Curriculum Vitaes
Profile Information
- Affiliation
- Professor, Institute of Space and Astronautical Science, Department of Astrophysics, Japan Aerospace Exploration Agency
- J-GLOBAL ID
- 201801002962836691
- researchmap Member ID
- B000323419
- External link
Research Interests
2Research Areas
1Research History
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Aug, 2005 - Present
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Apr, 1992 - Jul, 2005
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Aug, 2001 - Dec, 2004
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Apr, 1991 - Mar, 1992
Education
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Apr, 1986 - Mar, 1991
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Apr, 1980 - Mar, 1986
Committee Memberships
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Nov, 2020 - Present
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Apr, 2020 - Present
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Apr, 2020 - Present
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Apr, 2020 - Present
Papers
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Publications of the Astronomical Society of Japan, Oct 7, 2025
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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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International Journal of Modern Physics A, Jan 29, 2025Recent direct measurements of the energy spectra of the charged cosmic ray have revealed unexpected spectral features, most notably the onset of a progressive hardening at few hundreds of GeV/n not only of proton and He spectra but also observable for heavier nuclei. Thus, the study of the spectra behavior of heavy elements may shed light on understanding propagation and acceleration phenomena in our Galaxy. In particular, Fe and Ni provide favorable conditions for observations thanks to the low background contamination from spallation of higher mass elements they are affected by. The CALorimetric Electron Telescope, CALET, has been measuring high-energy cosmic rays on the International Space Station since October 2015. The instrument consists of two layers of segmented plastic scintillators, a 3 radiation length thick tungsten-scintillating fiber imaging calorimeter and a 27 radiation length thick PWO calorimeter. It identifies the charge of individual elements up to Ni and beyond and it measures the energy of cosmic-ray nuclei providing a direct measurement of their spectra. In this contribution, the iron and nickel spectra, resulted after 5 years of data acquisition, are presented in the energy range between 10 and 2000 GeV/n and between 8.8 and 240 GeV/n, respectively. The analysis procedure and the assessment of systematic errors are detailed, in addition to the ratio between the two fluxes. Both spectra show similar shape and energy dependence.
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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.
Misc.
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Meeting Abstracts of the Physical Society of Japan, 63 89-89, 2008
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Meeting abstracts of the Physical Society of Japan, 62(2) 111-111, Aug 21, 2007
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Meeting abstracts of the Physical Society of Japan, 62(2) 107-107, Aug 21, 2007
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Journal of social and information sciences, Nihon Fukushi University, 10 1-9, Mar 30, 2007We report on the current status of our astronomical data sonification project. This project aims to sonify astronomical data, that is, to convert a visual medium into an audio medium for both scientists and the visually impaired. We hope that sonification can lead to a new way of conceptualizing scientific data. The primary sources of the data used for this project come from Japanese satellites dedicated to X-ray astronomy and geophysics. This project is performed in collaboration with Nihon Fukushi University and the Center for Planning and Information Systems (PLAIN center) of the Japan Aerospace Exploration Agency (JAXA) Institute of Space and Astronautical Science (ISAS). Our project began in March 2006. Since this time we have sonified astronomical data sets, including data from X-ray pulsars, and have published these results. In this paper we also discuss future plans for the project, as well as its implications for visually impaired scientists and public.
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Meeting Abstracts of the Physical Society of Japan, 62 106-106, 2007
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IEEE Nuclear Science Symposium Conference Record, 4 2526-2531, 2007 Peer-reviewed
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日本物理学会講演概要集, 61(2) 76-76, Aug 18, 2006
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Meeting Abstracts of the Physical Society of Japan, 61 77-77, 2006
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Meeting Abstracts of the Physical Society of Japan, 61 78-78, 2006
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Astrophysical Journal, 631(2 I) 1062-1071, Oct 1, 2005
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Feb 2, 2004Cal 87 was observed with XMM-Newton in April of 2003. The source shows a rich<br /> emission line spectrum, where lines can be identified if they are red-shifted<br /> by 700-1200 km/s. These lines seem to have been emitted in a wind from the<br /> system. The eclipse is observed to be shifted in phase by 0.03 phi(orb), where<br /> phi(orb) is the phase of the optical light curve.
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PROCEEDINGS OF THE 5TH INTEGRAL WORKSHOP ON THE INTEGRAL UNIVERSE, 552 691-694, 2004
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PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT, (155) 67-70, 2004
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PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT, (155) 67-70, 2004
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ASTRONOMY & ASTROPHYSICS, 411(1) L59-L62, Nov, 2003
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Astrophysical Journal, 588(1 I) 338-343, May 1, 2003
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ASTRONOMISCHE NACHRICHTEN, 324(1-2) 158-158, 2003
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The Astronomical herald, 95(7) 325-333, Jun 20, 2002
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天文月報, 95(4) 194-195, Apr 20, 2002
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ASTRONOMY & ASTROPHYSICS, 385(2) 511-516, Apr, 2002
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Feb 1, 2002AX J1843.8-0352 is a new X-ray SNR identified to the radio complex G28.6-0.1<br /> with the ASCA satellite. Chandra discovered two distinct components from this<br /> SNR: non-thermal and thin thermal X-ray emissions. The non-thermal component is<br /> fitted with a power-law spectrum of photon index 2.0. The morphology is<br /> complicated, but roughly an elliptical shape with a mean diameter of about<br /> 7'-10'. The east to south rims of the ellipse are associated with the<br /> non-thermal radio sources C, F and G (Helfand et al. 1989). The power-law slope<br /> of the radio spectrum can be smoothly connected to that of X-rays with a break<br /> at around the optical-IR band, hence would be due to synchrotron X-rays<br /> accelerated probably to > 1 TeV at the shell of the SNR. The thermal component<br /> near the southeast rim is a thin plasma of about 0.8 keV temperature. It has<br /> the appearance of a "Tadpole" figure with a head of 30"x 40"-size and a tail of<br /> 30"-long. Although this emission is associated with the west part of the radio<br /> source F, the absorption is about two times larger than that of the non-thermal<br /> X-rays, the bulk of the SNR emission. Therefore, together with the peculiar<br /> morphology, whether the thermal plasma is a part of the SNR or a background<br /> object is unclear.
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Astrophysical Journal, 560(2) L147-L150, Oct 20, 2001
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Monthly Notices of the Royal Astronomical Society, 325(3), Mar 22, 2001
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Astrophysical Journal, 547(2 PART 1), 2001
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Astrophysical Journal, 543(2 PART 1), Jun 15, 2000
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Astrophysical Journal, 539(1 PART 1), Mar 16, 2000
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Astrophys.J.535:632,2000, 535(2) 632-643, Jan 3, 2000Studies were made of ASCA spectra of seven ultra-luminous compact X-ray<br /> sources (ULXs) in nearby spiral galaxies; M33 X-8 (Takano et al. 1994), M81 X-6<br /> (Fabbiano 1988b; Kohmura et al. 1994; Uno 1997), IC 342 Source 1 (Okada et al.<br /> 1998), Dwingeloo 1 X-1 (Reynolds et al. 1997), NGC 1313 Source B (Fabbiano &<br /> Trinchieri 1987; Petre et al. 1994), and two sources in NGC 4565 (Mizuno et al.<br /> 1999). With the 0.5--10 keV luminosities in the range 10^{39-40} ergs/s, they<br /> are thought to represent a class of enigmatic X-ray sources often found in<br /> spiral galaxies. For some of them, the ASCA data are newly processed, or the<br /> published spectra are reanalyzed. For others, the published results are quoted.<br /> The ASCA spectra of all these seven sources have been described successfully<br /> with so called multi-color disk blackbody (MCD) emission arising from<br /> optically-thick standard accretion disks around black holes. Except the case of<br /> M33 X-8, the spectra do not exhibit hard tails. For the source luminosities not<br /> to exceed the Eddington limits, the black holes are inferred to have rather<br /> high masses, up to ~100 solar masses. However, the observed innermost disk<br /> temperatures of these objects, Tin = 1.1--1.8 keV, are too high to be<br /> compatible with the required high black-hole masses, as long as the standard<br /> accretion disks around Schwarzschild black holes are assumed. Similarly high<br /> disk temperatures are also observed from two Galactic transients with<br /> superluminal motions, GRO 1655-40 and GRS 1915+105. The issue of unusually high<br /> disk temperature may be explained by the black hole rotation, which makes the<br /> disk get closer to the black hole, and hence hotter.
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Monthly Notices of the Royal Astronomical Society, 301(2), Jul 29, 1998
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ASTROPHYSICAL JOURNAL, 500(2) 1069-1069, Jun, 1998
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Meeting abstracts of the Physical Society of Japan, 53(1) 84-84, Mar 10, 1998
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Meeting abstracts of the Physical Society of Japan, 52(2) 78-78, Sep 2, 1997
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PROCEEDINGS OF THE FOURTH COMPTON SYMPOSIUM, PTS 1 AND 2, (410) 844-848, 1997
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Monthly Notices of the Royal Astronomical Society, 288(4), 1997
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Meeting Abstracts of the Physical Society of Japan, 52 78-78, 1997
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Astrophysical Journal, 485(2 PART II), Jan 1, 1997
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Astrophysical Journal, 489(1 PART I) 272-283, Jan 1, 1997
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The Astronomical herald, 89(8) 341-346, Aug, 1996
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The Astronomical herald, 89(7) 290-295, Jul, 1996
Presentations
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第1回 SPARC Japan セミナー2020 「研究データ公開：フルオープンと制限公開の境界線」, Oct 2, 2020 Invited
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JpGU-AGU Joint Meeting 2020:Virtual ユニオンセッション U-12 「地球惑星科学の進むべき道10 ビッグデータとオープンサイエンス」, Jul 15, 2020 Invited
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20 Years of Chandra Science Symposium
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The 29th annual international Astronomical Data Analysis Software & Systems (ADASS)
Professional Memberships
1Research Projects
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科学研究費助成事業, 日本学術振興会, Apr, 2024 - Mar, 2027
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Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Japan Society for the Promotion of Science, Apr, 2016 - Mar, 2019
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Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Japan Society for the Promotion of Science, 2009 - 2011
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Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Japan Society for the Promotion of Science, 2007 - 2009
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Grants-in-Aid for Scientific Research Grant-in-Aid for international Scientific Research, Japan Society for the Promotion of Science, 1992 - 1994
