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 助教総合研究大学院大学 宇宙観測科学講座 飛翔体天文学分野 助教
- 学位
- 博士(理学)(1998年3月 京都大学)修士(理学)(1995年3月 京都大学)
- 研究者番号
- 80342624
- ORCID ID
https://orcid.org/0000-0002-9099-5755- J-GLOBAL ID
- 202001011170717781
- researchmap会員ID
- R000011919
論文
214-
Astroparticle Physics 158 102944-102944 2024年6月 査読有り
-
Publications of the Astronomical Society of Japan 2024年2月9日 査読有りAbstract We develop a new deconvolution method to recover the precise Crab Nebula image taken by the Hitomi HXT, suppressing the artifact due to the bright Crab pulsar. We extend the Richardson–Lucy method, introducing two components corresponding to the nebula and pulsar with regularization for smoothness and flux, respectively, and performing simultaneous deconvolution of multi-pulse-phase images. The structures, including the torus and jets, seen in the deconvolved nebula image at the lowest energy band of 3.6–15 keV appear consistent with those identified in the high-resolution Chandra X-ray image. Above 15 keV, we confirm NuSTAR’s findings that the nebula size decreases in higher energy bands. We find that the north-east side of the nebula is fainter in higher energy bands. Our deconvolution method is applicable for any telescope images of faint diffuse objects containing a bright point source.
-
Monthly Notices of the Royal Astronomical Society 527(3) 7121-7135 2023年11月27日 査読有りABSTRACT We analyse the XMM–Newton RGS spectra of Wolf–Rayet (WR) 140, an archetype long-period eccentric WR+O colliding wind binary. We evaluate the spectra of O and Fe emission lines and find that the plasmas emitting these lines have the largest approaching velocities with the largest velocity dispersions between phases 0.935 and 0.968 where the inferior conjunction of the O star occurs. This behaviour is the same as that of the Ne line-emission plasma presented in our previous paper. We perform a diagnosis of the electron number density ne using the He-like triplet lines of O and Ne-like Fe–L lines. The former results in a conservative upper limit of ne ≲ 1010–1012 cm−3 on the O line-emission site, while the latter cannot impose any constraint on the Fe line-emission site because of statistical limitations. We calculate the line-of-sight velocity and its dispersion separately along the shock cone. By comparing the observed and calculated line-of-sight velocities, we update the distance of the Ne line-emission site from the stagnation point. By assuming radiative cooling of the Ne line-emission plasma using the observed temperature and the local stellar wind density, we estimate that the line-emission site extends along the shock cone by at most ±58 per cent (phase 0.816) of the distance from the stagnation point. In this framework, the excess of the observed velocity dispersion over that calculated is ascribed to turbulence in the hot-shocked plasma at earlier orbital phases of 0.816, 0.912, and 0.935, with the largest velocity dispersion of 340-630 km s−1 at phase 0.912.
-
Optics for EUV, X-Ray, and Gamma-Ray Astronomy XI 2023年10月5日
-
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 1048 167975-167975 2023年3月 査読有り
MISC
37-
大気球シンポジウム: 2022年度 = Balloon Symposium: 2022 2022年11月大気球シンポジウム 2022年度（2022年11月7-8日. ハイブリッド開催（JAXA相模原キャンパス& オンライン)) Balloon Symposium 2022 (November 7-8, 2022. Hybrid(in-person & online) Conference (Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan 著者人数: 87名 資料番号: SA6000177030 レポート番号: isas22-sbs-030
-
第32回宇宙構造・材料シンポジウム：講演集録 = Proceedings of 32nd Symposium on Aerospace Structure and Materials 2016年12月第32回宇宙構造・材料シンポジウム（2016年12月9日. 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)), 相模原市, 神奈川県資料番号: SA6000087012レポート番号: A11
-
Acta Polytechnica 53(1) 803-806 2013年A review of the Astro-H mission is presented here on behalf of the Astro-H collaboration. The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). One of the main uniquenesses of the ASTRO-H satellite is the high sensitivity and imaging capability of the wide energy band from 0.3 keV to 600 keV. The coverage is achieved by combining the four instruments of the SXS, SXI, HXI, and SGD. The other main uniqueness is a spectroscopic capability not only for a point-like source but also for an extended source with high spectral resolution of ΔE~4÷7eV of SXS. Using the unique powers of these instruments, ASTRO-H will address unresolved issues in high-energy astrophysics. © Czech Technical University in Prague, 2013.
-
Dynamics & Design Conference 2011 "706-1"-"706-8" 2011年9月5日In the present paper, vibration properties of mirror foils installed in a hard X-ray telescope (HXT) on-board a satellite were investigated. Vibration tests and FEM analysis of mirror foils installed in the part model of HXT were conducted. From the experimental results, it appeared that the mirror had resonant frequencies at 64, 73 and 11 OHz. The modal shapes of 64 and 73Hz showed that the maximum amplitude appeared at edges of the foil. On the other hand, vibration amplitude became maximum at the center in the modal shape of 11 OHz. Experimental results of frequency responses of these modes agreed well with analytical results except around 64Hz. It is considered that the resonant mode of 64Hz was strongly affected by nonlinear characteristics of friction constraint between the foils and HXT housing.
-
Journal of the Physical Society of Japan 78 133-137 2009年6月16日We assume that the energy source in the Galactic Center is the black hole Sgr A, which becomes active when a star is captured in a rate of ∼ 10-5yr-1. During the active phase relativistic protons with a characteristic energy ∼ 6 x 1052erg per capture are ejected. We suppose that the annihilation of secondary positrons produced by proton-proton collisions is observed as the 511 keV line flux from the Galactic bulge. Though these positron are generated with relatively high energies (> 30 MeV), our model satisfy the criterion derived by Beacom and Yiiksel based on the COMPTEL data in the range 1-30 MeV. From our estimations it follows also that a flux of gamma-ray de-excitation lines ∼ 2.5 x 10-5 ph cm-2 s-1 in the range below 8 MeV is produced by the relativistic protons in the Galactic center. A specific line is the one at 1.809 MeV from radioactivity of 26 Al. The predicted quasi-stationary flux of the 26Al 1.809 MeV line from the 1° x 1 central region is < 10-6 ph cm-2 s-1. We conclude also the the thermal 6.5 keV X-ray flux and the non-thermal hard X-ray flux in the range 14-40 keV observed by SUZAKU is emitted by subrelativistic protons produced by accretion processes. © 2009 The Physical Society of Japan.
-
2008 IEEE/LEOS INTERNATIONAL CONFERENCE ON OPTICAL MEMS AND NANOPHOTONICS 104-105 2008年 査読有りX-ray reflectivity of an ultra light-weight X-ray optic using MEMS technologies was measured in two different energies (0.28 keV and 1.49 keV). The obtained reflectivities can be understood by considering the mirror surface structures.
-
PASJ : publications of the Astronomical Society of Japan 57(1) 245-257 2005年2月25日
-
ASTRONOMISCHE NACHRICHTEN 324(1-2) 158-158 2003年We have carried out a deep X-ray observation on a typical Galactic plane<br /> region with the Chandra ACIS-I instrument with unprecedented sensitivity and<br /> spatial resolution, and detected 274 unidentified X-ray point sources in the<br /> \~500 arcmin2 region. In order to identify these new X-ray sources, we have<br /> carried out a near infrared follow-up observation using ESO/NTT infrared camera<br /> on 2002/7/28 and 2002/7/29. Initial results are briefly reported.
-
Astrophysical Journal Supplement Series 138(1) 19-34 2002年1月1日The ASCA satellite made 107 pointing observations on a 5 x 5 deg^2 region<br /> around the center of our Milky Way Galaxy (the Galactic Center) from 1993 to<br /> 1999. In the X-ray images of the 0.7--3 keV or 3--10 keV bands, we found 52<br /> point sources and a dozen diffuse sources. All the point sources are uniformly<br /> fitted with an absorbed power-law model. For selected bright sources, Sgr A*,<br /> AX J1745.6-2901, A 1742-294, SLX 1744-300, GRO J1744-28, SLX 1737-282, GRS<br /> 1734-292, AX J1749.2-2725, KS 1741-293, GRS 1741.9-2853, and an unusual flare<br /> source XTE J1739-302, we present further detailed spectral and timing analyses,<br /> and discuss their nature.<br /> The dozen extended X-ray sources comprise radio supernova remnants, giant<br /> molecular clouds, and some new discoveries. Most show emission lines from<br /> either highly ionized atoms or low-ionized irons.<br /> The X-ray spectra were fitted with either a thin thermal or power-law model.<br /> This paper summarizes the results and provides the ASCA X-ray source catalogue<br /> in the Galactic Center region.
-
SCIENCE 293(5535) 1633-1635 2001年8月The Galactic plane is a strong emitter of hard x-rays (2 to 10 kiloelectron volts), and the emission forms a narrow continuous ridge. The currently known hard x-ray sources are far too few to explain the ridge x-ray emission, and the fundamental question of whether the ridge emission is ultimately resolved into numerous dimmer discrete sources or truly diffuse emission has not yet been settled. In order to obtain a decisive answer, using the Chandra X-ray Observatory, we carried out the deepest hard x-ray survey of a Galactic plane region that is devoid of known x-ray point sources. We detected at least 36 new hard x-ray point sources in addition to strong diffuse emission within a 17' by 17' field of view. The surface density of the point sources is comparable to that at high Galactic latitudes after the effects of Galactic absorption are considered. Therefore, most of these point sources are probably extragalactic, presumably active galaxies seen through the Galactic disk. The Galactic ridge hard x-ray emission is diffuse, which indicates omnipresence within the Galactic plane of a hot plasma, the energy density of which is more than one order of magnitude higher than any other substance in the interstellar space.
-
NEW CENTURY OF X-RAY ASTRONOMY 251 310-311 2001年We present a Chandra observation of the giant molecular cloud Sgr B2 at the Galactic center region. We detected diffuse X-ray emission and 17 point sources in the cloud. The diffuse emission shows a strong 6.4 keV line from neutral iron, and is prominent on the Galactic center side. These features support the "X-ray Reflection Nebula" hypothesis, in which the cloud is irradiated by an external X-ray source in the direction of the Galactic center and emits fluorescent and scattered X-rays.
-
NEW CENTURY OF X-RAY ASTRONOMY 251 314-315 2001年Front the ASCA X-ray point-source list in the Galactic center 5 x 5 degree(2) region, we found the clear correlation between the position of the sources and the absorption. This fact implies that the major part of the absorption is due to the cold interstellar matter (ISM) in the line of sight. Using the correlation, we estimate the distribution of the cold ISM. We also found that the ratio of numbers of high mass binaries to low mass binaries is significantly smaller than that in the whole Galaxy or SMC, which implies that the past starburst activity in the Galactic center region was rather quiet.
-
PASJ : publications of the Astronomical Society of Japan 52(6) 1141-1145 2000年12月1日
-
PASJ : publications of the Astronomical Society of Japan 52(4) L25-L30 2000年8月25日
-
BROAD BAND X-RAY SPECTRA OF COSMIC SOURCES 25(3-4) 579-582 2000年We present the ASCA results of imaging spectroscopy of the giant molecular cloud Sgr B2. The X-ray spectrum is found to be very peculiar; it exhibits a strong emission line at 6.4 keV, a low energy cutoff below 4 keV and a pronounced edge-structure at 7.1 keV. The X-ray image is extended and its peak position is shifted in the direction of the Galactic center by about 1-2 arcminute from the core of the molecular cloud. The X-ray spectrum and morphology are well reproduced by a scenario that X-rays from a source located at the Galactic center side are scattered by the molecular cloud Sgr B2, and come into our line of sight. Thus Sgr B2 may be called an X-ray reflection nebula. (C) 2000 COSPAR. Published by Elsevier Science Ltd.
-
BROAD BAND X-RAY SPECTRA OF COSMIC SOURCES 25(3-4) 391-394 2000年The ASCA results of the bursting X-ray pulsar GRO J1744-28 are reported. The observations were made twice, in February 1996 and March 1997. We detected 12 and 17 Type II bursts during the two observations, with mean bursting intervals of about 27 min and 37 min. Each burst is followed by an intensity dip with the depleted flux depending on the burst fluence. The energy spectra are approximated by an absorbed power law with additional structure around 6-7 keV, which is most probably due to iron and maybe reproduced by the disk line model with additional broadening mechanism. The absorption column is constant ((5 - 6) x 10(22) cm(-2)), independent of the observation dates and emission phase (persistent, burst and dip). This means the source may be actually located near the galactic center (8.5kpc). (C) 2000 COSPAR. Published by Elsevier Science Ltd.
-
ASTROPHYSICAL JOURNAL 517(1) 436-448 1999年5月We report the ASCA results of the bursting X-ray pulsar GRO J1744-28, which was observed in 1996 February and 1997 March. The source flux in the 2-10 keV band was 2.0 x 10(-8) ergs s(-1) cm(2) in 1996 and 5.0 x 10(-9) ergs s(-1) cm2 in 1997. We detected 12 and 17 type II bursts during type two observations, with mean bursting intervals of about 27 min and 37 min. Each burst is followed by an intensity dip with the depleted flux depending on the burst fluence. The energy spectra are approximated by an absorbed power law with additional structure around 6-7 keV. The constant absorption column, (5-6) x 10(22) cm(-2), independent of the observation dates and emission phases (persistent, burst, and dir) is interpreted as an interstellar absorption. The source may be actually located near the Galactic center, at a distance of 8.5 kpc. The structure in the energy spectrum at 6 7 keV is most probably due to iron and may be reproduced by a disk line model with additional broadening mechanism.
-
Astronomische Nachrichten 320(4-5) 330-330 1999年
-
PASJ : publications of the Astronomical Society of Japan 48(3) 417-423 1996年6月25日
-
PASJ : publications of the Astronomical Society of Japan 48(2) 249-255 1996年
講演・口頭発表等
5-
44th COSPAR Scientific Assembly 2022年
-
nuclear burning in massive stars – towards the formation of binary black holes – 2021年7月28日
-
Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray 2020年12月19日
-
The 15th Symposium of Japanese Research Community on X-ray Imaging Optics 2019年10月26日 招待有り
担当経験のある科目(授業)
6-
2023年9月 - 2024年3月
-
2021年4月 - 2022年3月宇宙理学概論(オムニパス) (総合研究大学院大学)
-
2019年10月 - 2020年3月宇宙理学概論(オムニパス) (総合研究大学院大学)
-
2009年10月 - 2010年3月応用物理学講義 (中央大学)
-
2009年4月 - 2009年9月宇宙物理学講義 (中央大学)
共同研究・競争的資金等の研究課題
10-
日本学術振興会 科学研究費助成事業 基盤研究(B) 2022年4月 - 2025年3月
-
日本学術振興会 科学研究費助成事業 基盤研究(A) 2020年4月 - 2023年3月
-
日本学術振興会 科学研究費助成事業 挑戦的研究(萌芽) 2019年6月 - 2022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) 2013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(C) 2011年 - 2013年
