arXiv subjects

Misaki Mizumoto

Publications and source records attributed to Misaki Mizumoto.

At least 19 recordsLinked to original sources

arXiv2026

XRISM Resolve Spectroscopy of GX 5-1: Constraints on Iron Spectral Features in a Luminous Neutron-Star Binary

GX 5-1 is one of the brightest persistent neutron-star low-mass X-ray binaries in the Galaxy and one of the classical Z sources accreting at luminosities close to or above the Eddington limit. We present the first high-resolution X-ray spectroscopic study of GX 5-1 with the Resolve micro-calorimeter onboard the X-Ray Imaging and Spectroscopy Mission (XRISM), based on a 50 ks AO1 observation. With an energy resolution of approximately 5 eV at 6 keV, Resolve enables a sensitive non-dispersive search for weak and narrow spectral features in this luminous source. During the observation, GX 5-1 was located on the horizontal branch of the Z track. Although rapid spectral variability is detected on timescales of tens of ks, the variability is dominated by changes in the continuum spectral shape. No statistically significant emission or absorption features are detected in the time-averaged spectrum. Using matched-filter searches and time-resolved spectroscopy, we place stringent upper limits on the equivalent widths of low-ionization Fe K-alpha emission and highly ionized Fe XXV and Fe XXVI K-alpha transitions of $EW \lesssim$ a few eV. These results reinforce the picture that, in GX 5-1, classical Fe K diagnostics such as reflection- or wind-related features are either intrinsically weak, strongly ionized, geometrically diluted, or suppressed by rapid continuum variability. Placed in the context of the long observational history of GX 5-1 as a continuum-dominated Z source, the present XRISM result shows that this picture continues to hold even at calorimeter resolution. GX 5-1 therefore provides an important benchmark for high-resolution studies of luminous neutron-star accretion flows and demonstrates the capability of XRISM to place meaningful constraints on line formation even when no significant features are detected.

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arXiv2026

The Geometry of Ultra-Fast Outflows Probed by Soft X-ray Variability in PDS 456

Constraining the location and geometry of ultra-fast outflows (UFOs) is essential for identifying where they are launched and how they are accelerated. We investigate the soft X-ray variability of the luminous quasar PDS 456 using simultaneous March 2024 observations with XRISM/Xtend and NuSTAR. A model-independent comparison between the flare and quiescent phases reveals spectral variability around 1 keV in the rest frame, while the hard X-ray spectral shape remains nearly unchanged. Broadband spectral fitting shows that the soft X-ray structure is well described by a partial-covering low-ionization UFO with $\log (ξ/(\mathrm{erg~cm~s^{-1}})) \simeq 3.1$ and $v_{\mathrm{out}} \simeq 0.30c$. Time-sliced spectral analysis further reveals significant variability in the covering fraction of this absorber. Interpreting this variability as transverse motion across the X-ray source, we constrain the crossing velocity to be $v_{\mathrm{cross}} \lesssim 5 \times 10^{-3}c$ and derive a lower limit on the absorber distance of $r \gtrsim 4 \times 10^3 R_{\mathrm{g}}$. This location is substantially farther out than the high-ionization UFO previously inferred at ~200-600 $R_{\mathrm{g}}$, while the two phases have comparable outflow velocities. The resulting velocity-distance structure disfavors a self-similar magnetocentrifugal wind and instead suggests either radiation-pressure acceleration following a Castor-Abbott-Klein-like velocity law or compact magnetic acceleration through magnetic reconnection. These results demonstrate that soft X-ray partial-covering variability can provide a geometrical probe of UFOs and directly connect spectral variability to wind acceleration.

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arXiv2026

Vigorous turbulence driven by quasar-mode feedback in a cluster core

Quasars are among the most luminous objects. They are powered by accretion onto supermassive black holes. They are thought to impact cosmological evolution primarily through energetic winds, known as quasar-mode feedback, yet the efficiency and spatial extent of this process remain poorly constrained. Here we present X-Ray Imaging and Spectroscopy Mission (XRISM) observations of H1821+643---the nearest galaxy cluster with a central quasar (redshift z = 0.297)---which was a rare opportunity to directly probe quasar-mode feedback in the intracluster medium. High-resolution spectroscopy reveals exceptionally broadened Fe XXV emission lines from the intracluster medium, with a velocity dispersion of approximately 300 km/s, far exceeding values observed in nearby cluster cores. These lines originate predominantly at radii of 20-100 kpc from the centre. Assuming that turbulence from a quasar-driven shock led to the broadening of the lines, the energy injected by the quasar beyond galactic scales ($\gtrsim$20 kpc) is estimated to be $\gtrsim$1-10% of its radiative energy. Notably, this feedback efficiency exceeds previous multiwavelength estimates by orders of magnitude ($\lesssim$0.01%) and reaches the levels required by the latest cosmological hydrodynamical simulations. This finding of vigorous turbulence indicates that quasar-mode feedback plays a central role in regulating galaxy and cluster evolution at high redshift.

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arXiv2026

Chemical enrichment of the Perseus cluster core seen by XRISM/Resolve

The intracluster medium (ICM) is rich in chemical elements, produced by core-collapse (SNcc) and Type Ia supernovae (SNIa) over the last $\sim$12 Gyr. Whereas cluster outskirts are uniformly enriched with Fe at $\sim$0.3 solar - strongly suggesting that the gas had been pre-enriched during or before the assembly of galaxies into clusters, the Fe abundance is known to centrally increase in the core of relaxed clusters. The origin of these central Fe peaks however, as well as the apparent presence of mysterious drops previously reported in the very centre of a number of systems, remain to be clarified. In this paper, we address these two questions by measuring the spatial distribution of Fe and its relative Si/Fe, S/Fe, Ar/Fe, Ca/Fe, Cr/Fe, Mn/Fe, and Ni/Fe ratios in the X-ray bright, nearby Perseus cluster. We take advantage of the unprecedented spectral resolution ($\sim$5 eV) offered by the Resolve microcalorimeter on board XRISM, which observed four distinct pointings of Perseus out to $\sim$250 kpc ($\sim$0.2$r_{500}$) during its Performance Verification phase. Although the presence of an X-ray bright AGN challenges a precise quantification of absolute abundances in the very core, our baseline analysis rules out a strong drop with $>$2$σ$ confidence, at variance with previous CCD measurements. In addition, we find a remarkable spatial uniformity of X/Fe ratios, supporting the idea of negligible late SNIa enrichment from the brightest cluster galaxy NGC 1275. We also compare the overall chemical composition of the Perseus ICM with SNcc and SNIa nucleosynthesis yield models, finding that the co-existence of two separate SNIa enrichment channels is not needed to reproduce the ICM ratios satisfactorily.

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arXiv2026

Observation of A Solar Like Magnetic Reconnection Event in an AGN Corona with XRISM

The X-ray source in AGN is commonly referred to as the corona by analogy to stellar coronae. The similarities between the two suggest that the heating mechanism of AGN coronae is magnetic reconnection -- as in cool stars -- but this has not yet been directly observed. This work presents the first observational evidence for a magnetic reconnection flare in an AGN corona. We report on a flare in NGC 3783, which was observed with XRISM/Xtend and XMM-Newton/EPIC-PN exhibiting distinct temporal evolution in soft ($<2.0\,$keV) and hard ($>2.0\,$keV) X-rays. An Ultra-Fast Outflow (UFO) was detected during the event. The flare features the Neupert effect -- a temporal signature of the hard light curve correlating with the time derivative of the soft light curve, which shows that the flare is powered by magnetic reconnection, The Neupert effect is widely observed in the Sun, with Coronal Mass Ejections (CMEs) playing a role analogous to the UFO. We derive an upper limit of $30 \, R_g$ on the height of the magnetic loop from which the flare originates. Using the UFO's measured properties to characterize the magnetic field, we obtain $B > 1.3 \times 10^4\,$G for the field annihilated during the flare from total energy considerations, and $B \approx 500\,$G for the momentary magnetic field during reconnection from a dynamical consideration.

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arXiv2026

XRISM Time-resolved Fe K$α$ Spectroscopy of NGC 4395: Time-variable Inner-disk Emission

We report the first XRISM observation of the low-mass AGN in the nearby dwarf galaxy NGC 4395 ($M_{\rm BH}\sim10^{4-5}\,M_\odot$), complemented by a simultaneous NuSTAR observation. We constrained the continuum by jointly fitting the XRISM/Resolve (2-12 keV) and NuSTAR (3-30 keV) spectra while excluding the Fe K band (5.5-7.5 keV). Relative to this baseline continuum, the time-averaged Resolve spectrum revealed an unresolved neutral Fe K$α$ core with a velocity width of $\lesssim$110 km s$^{-1}$ and an adjacent redward wing. The red wing was well reproduced by an additional relativistically broadened Fe K component. Furthermore, time-resolved spectroscopy with $\approx$87 ks bins showed that the diskline profile varied significantly over the $\sim$400 ks observation. This evolution can be interpreted in terms of changes in the inner radius of the line-emitting region, together with a possible inclination modulation with a period of $\approx$210 ks. If interpreted as Lense-Thirring precession of a tilted inner flow, the observed period would favor the low end of the black hole mass estimates ($M_{\rm BH}\approx9\times10^3\,M_\odot$) and imply a moderate spin ($a\gtrsim0.6$). These results highlight the capability of XRISM to track relativistic disk dynamics in AGNs.

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arXiv2026

XRISM High-Resolution X-ray Spectroscopy of Cygnus X-1 -- Orbital and Short-Term Variability of Iron Absorption

We present the first high-resolution spectroscopy of the black hole high-mass X-ray binary Cygnus X-1 with XRISM, including orbital-phase-resolved analyses and tentative evidence of short-term variability in the Fe-K band on second timescales. Using data from the Performance Verification phase in April 2024, we analyzed spectral variability across orbital phases with the Resolve microcalorimeter and the Xtend CCD imager. The unprecedented resolution of Resolve reveals variability in highly ionized Fe absorption lines. The absorption features show orbital-phase-dependent variability in column density, ionization state, and blueshifted velocity, suggesting structural variations in the focused stellar wind along the line of sight. We also find indications of subtle broadening of the neutral Fe emission profile. In addition, intensity-sorted spectroscopy during dip phases suggests possible variability on timescales of a few seconds in the absorption features, consistent with cooler, denser and lower-ionized gas clumps. Although the statistical significance is limited, these results hint that the stellar wind and the X-rays from the accretion disk around the black hole may interact on timescales as short as a few seconds. These XRISM results constrain wind-fed accretion in Cyg X-1 and highlight Resolve's capability to probe plasma environments in high-mass X-ray binaries.

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arXiv2026

XRISM High-Resolution X-ray Spectroscopy of Cygnus X-1 -- highly ionized Iron absorption structures

We present the first high-resolution X-ray spectral analysis of Cygnus X-1 using XRISM. The observation was carried out from April 7 to 10, 2024, covering the orbital phase range 0.65--0.17 during its low/hard state. Taking advantage of the exceptional energy resolution of the Resolve instrument, we examined highly ionized iron absorption lines and characterized the ionization states, column densities, and line-of-sight velocities of the absorbing plasma. Spectral analysis revealed an ionization parameter of approximately 3, column densities of a few times 10^21 cm^-2, and a blueshifted velocity of approximately 100 km s^-1. The observation was divided into two phases: before and after orbital phase phi_orb = 0.9, corresponding to non-dipping and dipping intervals. While only weak absorption features were present before phi_orb = 0.9, strong absorption by He-like and H-like Fe appeared during the dipping phase. We measured equivalent widths of 2.3 eV, 0.4 eV, and 1.2 eV for He-like Fe K-alpha, and H-like Ly-alpha1 and Ly-alpha2, respectively, demonstrating the capability of XRISM Resolve to securely detect narrow absorption features of only a few eV. These measurements trace the motion of the absorbing material and offer insight into the kinematics and spatial distribution of the wind in the vicinity of the black hole. These findings enhance our understanding of wind-fed accretion in Cygnus X-1 and highlight the importance of continued high-resolution X-ray observations to further constrain the physical properties of winds and accretion flows in high-mass X-ray binaries.

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arXiv2026

Complex Nuclear Structure in Seyfert 2 Galaxy NGC 4388 Revealed by XRISM Observation

We report results from the simultaneous XRISM (183 ks) and NuSTAR (62 ks) observations of the Seyfert-2 galaxy NGC 4388. This AGN has the brightest Fe K$α$ line among Compton-thin, obscured sources. To model the reflection continuum and fluorescent lines, we employ an updated version of XCLUMPY and a broad line region model with a disk-like geometry. The profile of the neutral Fe-K fluorescent line is well described as the sum of three components convolved with Gaussians with FWHM values of $\sim 290\ \mathrm{km\ s^{-1}}$, $\sim 1470\ \mathrm{km\ s^{-1}}$, and $\sim 11100\ \mathrm{km\ s^{-1}}$. These line widths correspond to radii of 1.5 pc, 0.060 pc, and $1.0\times10^{-3}$ pc by assuming Keplerian motion, which we interpret as the dusty torus, its inner edge region, and the BLR, respectively. The data suggest that the Fe K$α$ BLR component is larger than that of H$α$ (FWHM of 4500 $\mathrm{km\ s^{-1}}$) in the polarized optical spectrum, implying that the velocity field of the BLR is dominated by that parallel to the equatorial plane. In addition, Fe XXVI Ly$α$ and Fe XXV absorption lines are detected, characterized by $\logξ \sim 3.50~\mathrm{erg\ cm\ s^{-1}}$, $\log{N_{\mathrm{H}}} \sim 22.1~\mathrm{cm^{-2}}$, $v_{\mathrm{out}} \sim 40\ \mathrm{km\ s^{-1}}$, and $σ_v \sim 160\ \mathrm{km\ s^{-1}}$. We infer that the absorber is gravitationally bound and is possibly associated with a failed wind, consistent with a radiation-driven fountain flow.

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arXiv2026

XRISM spectroscopy of a crowded Galactic center region -- I. Disentangling the sources in the field of view

The Galactic center is a complex and crowded region hosting the supermassive black hole Sgr A*, numerous accreting compact objects, and diffuse X-ray emission. This paper presents the first in a series of studies analyzing the XRISM observation of the X-ray transient MAXI J1744-294/Swift J174540.2-290037, located $\sim18''$ from Sgr A*. The observation, conducted in March 2025, along with XMM-Newton and NuSTAR coverage, aimed to investigate the Fe emission features of MAXI J1744-294 during its outburst. However, the region surrounding the source is heavily contaminated by X-ray emission from various diffuse and point sources, including strong line contributions from the supernova remnant Sgr A East and the Galactic center X-ray emission (GCXE). Additionally, the nearby neutron star low-mass X-ray binary (NS-LMXB) AX J1745.6-2901 was also in outburst during the XRISM observation, further complicating the spectral analysis. This study focuses on disentangling the contributions of these overlapping sources by robustly modeling the background contamination and spatial-spectral mixing. We describe the methodologies, region selection, and data reduction techniques applied to the different instruments. Two complementary approaches -- empirical and physical modeling -- are employed to characterize diffuse emission and point-source contributions. The results provide a foundation for the detailed spectral analysis of MAXI J1744-294, AX J1745.6-2901, and the surrounding interstellar medium (ISM), which will be presented in subsequent papers. This study highlights the challenges and robust solutions for analyzing XRISM/Resolve data from crowded regions in conjunction with other X-ray telescope data.

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arXiv2026

A Fast, Hot Wind from a Nuclear Starburst

Galaxies with intense star formation often host multiphase, galaxy-scale winds powered by supernovae and fast stellar winds. These are strong enough to disrupt the star-forming interstellar medium, and they chemically enrich the surrounding circumgalactic medium. However, their launching mechanism remains unknown. Here we show that thermal gas pressure is sufficient to drive the multiphase wind in the prototypical starburst galaxy M82. Using a high energy-resolution ($ΔE = 4.5$ eV) XRISM Resolve spectrum, including detections of FeXXV 6.7 keV, ArXVII 3.1 keV, and SXVI 2.6 keV, we measure the temperature ($T = 2.3^{+0.5}_{-0.2} \times 10^7$ K) and mass ($M \approx 6 \pm 2 \times 10^5$ M$_\odot$) of the hot gas in the starburst and provide the first direct measurement of its line-of-sight velocity dispersion ($σ= 595^{+464}_{-128}$ km s$^{-1}$). These values are consistent with a freely-expanding wind exceeding the galactic escape velocity. The size of the FeXXV-emitting region suggests a hot gas outflow rate of $\dot{M} \approx 4$ M$_\odot$ yr$^{-1}$, carrying a total energy of $\dot{E} \approx 2 \times 10^{42}$ erg s$^{-1}$. This is sufficient to drive the molecular, atomic, and ionized outflows while transporting up to $\approx 2$ M$_\odot$ yr$^{-1}$ of hot gas to the intergalactic medium. The estimated supernova rate implies that $\approx$ 60% of the supernova energy must be thermalized in hot gas. Our results suggest that additional driving mechanisms, such as cosmic-ray pressure, are not required to launch the wind.

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arXiv2026

High Spectral Resolution X-ray Observations of the Evolved Supermassive Stellar Binary System $η$ Carinae - Iron K$α$ Band Profile Revealed with XRISM

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.

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arXiv2026

XRISM Discovery of Multiple Ionized Fe-K Emission and Absorption Components in Centaurus A

We present the first clear detection of ionized Fe-K emission and absorption components in the nearby radio galaxy Centaurus A, revealed by the high-resolution XRISM/Resolve detector. In the 6.5-6.9 keV band, XRISM reveals multiple Fe XXV and Fe XXVI emission components. One is a broad (with a width of sigma = 3000 km/s) and redshifted (+3400 km/s) component, originating at D = 0.02 pc from the central black hole. The other two components are narrow (with a width of sigma = 500 km/s) and exhibit redshifted and blueshifted velocities (+2600 km/s and -1500 km/s), originating from more distant regions (D = 0.1 pc). The photo-ionized model explains the broader component, while the two narrower components can be explained by either photo-ionization or collisional ionization. One interpretation is that the broader component is an outflow at ~10^2 R_S (R_S; Schwarzschild radius) and the narrow component is a shock-heated plasma close to the torus, with a possible connection to the JWST-discovered outflow outside the torus. Two blueshifted absorption lines are detected at ~7.1 keV (~10^4 km/s) and ~10.6 keV (~10^5 km/s). The line significance of the 10.6 keV line is above 98%. The absorption line components might be attributed to the broad emission component. These results demonstrate the high potential of XRISM/Resolve to characterize ionized emission and absorption features in the Fe-K band. Our findings establish a new benchmark in the study of circumnuclear environments in low-luminosity radio galaxies, thereby contributing to a broader understanding of AGN unification.

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arXiv2026

Resolving the Multiple Component Outflows in PG 1211+143: II. The Soft X-ray View of the Ultra Fast Outflow

The nearby quasar, PG 1211+143, has one of the prototype examples of an ultra fast outflow (UFO), as seen in several past XMM-Newton and Chandra observations. In December 2024, PG 1211+143 was observed simultaneously with XRISM Resolve and XMM-Newton, allowing both the Fe K and soft X-ray outflows to be examined at high resolution simultaneously. The Resolve spectrum revealed a forest of Fe K band absorption lines from the UFO (Mizumoto et al. 2026), comprising of up to six discrete velocity components ranging from $v/c=-0.074$ to $v/c=-0.40$. Here we present the simultaneous XMM-Newton RGS (Reflection Grating Spectrometer) spectrum, where three lower ionization counterparts of the Fe K velocity zones are observed; at $v/c=-0.074, -0.12$ and $-0.33$. The soft X-ray absorbers tend to be somewhat less ionized than their Fe K counterparts, with their opacity mainly arising from Fe L shell lines and highly ionized Oxygen. From comparing the Resolve and RGS absorbers, we show that the outflow can be parameterized with a density profile varying with radius as $r^{-5/3}$, while the lower ionization zones likely originate from denser clumps of gas. Pure electron scattering appears insufficient to provide enough thrust to power the wind, unless sufficient low ionization gas capable of radiative line driving exists outside of the line of sight. Overall, PG 1211+143 provides further evidence for the clumpy nature of accretion disk winds, as was recently revealed in the quasar PDS 456 with XRISM.

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arXiv2026

Indication of the Less-ionized Clumpy Ultra-Fast Outflows in Seyfert Galaxies

We present a systematic investigation of X-ray spectral variability of Seyfert 1 galaxies using a ``spectral-ratio model fitting'' technique, which we developed to estimate contribution of the putative clumpy absorbers to the spectral variations. Archival XMM-Newton observations of 12 active galactic nuclei were analyzed to constrain properties of these absorbers. Our analysis demonstrates that the soft X-ray variability is primarily governed by fluctuation of the partial covering fraction of mildly ionized clumpy clouds. In particular, for Mrk 335, PDS 456, and 1H 0707-495, outflow velocities of the clumpy absorbers are constrained from the blue-shifts of the Fe-L edge structure. The blue-shifted Fe-L edge successfully reproduces the well-known complex spectral feature near 1 keV in 1H 0707--495, which was often explained by invoking an ad hoc absorption structure. Notably, the inferred outflow velocities of the clumpy absorbers are comparable to, or even exceed, those associated with the Ultra-Fast Outflows (UFOs). Furthermore, we found a positive correlation between the outflow velocities and the intrinsic X-ray fluxes in two of four data sets, and the remaining two datasets also agree with this positive correlation, which supports a radiative-driven wind scenario that the X-ray/UV emission from the central black holes is causing the UFOs and the outflowing clumpy absorbers. In addition, the line-driven acceleration is likely playing a significant role, since the line opacities of the clumpy absorbers are highly sensitive to the flux changes. These findings provide a robust observational support for the ``hot inner and clumpy outer wind'' paradigm, suggesting a common origin for both the UFOs and the clumpy absorbers.

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arXiv2025

Delving into the depths of NGC 3783 with XRISM IV. Mapping of the accretion flow with Fe K$α$ emission lines

Using XRISM/Resolve $439 \, \rm ks$ time-averaged spectra of the well-known Seyfert-1.5 active galactic nucleus (AGN) in NGC 3783, we investigate the nature of the Fe K$α$ emission line at 6.4 keV, the strongest and most common X-ray line observed in AGN. Even the narrow 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 a neutral gas with negligible bulk velocity. The narrow and intermediate-width components have a full-width at half maximum (FWHM) of 350 $\pm$ 50 km/s and $3510 \pm 470 \, \rm km/s$, respectively, suggesting that they arise in the outer disk/torus and/or BLR. We detect a $10\%$ excess flux around 4 $-$ 7 keV that is not well described by a symmetric Gaussian line, but is consistent with a relativistically broadened emission line. In this paper, we take the simplest approach to model the asymmetric line as a single emission line (assuming either neutral, He-like or H-like iron) convolved with a relativistic disk line model. As expected, the inferred inclination angle is highly sensitive to the assumed ionization state, and ranges between $i=17-44^{ \circ}$. This model also constrains the black hole spin via the extent of the red wing: the required gravitational redshift in the fitted disk-line profile disfavors a non-spinning (Schwarzschild) black hole. The derived inner radius is close to the radius of the innermost stable circular orbit $r_{\rm ISCO}$ and strongly correlated with the black hole spin. To better constrain the spin, we fix the inner radius at $r_{\rm ISCO}$ and derive a lower limit on the spin of $a \ge 0.29$ at the 3 $σ$ confidence level. A Compton shoulder is detected in our data as well as a $2-3 \, σ$ detection of the Cr K$α$ and Ni K$α$ lines.

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arXiv2025

Disentangling Multiple Gas Kinematic Drivers in the Perseus Galaxy Cluster

Galaxy clusters, the Universe's largest halo structures, are filled with 10-100 million degree X-ray-emitting gas. Their evolution is shaped by energetic processes such as feedback from supermassive black holes (SMBHs) and mergers with other cosmic structures. The imprints of these processes on gas kinematic properties remain largely unknown, restricting our understanding of gas thermodynamics and energy conversion within clusters. High-resolution spectral mapping across a broad spatial-scale range provides a promising solution to this challenge, enabled by the recent launch of the XRISM X-ray Observatory. Here, we present the kinematic measurements of the X-ray-brightest Perseus cluster with XRISM, radially covering the extent of its cool core. We find direct evidence for the presence of at least two dominant drivers of gas motions operating on distinct physical scales: a small-scale driver in the inner ~60 kpc, likely associated with the SMBH feedback; and a large-scale driver in the outer core, powered by mergers. The inner driver sustains a heating rate at least an order of magnitude higher than the outer one. This finding suggests that, during the active phase, the SMBH feedback generates turbulence, which, if fully dissipated into heat, could play a significant role in offsetting radiative cooling losses in the Perseus core. Our study underscores the necessity of kinematic mapping observations of extended sources for robust conclusions on the properties of the velocity field and their role in the assembly and evolution of massive halos. It further offers a kinematic diagnostic for theoretical models of SMBH feedback.

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arXiv2025

Delving into the depths of NGC 3783 with XRISM III. Birth of an ultrafast outflow during a soft flare

The 2024 X-ray/UV observation campaign of NGC 3783, led by XRISM, revealed the launch of an ultrafast outflow (UFO) with a radial velocity of 0.19c (57000 km/s). This event is synchronized with the sharp decay, within less than half a day, of a prominent soft X-ray/UV flare. Accounting for the look-elsewhere effect, the XRISM Resolve data alone indicate a low probability of 2e-5 that this UFO detection is due to random chance. The UFO features narrow H-like and He-like Fe lines with a velocity dispersion of 1000 km/s, suggesting that it originates from a dense clump. Beyond this primary detection, there are hints of weaker outflow signatures throughout the rise and fall phases of the soft flare. Their velocities increase from 0.05c to 0.3c over approximately three days, and they may be associated with a larger stream in which the clump is embedded. The radiation pressure is insuffcient to drive the acceleration of this rapidly evolving outflow. The observed evolution of the outflow kinematics instead closely resembles that of solar coronal mass ejections, implying magnetic driving and, conceivably, reconnection near the accretion disk as the likely mechanisms behind both the UFO launch and the associated soft flare.

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