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 教授東京工業大学 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
213-
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.
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Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave 81-81 2024年9月10日
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The Astrophysical Journal Letters 973(1) L25-L25 2024年9月1日Abstract We present an analysis of the first two XRISM/Resolve spectra of the well-known Seyfert-1.5 active galactic nucleus (AGN) in NGC 4151, obtained in 2023 December. Our work focuses on the nature of the narrow Fe K α emission line at 6.4 keV, the strongest and most common X-ray line observed in AGN. The total line is found to consist of three components. Even the narrowest component of the line is resolved with evident Fe K α,1 (6.404 keV) and K α,2 (6.391 keV) contributions in a 2:1 flux ratio, fully consistent with neutral gas with negligible bulk velocity. Subject to the limitations of our models, the narrowest and intermediate-width components are consistent with emission from optically thin gas, suggesting that they arise in a disk atmosphere and/or wind. Modeling the three line components in terms of Keplerian broadening, they are readily associated with (1) the inner wall of the “torus,” (2) the innermost optical “broad-line region” (or “X-ray BLR”), and (3) a region with a radius of r ≃ 100 GM/c 2 that may signal a warp in the accretion disk. Viable alternative explanations of the broadest component include a fast-wind component and/or scattering; however, we find evidence of variability in the narrow Fe K α line complex on timescales consistent with small radii. The best-fit models are statistically superior to simple Voigt functions, but when fit with Voigt profiles the time-averaged lines are consistent with a projected velocity broadening of FWHM . Overall, the resolution and sensitivity of XRISM show that the narrow Fe K line in AGN is an effective probe of all key parts of the accretion flow, as it is currently understood. We discuss the implications of these findings for our understanding of AGN accretion, future studies with XRISM, and X-ray-based black hole mass measurements.
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray 228-228 2024年8月21日
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Cryogenics 138 103795-103795 2024年3月
MISC
200-
Publications of the Astronomical Society of Japan 70(2) 2018年3月1日© The Author(s) 2017. Published by Oxford University Press on behalf of the Astronomical Society of Japan. To search for giant X-ray pulses correlated with the giant radio pulses (GRPs) from the Crab pulsar, we performed a simultaneous observation of the Crab pulsar with the X-ray satellite Hitomi in the 2-300 keV band and the Kashima NICT radio telescope in the 1.4-1.7 GHz band with a net exposure of about 2 ks on 2016 March 25, just before the loss of the Hitomi mission. The timing performance of the Hitomi instruments was confirmed to meet the timing requirement and about 1000 and 100 GRPs were simultaneously observed at the main pulse and inter-pulse phases, respectively, and we found no apparent correlation between the giant radio pulses and the X-ray emission in either the main pulse or inter-pulse phase. All variations are within the 2 σ fluctuations of the X-ray fluxes at the pulse peaks, and the 3 σ upper limits of variations of main pulse or inter-pulse GRPs are 22% or 80% of the peak flux in a 0.20 phase width, respectively, in the 2-300 keV band. The values for main pulse or inter-pulse GRPs become 25% or 110%, respectively, when the phase width is restricted to the 0.03 phase. Among the upper limits from the Hitomi satellite, those in the 4.5-10 keV and 70-300 keV bands are obtained for the first time, and those in other bands are consistent with previous reports. Numerically, the upper limits of the main pulse and inter-pulse GRPs in the 0.20 phase width are about (2.4 and 9.3) × 10−11 erg cm−2, respectively. No significant variability in pulse profiles implies that the GRPs originated from a local place within the magnetosphere. Although the number of photon-emitting particles should temporarily increase to account for the brightening of the radio emission, the results do not statistically rule out variations correlated with the GRPs, because the possible X-ray enhancement may appear due to a >0.02% brightening of the pulse-peak flux under such conditions.
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J. Astron. Telesc. Instrum. Syst. 4(1), 011211 (2018) 4(1) 2018年1月22日The Soft X-ray Imager (SXI) is an imaging spectrometer using charge-coupled<br /> devices (CCDs) aboard the Hitomi X-ray observatory. The SXI sensor has four<br /> CCDs with an imaging area size of $31~{\rm mm} \times 31~{\rm mm}$ arranged in<br /> a $2 \times 2$ array. Combined with the X-ray mirror, the Soft X-ray Telescope,<br /> the SXI detects X-rays between $0.4~{\rm keV}$ and $12~{\rm keV}$ and covers a<br /> $38^{\prime} \times 38^{\prime}$ field-of-view. The CCDs are P-channel<br /> fully-depleted, back-illumination type with a depletion layer thickness of<br /> $200~\mu{\rm m}$. Low operation temperature down to $-120~^\circ{\rm C}$ as<br /> well as charge injection is employed to reduce the charge transfer inefficiency<br /> of the CCDs. The functionality and performance of the SXI are verified in<br /> on-ground tests. The energy resolution measured is $161$-$170~{\rm eV}$ in full<br /> width at half maximum for $5.9~{\rm keV}$ X-rays. In the tests, we found that<br /> the CTI of some regions are significantly higher. A method is developed to<br /> properly treat the position-dependent CTI. Another problem we found is pinholes<br /> in the Al coating on the incident surface of the CCDs for optical light<br /> blocking. The Al thickness of the contamination blocking filter is increased in<br /> order to sufficiently block optical light.
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Proceedings of SPIE - The International Society for Optical Engineering 10699 2018年1月1日© 2018 SPIE. The ASTRO-H mission was designed and developed through an international collaboration of JAXA, NASA, ESA, and the CSA. It was successfully launched on February 17, 2016, and then named Hitomi. During the in-orbit verification phase, the on-board observational instruments functioned as expected. The intricate coolant and refrigeration systems for soft X-ray spectrometer (SXS, a quantum micro-calorimeter) and soft X-ray imager (SXI, an X-ray CCD) also functioned as expected. However, on March 26, 2016, operations were prematurely terminated by a series of abnormal events and mishaps triggered by the attitude control system. These errors led to a fatal event: the loss of the solar panels on the Hitomi mission. The X-ray Astronomy Recovery Mission (or, XARM) is proposed to regain the key scientific advances anticipated by the international collaboration behind Hitomi. XARM will recover this science in the shortest time possible by focusing on one of the main science goals of Hitomi,"Resolving astrophysical problems by precise high-resolution X-ray spectroscopy".1This decision was reached after evaluating the performance of the instruments aboard Hitomi and the mission's initial scientific results, and considering the landscape of planned international X-ray astrophysics missions in 2020's and 2030's. Hitomi opened the door to high-resolution spectroscopy in the X-ray universe. It revealed a number of discrepancies between new observational results and prior theoretical predictions. Yet, the resolution pioneered by Hitomi is also the key to answering these and other fundamental questions. The high spectral resolution realized by XARM will not offer mere refinements; rather, it will enable qualitative leaps in astrophysics and plasma physics. XARM has therefore been given a broad scientific charge: "Revealing material circulation and energy transfer in cosmic plasmas and elucidating evolution of cosmic structures and objects". To fulfill this charge, four categories of science objectives that were defined for Hitomi will also be pursued by XARM; these include (1) Structure formation of the Universe and evolution of clusters of galaxies; (2) Circulation history of baryonic matters in the Universe; (3) Transport and circulation of energy in the Universe; (4) New science with unprecedented high resolution X-ray spectroscopy. In order to achieve these scientific objectives, XARM will carry a 6 × 6 pixelized X-ray micro-calorimeter on the focal plane of an X-ray mirror assembly, and an aligned X-ray CCD camera covering the same energy band and a wider field of view. This paper introduces the science objectives, mission concept, and observing plan of XARM.
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70(2) 2017年7月1日The Crab nebula originated from a core-collapse supernova (SN) explosion<br /> observed in 1054 A.D. When viewed as a supernova remnant (SNR), it has an<br /> anomalously low observed ejecta mass and kinetic energy for an Fe-core collapse<br /> SN. Intensive searches were made for a massive shell that solves this<br /> discrepancy, but none has been detected. An alternative idea is that the SN1054<br /> is an electron-capture (EC) explosion with a lower explosion energy by an order<br /> of magnitude than Fe-core collapse SNe. In the X-rays, imaging searches were<br /> performed for the plasma emission from the shell in the Crab outskirts to set a<br /> stringent upper limit to the X-ray emitting mass. However, the extreme<br /> brightness of the source hampers access to its vicinity. We thus employed<br /> spectroscopic technique using the X-ray micro-calorimeter onboard the Hitomi<br /> satellite. By exploiting its superb energy resolution, we set an upper limit<br /> for emission or absorption features from yet undetected thermal plasma in the<br /> 2-12 keV range. We also re-evaluated the existing Chandra and XMM-Newton data.<br /> By assembling these results, a new upper limit was obtained for the X-ray<br /> plasma mass of <~ 1Mo for a wide range of assumed shell radius, size, and<br /> plasma temperature both in and out of the collisional equilibrium. To compare<br /> with the observation, we further performed hydrodynamic simulations of the Crab<br /> SNR for two SN models (Fe-core versus EC) under two SN environments (uniform<br /> ISM versus progenitor wind). We found that the observed mass limit can be<br /> compatible with both SN models if the SN environment has a low density of <~<br /> 0.03 cm-3 (Fe core) or <~ 0.1 cm-3 (EC) for the uniform density, or a<br /> progenitor wind density somewhat less than that provided by a mass loss rate of<br /> 10-5 Mo yr-1 at 20 km s-1 for the wind environment.
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ASTROPHYSICAL JOURNAL LETTERS 837(1) 2017年3月X-ray spectroscopy with Hitomi was expected to resolve the origin of the faint unidentified E approximate to 3.5 keV emission line reported in several low-resolution studies of various massive systems, such as galaxies and clusters, including the Perseus cluster. We have analyzed the Hitomi first-light observation of the Perseus cluster. The emission line expected for Perseus based on the XMM-Newton signal from the large cluster sample under the dark matter decay scenario is too faint to be detectable in the Hitomi data. However, the previously reported 3.5 keV flux from Perseus was anomalously high compared to the sample-based prediction. We find no unidentified line at the reported high flux level. Taking into account the XMM measurement uncertainties for this region, the inconsistency with Hitomi is at a 99% significance for a broad dark matter line and at 99.7% for a narrow line from the gas. We do not find anomalously high fluxes of the nearby faint K line or the Ar satellite line that were proposed as explanations for the earlier 3.5 keV detections. We do find a hint of a broad excess near the energies of high-n transitions of S XVI (E similar or equal to 3.44 keV rest-frame)-a possible signature of charge exchange in the molecular nebula and another proposed explanation for the unidentified line. While its energy is consistent with XMM pn detections, it is unlikely to explain the MOS signal. A confirmation of this interesting feature has to wait for a more sensitive observation with a future calorimeter experiment.
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SPACE TELESCOPES AND INSTRUMENTATION 2016: OPTICAL, INFRARED, AND MILLIMETER WAVE 9904 2016年 査読有り
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日本物理学会講演概要集 69(2) 37-37 2014年8月22日
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日本物理学会講演概要集 69(1) 129-129 2014年3月5日
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日本物理学会講演概要集 68(1) 134-134 2013年3月26日
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PASJ : publications of the Astronomical Society of Japan 64(5) "112-1"-"112-11" 2012年10月25日
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電子情報通信学会技術研究報告. SANE, 宇宙・航行エレクトロニクス 112(229) 17-22 2012年10月3日Japan Aerospace Exploration Agency (JAXA) has been developing an X-ray astronomy satellite named "ASTRO-H", which will be launched in 2014. This paper provides a summary of the design overview and development status of an electrical power subsystem for ASTRO-H. The subsystem consists of rigid solar array paddles that generate approximately 3500W at the end of life of the system, a power control unit that delivers an unregulated 50V bus power supply, shunt dissipators, battery charge control units, two 100-Ah Li-ion batteries, and a non-explosive actuator controller. Currently, manufacturing and verification tests for the satellite system have been implemented for the launch.
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日本物理学会講演概要集 67(2) 119-119 2012年8月24日
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日本物理学会講演概要集 67(2) 119-119 2012年8月24日
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Astrophysical Journal 753(2) 2012年7月10日We combine data from two all-sky surveys in order to study the connection between the infrared and hard X-ray (>10keV) properties for local active galactic nuclei (AGNs). The Swift Burst Alert Telescope all-sky survey provides an unbiased, flux-limited selection of hard X-ray-detected AGNs. Cross-correlating the 22month hard X-ray survey with the AKARI all-sky survey, we studied 158 AGNs detected by the AKARI instruments. We find a strong correlation for most AGNs between the infrared (9, 18, and 90 μm) and hard X-ray (14-195keV) luminosities, and quantify the correlation for various subsamples of AGNs. Partial correlation analysis confirms the intrinsic correlation after removing the redshift contribution. The correlation for radio galaxies has a slope and normalization identical to that for Seyfert 1 galaxies, implying similar hard X-ray/infrared emission processes in both. In contrast, Compton-thick (CT) sources show a large deficit in the hard X-ray band, because high gas column densities diminish even their hard X-ray luminosities. We propose two photometric diagnostics for source classification: one is an X-ray luminosity versus infrared color diagram, in which type 1 radio-loud AGNs are well isolated from the others in the sample. The other uses the X-ray versus infrared color as a useful redshift-independent indicator for identifying CT AGNs. Importantly, CT AGNs and starburst galaxies in composite systems can also be differentiated in this plane based upon their hard X-ray fluxes and dust temperatures. This diagram may be useful as a new indicator to classify objects in new and upcoming surveys such as WISE and NuSTAR. © 2012. The American Astronomical Society. All rights reserved..
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PASJ : publications of the Astronomical Society of Japan 64(3) "53-1"-"53-12" 2012年6月25日
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日本物理学会講演概要集 67(1) 139-139 2012年3月5日
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SUZAKU 2011: Exploring the X-ray Universe: Suzaku and Beyond. AIP Conference Proceedings 1427 247-248 2012年3月
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SUZAKU 2011: EXPLORING THE X-RAY UNIVERSE: SUZAKU AND BEYOND 1427 253-254 2012年 査読有りWe have developed the back-illuminated X-ray CCD camera (BI-CCD) to observe X-ray in space. The X-ray CCD has a sensitivity not only for in X-ray but also in both Optical and UV light, X-ray CCD has to equip a filter to cut off optical light as well as UV light. The X-ray Imaging Spectrometer (XIS) onboard Suzaku satellite equipped with a thin film (OBF : Optical Blocking Filter) to cut off optical light and UV light. OBF is always in danger tearing by the acousmato or vibration during the launch, and it is difficult to handle on the ground because of its thickness. Instead of OBF, we have newly developed and produced OBL (Optical Blocking Layer), which is directly coating on the X-ray CCD surface.
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Astrophysical Journal 746(2) 2012年 査読有りA systematic study of the synchrotron X-ray emission from supernova remnants (SNRs) has been conducted. We selected a total of 12 SNRs whose synchrotron X-ray spectral parameters are available in the literature with reasonable accuracy, and studied how their luminosities change as a function of radius. It is found that the synchrotron X-ray luminosity tends to drop especially when the SNRs become larger than ~5 pc, despite large scatter. This may be explained by the change of spectral shape caused by the decrease of the synchrotron roll-off energy. A simple evolutionary model of the X-ray luminosity is proposed and is found to reproduce the observed data approximately, with reasonable model parameters. According to the model, the total energy of accelerated electrons is estimated to be 10^(47-48) ergs, which is well below the supernova explosion energy. The maximum energies of accelerated electrons and protons are also discussed.
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日本物理学会講演概要集 66(2) 112-112 2011年8月24日
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日本物理学会講演概要集 65(2) 83-83 2010年8月18日
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日本物理学会講演概要集 65(1) 106-106 2010年3月1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)
