寺田 幸功

The follow-up XRISM observation has been performed for the black hole binary MAXI J1543-564. The X-ray transient event from this object was reported and identified by MAXI in December 2025 (ATels #17552, #17559, and #17560)....

Swift/BAT triggered a new outburst of the Be X-ray binary 1A 1118-61 on 2026-01-18 (ATel #17608). Since then, X-ray and optical follow-up observations have been carried out (ATel #17613, #17616, #17620, #17626, #17627)....

The XRISM/Resolve microcalorimeter directly measured the gas velocities in the core of the Virgo Cluster, the closest example of active galactic nucleus (AGN) feedback in a cluster. This proximity allows us to resolve the kinematic impact of feedback on scales down to 5 kpc. Our spectral analysis reveals a high velocity dispersion of <inline-formula> <mml:math><mml:msub><mml:mrow><mml:mi>σ</mml:mi></mml:mrow><mml:mrow><mml:mi>v</mml:mi></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:mn>26</mml:mn><mml:msubsup><mml:mrow><mml:mn>2</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>38</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>45</mml:mn></mml:mrow></mml:msubsup></mml:math> </inline-formula> km s⁻¹ near the AGN, which steeply declines to ∼60 km s⁻¹ between 5 and 25 kpc in the northwest direction. The observed line-of-sight bulk velocity in all regions is broadly consistent with the central galaxy, M87, with a mild trend toward blueshifted motions at larger radii. Systematic uncertainties have been carefully assessed and do not affect the measurements. The central velocities, if attributed entirely to isotropic turbulence, correspond to a transonic intracluster medium at sub-6 kpc scales with 3D Mach number <inline-formula> <mml:math><mml:mn>0</mml:mn><mml:mo>.</mml:mo><mml:msubsup><mml:mn>69</mml:mn><mml:mi>-0.11</mml:mi><mml:mi>+0.14</mml:mi></mml:msubsup></mml:math> </inline-formula> and a nonthermal pressure fraction of <inline-formula> <mml:math><mml:msubsup><mml:mn>21</mml:mn><mml:mi>-5</mml:mi><mml:mi>+7</mml:mi></mml:msubsup><mml:mo>%</mml:mo></mml:math> </inline-formula>. Simple models of weak shocks and sound waves and calculations assuming isotropic turbulence both support the hypothesis that the velocity field reflects a mix of shock-driven expansion and turbulence. Compared to other clusters observed by XRISM to date, M87's central region stands out as the most kinematically disturbed, exhibiting both the highest velocity dispersion and the largest 3D Mach number, concentrated at the smallest physical scales....

Galaxy clusters, the Universe's largest halo structures, are filled with an X-ray-emitting gas with a temperature between 10 million and 100 million degrees. Their evolution is shaped by energetic processes such as feedback from supermassive black holes (SMBHs) and mergers with other cosmic structures^{1, 2─3}. The imprints of these processes on gas kinematics remain largely unknown, restricting our understanding of energy conversion within clusters⁴. High-resolution spectral mapping with the X-Ray Imaging and Spectroscopy Mission (XRISM) observatory⁵ offers a way forward^6,7. Here we present XRISM kinematic measurements of the Perseus cluster, radially covering the extent of its cool core. We find direct evidence for at least two dominant drivers of gas motions operating on distinct physical scales: a small-scale driver in the inner approximately 60 kpc, probably associated with the SMBH feedback; and a large-scale driver in the outer core, powered by mergers. This finding suggests that, during the active phase, SMBH feedback drives gas motions, which, if fully dissipated into heat, could have a substantial role in offsetting radiative cooling losses in the Perseus core. Our study underscores the necessity of kinematic mapping observations of extended sources to robustly characterize the velocity fields and their role in the evolution of massive halos. It further offers a kinematic diagnostic for SMBH feedback models....

The supermassive binary system, $η$ Carinae, is experiencing enormous wind-driven mass loss at a rate unparalleled in the rest of the Galaxy. Their wind-wind collision (WWC) continuously produces shock heated, X-ray emitting plasmas. The XRISM X-ray observatory observed the system in 2023 and 2024 when the X-ray emission began to increase toward periastron passage in 2025. This manuscript reports unprecedentedly high-resolution X-ray spectra in the iron K$α$ band between 6.2 and 7.1 keV, obtained with the Resolve X-ray microcalorimeter. The hydrogen-like (Ly$α$) and helium-like (He$α$) lines reveal three velocity components. Two of them are broadened with maximum velocities of 2000-3000 km/s, likely originating from the post-shock companion wind. The other is relatively narrow, with a Gaussian broadening of only ~290 km/s in 1 sigma, which may originate from the post-shock companion wind at the WWC stagnation point or penetrating the primary wind. The iron fluorescent lines exhibit a moderate blueshift and broadening with velocities at 100-200 km/s, consistent with the primary wind's velocity field. The spectra also confirm a Compton shoulder of the He$α$ line complex for the first time. Both fluorescing and scattering spectral profiles indicate that the binary system is seen from the companion side during these observations. The flux ratio of the Compton scattering emission to the fluorescent line suggests substantial hydrogen depletion of the primary wind, expected from CNO-cycled hydrogen nuclear fusion gas....

Context. The Galactic magnetar SGR 1935+2154 has exhibited prolific high-energy (HE) bursting activity in recent years. Aims. Investigating its potential tera-electronvolt counterpart could provide insights into the underlying mechanisms of magnetar emission and very high-energy (VHE) processes in extreme astrophysical environments. We aim to search for a possible tera-electronvolt counterpart to both its persistent and sub-second-scale burst emission. Methods. We analysed over 25 hour of observations from the Large-Sized Telescope prototype (LST−1) of the Cherenkov Telescope Array Observatory (CTAO) during periods of HE activity from SGR 1935+2154 in 2021 and 2022 to search for persistent emission. For bursting emission, we selected and analysed nine 0.1 s time windows centred around known short X-ray bursts, targeting potential sub-second-scale tera-electronvolt counterparts in a low-photon-statistics regime. Results. While no persistent or bursting emission was detected in our search, we establish upper limits for the tera-electronvolt emission of a short magnetar burst simultaneous to its soft gamma-ray flux. Specifically, for the brightest burst in our sample, the ratio between tera-electronvolt and X-ray flux is ≲10⁻³. Conclusions. The non-detection of either persistent or bursting tera-electronvolt emission from SGR 1935+2154 suggests that if such components exist, they may occur under specific conditions not covered by our observations. This aligns with theoretical predictions of VHE components in magnetar-powered fast radio bursts and the detection of MeV─GeV emission in giant magnetar flares. These findings underscore the potential of magnetars, fast radio bursts, and other fast transients as promising candidates for future observations in the low-photon-statistics regime with Imaging Atmospheric Cherenkov Telescopes, particularly with the CTAO....

MAXI/GSC found a new outburst of the black hole X-ray binary GS 1354-64 on 2025-12-25 (ATel #17563). Since then, multi-wavelength follow-up observations have been carried out (ATel #17582, #17583, #17586, #17611, #17612, #17618)....

The elements in the Universe are synthesized primarily in stars and supernovae, where nuclear fusion favours the production of even-Z elements. In contrast, odd-Z elements are less abundant and their yields are highly dependent on detailed stellar physics, making theoretical predictions of their cosmic abundance uncertain. In particular, the origin of odd-Z elements such as phosphorus (P), chlorine (Cl) and potassium (K), which are important for planet formation and life, is poorly understood. While the abundances of these elements in Milky Way stars are close to solar values, supernova explosion models systematically underestimate their production by up to an order of magnitude, indicating that key mechanisms for odd-Z nucleosynthesis are currently missing from theoretical models. Here we report the observation of P, Cl and K in the Cassiopeia A supernova remnant using high-resolution X-ray spectroscopy with X-Ray Imaging and Spectroscopy Mission data, with the detection of K at above the 6σ level being the most significant finding. Supernova explosion models of normal massive stars cannot explain the element abundance pattern, especially the high abundances of Cl and K, while models that include stellar rotation, binary interactions or shell mergers agree closely with the observations. Our observations suggest that such stellar activity plays an important role in supplying these elements to the Universe....

The elemental abundances of the Fe-peak elements (such as Cr, Mn, Fe and Ni) and Ti are important for understanding the environment of explosive nuclear burning for the core-collapse supernovae (CC SNe). In particular, the supernova remnant Cassiopeia A, which is well known for its asymmetric structure, contains three ``Fe-rich blobs,'' and the composition of the Fe-peak elements within these structures could be related to the asymmetry of the supernova explosion. We report a highly asymmetric distribution of the Fe-peak elements in Cassiopeia A as revealed by XRISM observations. We found that the southeastern Fe-rich region has a significant Mn emission above the 4$σ$ confidence level, while the northwestern Fe-rich region has no clear signature. In addition to the significant difference in Mn abundance across these regions, our observations show that the Ti/Fe, Mn/Cr, and Ni/Fe ratios vary from region to region. The observed asymmetric distribution of Fe-peak elements could be produced by (1) the mixing of materials from different burning layers of the supernova, (2) the asymmetric distribution of the electron fraction in the progenitor star and/or (3) the local dependence of the neutrino irradiation in the supernova innermost region. Future spatially resolved spectroscopy of Cassiopeia A using X-ray microcalorimeters will enable more detailed measurements of the distribution and composition of these elements, providing a unique tool for testing asymmetric supernova physics....

Abstract The timing (cross-)calibration of astronomical instruments is often done by comparing pulsar times-of-arrival (TOAs) to a reference timing model. In high-energy astronomy, the choice of solar system ephemerides and source positions used to barycenter the photon arrival times has a significant impact on the procedure, requiring a full reprocessing of the data each time a new convention is used. Our method, developed as part of the activities of the International Astronomical Consortium for High Energy Calibration, adapts an existing pulsar solution to arbitrary JPL ephemerides and source positions by simulating geocentric TOAs and refitting timing models (implemented with PINT). We validate the procedure and apply it to thousands of observations of the Crab pulsar from 15 missions spanning 1996–2025, demonstrating inter-ephemeris TOA consistency at the ≲5 μ s level, using the DE200/FK5-based Jodrell Bank Monthly Ephemeris as a common reference. We release the TOAExtractor open-source tool and a TOA database to support future calibration and scientific studies. Instrument timing performance is broadly consistent with mission specifications; the X-ray-to-radio phase offset varies with energy and time at a level that is marginally consistent with the uncertainties of the radio ephemeris, motivating coordinated multiwavelength follow-up.

The follow-up XRISM observation has been performed for the interstellar comet C/2025 N1, also known as 3I/ATLAS, discovered by the ATLAS survey telescope on July 01, 2025....

XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J0923-6258 on 2025-12-08 TT. The source position is determined to be (R.A., Dec.) = (140.824,-62.964), with a systematic error of &amp; sim; 40 arcsec....

We present results from XRISM/Resolve observations of the core of the galaxy cluster Abell 2319, focusing on its kinematic properties. The intracluster medium (ICM) exhibits temperatures of approximately 8 keV across the core, with a prominent cold front and a high-temperature region (<inline-formula><tex-math>$\sim$</tex-math></inline-formula>11 keV) in the north-west. The average gas velocity in the <inline-formula><tex-math>$3{^{\prime } } \times$</tex-math></inline-formula> <inline-formula><tex-math>$4 {^{\prime } }$</tex-math></inline-formula> region around the brightest cluster galaxy (BCG) covered by two Resolve pointings is consistent with that of the BCG to within 40 km s<inline-formula><tex-math>$^{-1}$</tex-math></inline-formula> and we found modest average velocity dispersion of 230─250 km s<inline-formula><tex-math>$^{-1}$</tex-math></inline-formula>. On the other hand, spatially resolved spectroscopy reveals interesting variations. A blueshift of up to <inline-formula><tex-math>$\sim$</tex-math></inline-formula>230 km s<inline-formula><tex-math>$^{-1}$</tex-math></inline-formula> is observed around the east edge of the cold front, where the gas with the lowest specific entropy is found. The region further south inside the cold front shows only a small velocity difference from the BCG; however, its velocity dispersion is enhanced to <inline-formula><tex-math>$\sim$</tex-math></inline-formula>400 km s<inline-formula><tex-math>$^{-1}$</tex-math></inline-formula>, implying the development of turbulence. These characteristics indicate that we are observing sloshing motion with some inclination angle following BCG and that gas phases with different specific entropy participate in sloshing with their own velocities, as expected from simulations. No significant evidence for a high-redshift ICM component associated with the subcluster Abell 2319B was found in the region covered by the current Resolve pointings. These results highlight the importance of sloshing and turbulence in shaping the internal structure of Abell 2319. Further deep observations are necessary to better understand the mixing and turbulent processes within the cluster....

XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J1703+7849 on 2025-11-01 TT. The source position is determined to be (R.A., Dec.) = (255.836, +78.820), with a systematic error of &amp; sim; 40 arcsec....

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 (&lt;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....

We stack 3.75 Ms of early XRISM Resolve observations of 10 galaxy clusters to search for unidentified spectral lines in the E = 2.5─15 keV band (rest frame), including the E = 3.5 keV line reported in earlier low spectral resolution studies of cluster samples. Such an emission line may originate from the decay of the sterile neutrino, a warm dark matter (DM) candidate. No unidentified lines are detected in our stacked cluster spectrum, with the 3σ upper limit on the m_s ∼ 7.1 keV DM particle decay rate (which corresponds to an E = 3.55 keV emission line) of Γ ∼ 1.0 × 10⁻²⁷ s⁻¹. This upper limit is 3─4 times lower than the one derived by Hitomi Collaboration from the Perseus observation but still 5 times higher than the XMM-Newton detection reported by E. Bulbul et al. in the stacked cluster sample. XRISM Resolve, with its high spectral resolution but small field of view, may reach the sensitivity needed to test the XMM-Newton cluster sample detection by combining several years worth of future cluster observations....

Cherenkov Telescope Array Observatory (CTAO) is the next-generation ground-based <inline-formula><tex-math>$\gamma$</tex-math></inline-formula>-ray observatory operating in the energy range from <inline-formula><tex-math>$20\, \mathrm{GeV}$</tex-math></inline-formula> up to <inline-formula><tex-math>$300\, \mathrm{TeV}$</tex-math></inline-formula>, with two sites in La Palma (Spain) and Paranal (Chile). It will consist of telescopes of three sizes, covering different parts of the large energy range. We report on the performance of Large-Sized Telescope prototype (LST-1) in the detection and characterization of extragalactic <inline-formula><tex-math>$\gamma$</tex-math></inline-formula>-ray sources, with a focus on the reconstructed <inline-formula><tex-math>$\gamma$</tex-math></inline-formula>-ray spectra and variability of classical bright BL Lacertae objects, which were observed during the early commissioning phase of the instrument. LST-1 data from known bright <inline-formula><tex-math>$\gamma$</tex-math></inline-formula>-ray blazars ─ Markarian 421, Markarian 501, 1ES 1959+650, 1ES 0647+250, and PG 1553 + 113 ─ were collected between 2020 July 10, and 2022 May 23, covering a zenith angle range of 4<inline-formula><tex-math>$^\circ$</tex-math></inline-formula> to 57<inline-formula><tex-math>$^\circ$</tex-math></inline-formula>. The reconstructed light curves were analysed using a Bayesian block algorithm to distinguish the different activity phases of each blazar. Simultaneous Fermi-LAT data were utilized to reconstruct the broad-band <inline-formula><tex-math>$\gamma$</tex-math></inline-formula>-ray spectra for the sources during each activity phase. High-level reconstructed data in a format compatible with gammapy are provided together with measured light curves and spectral energy distributions (SEDs) for several bright blazars and an interpretation of the observed variability in long and short time-scales. Simulations of historical flares are generated to evaluate the sensitivity of LST-1. This work represents the first milestone in monitoring bright BL Lacertae objects with a CTAO telescope....

We present the first results from the X-ray Transient Search (XTS) system using the Xtend instrument (38.5^'×38.5^' field of view) onboard the X-ray Imaging and Spectroscopy Mission. XTS enables automatic detection and characterization of variable and transient X-ray sources using data from the large-format imaging CCD camera Xtend. It operates as a semi-automated pipeline that processes quick-look data within hours of downlink, identifies candidate transients, and reports confirmed events through The Astronomer's Telegram. During the performance verification phase, XTS successfully detected and publicly reported 17 transient events, including eleven stellar flares, one outburst from a high-mass X-ray binary, and one supernova. Xtend's field of view of 38.5^'×38.5^' and its continuous multiday observations provide a unique capability for monitoring variability over hour-to-day timescales with a 1-day point-source sensitivity of ∼10^-14 erg cm^-2 s^-1. This 1-day sensitivity is well below that of all-sky monitors (∼10^-9 erg cm^-2 s^-1) and is below that of scanning surveys such as SRG/eROSITA and Einstein Probe/WXT (∼10^-13 erg cm^-2 s^-1). Although Xtend lacks the wide instantaneous coverage and rapid cadence of these surveys, its uninterrupted observations enable the complete tracking of longer-duration phenomena, such as stellar flares or X-ray binary outbursts, over a period of 1 to 4 days. XTS thus provides a new observational regime in time-domain X-ray astronomy: combining high sensitivity, uninterrupted day-scale coverage, and near real-time alert capability within a pointed mission. It complements both high-cadence all-sky monitors and deep pointed observatories by enabling detailed monitoring of intermediate-brightness phenomena over medium timescales. With future improvements in automation and coordination, XTS will serve as a key link between X-ray transient discovery and follow-up spectroscopy, contributing to the growing field of time-domain astrophysics....

XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J0915+4102on 2025-10-21 TT. The source position is determined to be (R.A., Dec.) = (138.787, 41.035), with a systematic error of &amp; sim; 40 arcsec....

XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J2202-3206 on 2025-10-25 TT. The source position is determined to be (R.A., Dec.) = (330.444, -32.106), with a systematic error of &amp; sim; 40 arcsec....

We report the results from the ground and on-orbit verifications of the X-ray Imaging and Spectroscopy Mission timing system when the satellite clock is not synchronized to the Ground Positioning System (GPS) time. In this case, the time is determined by a free-run quartz oscillator of the clock, whose frequency changes depending on its temperature. In the thermal vacuum test performed in 2022, we obtained the GPS unsynchronized mode data and the temperature-versus-clock frequency trend. Comparing the time values calculated from the data and the true GPS times when the data were obtained, we confirmed that the requirement (within a 350-μs error in the absolute time, accounting for both the spacecraft bus and ground systems) was satisfied in the temperature conditions of the thermal vacuum test. We also simulated the variation of the timing accuracy in the on-orbit temperature conditions using the Hitomi on-orbit temperature data and found that the error remained within the requirement over ∼3×10⁵ s. The on-orbit tests were conducted in 2023 September and October as part of the bus system checkout. The temperature-versus-clock frequency trend remained unchanged from that obtained in the thermal vacuum test, and the observed time drift was consistent with that expected from the trend....

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)^{1, 2, 3─4} and supermassive black holes⁵. 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 (L ≳ L_Edd). 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 galaxies⁶. 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 (L ≳ L_Edd). 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 (v ~ 0.3c) winds seen in recent Resolve observations of a supermassive black hole at a similarly high Eddington ratio⁷....

The AXIS Community Science Book represents the collective effort of 592 scientists worldwide to define the transformative science enabled by the Advanced X-ray Imaging Satellite (AXIS), a next-generation X-ray mission selected by NASA's Astrophysics Probe Program for Phase A study. AXIS will advance the legacy of high-angular-resolution X-ray astronomy with ~1.5'' imaging over a wide 24' field of view and an order of magnitude greater collecting area than Chandra in the 0.3-12 keV band. Combining sharp imaging, high throughput, and rapid response capabilities, AXIS will open new windows on virtually every aspect of modern astrophysics, exploring the birth and growth of supermassive black holes, the feedback processes that shape galaxies, the life cycles of stars and exoplanet environments, and the nature of compact stellar remnants, supernova remnants, and explosive transients. This book compiles 138 community-contributed science cases developed by five Science Working Groups focused on AGN and supermassive black holes, galaxy evolution and feedback, compact objects and supernova remnants, stellar physics and exoplanets, and time-domain and multi-messenger astrophysics. Together, these studies establish the scientific foundation for next-generation X-ray exploration in the 2030s and highlight strong synergies with facilities of the 2030s, such as JWST, Roman, Rubin/LSST, SKA, ALMA, ngVLA, and next-generation gravitational-wave and neutrino networks....

We present very high-energy optical photometry and spectroscopic observations of SN 2024bch in the nearby galaxy NGC 3206 (∼20 Mpc). We used gamma-ray observations performed with the first Large-Sized Telescope (LST-1) of the Cherenkov Telescope Array Observatory (CTAO) and optical observations with the Liverpool Telescope (LT) combined with data from public repositories to evaluate the general properties of the event and the progenitor star. No significant emission above the LST-1 energy threshold for this observation (∼100 GeV) was detected in the direction of SN 2024bch, and we computed an integral upper limit on the photon flux of F_γ(&gt; 100 GeV)≤3.61 × 10⁻¹² cm⁻² s⁻¹ based on six nonconsecutive nights of observations with the LST-1, between 16 and 38 days after the explosion. Employing a general model for the gamma-ray flux emission, we found an upper limit on the mass-loss-rate to wind-velocity ratio of <inline-formula> Ṁ/u_w ≤ 10⁻⁴ M_⊙/ yr s/km <mml:math> <mml:mrow> <mml:mover> <mml:mi>M</mml:mi> <mml:mo>˙</mml:mo> </mml:mover> <mml:mo>/</mml:mo> <mml:msub> <mml:mi>u</mml:mi> <mml:mrow> <mml:mtext>w</mml:mtext> </mml:mrow> </mml:msub> <mml:mo>≤</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:msup> <mml:mfrac> <mml:msub> <mml:mi>M</mml:mi> <mml:mo>⊙</mml:mo> </mml:msub> <mml:mrow> <mml:mspace></mml:mspace> <mml:mtext>yr</mml:mtext> </mml:mrow> </mml:mfrac> <mml:mfrac> <mml:mrow> <mml:mtext>s</mml:mtext> </mml:mrow> <mml:mrow> <mml:mspace></mml:mspace> <mml:mtext>km</mml:mtext> </mml:mrow> </mml:mfrac> </mml:mrow> </mml:math> </inline-formula>, although gamma-gamma absorption could potentially have skewed this estimation, effectively weakening our constraint. From spectro-photometric observations we found progenitor parameters of M_pr = 11 ─ 20 M_⊙ and R_pr = 531 ± 125 R_⊙. Finally, using archival images from the Hubble Space Telescope, we constrained the luminosity of the progenitor star to log (L_pr/L_⊙) ≤ 4.82 and its effective temperature to T_pr ≤ 4000 K. Our results suggest that SN 2024bch is a type IIn-L supernova that originated from a progenitor star consistent with a red supergiant. We show how the correct estimation of the mass-loss history of a supernova will play a major role in future multiwavelength observations....

Context. 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. Aims. We revised the status of the cross-calibration among the scientific payload on board four operation missions: Chandra, NuSTAR, XMM-Newton, 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. Methods. 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. Results. 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....

This paper describes the development, design, ground verification, and in-orbit verification, performance measurement, and calibration of the timing system for the X-Ray Imaging and Spectroscopy Mission (XRISM). The scientific goals of the mission require an absolute timing accuracy of 1.0~ms. All components of the timing system were designed and verified to be within the timing error budgets, which were assigned by component to meet the requirements. After the launch of XRISM, the timing capability of the ground-tuned timing system was verified using the millisecond pulsar PSR~B1937+21 during the commissioning period, and the timing jitter of the bus and the ground component were found to be below $15~\mu$s compared to the NICER (Neutron star Interior Composition ExploreR) profile. During the performance verification and calibration period, simultaneous observations of the Crab pulsar by XRISM, NuSTAR (Nuclear Spectroscopic Telescope Array), and NICER were made to measure the absolute timing offset of the system, showing that the arrival time of the main pulse with XRISM was aligned with that of NICER and NuSTAR to within $200~\mu$s. In conclusion, the absolute timing accuracy of the bus and the ground component of the XRISM timing system meets the timing error budget of $500~\mu$s....

XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J1045-5941 on 2025-09-04 TT. The source position is determined to be (R.A., Dec.) = (161.422, -59.806), with a systematic error of &amp; sim; 40 arcsec....

XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J1044-5941 on 2025-09-05 TT. The source position is determined to be (R.A., Dec.) = (160.944, -59.678), with a systematic error of &amp; sim; 40 arcsec....

XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J0450-5858 on 2025-09-14 TT. The source position is determined to be (R.A., Dec.) = (72.541, -58.960), with a systematic error of &amp; sim; 40 arcsec....

XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J0525+0135 on 2025-09-17 TT. The source position is determined to be (R.A., Dec.) = (81.292, 1.599) with a systematic error of &amp; sim; 40 arcsec....

XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J0525+0135 on 2025-09-18 TT. The source position is determined to be (R.A., Dec.) = (81.257, 1.582) with a systematic error of &amp; sim; 40 arcsec....

XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J0525+0135 on 2025-09-22 TT. The source position is determined to be (R.A., Dec.) = (81.257, 1.582) with a systematic error of &amp; sim; 40 arcsec....

XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J0525+0201 on 2025-09-22 TT. The source position is determined to be (R.A., Dec.) = (81.416, 2.022) with a systematic error of &amp; sim; 40 arcsec....

XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J0655-5848 on 2025-09-09 TT. The source position is determined to be (R.A., Dec.) = (103.805, -58.807), with a systematic error of &amp; sim; 40 arcsec....

XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J0629-5857 on 2025-09-10 TT. The source position is determined to be (R.A., Dec.) = (97.207, -58.942), with a systematic error of &amp; sim; 40 arcsec....

XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J0631-5849 on 2025-09-10 TT. The source position is determined to be (R.A., Dec.) = (97.865, -58.818), with a systematic error of &amp; sim; 40 arcsec....

The XRISM observatory is observing the &amp; psi; Orionis cluster (R.A., Dec.) = (81.25, 1.7), and has detected flares from two stars during this observation. XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J0525+0142 on 2025-09-20 TT. The source position is determined to be (R.A., Dec.) = (81.141, 1.698), with a systematic error of &amp; sim; 40 arcsec....

Cassiopeia A (Cas A) is the youngest known core-collapse supernova remnant in the Galaxy and is perhaps the best-studied supernova remnant in X-rays. Cas A has a line-rich spectrum dominated by thermal emission and, given its high flux, it is an appealing target for high-resolution X-ray spectroscopy. Cas A was observed at two different locations during the Performance Verification phase of the X-ray Imaging and Spectroscopy Mission (XRISM), one location in the south-eastern part of the remnant and one in the north-western part. This paper serves as an overview of these observations and in it we discuss some of the issues relevant for the analysis of the data. We present maps of the so-called spatial-spectral mixing effect due to the fact that the XRISM point-spread function is larger than a pixel in the Resolve calorimeter array. We analyze spectra from two bright, on-axis regions such that the effects of spatial-spectral mixing are minimized. We fit these spectra with a semi-empirical model consisting of two thermal components, a non-thermal component, and a background model. We find that it is critical to include redshifts/blueshifts and broadening of the emission lines in the two thermal components to achieve a reasonable fit, given the high spectral resolution of the Resolve calorimeter. We fit the spectra with two versions of the AtomDB atomic database (3.0.9 and 3.1.0) and two versions of the SPEX (3.08.00 and 3.08.01<inline-formula><tex-math>$^{*}$</tex-math></inline-formula>) spectral fitting software. We report the significant differences in the fitted parameters so that users might understand which results are sensitive to the atomic data version. Overall we find good agreement between AtomDB 3.1.0 and SPEX 3.08.01<inline-formula><tex-math>$^{*}$</tex-math></inline-formula> for the spectral models considered in this paper. The most significant difference we found between AtomDB 3.0.9 and 3.1.0 and between AtomDB 3.1.0 and SPEX 3.08.01<inline-formula><tex-math>$^{*}$</tex-math></inline-formula> is the Ni abundance, with the new atomic data favoring a considerably lower (up to a factor of 3) Ni abundance compared with the previous versions. Both regions exhibit significantly enhanced abundances compared to Solar values, indicating that supernova ejecta dominate the emission in these regions. We find that the abundance ratios of <inline-formula><tex-math>${\rm Ti/Fe}$</tex-math></inline-formula>, <inline-formula><tex-math>${\rm Mn/Fe}$</tex-math></inline-formula>, and <inline-formula><tex-math>${\rm Ni/Fe}$</tex-math></inline-formula> are significantly lower in the north-west than the south-east, with the <inline-formula><tex-math>${\rm Ti/Fe}$</tex-math></inline-formula> and <inline-formula><tex-math>${\rm Mn/Fe}$</tex-math></inline-formula> ratios consistent with zero in the north-west. These different abundance ratios from regions on opposite sides of the remnant strengthen the case for an asymmetric explosion of the progenitor. We describe the semi-empirical models that were developed and suggest that they might be useful in the calibration of moderate spectral resolution instruments....

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 <inline-formula><tex-math>$R_{2500}$</tex-math></inline-formula> (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....

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 Heα emission, which is the brightest feature in the Resolve spectrum, to vary by ±300 km s^‑1 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 Heα emission, and also for intermediate-mass elements Si, S, Ar, and Ca, traced by the Lyα 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....

Abstract 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 λ _Edd ∼ 0.05 (10 M _⊙/M _BH). 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 XXV separated into resonance and intercombination components and H-like Fe XXVI 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 (v = 0.026–0.033c). 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.

Abstract The Galactic Center region was observed with the X-Ray Imaging and Spectroscopy Mission (XRISM) X-ray observatory during the performance verification phase in 2024 and a point-like X-ray source was detected with the X-ray imager Xtend at a position of $(\alpha , \delta )_{\rm J2000.0}=({17^{\rm h}46^{\rm m}10{_{.}^{\rm s } }8}, {-29^{\circ}00^{\prime }21^{\prime \prime } })$, which is thus named XRISM J174610.8-290021. This source was bright in February to March and showed time variations in count rate by more than one order of magnitude in one week. The 2–10 keV X-ray luminosity was ${\sim }10^{35}$ erg s$^{-1}$ for the assumed distance of 8 kpc. However, after six months, it was below the detection limit. We found a hint of periodicity of 1537 s from timing analysis. The XRISM/Xtend spectrum has emission lines from helium-like iron (Fe xxv–He$\alpha$) at 6.7 keV and hydrogen-like iron (Fe xxvi–Ly$\alpha$) at 6.97 keV; their intensity ratio is unusual with the latter being four times stronger than the former. If the emission is of thermal origin, the ionization temperature estimated from the iron-line intensity ratio is $\sim$30 keV, which is inconsistent with the electron temperature estimated from the thermal bremsstrahlung, $\sim$7 keV. Spectral models of magnetic cataclysmic variables, which are often seen in the Galactic Center in this luminosity range, are found to fail to reproduce the obtained spectrum. By contrast, we found that the spectrum is well reproduced with the models of low-mass X-ray binaries containing a neutron star plus two narrow Gaussian lines. We consider that the source is intrinsically bright reaching $10^{37}$ erg s$^{-1}$, but is blocked from direct view due to a high inclination and only the scattered emission is visible. The photo-ionized plasma above the accretion disk with an ionization parameter of ${\sim }10^{5}$ may explain the unusual iron line ratio. We further discuss the potential contribution of point sources of the type of XRISM J174610.8-290021 to the diffuse Galactic Center X-ray emission.

Abstract Young supernova remnants (SNRs) provide crucial insights into explosive nucleosynthesis products and their velocity distribution soon after the explosion. However, these velocities are influenced by the dynamics of the circumstellar medium (CSM), which in young core-collapse SNRs originates from the progenitor’s late-phase mass loss. Cassiopeia A (Cas A), the youngest known Galactic core-collapse SNR, was studied to analyze the spatial distribution of silicon and sulfur radial velocities using two high-spectral-resolution observations from the XRISM/Resolve imaging spectrometer. Resolve’s capabilities enabled the detailed characterization of Si xiii, Si xiv, S xv, and S xvi lines, whose line shapes can be resolved and modeled using Gaussian radial velocity components. The radial velocities measured generally align with previous CCD-based results, confirming that they were not artifacts caused by blended lines or ionization variations. Modeling line profiles with two-component Gaussians improved fits in some regions, revealing distinct redshifted (back side) and blueshifted (front side) components only in a few specific areas. In most regions, however, both components were either both redshifted (north-west) or both blueshifted (south-east), consistent with the patchy ejecta shell morphology seen in optically emitting fast-moving knots. The individual line components revealed line broadening ranging from $\sigma _v \approx 200$ to $\sigma _v \approx 2000$ ${\rm km\, s^{-1 } }$. Components with $1000 \lesssim \sigma _v \lesssim 2000$ ${\rm km\, s^{-1 } }$ are consistent with previously determined reverse-shock velocities, suggesting non-equilibrated or partially equilibrated ion temperatures. Narrow components with small radial velocities found near Cas A’s projected center likely originate from shocked CSM plasma. But the low radial velocity and small $\sigma _v$ poses a challenge to identify these components with either the front side or back side of the SNR, or a blend of both sides.

Abstract The expansion structure of supernova remnants is important for understanding not only how heavy elements are distributed into space, but also how supernovae explode. The ejecta expansion structure of the young core-collapse supernova remnant Cas A is investigated, with Doppler parameter mapping of the Fe–K complex by the Resolve microcalorimeter onboard the X-ray Imaging and Spectroscopy Mission (XRISM). It is found that the Fe ejecta are blueshifted in the south-east and redshifted in the north-west, indicating an incomplete shell structure, similar to intermediate-mass elements (IMEs) such as Si and S. The Fe has a velocity shift of $\sim$1400 and $\sim$2160 km s$^{-1}$ in the north-west and south-east regions, respectively, with the error range of a few hundred km s$^{-1}$. These values are consistent with those for the IMEs in the north-west region, but larger than those for the IMEs in the south-east region, although the large error region prevented us from concluding which component has significantly higher velocity. The line broadening is larger in the center with values of $\sim$2000–3000 km s$^{-1}$, and smaller near the edges of the remnant. The radial profiles of the Doppler shift and broadening of the IMEs and Fe indicate that the Fe ejecta may expand asymmetrically as IME ejecta, although the large error regions do not allow us to confirm this. Moreover, we see little bulk Doppler broadening of the Fe lines in the north-eastern jet region whereas the IME lines exhibit significant broadening. No such narrow lines are detected in the north-west region. These findings suggest an asymmetric expansion of the ejecta potentially driven by large-scale asymmetries originating from the supernova explosion. This interpretation aligns with the large-scale asymmetries predicted by models of neutrino-driven supernova explosions.