Curriculum Vitaes
Profile Information
- Affiliation
- Assistant professor, Institute of Space and Astronautical Science, Japan Aerospace Exploration AgencyAssistant professor, Space and Astronautical Science program, The Graduate University for Advanced Studies
- Degree
- Ph. D.(Mar, 1998, Kyoto University)master's degree(Mar, 1995, Kyoto University)
- Researcher number
- 80342624
- ORCID ID
https://orcid.org/0000-0002-9099-5755- J-GLOBAL ID
- 202001011170717781
- researchmap Member ID
- R000011919
Papers
241-
Journal of Astronomical Telescopes, Instruments, and Systems, 11(04), Aug 21, 2025 Peer-reviewedLead authorCorresponding author
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Monthly Notices of the Royal Astronomical Society: Letters, 540(1) L34-L40, Mar 19, 2025ABSTRACT We report measurements of the linear polarization degree (PD) and angle (PA) for hard X-ray emission from the Crab pulsar and wind nebula. Measurements were made with the XL-Calibur ($\sim$15–80 keV) balloon-borne Compton-scattering polarimeter in July 2024. The polarization parameters are determined using a Bayesian analysis of Stokes parameters obtained from X-ray scattering angles. Well-constrained ($\sim 8.5\sigma$) results are obtained for the polarization of the $\sim$19–64 keV signal integrated over all pulsar phases: PD = (25.1$\pm$2.9) per cent and PA = (129.8$\pm 3.2)^\circ$. In the off-pulse (nebula-dominated) phase range, the PD is constrained at $\sim 4.5\sigma$ and is compatible with the phase-integrated result. The PA of the nebular hard X-ray emission aligns with that measured by IXPE in the 2–8 keV band for the toroidal inner region of the pulsar wind nebula, where the hard X-rays predominantly originate. For the main pulsar peak, PD = (32.8$^{+18.2}_{-28.5}$) per cent and PA = (156.0 $\pm$ 21.7)$^\circ$, while for the second peak (inter-pulse), PD = (0.0$^{+33.6}_{-0.0}$) per cent and PA = (154.5 $\pm$ 34.5)$^\circ$. A low level of polarization in the pulsar peaks likely does not favour emission originating from the inner regions of the pulsar magnetosphere. Discriminating between Crab pulsar emission models will require deeper observations, e.g. with a satellite-borne hard X-ray polarimeter.
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Nature, 638(8050) 365-369, Feb 12, 2025 Peer-reviewed
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Publications of the Astronomical Society of Japan, 77(1) L1-L8, Dec 26, 2024 Peer-reviewedAbstract 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, Dec 11, 2024 Peer-reviewedAbstract 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.
Misc.
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日本物理学会講演概要集(CD-ROM), 78(2), 2023
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大気球シンポジウム: 2022年度 = Balloon Symposium: 2022, Nov, 2022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
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日本物理学会講演概要集(CD-ROM), 75(1), 2020
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日本物理学会講演概要集(CD-ROM), 75(2), 2020
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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, Dec, 2016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
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Dynamics & Design Conference, 2011 "706-1"-"706-8", Sep 5, 2011In 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.
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Journal of the Physical Society of Japan, 78 133-137, Jun 16, 2009
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2008 IEEE/LEOS INTERNATIONAL CONFERENCE ON OPTICAL MEMS AND NANOPHOTONICS, 104-105, 2008 Peer-reviewed
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Meeting abstracts of the Physical Society of Japan, 62(2) 116-116, Aug 21, 2007
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Meeting abstracts of the Physical Society of Japan, 62(1) 95-95, Feb 28, 2007
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Meeting abstracts of the Physical Society of Japan, 61(2) 78-78, Aug 18, 2006
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Meeting abstracts of the Physical Society of Japan, 61(2) 75-75, Aug 18, 2006
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日本物理学会講演概要集, 61(2) 77-77, Aug 18, 2006
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Publications of the Astronomical Society of Japan, 57(1) 245-257, Feb 25, 2005<jats:title>Abstract</jats:title> <jats:p>We present the design and fabrication of the pre-collimator for the X-ray telescope onboard the X-ray astronomy satellite Astro-E2, and its effect on stray-light reduction. The pre-collimator was designed to efficiently reduce secondary reflection, which is the brightest component of stray light, giving rise to a ghost image in the field of view of the focal-plane detector. With the pre-collimator, composed of blades with an effective height of 30 mm, we confirmed from X-ray measurements that the intensity of the secondary reflection is reduced by roughly a few orders of magnitude on average in the off-axis angle range of $20' \hbox{--} 70'$. We also confirmed that the loss of the on-axis effective area due to installation of the pre-collimator is only $0.5 \pm 0.2\%$. The field of view becomes narrower, but the reduction factor amounts only to 8%. Ray-tracing simulations of in-flight observations also demonstrate that introduction of the pre-collimator is expected to be highly significant for improving data quality, due to a reduction of secondary reflection.</jats:p>
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ASTRONOMISCHE NACHRICHTEN, 324(1-2) 158-158, 2003
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Astrophysical Journal, Supplement Series, 138(1) 19-34, Jan 1, 2002
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NEW CENTURY OF X-RAY ASTRONOMY, 251 310-311, 2001
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NEW CENTURY OF X-RAY ASTRONOMY, 251 314-315, 2001
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Publications of the Astronomical Society of Japan, 52(6) 1141-1145, Dec 1, 2000<jats:p>We report the discovery of an X-ray pulsar, AX J1740.1–2847, from the Galactic center region. This source was found as a faint hard X-ray object on 1998 September 7–8 with the ASCA Galactic center survey observation. Then, coherent pulsations of P = 729± 14 s period were detected. The X-ray spectrum is described by a flat power-law of ∼ 0.7 photon index. The large absorption column of log NH ∼ 22.4 cm−2 indicates that AX J1740.1–2847 is a distant source, larger than 2.4 kpc, and possibly near to the Galactic center region. The luminosity in the 2–10 keV band is larger than 2.5×1033 erg s−1, or likely to be 3.2×1034 erg s−1 at the Galactic-center distance. Although the slow-pulse period does not discriminate whether AX J1740.1–2847 is a white dwarf or neutron-star binary, the flat power-law and moderate luminosity strongly favor a neutron-star binary.</jats:p>
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Publications of the Astronomical Society of Japan, 52(4) L25-L30, Aug 25, 2000<jats:p>The X-ray spectrum in a 1° × 1° region of the Galactic center observed with the ASCA satellite is examined in detail, following the first report by Koyama et al. (1996, AAA 65.155.208). The observed spectrum contains prominent emission lines from helium-like and hydrogen-like ions of various elements, and is essentially the same all over the region. If the observed spectrum is thermal emission from hot plasmas, it requires multi-temperature plasma components, each at a different degree of ionization and with a different amount of absorption. The absence of adiabatic cooling and of systematic changes in the degree of ionization over the region is against the Galactic center origin of hot plasmas. A significant broadening of the helium-like and hydrogen-like iron K-lines is confirmed. The line width corresponds to a rms velocity of ∼ 3300 km s−1, which far exceeds the sound velocity in a plasma of kT ∼ 14 keV measured with the Ginga satellite. These facts cast doubt on a thermal origin of the observed X-ray emission.</jats:p>
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BROAD BAND X-RAY SPECTRA OF COSMIC SOURCES, 25(3-4) 579-582, 2000
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BROAD BAND X-RAY SPECTRA OF COSMIC SOURCES, 25(3-4) 391-394, 2000
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ASTRONOMISCHE NACHRICHTEN, 320(4-5) 330-330, 1999
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Meeting abstracts of the Physical Society of Japan, 52(1) 82-82, Mar 17, 1997
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Publications of the Astronomical Society of Japan, 48(3) 417-423, Jun 25, 1996<jats:p>With ASCA, we found highly absorbed X-rays from the position of the bright transient source A1742–289 with a variable flux ranging from 8 × 10−12 to 4 × 10−11 erg s−1 cm−2 in the 3–10 keV band. We discovered an X-ray burst and eclipses from A1742–289, establishing that A1742–289 is an eclipsing low-mass X-ray binary. Using the black-body radius during an X-ray burst, we estimated the distance of A1742–289 to be about 10 kpc, or near to the galactic center. The burst peak flux was then found below the Eddington limit of a neutron star. Excess soft X-rays during the eclipse were detected, which are interpreted to be scattering by interstellar dust-grains. Since A1742–289 was found to be an X-ray emitter, even in the quiescent state with a moderate but variable flux, and since A1742–289 is lying only 1′.3 from the galactic center, previously reported X-ray fluxes of the galactic center (Sgr A*) with non-imaging instruments might have suffered due to possible contamination of A1742–289.</jats:p>
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Publications of the Astronomical Society of Japan, 48(2) 249-255, 1996<jats:p>Detailed X-ray images and spectra of the galactic-center region up to 10 keV were obtained with ASCA. Diffuse thermal-emission with distinct Kα lines from highly ionized ions of various elements has confirmed the presence of an extended high-temperature plasma. The fluorescent X-ray emission from cold iron atoms in molecular clouds was also found, possibly due to irradiation by X-rays from the center, which was bright in the past, but is presently dim. The results suggest that the galactic center exhibited intermittent activities with a time-averaged energy generation rate comparable to Seyfert nuclei, a class of active galactic nuclei.</jats:p>
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WOLF-RAYET STARS: BINARIES, COLLIDING WINDS, EVOLUTION, (163) 471-475, 1995
Presentations
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Optics & Photonics Japan 2023, Nov 29, 2023 Invited
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44th COSPAR Scientific Assembly, 2022
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nuclear burning in massive stars – towards the formation of binary black holes –, Jul 28, 2021
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Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray, Dec 19, 2020
Teaching Experience
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Sep, 2023 - Mar, 2024
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Apr, 2021 - Mar, 2022Space Science Review (The Graduate University for Advanced Studies)
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Oct, 2019 - Mar, 2020Space Science Review (The Graduate University for Advanced Studies)
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Oct, 2009 - Mar, 2010Applied Physics (Chuo University)
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Apr, 2009 - Sep, 2009Astrophysics (Chuo University)
Professional Memberships
4-
Jul, 1998 - Present
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Mar, 1998 - Present
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Jan, 1997 - Present
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Aug, 1993 - Present
Research Projects
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Apr, 2023 - Mar, 2027
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Apr, 2022 - Mar, 2025
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Apr, 2022 - Mar, 2025
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Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A), Japan Society for the Promotion of Science, Apr, 2020 - Mar, 2023
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科学研究費助成事業 挑戦的研究(萌芽), 日本学術振興会, Jun, 2019 - Mar, 2022
