研究者業績
基本情報
- 所属
- 国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 宇宙物理学研究系 教授総合研究大学院大学 先端学術院 宇宙科学コース 教授東京科学大学 理学院物理学系物理学コース 特定教授関西学院大学 大学院理工学研究科 客員教授
- 学位
- 理学博士(東京大学)
- J-GLOBAL ID
- 200901025041369206
- researchmap会員ID
- 1000144439
専門はX線天文学。特に、中性子星やブラックホールを含むX線連星の観測的研究および衛星搭載X線CCDカメラの開発研究。
受賞
1-
1996年
論文
246-
The Astrophysical Journal 998(2) 210-210 2026年2月11日Abstract The XRISM/Resolve microcalorimeter directly measured the gas velocities in the core of the Virgo Cluster, the closest example of active galactic nucleus (AGN) feedback in a cluster. This proximity allows us to resolve the kinematic impact of feedback on scales down to 5 kpc. Our spectral analysis reveals a high velocity dispersion of km s −1 near the AGN, which steeply declines to ∼60 km s −1 between 5 and 25 kpc in the northwest direction. The observed line-of-sight bulk velocity in all regions is broadly consistent with the central galaxy, M87, with a mild trend toward blueshifted motions at larger radii. Systematic uncertainties have been carefully assessed and do not affect the measurements. The central velocities, if attributed entirely to isotropic turbulence, correspond to a transonic intracluster medium at sub-6 kpc scales with 3D Mach number and a nonthermal pressure fraction of . Simple models of weak shocks and sound waves and calculations assuming isotropic turbulence both support the hypothesis that the velocity field reflects a mix of shock-driven expansion and turbulence. Compared to other clusters observed by XRISM to date, M87’s central region stands out as the most kinematically disturbed, exhibiting both the highest velocity dispersion and the largest 3D Mach number, concentrated at the smallest physical scales.
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Nature 650(8101) 309-313 2026年1月28日
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NATURE ASTRONOMY 10(1) 2026年1月
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The Astrophysical Journal Letters 994(1) L28-L28 2025年11月18日Abstract We stack 3.75 Ms of early XRISM Resolve observations of 10 galaxy clusters to search for unidentified spectral lines in the E = 2.5–15 keV band (rest frame), including the E = 3.5 keV line reported in earlier low spectral resolution studies of cluster samples. Such an emission line may originate from the decay of the sterile neutrino, a warm dark matter (DM) candidate. No unidentified lines are detected in our stacked cluster spectrum, with the 3 σ upper limit on the m s ∼ 7.1 keV DM particle decay rate (which corresponds to an E = 3.55 keV emission line) of Γ ∼ 1.0 × 10 −27 s −1 . This upper limit is 3–4 times lower than the one derived by Hitomi Collaboration from the Perseus observation but still 5 times higher than the XMM-Newton detection reported by E. Bulbul et al. in the stacked cluster sample. XRISM Resolve, with its high spectral resolution but small field of view, may reach the sensitivity needed to test the XMM-Newton cluster sample detection by combining several years worth of future cluster observations.
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Publications of the Astronomical Society of Japan 77(6) 1278-1289 2025年11月17日Abstract We present results from XRISM/Resolve observations of the core of the galaxy cluster Abell 2319, focusing on its kinematic properties. The intracluster medium (ICM) exhibits temperatures of approximately 8 keV across the core, with a prominent cold front and a high-temperature region ($\sim$11 keV) in the north-west. The average gas velocity in the $3{^{\prime } } \times$ $4 {^{\prime } }$ region around the brightest cluster galaxy (BCG) covered by two Resolve pointings is consistent with that of the BCG to within 40 km s$^{-1}$ and we found modest average velocity dispersion of 230–250 km s$^{-1}$. On the other hand, spatially resolved spectroscopy reveals interesting variations. A blueshift of up to $\sim$230 km s$^{-1}$ is observed around the east edge of the cold front, where the gas with the lowest specific entropy is found. The region further south inside the cold front shows only a small velocity difference from the BCG; however, its velocity dispersion is enhanced to $\sim$400 km s$^{-1}$, implying the development of turbulence. These characteristics indicate that we are observing sloshing motion with some inclination angle following BCG and that gas phases with different specific entropy participate in sloshing with their own velocities, as expected from simulations. No significant evidence for a high-redshift ICM component associated with the subcluster Abell 2319B was found in the region covered by the current Resolve pointings. These results highlight the importance of sloshing and turbulence in shaping the internal structure of Abell 2319. Further deep observations are necessary to better understand the mixing and turbulent processes within the cluster.
MISC
203-
X-RAY AND GAMMA-RAY TELESCOPES AND INSTRUMENTS FOR ASTRONOMY, PTS 1 AND 2 4851 1071-1079 2003年
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PASJ : publications of the Astronomical Society of Japan 54(3) 373-386 2002年6月25日
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X-RAY AND GAMMA-RAY INSTRUMENTATION FOR ASTRONOMY XII 4497 158-165 2002年
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PASJ : publications of the Astronomical Society of Japan 53(6) 1171-1177 2001年12月25日
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Astrophysical Journal, Supplement Series 131 571-591 2000年12月1日
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ASTROPHYSICAL JOURNAL 543(2) L145-L148 2000年11月
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Astrophys.J. 539 (2000) 413; Erratum-ibid. 651 (2006) 615-616 2000年3月16日We have discovered errors in the calculation of some of the Einstein<br /> coefficients in Table 5 and some plots in Figure 3. Due to the errors, the<br /> square-root section of the curves of growth of Fe xxvi Ka and Kb, and Ni xxviii<br /> Ka in Figure 3 were a few times underestimated. We correct Table 5 and re-plot<br /> Figure 3 together with the unaffected curves. The program to calculate the<br /> corrected curves of growth is available at<br /> http://www.hp.phys.titech.ac.jp/kotani/cog/index.html
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Astrophys.J.535:632,2000 535(2) 632-643 2000年1月3日Studies 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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BROAD BAND X-RAY SPECTRA OF COSMIC SOURCES 25(3-4) 669-672 2000年
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BROAD BAND X-RAY SPECTRA OF COSMIC SOURCES 25(3-4) 391-394 2000年
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BROAD BAND X-RAY SPECTRA OF COSMIC SOURCES 25(3-4) 375-378 2000年
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Astronomy and Astrophysics 343 197-201 1999年12月1日
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PASJ : publications of the Astronomical Society of Japan 51(4) 519-524 1999年
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PASJ : publications of the Astronomical Society of Japan 50(6) 667-673 1998年12月1日
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PASJ : publications of the Astronomical Society of Japan 50(6) 611-619 1998年12月1日
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PASJ : publications of the Astronomical Society of Japan 50(2) 249-255 1998年4月25日
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X-RAY TIMING AND COSMIC GAMMA RAY BURSTS 22(7) 961-964 1998年
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Proceedings of SPIE - The International Society for Optical Engineering 3445 278-290 1998年 査読有り
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Publications of the Astronomical Society of Japan 49(6) 653-658 1997年12月1日
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Astronomy and Astrophysics 322 857-867 1997年6月20日
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東海大学紀要. 理学部 32 125-133 1997年3月An eclipsing X-ray binary pulsar, Centaurus X-3 was observed with the ASCA satellite on Februarly 1-2 1995,during a non-eclipse phase of 0.11 to 0.81. We found that the X-ray pulse profiles observed with ASCA change in shape and amplitude according with the orbital phase. The three K_α lines at 6.4,6.67,and 6.96 keV from neutral, He-like, and H-like ironions, respectively, could be resolved in the observed energy spectrum owing to the high energy resolution of the CCD cameras on board ASCA. We found that the intensity of the 6.4 keV line changes with pulse phase. Distribution and ionization degree of matter surrounding the neutron star are discussed based on this result.
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PROCEEDINGS OF THE FOURTH COMPTON SYMPOSIUM, PTS 1 AND 2 (410) 844-848 1997年
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Astrophysical Journal 489(1) 272-283 1997年
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IEEE Transactions on Nuclear Science 44(3) 847-853 1997年
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1996 IEEE NUCLEAR SCIENCE SYMPOSIUM - CONFERENCE RECORD, VOLS 1-3 1 261-262 1997年
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ASTROPHYSICAL JOURNAL 437(1) 449-457 1994年12月
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ASTROPHYSICAL JOURNAL 436(2) 871-874 1994年12月
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ASTROPHYSICAL JOURNAL 427(1) 400-405 1994年5月
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ASTROPHYSICAL JOURNAL 422(2) 799-809 1994年2月
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ASTROPHYSICAL JOURNAL 421(2) 738-752 1994年2月
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 44(6) 633-640 1992年
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 43(4) L43-L50 1991年
所属学協会
4-
2000年1月 - 現在
共同研究・競争的資金等の研究課題
15-
日本学術振興会 科学研究費助成事業 基盤研究(C) 2019年4月 - 2023年3月
-
日本学術振興会 科学研究費助成事業 新学術領域研究(研究領域提案型) 2012年6月 - 2017年3月
-
日本学術振興会 科学研究費助成事業 2012年4月 - 2015年3月
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日本学術振興会 科学研究費助成事業 基盤研究(B) 2010年4月 - 2013年3月
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日本学術振興会 科学研究費助成事業 特別研究員奨励費 2005年 - 2007年
● 指導学生等の数
1-
年度2021年度(FY2021)修士課程学生数2連携大学院制度による学生数2学術特別研究員数1
● 専任大学名
1-
専任大学名総合研究大学院大学(SOKENDAI)