-S24,2008, Mar 5, 2008One of the advantages of the X-ray Imaging Spectrometer (XIS) system on board<br /> Suzaku is its low and stable non-X-ray background (NXB). In order to make the<br /> best use of this advantage, modeling the NXB spectra with high accuracy is<br /> important to subtract them from the spectra of on-source observations. We<br /> construct an NXB database by collecting XIS events when the dark Earth covers<br /> the XIS FOV. The total exposure time of the NXB data is about 785 ks for each<br /> XIS. It is found that the count rate of the NXB anti-correlates with the<br /> cut-off-rigidity and correlates with the count rate of the PIN upper<br /> discriminator (PIN-UD) in Hard X-ray Detector on board Suzaku. We thus model<br /> the NXB spectrum for a given on-source observation by employing either of these<br /> parameters and obtain a better reproducibility of the NXB for the model with<br /> PIN-UD than that with the cut-off-rigidity. The reproducibility of the NXB<br /> model with PIN-UD is 4.55-5.63% for each XIS NXB in the 1-7 keV band and<br /> 2.79-4.36% for each XIS NXB in the 5-12 keV band for each 5 ks exposure of the<br /> NXB data. This NXB reproducibility is much smaller than the spatial fluctuation<br /> of the cosmic X-ray background in the 1-7 keV band, and is almost comparable to<br /> that in the 5-12 keV band.
-
Publications of the Astronomical Society of Japan, 60(1) S57-S68, Feb 20, 2008
-
Proceedings of SPIE - The International Society for Optical Engineering, 7011, 2008 Peer-reviewed
-
Meeting abstracts of the Physical Society of Japan, 62(2) 106-106, Aug 21, 2007
-
Publications of the Astronomical Society of Japan, 59(1 SPEC. ISS.), Apr 8, 2007
-
Meeting abstracts of the Physical Society of Japan, 62(1) 94-94, Feb 28, 2007
-
Publications of the Astronomical Society of Japan, 59(1) S185-S198, Jan 31, 2007
-
Meeting Abstracts of the Physical Society of Japan, 62 106-106, 2007
-
ASTROPHYSICAL JOURNAL, 651(1) 615-616, Nov, 2006
-
Meeting abstracts of the Physical Society of Japan, 61(2) 76-76, Aug 18, 2006
-
日本物理学会講演概要集, 61(1) 93-93, Mar 4, 2006
-
Meeting Abstracts of the Physical Society of Japan, 61 77-77, 2006
-
Proceedings of SPIE - The International Society for Optical Engineering, 6266 II, 2006 Peer-reviewed
-
HIGH-ENERGY DETECTORS IN ASTRONOMY, 5501 296-303, 2004 Peer-reviewed
-
Proceedings of SPIE - The International Society for Optical Engineering, 5488(PART 2) 549-560, 2004 Peer-reviewed
-
Publications of the Astronomical Society of Japan, 55(4) 827-840, Aug 25, 2003
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
-
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
-
Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Apr, 2012 - Mar, 2015
-
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Japan Society for the Promotion of Science, Apr, 2010 - Mar, 2013
-
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)
