Curriculum Vitaes
Profile Information
- Affiliation
- Project Assistant Professor, Department of Space Astronomy and Astrophysics, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
- Contact information
- hiromasa050701
gmail.com - Researcher number
- 50915402
- ORCID ID
https://orcid.org/0000-0002-8152-6172- J-GLOBAL ID
- 202301003397839297
- researchmap Member ID
- R000055343
- External link
Interested in high energy phenomena, especially supernovae, supernova remnants, neutron stars, and cosmic rays. Also working on X-ray/gamma-ray detector development.
Research Interests
8Research Areas
2Research History
4-
Apr, 2021 - Aug, 2023
-
Apr, 2019 - Mar, 2021
Education
3-
Aug, 2019 - Dec, 2019
-
Apr, 2016 - Mar, 2018
Committee Memberships
2-
Aug, 2018 - Jul, 2019
-
Jun, 2018 - Jun, 2019
Awards
4-
Nov, 2022
Papers
59-
The Astrophysical Journal, 976(2) 180-180, Nov 21, 2024 Peer-reviewedAbstract X-ray observations of shock-heated plasmas, such as those found in supernova remnants (SNRs), often exhibit features of temperature and ionization nonequilibrium. For accurate interpretation of these observations, proper calculations of the equilibration processes are essential. Here, we present a self-consistent model of thermal X-ray emission from shock-heated plasmas that accounts for both temperature and ionization nonequilibrium conditions. For a given pair of shock velocity and initial electron-to-ion temperature ratio, the temporal evolution of the temperature and ionization state of each element was calculated by simultaneously solving the relaxation processes of temperature and ionization. The resulting thermal X-ray spectrum was synthesized by combining our model with the AtomDB spectral code. Comparison between our model and the nei model, a constant-temperature nonequilibrium ionization model available in the XSPEC software package, reveals a 30% underestimation of the ionization timescale in the nei model. We implemented our model in XSPEC to directly constrain the shock wave’s properties, such as the shock velocity and collisionless electron heating efficiency, from the thermal X-ray emission from postshock plasmas. We applied this model to archival Chandra data of the SNR N132D, providing a constraint on the shock velocity of ∼800 km s−1, in agreement with previous optical studies.
-
Publications of the Astronomical Society of Japan, Oct 10, 2024 Peer-reviewedCorresponding authorAbstract 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.
-
The Astrophysical Journal Letters, 973(1) L25-L25, Sep 1, 2024 Peer-reviewedAbstract 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.
-
Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 228-228, Aug 21, 2024
-
Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 54-54, Aug 21, 2024
Misc.
94-
Oct 30, 2023Supernova remnants (SNRs) are thought to be the most plausible sources of Galactic cosmic rays. One of the principal questions is whether they are accelerating particles up to the maximum energy of Galactic cosmic rays ($\sim$PeV). In this paper, we summarize our recent studies on gamma-ray-emitting SNRs. We first evaluated the reliability of SNR age estimates to quantitatively discuss time dependence of their acceleration parameters. Then we systematically modeled their gamma-ray spectra to constrain the acceleration parameters. The current maximum energy estimates were found to be well below PeV for most sources. The basic time dependence of the maximum energy assuming the Sedov evolution ($\approx t^{-0.8\pm0.2}$) cannot be explained with the simplest acceleration condition (Bohm limit) and requires shock-ISM (interstellar medium) interaction. The inferred maximum energies during lifetime averaged over the sample can be expressed as $\lesssim 20$ TeV ($t_{ { \rm M } }/\text{1 kyr})^{-0.8}$ with $t_{\rm M}$ being the age at the maximum, which reaches $\sim$PeV only if $t_{\rm M} \lesssim 10$ yr. The maximum energies during lifetime are suggested to have a variety of 1-2 orders of magnitude from object to object on the other hand. This variety will reflect the dependence on environments.
-
SPACE TELESCOPES AND INSTRUMENTATION 2022: ULTRAVIOLET TO GAMMA RAY, 12181, Mar 14, 2023In this multi-messenger astronomy era, all the observational probes are improving their sensitivities and overall performance. The Focusing on Relativistic universe and Cosmic Evolution (FORCE) mission, the product of a JAXA/NASA collaboration, will reach a 10 times higher sensitivity in the hard X-ray band ($E >$ 10~keV) in comparison with any previous hard X-ray missions, and provide simultaneous soft X-ray coverage. FORCE aims to be launched in the early 2030s, providing a perfect hard X-ray complement to the ESA flagship mission Athena. FORCE will be the most powerful X-ray probe for discovering obscured/hidden black holes and studying high energy particle acceleration in our Universe and will address how relativistic processes in the universe are realized and how these affect cosmic evolution. FORCE, which will operate over 1--79 keV, is equipped with two identical pairs of supermirrors and wideband X-ray imagers. The mirror and imager are connected by a high mechanical stiffness extensible optical bench with alignment monitor systems with a focal length of 12~m. A light-weight silicon mirror with multi-layer coating realizes a high angular resolution of $<15''$ in half-power diameter in the broad bandpass. The imager is a hybrid of a brand-new SOI-CMOS silicon-pixel detector and a CdTe detector responsible for the softer and harder energy bands, respectively. FORCE will play an essential role in the multi-messenger astronomy in the 2030s with its broadband X-ray sensitivity.
-
SPACE TELESCOPES AND INSTRUMENTATION 2022: ULTRAVIOLET TO GAMMA RAY, 12181, Mar 14, 2023Xtend is a soft X-ray imaging telescope developed for the X-Ray Imaging and Spectroscopy Mission (XRISM). XRISM is scheduled to be launched in the Japanese fiscal year 2022. Xtend consists of the Soft X-ray Imager (SXI), an X-ray CCD camera, and the X-ray Mirror Assembly (XMA), a thin-foil-nested conically approximated Wolter-I optics. The SXI uses the P-channel, back-illuminated type CCD with an imaging area size of 31 mm on a side. The four CCD chips are arranged in a 2$\times$2 grid and can be cooled down to $-120$ $^{\circ}$C with a single-stage Stirling cooler. The XMA nests thin aluminum foils coated with gold in a confocal way with an outer diameter of 45~cm. A pre-collimator is installed in front of the X-ray mirror for the reduction of the stray light. Combining the SXI and XMA with a focal length of 5.6m, a field of view of $38^{\prime}\times38^{\prime}$ over the energy range from 0.4 to 13 keV is realized. We have completed the fabrication of the flight model of both SXI and XMA. The performance verification has been successfully conducted in a series of sub-system level tests. We also carried out on-ground calibration measurements and the data analysis is ongoing.
-
応用物理学会春季学術講演会講演予稿集(CD-ROM), 70th, 2023
-
日本物理学会講演概要集(CD-ROM), 78(1), 2023
-
日本物理学会講演概要集(CD-ROM), 78(1), 2023
-
日本物理学会講演概要集(CD-ROM), 78(1), 2023
-
日本物理学会講演概要集(CD-ROM), 78(2), 2023
Teaching Experience
2-
Apr, 2023 - Aug, 2023exercise for basic physical mathematics (Konan University)
-
Sep, 2021 - Mar, 2023student experiments (Konan University)
Professional Memberships
5-
Oct, 2022 - Present
-
Sep, 2021 - Present
-
Jan, 2020 - Present
-
Jun, 2016 - Present
-
May, 2016 - Present
Research Projects
4-
科学研究費助成事業, 日本学術振興会, Apr, 2024 - Mar, 2027
-
科学研究費助成事業, 日本学術振興会, Mar, 2023 - Mar, 2024
-
科学研究費助成事業, 日本学術振興会, Apr, 2021 - Mar, 2024
-
Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Apr, 2019 - Mar, 2021
