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
231-
The Astrophysical Journal Letters 982(1) L5-L5 2025年3月12日Abstract 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 2025年2月12日
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Publications of the Astronomical Society of Japan 2024年12月26日Abstract 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 2024年12月11日Abstract 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 2024年10月10日Abstract 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-
日本物理学会講演概要集 65(1) 106-106 2010年3月1日
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日本物理学会講演概要集 65(1) 102-102 2010年3月1日
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宇宙航空研究開発機構特別資料: = JAXA Special Publication: The Energetic Cosmos; from Suzaku to ASTRO-H (9) 414-415 2010年2月26日著者人数: 25人(含チーム1)資料番号: AA0064574159レポート番号: JAXA-SP-09-008E
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Proceedings of SPIE - The International Society for Optical Engineering 7732 2010年
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Journal of the Korean Physical Society 54(6,Pt.1) 2552-2565 2009年
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日本物理学会講演概要集 63(2) 89-89 2008年8月25日
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Publ.Astron.Soc.Jap.60:S11-S24,2008 2008年3月5日One 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.
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PASJ : publications of the Astronomical Society of Japan 60(1) S57-S68 2008年2月20日The accretion-powered pulsar Her X-1 was observed with Suzaku twice in its main-on state, on 2005 October 5-6 and 2006 March 29-30, for a net exposure of 30.5 ks and 34.4 ks, respectively. In the 2005 and 2006 observations, the source was detected at an average 10-30 keV intensity of 290 mCrab and 230 mCrab, respectively. The intrinsic pulse period was measured on both occasions at 1.23776 s by HXD-PIN, after barycentric and binary corrections. The pulse phase-averaged spectra in the energy range above 10 keV were well fitted by the "Negative and Positive power-law times EXponential" (NPEX) model, multiplied by a fundamental cyclotron resonance scattering feature at similar to 36 keV, which appears very significantly in the HXD-PIN data. The resonance profiles were successfully reproduced by a Lorentzian-type scattering cross section, rather than by a Gaussian-type alternative. The pulse phase-averaged HXD-GSO data, covering 50-120 keV, are featureless. However, in a differential spectrum between the pulse-decay phase and off-pulse phase, the second-harmonic cyclotron resonance was detected in the GSO data at similar to 73 keV, with a depth of 1.6(-0.7)(+0.9) This makes Her X-1 a 6th pulsar with established second-harmonic resonance. The implications of these results are briefly discussed.
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Proceedings of SPIE - The International Society for Optical Engineering 7011 2008年 査読有り
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日本物理学会講演概要集 62(2) 106-106 2007年8月21日
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Publications of the Astronomical Society of Japan 59(1 SPEC. ISS.) 2007年4月8日
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日本物理学会講演概要集 62(1) 94-94 2007年2月28日
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PASJ : publications of the Astronomical Society of Japan 59(1) S185-S198 2007年1月31日
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ASTROPHYSICAL JOURNAL 651(1) 615-616 2006年11月
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日本物理学会講演概要集 61(2) 76-76 2006年8月18日
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Proceedings of SPIE - The International Society for Optical Engineering 6266 II 2006年 査読有り
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HIGH-ENERGY DETECTORS IN ASTRONOMY 5501 296-303 2004年 査読有り
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Proceedings of SPIE - The International Society for Optical Engineering 5488(PART 2) 549-560 2004年 査読有り
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PASJ : publications of the Astronomical Society of Japan 55(4) 827-840 2003年8月25日
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
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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
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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)
