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
252-
The Astrophysical Journal 1003(2) 156-156 2026年5月22日Abstract The supermassive binary system, η Carinae, is experiencing enormous wind-driven mass loss at a rate unparalleled in the rest of the Galaxy. Their wind–wind collision (WWC) continuously produces shock heated, X-ray-emitting plasmas. The XRISM X-ray observatory observed the system in 2023 and 2024 when the X-ray emission began to increase toward periastron passage in 2025. This paper reports unprecedentedly high-resolution X-ray spectra in the Fe K α band between 6.2 and 7.1 keV, obtained with the Resolve X-ray microcalorimeter. The hydrogen-like (Ly α ) and helium-like (He α ) lines reveal three velocity components. Two of them are broadened with maximum velocities of 2000–3000 km s −1 , likely originating from the postshock companion wind. The other is relatively narrow, with a Gaussian broadening of only ∼290 km s −1 in 1 σ , which may originate from the postshock companion wind at the WWC stagnation point or penetrating the primary wind. The Fe fluorescent lines exhibit a moderate blueshift and broadening with velocities at 100–200 km s −1 , consistent with the primary wind’s velocity field. The spectra also confirm a Compton shoulder of the He α line complex for the first time. Both fluorescing and scattering spectral profiles indicate that the binary system is seen from the companion side during these observations. The flux ratio of the Compton-scattering emission to the fluorescent line suggests substantial hydrogen depletion of the primary wind, expected from CNO-cycled hydrogen nuclear fusion gas.
-
Publications of the Astronomical Society of Japan 2026年4月9日Abstract We report the presence of a highly ionized absorber in the transient, eclipsing low-mass X-ray binary AX J1745.6-2901, observed from 2024 February 26–29 with XRISM’s Resolve and Xtend instruments. During a soft/high state without dips, Resolve’s high spectral resolution ($E/\Delta E \sim 1000$, full width at half-maximum) revealed narrow velocity widths ($\sigma \sim 110~{\rm km~s^{-1 } }$) for Fe xxvi and Ni xxviii lines, even with low photon statistics. These widths are consistent with binary orbital motion. The observed modest blueshift velocity (${\sim }160~{\rm km~s^{-1 } }$) indicates that the absorber is located sufficiently far from the neutron star (${>}10^9$ cm), so that gravitational redshift effects are not dominant. On the other hand, broad-band spectral analysis using a photoionized plasma model applied to the Xtend data constrains the absorber to lie within a radius of ${\lesssim }10^{9.5}$ cm, as inferred from the upper limits of the best-fitting ionization parameter ($\log \xi \sim 4.4$) and the large column density (${\sim }1.6\times 10^{24}~{\rm cm^{-2 } }$). At this distance, the observed outward velocity of the absorber is about an order of magnitude smaller than the escape velocity from the neutron star.
-
Astronomy & Astrophysics 708 A130-A130 2026年4月1日Context. The origin of accretion-disc winds remains disputed. High-inclination, dipping, neutron-star (NS) low-mass X-ray binaries (LMXBs) provide an excellent testbed for studying the launching mechanism of such winds due to them persistently accreting and showing a nearly ubiquitous presence of highly ionised plasmas. Aims. We aim to establish or rule out the presence of a wind in the high-inclination LMXB 4U 1624−49, for which a highly ionised plasma has been repeatedly observed in X-ray spectra by Chandra and XMM-Newton, and a thermal–radiative pressure wind is expected. Methods. We leveraged the exquisite spectral resolution of the X-ray Imaging and Spectroscopy Mission (XRISM) to perform phase-resolved spectroscopy of the full binary orbit to characterise the highly ionised plasma at all phases except during absorption dips. Results. An outflow is clearly detected via phase-resolved spectroscopy of the source with XRISM Resolve. Based on analysis of the radial-velocity curve, we determine an average velocity of ∼200−320 km s −1 and a column density above 10 23 cm −2 . The line profiles are generally narrow, spanning ∼50−100 km s −1 , depending on the orbital phase; this points to a low-velocity sheer or turbulence of the highly ionised outflow and a potential increase of turbulence as the absorption dip is approached, likely due to turbulent mixing. Conclusions. The line profiles, together with the derived launching radius and wind velocity, are consistent with a wind being launched from the outskirts of the disc and without stratification, pointing to a thermal-radiative pressure origin.
-
Nature Astronomy 2026年3月31日
-
Nature 651(8107) 909-913 2026年3月25日
MISC
207-
日本物理学会講演概要集 65(2) 83-83 2010年8月18日
-
日本物理学会講演概要集 65(1) 106-106 2010年3月1日
-
日本物理学会講演概要集 65(1) 102-102 2010年3月1日
-
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
-
Proceedings of SPIE - The International Society for Optical Engineering 7732 2010年
-
Journal of the Korean Physical Society 54(6,Pt.1) 2552-2565 2009年
-
日本物理学会講演概要集 63(2) 89-89 2008年8月25日
-
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.
-
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.
-
Proceedings of SPIE - The International Society for Optical Engineering 7011 2008年 査読有り
-
日本物理学会講演概要集 62(2) 106-106 2007年8月21日
-
Publications of the Astronomical Society of Japan 59(1 SPEC. ISS.) 2007年4月8日
-
日本物理学会講演概要集 62(1) 94-94 2007年2月28日
-
PASJ : publications of the Astronomical Society of Japan 59(1) S185-S198 2007年1月31日
-
ASTROPHYSICAL JOURNAL 651(1) 615-616 2006年11月
-
日本物理学会講演概要集 61(2) 76-76 2006年8月18日
-
Proceedings of SPIE - The International Society for Optical Engineering 6266 II 2006年 査読有り
-
HIGH-ENERGY DETECTORS IN ASTRONOMY 5501 296-303 2004年 査読有り
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
-
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
-
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)
