Curriculum Vitaes
Profile Information
- Affiliation
- Aerospace Project Research Associate, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
- Degree
- Doctor of Philosophy(University of Miyazaki)
- ORCID ID
https://orcid.org/0000-0002-4541-1044- J-GLOBAL ID
- 202301012755167955
- researchmap Member ID
- R000052242
Research Areas
2Research History
2Awards
2Papers
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The Astrophysical Journal Letters, Nov 1, 2025 Peer-reviewed<jats:title>Abstract</jats:title> <jats:p>The dynamics of the intracluster medium (ICM), the hot plasma that fills galaxy clusters, are shaped by gravity-driven cluster mergers and feedback from supermassive black holes (SMBHs) in the cluster cores. XRISM measurements of ICM velocities in several clusters offer insights into these processes. We compare XRISM measurements for nine galaxy clusters (Virgo, Perseus, Centaurus, Hydra-A, PKS 0745–19, A2029, Coma, A2319, and Ophiuchus) with predictions from three state-of-the-art cosmological simulation suites, TNG-Cluster, the Three Hundred Project GADGET-X, and GIZMO-SIMBA, that employ different models of feedback. In cool cores, XRISM reveals systematically lower velocity dispersions than the simulations predict, with all 10 measurements below the median simulated values by a factor of 1.5–1.7 on average and all falling within the bottom 10% of the predicted distributions. The observed kinetic-to-total pressure ratio is also lower, with a median value of 2.2%, compared to the predicted 5.0%–6.5% for the three simulations. Outside the cool cores and in non-cool-core (NCC) clusters, simulations show better agreement with XRISM measurements, except for the outskirts of the relaxed, cool-core cluster A2029, which exhibits an exceptionally low kinetic pressure support (<1%), with none of the simulated systems in either of the three suites reaching such low levels. The NCC Coma and A2319 exhibit dispersions at the lower end but within the simulated spread. Our comparison suggests that the three numerical models may overestimate the kinetic effects of SMBH feedback in cluster cores. Additional XRISM observations of NCC clusters will clarify if there is a systematic tension in the gravity-dominated regime as well.</jats:p>
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Journal of Astronomical Telescopes, Instruments, and Systems, 11(04), Oct 6, 2025
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Nature, Oct 2, 2025 Peer-reviewed<jats:title>Abstract</jats:title> <jats:p>Accretion disks in strong gravity ubiquitously produce winds, seen as blueshifted absorption lines in the X-ray band of both stellar mass X-ray binaries (black holes and neutron stars)<jats:sup>1–4</jats:sup> and supermassive black holes<jats:sup>5</jats:sup>. Some of the most powerful winds (termed Eddington winds) are expected to arise from systems in which radiation pressure is sufficient to unbind material from the inner disk (<jats:italic>L</jats:italic> ≳ <jats:italic>L</jats:italic> <jats:sub>Edd</jats:sub>). These winds should be extremely fast and carry a large amount of kinetic power, which, when associated with supermassive black holes, would make them a prime contender for the feedback mechanism linking the growth of those black holes with their host galaxies<jats:sup>6</jats:sup>. Here we show the XRISM Resolve spectrum of the galactic neutron star X-ray binary, GX 13+1, which reveals one of the densest winds ever seen in absorption lines. This Compton-thick wind significantly attenuates the flux, making it appear faint, although it is intrinsically more luminous than usual (<jats:italic>L</jats:italic> ≳ <jats:italic>L</jats:italic> <jats:sub>Edd</jats:sub>). However, the wind is extremely slow, more consistent with the predictions of thermal-radiative winds launched by X-ray irradiation of the outer disk than with the expected Eddington wind driven by radiation pressure from the inner disk. This puts new constraints on the origin of winds from bright accretion flows in binaries, but also highlights the very different origin required for the ultrafast (<jats:italic>v</jats:italic> ~ 0.3<jats:italic>c</jats:italic>) winds seen in recent Resolve observations of a supermassive black hole at a similarly high Eddington ratio<jats:sup>7</jats:sup>.</jats:p>
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Astronomy & Astrophysics, Oct, 2025 Peer-reviewed<jats:p><jats:italic>Context.</jats:italic> Accurate X-ray spectroscopic measurements are fundamental for deriving basic physical parameters of the most abundant baryon components in the Universe. The plethora of X-ray observatories currently operational enables a panchromatic view of the high-energy emission of celestial sources. However, uncertainties in the energy-dependent calibration of the instrument transfer functions (e.g. the effective area, energy redistribution, or gain) can limit - and historically, did limit - the accuracy of X-ray spectroscopic measurements.</jats:p> <jats:p><jats:italic>Aims.</jats:italic> We revised the status of the cross-calibration among the scientific payload on board four operation missions: <jats:italic>Chandra</jats:italic>, <jats:italic>NuSTAR</jats:italic>, <jats:italic>XMM-Newton</jats:italic>, and the recently launched XRISM. XRISM carries the micro-calorimeter Resolve, which yields the best energy resolution at energies ≥2 keV. For this purpose, we used the data from a 10-day-long observational campaign targeting the nearby active galactic nucleus NGC 3783, carried out in July 2024.</jats:p> <jats:p><jats:italic>Methods.</jats:italic> We present a novel model-independent method for assessing the cross-calibration status that is based on a multi-node spline of the spectra with the highest-resolving power (XRISM/Resolve in our campaign). We also estimated the impact of the intrinsic variability of NGC 3783 on the cross-calibration status due to the different time coverages of participating observatories and performed an empirical reassessment of the Resolve throughput at low energies.</jats:p> <jats:p><jats:italic>Results.</jats:italic> Based on this analysis, we derived a set of energy-dependent correction factors of the observed responses, enabling a statistically robust analysis of the whole spectral dataset. They will be employed in subsequent papers describing the astrophysical results of the campaign.</jats:p>
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Publications of the Astronomical Society of Japan, Sep 30, 2025 Peer-reviewed<jats:title>Abstract</jats:title> <jats:p>We report on a detailed spectroscopic study of the gas dynamics and hydrostatic mass bias of the galaxy cluster Abell 2029, utilizing high-resolution observations from XRISM Resolve. Abell 2029, known for its cool core and relaxed X-ray morphology, provides an excellent opportunity to investigate the influence of gas motions beyond the central region. Expanding upon prior studies that revealed low turbulence and bulk motions within the core, our analysis covers regions out to the scale radius $R_{2500}$ (670 kpc) based on three radial pointings extending from the cluster center toward the northern side. We obtain accurate measurements of bulk and turbulent velocities along the line of sight. The results indicate that non-thermal pressure accounts for no more than 2% of the total pressure at all radii, with a gradual decrease outward. The observed radial trend differs from many numerical simulations, which often predict an increase in non-thermal pressure fraction at larger radii. These findings suggest that deviations from hydrostatic equilibrium are small, leading to a hydrostatic mass bias of around 2% across the observed area.</jats:p>
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Publications of the Astronomical Society of Japan, Sep 30, 2025 Peer-reviewedCorresponding author<jats:title>Abstract</jats:title> <jats:p>We present a summary of the in-orbit performance of the soft X-ray imaging telescope Xtend onboard the X-Ray Imaging and Spectroscopy Mission (XRISM), based on in-flight observation data, including first-light celestial objects, calibration sources, and results from the cross-calibration campaign with other currently operating X-ray observatories. XRISM/Xtend has a large field of view of ${38{^{\prime }_{. } }5}$ $\times$ ${38{^{\prime }_{. } }5}$, covering an energy range of 0.4–13 keV, as demonstrated by the first-light observation of the galaxy cluster Abell 2319. It also features an energy resolution of 170–180 eV at 6 keV, which meets the mission requirement and enables us to resolve He-like and H-like Fe K$\alpha$ lines. Throughout the observation during the performance verification phase, we confirm that two issues identified in the Soft X-ray Imager (SXI) onboard the previous Hitomi mission—light leakage and crosstalk events—are addressed and suppressed in the case of Xtend. A joint cross-calibration observation of the bright quasar 3C 273 results in an effective area measured to be $\sim$420 cm$^{2}$ at1.5 keV and $\sim$310 cm$^{2}$ at 6.0 keV, which matches values obtained in ground tests. We also continuously monitor the health of Xtend by analyzing overclocking data, calibration source spectra, and day-Earth observations; the readout noise is stable and low, and contamination is negligible even one year after launch. A low background level compared with other major X-ray instruments onboard satellites, combined with the largest grasp ($\Omega _{\rm eff}\sim 60$ cm$^2$ deg$^2$) of Xtend, will not only support Resolve analysis, but also enable significant scientific results on its own. This includes near-future follow-up observations and transient searches in the context of time-domain and multi-messenger astrophysics.</jats:p>
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Publications of the Astronomical Society of Japan, Sep 30, 2025 Peer-reviewed<jats:title>Abstract</jats:title> <jats:p>The X-Ray Imaging and Spectroscopy Mission (XRISM) is a joint mission between the Japan Aerospace Exploration Agency (JAXA) and the National Aeronautics and Space Administration (NASA) in collaboration with the European Space Agency (ESA). In addition to the three space agencies, universities and research institutes from Japan, North America, and Europe have joined to contribute to developing satellite and onboard instruments, data-processing software, and the scientific observation program. XRISM is the successor to the ASTRO-H (Hitomi) mission, which ended prematurely in 2016. Its primary science goal is to examine astrophysical problems with precise, high-resolution X-ray spectroscopy. XRISM promises to discover new horizons in X-ray astronomy. It carries a 6 × 6 pixelized X-ray microcalorimeter on the focal plane of an X-ray mirror assembly (Resolve) and a co-aligned X-ray CCD camera (Xtend) that covers the same energy band over a large field of view. XRISM utilizes the Hitomi heritage, but all designs were reviewed. The attitude and orbit control system was improved in hardware and software. The spacecraft was launched from the JAXA Tanegashima Space Center on 2023 September 6 (UTC). During the in-orbit commissioning phase, the onboard components were activated. Although the gate valve protecting the Resolve sensor with a thin beryllium X-ray entrance window was not yet opened, scientific observation started in 2024 February with the planned performance verification observation program. The nominal observation program commenced with the following guest observation program beginning in 2024 September.</jats:p>
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Publications of the Astronomical Society of Japan, Sep 30, 2025 Peer-reviewed<jats:title>Abstract</jats:title> <jats:p>The Soft X-ray Imager (SXI) is the X-ray charge-coupled device (CCD) camera for the soft X-ray imaging telescope Xtend installed on the X-ray Imaging and Spectroscopy Mission (XRISM), which was adopted as a recovery mission for the Hitomi X-ray satellite and was successfully launched on 2023 September 7 (JST). In order to maximize the science output of XRISM, we set the requirements for Xtend and found that the CCD set employed in the Hitomi/SXI or similar, i.e., a $2 \times 2$ array of back-illuminated CCDs with a $200\, \mu$m-thick depletion layer, would be practically best among the available choices, when used in combination with the X-ray mirror assembly. We designed the XRISM/SXI, based on the Hitomi/SXI, to have a wide field of view of $38^{\prime } \times 38^{\prime }$ in the 0.4–13 keV energy range. We incorporated several significant improvements from the Hitomi/SXI into the CCD chip design to enhance the optical-light blocking capability and to increase the cosmic-ray tolerance, reducing the degradation of charge-transfer efficiency in orbit. By the time of the launch of XRISM, the imaging and spectroscopic capabilities of the SXI had been extensively studied in on-ground experiments with the full flight-model configuration or equivalent setups and confirmed to meet the requirements. The optical blocking capability, the cooling and temperature control performance, and the transmissivity and quantum efficiency to incident X-rays of the CCDs were also all confirmed to meet the requirements. Thus, we successfully completed the pre-flight development of the SXI for XRISM.</jats:p>
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Publications of the Astronomical Society of Japan, Sep 30, 2025 Peer-reviewed<jats:title>Abstract</jats:title> <jats:p>We present an analysis of high-resolution spectra from the shock-heated plasmas in SN 1987A, based on an observation using the Resolve instrument onboard the X-Ray Imaging and Spectroscopy Mission (XRISM). The 1.7–10 keV Resolve spectra are accurately represented by a single-component, plane-parallel shock plasma model, with a temperature of $2.84_{-0.08}^{+0.09}$ keV and an ionization parameter of $2.64_{-0.45}^{+0.58}$ × $10^{11}\,\,{\rm s\,\, cm}^{-3}$. The Resolve spectra are also well reproduced by the 3D magneto-hydrodynamic simulation presented by Orlando et al. (2020, A&A, 636, A22) suggesting substantial contribution from the ejecta. The metal abundances obtained with Resolve align with the Large Magellanic Cloud value, indicating that the X-rays in 2024 originate from “non-metal-rich” shock-heated ejecta and the reverse shock has not reached the inner metal-rich region of ejecta. Doppler widths of the atomic lines from Si, S, and Fe correspond to velocities of 1500–1700 km s$^{-1}$, where the thermal broadening effects in this non-metal-rich plasma are negligible. Therefore, the line broadening seen in Resolve spectra is determined by the large bulk motion of ejecta. For reference, we determined a $90\%$ upper limit on non-thermal emission from a pulsar wind nebula at $4.3 \times 10^{-13}$ erg cm$^{-2}$ s$^{-1}$ in the 2–10 keV range, aligning with NuSTAR findings by Greco et al. (2022, ApJ, 931, 132). Additionally, we searched for the $^{44}$Sc K line feature and found a $1\sigma$ upper limit of $1.0 \times 10^{-6}$ photons cm$^{-2}$ s$^{-1}$, which translates to an initial $^{44}$Ti mass of approximately $2 \times 10^{-4}\, M_{\odot }$, consistent with previous X-ray to soft gamma-ray observations (Boggs et al. 2015, Science, 348, 670; Grebenev et al. 2012, Nature, 490, 373; Leising 2006, ApJ, 651, 1019).</jats:p>
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Publications of the Astronomical Society of Japan, Sep 30, 2025 Peer-reviewed
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Publications of the Astronomical Society of Japan, Sep 30, 2025 Peer-reviewed
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Journal of Astronomical Telescopes, Instruments, and Systems, Sep 8, 2025 Peer-reviewed
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Journal of Astronomical Telescopes, Instruments, and Systems, Aug 28, 2025 Peer-reviewed
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Journal of Astronomical Telescopes, Instruments, and Systems, Aug 21, 2025 Peer-reviewed
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The Astrophysical Journal Letters, Aug 1, 2025 Peer-reviewed<jats:title>Abstract</jats:title> <jats:p>W49B is a unique Galactic supernova remnant with centrally peaked, “bar”-like ejecta distribution, which was once considered evidence for a hypernova origin that resulted in a bipolar ejection of the stellar core. However, chemical abundance measurements contradict this interpretation. Closely connected to the morphology of the ejecta is its velocity distribution, which provides critical details for understanding the explosion mechanism. We report the first ever observational constraint on the kinematics of the ejecta in W49B using the Resolve microcalorimeter spectrometer on the X-ray Imaging and Spectroscopy Mission (XRISM). Using XRISM/Resolve, we measured the line-of-sight velocity traced by the Fe He<jats:italic>α</jats:italic> emission, which is the brightest feature in the Resolve spectrum, to vary by ±300 km s<jats:sup>−1</jats:sup> with a smooth east-to-west gradient of a few tens of kilometers per second per parsec along the major axis. Similar trends in the line-of-sight velocity structure were found for other Fe-group elements Cr and Mn, traced by the He<jats:italic>α</jats:italic> emission, and also for intermediate-mass elements Si, S, Ar, and Ca, traced by the Ly<jats:italic>α</jats:italic> emission. The discovery of the east–west gradient in the line-of-sight velocity, together with the absence of a twin-peaked line profile or enhanced broadening in the central region, clearly rejects the equatorially expanding disk model. In contrast, the observed velocity structure suggests bipolar flows reminiscent of a bipolar explosion scenario. An alternative scenario would be a collimation of the ejecta by an elongated cavity sculpted by bipolar stellar winds.</jats:p>
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The Astrophysical Journal Letters, Jul 20, 2025 Peer-reviewed<jats:title>Abstract</jats:title> <jats:p>We report on XRISM/Resolve spectroscopy of the recurrent transient and well-known black hole candidate 4U 1630−472 during its 2024 outburst. The source was captured at the end of a disk-dominated high/soft state at an Eddington fraction of <jats:italic>λ</jats:italic> <jats:sub>Edd</jats:sub> ∼ 0.05 (10 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>/<jats:italic>M</jats:italic> <jats:sub>BH</jats:sub>). A variable absorption spectrum with unprecedented complexity is revealed with the Resolve calorimeter. This marks one of the lowest Eddington fractions at which highly ionized absorption has been detected in an X-ray binary. The strongest lines are fully resolved, with He-like Fe <jats:sc>XXV</jats:sc> separated into resonance and intercombination components and H-like Fe <jats:sc>XXVI</jats:sc> seen as a spin–orbit doublet. The depth of some absorption lines varied by almost an order of magnitude, far more than expected based on a 10% variation in apparent X-ray flux and ionization parameter. The velocity of some absorption components also changed significantly. Jointly modeling two flux segments with a consistent model including four photoionization zones, the spectrum can be described in terms of highly ionized but likely failed winds that sometimes show redshifts, variable obscuration that may signal asymmetric structures in the middle and outer accretion disk, and a tentative very fast outflow (<jats:italic>v</jats:italic> = 0.026–0.033<jats:italic>c</jats:italic>). We discuss the impact of these findings on our understanding of accretion and winds in stellar-mass black holes and potential consequences for future studies.</jats:p>
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Journal of Astronomical Telescopes, Instruments, and Systems, 11(04), Jul 4, 2025
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Journal of Astronomical Telescopes, Instruments, and Systems, 11(04), Jun 3, 2025
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The Astrophysical Journal Letters, May 20, 2025 Peer-reviewed<jats:title>Abstract</jats:title> <jats:p>The XRISM Resolve microcalorimeter array measured the velocities of hot intracluster gas at two positions in the Coma galaxy cluster: <jats:inline-formula> <jats:tex-math> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mi>′</mml:mi> </mml:mrow> </mml:msup> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mi>′</mml:mi> </mml:mrow> </mml:msup> </mml:math> </jats:inline-formula> squares at the center and at 6<jats:inline-formula> <jats:tex-math> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>′</mml:mi> </mml:math> </jats:inline-formula> (170 kpc) to the south. We find the line-of-sight velocity dispersions in those regions to be <jats:italic>σ</jats:italic> <jats:sub> <jats:italic>z</jats:italic> </jats:sub> = 208 ± 12 km s<jats:sup>−1</jats:sup> and 202 ± 24 km s<jats:sup>−1</jats:sup>, respectively. The central value corresponds to a 3D Mach number of <jats:italic>M</jats:italic> = 0.24 ± 0.015 and a ratio of the kinetic pressure of small-scale motions to thermal pressure in the intracluster plasma of only 3.1% ± 0.4%, at the lower end of predictions from cosmological simulations for merging clusters like Coma, and similar to that observed in the cool core of the relaxed cluster A2029. Meanwhile, the gas in both regions exhibits high line-of-sight velocity differences from the mean velocity of the cluster galaxies, Δ<jats:italic>v</jats:italic> <jats:sub> <jats:italic>z</jats:italic> </jats:sub> = 450 ± 15 km s<jats:sup>−1</jats:sup> and 730 ± 30 km s<jats:sup>−1</jats:sup>, respectively. A small contribution from an additional gas velocity component, consistent with the cluster optical mean, is detected along a sight line near the cluster center. The combination of the observed velocity dispersions and bulk velocities is not described by a Kolmogorov velocity power spectrum of steady-state turbulence; instead, the data imply a much steeper effective slope (i.e., relatively more power at larger linear scales). This may indicate either a very large dissipation scale, resulting in the suppression of small-scale motions, or a transient dynamic state of the cluster, where large-scale gas flows generated by an ongoing merger have not yet cascaded down to small scales.</jats:p>
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Nature, May 14, 2025 Peer-reviewed
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Journal of Astronomical Telescopes, Instruments, and Systems, Apr 7, 2025 Peer-reviewed
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Journal of Astronomical Telescopes, Instruments, and Systems, 11(04), Mar 29, 2025 Peer-reviewed
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The Astrophysical Journal Letters, Mar 20, 2025 Peer-reviewed<jats:title>Abstract</jats:title> <jats:p>We present XRISM Resolve observations of the core of the hot, relaxed galaxy cluster Abell 2029 (A2029). We find that the line-of-sight bulk velocity of the intracluster medium (ICM) within the central 180 kpc is at rest with respect to the brightest cluster galaxy, with a 3<jats:italic>σ</jats:italic> upper limit of ∣<jats:italic>v</jats:italic> <jats:sub>bulk</jats:sub>∣ < 100 km s<jats:sup>−1</jats:sup>. We robustly measure the field-integrated ICM velocity dispersion to be <jats:italic>σ</jats:italic> <jats:sub> <jats:italic>v</jats:italic> </jats:sub> = 169 ± 10 km s<jats:sup>−1</jats:sup>, obtaining similar results for both single-temperature and two-temperature plasma models to account for the cluster cool core. This result, if ascribed to isotropic turbulence, implies a subsonic ICM with Mach number <jats:inline-formula> <jats:tex-math> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi class="MJX-tex-calligraphic" mathvariant="script">M</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> <mml:mrow> <mml:mi mathvariant="normal">D</mml:mi> </mml:mrow> </mml:mrow> </mml:msub> <mml:mo>≈</mml:mo> <mml:mn>0.22</mml:mn> </mml:math> </jats:inline-formula> and a nonthermal pressure fraction of 2.6 ± 0.3%. The turbulent velocity is similar to what was measured in the core of the Perseus cluster by Hitomi, but here in a more massive cluster with an ICM temperature of 7 keV, the limit on the nonthermal pressure fraction is even more stringent. Our result is consistent with expectations from simulations of relaxed clusters, but it is on the low end of the predicted distribution, indicating that A2029 is an exceptionally relaxed cluster with no significant impacts from either a recent minor merger or active galactic nucleus activity.</jats:p>
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Journal of Astronomical Telescopes, Instruments, and Systems, 11(04), Mar 11, 2025 Peer-reviewed
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Journal of Astronomical Telescopes, Instruments, and Systems, 11(04), Mar 11, 2025 Peer-reviewed
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Nature, Feb 13, 2025 Peer-reviewed
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Publications of the Astronomical Society of Japan, Feb 5, 2025 Peer-reviewed<jats:title>Abstract</jats:title> <jats:p>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.</jats:p>
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The Astrophysical Journal Letters, Jan 10, 2025 Peer-reviewed
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The Astrophysical Journal Letters, Dec 20, 2024 Peer-reviewed<jats:title>Abstract</jats:title> <jats:p>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 <jats:sc>xxv</jats:sc> He<jats:italic>α</jats:italic> and Fe <jats:sc>xxvi</jats:sc> Ly<jats:italic>α</jats:italic> 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<jats:sup>−1</jats:sup>. 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.</jats:p>
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Publications of the Astronomical Society of Japan, Dec 4, 2024 Peer-reviewed<jats:title>Abstract</jats:title> <jats:p>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.</jats:p>
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The Astrophysical Journal Letters, Sep 1, 2024 Peer-reviewed<jats:title>Abstract</jats:title> <jats:p>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<jats:sub> <jats:italic>α</jats:italic> </jats:sub> 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<jats:sub> <jats:italic>α</jats:italic>,1</jats:sub> (6.404 keV) and K<jats:sub> <jats:italic>α</jats:italic>,2</jats:sub> (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 <jats:italic>r</jats:italic> ≃ 100 <jats:italic>GM</jats:italic>/<jats:italic>c</jats:italic> <jats:sup>2</jats:sup> 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<jats:sub> <jats:italic>α</jats:italic> </jats:sub> 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<jats:inline-formula> <jats:tex-math> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mspace width="0.25em"/> <mml:mo>=</mml:mo> <mml:mspace width="0.25em"/> <mml:msubsup> <mml:mrow> <mml:mn>1600</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>200</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>400</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.25em"/> <mml:mi>km</mml:mi> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> </jats:inline-formula>. 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.</jats:p>
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 55-55, Aug 22, 2024
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 53-53, Aug 22, 2024
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 56-56, Aug 21, 2024
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 235-235, Aug 21, 2024
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 232-232, Aug 21, 2024
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 52-52, Aug 21, 2024
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 59-59, Aug 21, 2024
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 54-54, Aug 21, 2024
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 61-61, Aug 21, 2024
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 58-58, Aug 21, 2024
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 233-233, Aug 21, 2024
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 228-228, Aug 21, 2024
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 224-224, Aug 21, 2024 Lead authorCorresponding author
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 60-60, Aug 21, 2024
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 236-236, Aug 21, 2024
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray, 226-226, Aug 21, 2024
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Proceedings of 10th International Workshop on Semiconductor Pixel Detectors for Particles and Imaging — PoS(Pixel2022), Mar 16, 2023 Peer-reviewed
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Proceedings of SPIE - The International Society for Optical Engineering, 12181, 2022
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Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 985, Jan 1, 2021 Peer-reviewed
Misc.
14Professional Memberships
3-
Jul, 2025 - Present
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Apr, 2023 - Present
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Sep, 2018 - Present
Research Projects
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科学研究費助成事業, 日本学術振興会, Apr, 2024 - Mar, 2027
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科学研究費助成事業 特別研究員奨励費, 日本学術振興会, Apr, 2021 - Mar, 2023
