arXiv subjects

Daniele Rogantini

Publications and source records attributed to Daniele Rogantini.

At least 19 recordsLinked to original sources

arXiv2026

Relativistic outflows power a quasi-periodic eruption: constraints on energetics, mass loss, and emission mechanisms

Quasi-periodic eruptions (QPEs) are recurring bursts of X-ray radiation originating from supermassive black holes (SMBHs). They are an unprecedented type of structured, high-amplitude SMBH variability, but the physical origins of their regularity, timescales, energetics, and emission are uncertain. We present new XMM-Newton observations of the QPEs in ZTF19acnskyy/``Ansky'', constituting the deepest observations of individual bursts in any source thus far. The X-ray spectra reveal time-evolving P Cygni profiles comprising blueshifted absorption and redshifted emission from L-shell transitions of Fe XIX-XXIV, with column densities $N_H\sim 10^{22-23}$ cm$^{-2}$ and bulk velocities of $|v_w/c|\sim 0.2$, indicating relativistic mass ejections during each eruption. We construct a time-dependent analytical model of a wind turning on to self-consistently compute its evolving luminosity and ionization properties, and find that the light curve and spectral lines can be simultaneously produced by a wide-angle outflow with $\dot{M}\sim 10^{-9}-10^{-8}\,M_\odot$ s$^{-1}$ kinetically powering the X-rays with an efficiency of $L_X/\dot{E}_K\sim 0.1$. Each eruption ejects $\sim 10^{-3}\,M_\odot$ and $\gtrsim 10^{49}$ erg of kinetic energy, setting an upper bound on the QPE lifetime of $\lesssim30$ years if the underlying mass reservoir is $\sim1 M_\odot$, and implying that the bursts may result in detectable multiwavelength signatures of reverberation and feedback. These measurements provide new quantitative constraints on QPE energetics, emission mechanisms, and the mass/energy they recycle into their circumnuclear environments, as well as an observational probe for direct comparison with physical models and hydrodynamical simulations of QPEs.

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arXiv2026

Lynx2030 Science Analysis Group: Final Report

The Lynx2030 Science Analysis Group (SAG) was convened to reassess the scientific goals and technical drivers of the Lynx mission concept amid a rapidly evolving astrophysics landscape. Building on the original Lynx Concept Study, the SAG examined how recent discoveries, emerging facilities, and advances in instrumentation influence the scientific opportunities for a next-generation flagship X-ray observatory. Through focused working groups, the SAG investigated the scientific impact of enhanced capabilities: (i) improved angular resolution, (ii) broader bandpass coverage, (iii) an enhanced microcalorimeter, (iv) new capabilities and observing modes, and (v) larger fields of view. Across a broad range of topics, from the formation of the first black holes and the evolution of galaxies to the baryon cycle, compact objects, stellar explosions, multi-messenger astrophysics, and the dynamic high-energy Universe, the SAG finds that the scientific motivation for a Lynx-class observatory remains compelling and, in many areas, has significantly strengthened over the past decade, prominently through JWST's discovery of the "Little Red Dots", likely massive accreting black holes in infant galaxies whose nature is fundamentally an X-ray question. This report shows that modest extensions beyond the original Lynx design reference mission can unlock transformative science while preserving the observatory's core architecture. Powerful current and future facilities such as Roman, Rubin, JWST, SKA, ngVLA, LISA, and NewAthena highlight the unique role a high-angular-resolution, high-throughput X-ray observatory would play in the multi-wavelength and multi-messenger ecosystem of the 2030s and beyond. The findings of the Lynx2030 SAG confirm Lynx's central vision: an unprecedented view of the hot and energetic Universe, enabling discoveries that will define high-energy astrophysics in the coming decades.

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arXiv2026

The major cluster merger in Abell 2034 as seen by XRISM: Strong turbulence and spectral anomalies?

XRISM observations to date have shown that gas kinetic pressures in the intracluster medium (ICM) tend towards the low end of predictions from cosmological simulations. Here, we present a XRISM observation of the merging cluster Abell 2034, which exhibits the broadest emission lines yet observed in a galaxy cluster. We measure a velocity dispersion of ~470 km/s, corresponding to a kinetic pressure fraction of ~15%. This places A2034 at or above the high end of the theoretical predictions for similar-mass clusters. This large velocity dispersion may reflect Mach ~0.5 turbulence in the ICM and/or result from a core disruption driven by the ongoing head-on merger. We also detect a ~380 km/s gas bulk velocity gradient along the merger axis with an opposite sign to the galaxy velocity gradient, indicating a decoupling of the cluster galaxies (and dark matter) from the ICM. Finally, we report tentative evidence of several spectral anomalies, including a suppressed Fe He$α$-z line, an enhanced Fe Ly$α$-2 line, and a potential absorption feature at ~8.7 keV. The first two features may be explained by the combination of a multi-component ICM and a non-equilibrium ionization state in the wake of a merger shock. Deeper XRISM observations of this cluster are required to confirm these features. This work highlights the importance of kinematic measurements across a large sample of merging clusters as well as the need for deep XRISM observations to unveil more exotic physics in the ICM.

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arXiv2026

Investigation of Calcium Dust in the Interstellar Medium

Calcium is a highly depleted element in the interstellar medium (ISM), however its composition in the solid phase remains elusive. The detection of Ca-bearing dust has been limited due to its lack of distinct spectral features in the cold phase of the diffuse ISM. X-rays provide a direct method for exploring the absorption and scattering properties of interstellar dust. In this study, we utilize high-resolution X-ray absorption spectroscopy to characterize Ca-bearing dust analogs at the Ca K-edge using X-ray Absorption Fine Structure (XAFS). We present new X-ray absorption spectra of seven calcium-bearing interstellar dust analogs measured at the National Synchrotron Radiation Research Center (NSRRC) in Taiwan. The extinction cross sections, calculated from the laboratory measurements are incorporated in the dust absorption model AMOL of the X-ray spectral fitting tool SPEX. We select three Low Mass X-ray Binaries (LMXBs) with high column densities, GX 340+00, GX 5-1, and GX 13+1, as background sources to study the intervening ISM along their sightlines. The best-fit models are compared with Chandra archive data using SPEX. Additionally, we employ simulations with the XRISM and NewAthena telescopes to achieve enhanced resolution and more effective coverage at the energy range near the Ca K-edge. These simulations set the boundary conditions for the future X-ray observation of calcium in the interstellar medium.

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arXiv2026

Kinematically Resolving the Fe K Complex in Her X-1: The Accretion Disk and Ionized Wind Across X-ray Eclipses

We present XRISM/Resolve spectroscopy of Her X-1 across three X-ray eclipses observed in September 2024, resolving its iron K complex through the ingress, mid-eclipse, and egress phases. The 5 eV high energy resolution of Resolve enabled us to disentangle and detect all primary components of the iron K complex: neutral iron fluorescence (Fe K$α$ and K$β$), highly ionized emission lines (Fe XXV He$α$ and Fe XXVI Ly$α$). The neutral Fe K$α$ emission is not significantly detected during mid-eclipse, indicating a compact origin near the neutron star. At ingress and egress, the line centroid exhibits red- and blue-shifts of $\sim 200$ km s$^{-1}$ after correcting for the systemic velocity and the neutron star's orbital motion. This residual shift corresponds to Keplerian rotation at a characteristic radius of $r_{\rm disk} \sim 6.6\times10^{6}$ km, suggesting an association with the outer accretion disk. In contrast, the highly ionized Fe XXV He$α$ and Fe XXVI Ly$α$ lines remain visible during eclipses, indicating an extended origin. Photoionization modeling (SPEX pion model) yields $\log_{10}(ξ/{\rm erg\,cm\,s^{-1}}) \sim 3.4$ and $N_{\rm H} \sim 3.1\times10^{22}$ cm$^{-2}$ consistent with the ionized disk wind of Her X-1. Flux-ratio diagnostics constrain the geometric inner boundary of the clumpy disk wind to $R_{\rm in} = 3^{+5}_{-2} \times 10^{10}$ cm ($1σ$), consistent with the Compton-heated thermal winds. The inferred mass outflow rate is $\dot{M}_{\rm out} \approx 3.2 \times 10^{-9}\,M_{\odot}$ yr$^{-1}$ (half the supplied mass), consistent with absorption line measurements of the disk wind obtained out of eclipse.

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arXiv2026

Dissecting the Nuclear Structure of NGC 5548 with XRISM. I. Physical Properties of the Highly Ionized Outflows

We present a detailed spectral analysis of an X-Ray Imaging and Spectroscopy Mission (XRISM) observation of the prototypical Seyfert 1 galaxy NGC 5548. XRISM's Resolve microcalorimeter reveals, for the first time, highly ionized outflows in this active galactic nucleus (AGN) through the detection of Fe XXV and Fe XXVI absorption lines in the Fe K band. Modeling the XRISM/Resolve spectrum alongside XMM-Newton Reflection Grating Spectrometer (RGS) data allows us to probe the ionization and kinematic structure of the outflows in this AGN. We identify four distinct ionization components, with ionization parameters log $ξ$ ranging from 0.9 to 3.4. Three of these components are further resolved into two velocity sub-components, demonstrating the multiphase structure of the outflows. The measured outflow velocities span 240 to 2730 km/s. We find a trend of increasing column density with ionization parameter ($ξ$), along with a general pattern of increasing outflow velocity with $ξ$. The XRISM/Resolve spectrum provides a far more detailed absorption measure distribution (AMD) than was previously possible, revealing two distinct slopes above and below $\logξ\sim 2.6$. A comparison of the Fe XXV absorption line profile with UV absorption lines (C IV and Ly$α$) observed with the Hubble Space Telescope reveals both overlaps and deviations. The XRISM/Resolve results suggest a multiphase, clumpy outflow in NGC 5548, consistent with a "hybrid wind" scenario in which the observed parameter trends arise from multiple origins and driving mechanisms.

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arXiv2026

Peering through the dip: IXPE unveils the extended scattering environment of GX 13+1

Neutron star low-mass X-ray binaries feature complex accretion geometries, often including an accretion disk corona or disk winds. Here, a study of the highly inclined dipping source GX 13+1, using coordinated observations from the IXPE, NuSTAR, and Swift-XRT, is presented; this is the first time that such a campaign was conducted to monitor its periodic dip. Our analysis reveals significant variations in polarimetric properties tracking the dip. At the center of the dip, the polarization degree reaches a maximum of ${\sim}$9% (at more than $8σ$ confidence level). This is accompanied by a highly significant polarization angle rotation of roughly 60$^\circ$ when passing from the dip to the subsequent off-dip state. Furthermore, the dip state exhibits energy-dependent polarization. By modeling the polarization during the periodic dip, we constrain the geometry of the scattering medium. In the scenario of an oblate extended accretion disk corona (ADC), an equatorial radius at least 1.5 times its polar radius is needed with $τ{\sim}0.3$. Alternatively, the results can be modeled as scattering in a disk wind with a most probable electron density of $1.3\times10^{14}$ cm$^{-3}$ and an opening angle near 40$^\circ$, corresponding to an optical depth of ${\sim}0.2$. The obtained results highlight the crucial role of X-ray polarimetric data to unveil the geometry of the extended scattering environment surrounding the accretion disks, advancing our understanding of neutron star low-mass X-ray binaries.

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arXiv2026

XRISM/Resolve observations of Hercules X-1: a pulsating, highly broadened Fe K emission line from the neutron star accretion column

The study of X-ray pulsar accretion columns helps us characterize accretion physics in this extreme regime of strong gravity and strong magnetic fields. Previous observations of the X-ray pulsar Hercules X-1 revealed a highly broadened Fe K emission line, associated with Doppler motions exceeding 0.1c, suggesting its origin in the accretion column. We obtained a high-spectral resolution view of the Fe K energy band of Hercules X-1 thanks to a 200 ks observation with the XRISM observatory. The XRISM/Resolve microcalorimeter spectra allow us to separate the different spectral components and accurately model them with phenomenological models. We confirm the presence of a broad line near 6.5 keV with a typical $1σ$ width of 1 keV. Performing a pulse-phase-resolved analysis, we find that the feature is strongly variable with Her X-1 pulse phase. This is consistent with the proposed origin due to collisional recombination or by reprocessing of the primary X-ray emission in the accretion column, where strong variability with pulse phase is expected due to the rotation of the columns alongside with the neutron star. Additionally, the Fe K line pulsation pattern evolves with the 35-day cycle of Hercules X-1, supporting the scenario that the neutron star and its accretion columns undergo precession, in agreement with recent polarimetric results from the IXPE observatory. We discuss the future applications of modeling of this broad line in X-ray pulsars with physical spectral models. This could be used to detect and track neutron star precession, advancing our understanding of neutron star interiors.

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arXiv2026

Variability of the X-ray obscuring wind in Mrk 335 with XMM-Newton/RGS

Transient X-ray obscuration in Seyfert 1 galaxies likely arises from clumpy accretion-disk winds near the broad-line region (BLR), but the wind structure and short-timescale variability are difficult to measure because high-resolution spectra are often suppressed during deep low states. We analyse a coordinated XMM-Newton/NuSTAR campaign on Mrk 335 in June 2021, with long-term Swift monitoring, capturing the source in an intermediate-flux state with strong RGS absorption features. We model the broadband SED to determine the ionising continuum for self-consistent photoionisation modelling of the RGS spectra. The stacked RGS spectrum requires three photoionised absorbers with log xi ~ 3.69, 2.97, and 1.91, outflowing at |v_out| ~ 5800, 3200, and 2100 km/s, respectively. Their properties are consistent with the three-phase obscurer reported in 2009, indicating that a similar multi-phase obscuring wind can persist over decade timescales. Using five consecutive RGS observations, we track the wind evolution on day timescales and find strong variability in column density and ionisation in all phases, together with smaller but coherent velocity changes. During a flare, the low-ionisation phase shows a significant drop in opacity, while in the subsequent epoch all phases show increased outflow velocities, suggesting a possible connection between continuum variability and changes in the line-of-sight absorber. The high-ionisation phase responds most directly to changes in ionising luminosity, while the lowest-ionisation phase shows at most a delayed response. Order-of-magnitude constraints place the obscurer at BLR scales, ~10^3-10^5 Rg, with kinetic power potentially reaching the percent level of L_bol for plausible assumptions on geometry and clumpiness.

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arXiv2026

Kinematics of Weak Cool-Core Cluster A3571 Observed with XRISM: Low Cooling Rate Balanced by Low Heating Rate

Most XRISM galaxy cluster observations to date have focused on AGN feedback or actively merging systems. The weak cool-core cluster A3571 was observed in four XRISM Cycle 1 pointings, enabling the study of gas kinematics in a relaxed, AGN-feedback-free system. We present measurements of the velocity dispersion and bulk velocity in the core regions of A3571, out to $120$ kpc. The velocity dispersion is relatively uniform across all regions ($\sim100-120 ~\mathrm{km~s^{-1}}$), except in the northern gas sloshing elongation, where a $68\%$ upper limit of $68~\mathrm{km~s^{-1}}$ is obtained. The core Mach number and non-thermal pressure fraction of A3571 are lower than in the extremely relaxed cluster A2029 and below predictions from cosmological simulation suites. Despite relatively low velocity dispersion values, the derived turbulent heating rate is sufficient to offset cooling losses in all studied regions. This suggests that sloshing motions contribute significantly to the heating budget. Comparing XRISM observations of merging and relaxed clusters, we find that mergers exhibit an average Mach number of $0.29\pm0.07$, nearly twice that of the relaxed sample, which is consistent with predictions from non-radiative cosmological simulations. A3571 is a promising target for resonant scattering studies; however, simulations indicate that deeper observations are required to obtain reliable turbulent velocities via the $z/w$ line ratio.

astro-ph.GA↗

arXiv2026

Sloshing Motions in Abell 3571 Revealed by XRISM/Resolve Velocity Mapping

Minor mergers can induce sloshing motions in the intracluster medium, leaving characteristic signatures in the thermodynamic structure and gas kinematics of cluster cores. Abell 3571 is an X-ray-bright, apparently relaxed cluster at $z \sim 0.04$. We observed the central $\sim 300$ kpc region of Abell 3571 with four partially overlapping XRISM Resolve pointings, covering three contiguous Resolve fields to the north, south and east with a total exposure time of approximately 575 ks. The velocity dispersions are subsonic and are at the level of $\sim 100$--$150 \, \mathrm{km~ \, s^{-1}}$ across most regions. The cooler region associated with the northern surface-brightness excess is blueshifted by up to $\sim -60 \, \mathrm{km \, s^{-1}}$ relative to the brightest cluster galaxy (BCG), while the hotter region in the southern and eastern surface-brightness deficit regions is redshifted by up to $\sim 170 \, \mathrm{km \, s^{-1}}$. Numerical simulations suggest that this large-scale thermodynamic and kinematic asymmetry is broadly consistent with early-phase sloshing induced by an off-axis minor merger. Abell 3572, an X-ray-faint gas-poor cluster located 1.6 Mpc to the south, is a promising candidate for the perturber. Given the lack of clear signatures of prominent AGN feedback in Abell 3571, these results suggest that sloshing-driven gas redistribution may contribute to delaying the re-establishment of a strong cool core in Abell 3571.

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arXiv2026

XRISM/Resolve observations of Hercules X-1: vertical structure and kinematics of the disk wind

X-ray binary accretion disk winds can carry away a significant fraction of the matter transferred from the companion and hence strongly affect the accretion flow and the long-term evolution of the binary. However, accurate mass outflow rate measurements are challenging due to uncertainties in our understanding of the 3D wind structure. Most studies employ absorption line spectroscopy that only gives us a single sightline through the wind streamlines. Hercules X-1 is a peculiar X-ray binary which allows us to avoid this issue, as its warped, precessing accretion disk naturally presents a range of sightlines through the vertical structure of its disk wind. Here we present the first results from a large, coordinated campaign on Her X-1 led by the new XRISM observatory (with an exposure of 210 ks) and supported by XMM-Newton, NuSTAR and Chandra. We perform a time-resolved analysis and constrain the wind properties. With XRISM/Resolve, we directly detect the Her X-1 orbital motion with an amplitude of 170 km/s in the evolution of the wind velocity. After correcting for this effect, we observe an increase in wind velocity from 250 km/s to 600 km/s as the wind rises to greater heights above the disk. The wind column density decreases with increasing height, as expected, but its ionization parameter log($ξ$/erg cm s$^{-1}$) evolves only weakly from 3.65 to 3.9 as the wind expands away. Additionally, we detect a new orbital dependence of the wind properties, revealing a likely second component that appears only briefly after the eclipse by the secondary star.

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arXiv2026

Silicon, sulfur and iron in the interstellar medium: a high-resolution X-ray spectral study of GX 340+0

High-resolution X-ray spectroscopy provides a powerful probe of the interstellar medium (ISM), giving direct access to the composition and physical state of dust grains and atomic species in dense environments. We present a study of the gas and dust along the line of sight to the bright low-mass X-ray binary GX 340+0, which samples higher-density gases in the ISM. Using deep Chandra/HETG spectra, we characterize X-ray absorption fine structure from dust, gas absorption lines, and the optical depths of the Si, S, and Fe K-edges. By fitting these three edges simultaneously, we reduce degeneracies in the dust composition and find that amorphous olivine dominates the fractional contribution among the dust columns ($\sim$65%), followed by metallic iron ($\sim$19%), iron sulfides (pyrrhotite and troilite; $\sim$10%), and fayalite ($\sim$5%), with the remaining species contributing only a few percent in total. From the inferred stoichiometry, we estimate that $\sim$74% of Fe is associated with silicates, $\sim$8% with sulfides, and $\sim$18% with metallic iron, suggesting that Fe is predominantly incorporated in iron rich silicate grains along this sightline. We detect S ii absorption and infer a sulfur dust fraction of $\sim$35%. We also detect absorption structure near the Ca and Ar K edges, highlighting the need for improved atomic photoabsorption data. The Chandra/HETG spectral resolution remains essential to disentangle dust and gas contributions at the Si and S K edges, providing a benchmark for dust characterization in high-density regions in the ISM.

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arXiv2026

Mapping plasma properties of Cassiopeia A with XRISM/Resolve: a Bayesian analysis via UltraSPEX

Mapping the physical conditions of the shocked plasma of young supernova remnants (SNR) is crucial for understanding their explosion mechanisms, ejecta structure, and large-scale asymmetries. Using $>350$ ks of XRISM/Resolve high spectral resolution observations of Cassiopeia A (Cas A), the youngest known Galactic core-collapse SNR, we present the first microcalorimeter-based plasma parameter maps of any SNR. We tessellate Cas A into $1'\times1'$ regions and fit the broadband spectra as thermal emission from two pure-metal ejecta components -- corresponding to intermediate-mass elements (IMEs) and iron-group elements (IGEs) -- plus nonthermal synchrotron radiation. For robust inference, we introduce UltraSPEX, a Bayesian framework that couples the SPEX plasma code with the UltraNest nested-sampling algorithm, yielding full posterior distributions and exploration of parameter degeneracies. Key findings include enhanced Ar/Si and Ca/Si abundance ratios near the base of the Si-rich jets, and a high Ni/Fe mass ratio ($0.08\pm0.015$) in the base of NE jet. IGEs ejecta exhibit systematically higher Doppler velocities and broadenings than IMEs ejecta in most regions, with maximum differences of $\sim800$ km/s and $\sim1200$ km/s, respectively; Ca shows distinct (faster) kinematics from other IMEs in several SE regions. The ionization timescale and electron temperature show a robust anti-correlation, particularly for IGEs. This relation and measured parameter values could be explained by semi-analytical models with significant ejecta clumping (overdensities of $\sim10$ for IGEs and up to $\sim100$ for IMEs) and reduced historical reverse-shock velocities. Nonthermal emission accounts for a substantial fraction, with at least 47% of the 4--6 keV continuum and dominates in the western regions, where the spectrum hardens.

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arXiv2026

XRISM finds the Changing-Look AGN NGC 1365 in an extended low state: A dense, highly ionized outflow obscures the central source

We present the first XRISM/Resolve observations of the active galactic nucleus, NGC 1365, obtained in 2024 February and July. NGC 1365 is known for rapid transitions between Compton-thick and Compton-thin states, along with strong absorption from a highly ionized wind. During our observations, the source is found in a persistent low-flux state, characterized by a decrease in hard-X-ray luminosity and significant line-of-sight obscuration. In this state, XRISM/Resolve reveals clear Fe\,\textsc{xxv} and Fe\,\textsc{xxvi} absorption lines together with, for the first time in this source, corresponding emission lines. These features may arise either from reemission from a photoionized wind (P Cygni profile) or from collisionally ionized gas associated with outflow-driven shocks in the interstellar medium. We estimate the wind launch radius to be approximately $10^{16}~\mathrm{cm}$ ($\sim 10^4 R_{\mathrm{g}}$), consistent with the location of the X-ray broad-line region. We also resolve a broadened Fe K$α$ line by $σ\sim 1300$ km s$^{-1}$ placing it at similar scales to the wind, consistent with radii inferred from disk-broadening models and the variability of the Fe K$α$ broad line. The similarity of the Fe K$α$ profile to the H$β$ wing and broad Pa$α$ width indicates that the X-ray-emitting region is likely cospatial with the optical/IR broad-line region and originates from the same gas.

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arXiv2025

The dynamic central environment of NGC 3516 revealed by XRISM

We present a detailed, time-resolved analysis of the Fe K band of the Seyfert 1.5 galaxy NGC 3516 observed with XRISM. The 249 ks observation spanning $\sim$310 ks in elapsed time reveals an exceptionally rich and time-variable absorption spectrum. Six distinct absorption components are detected across multiple ionization states, spanning more than an order of magnitude in ionization parameter and a wide range of systemic velocities, from a potential inflow ($+4300~\rm km~s^{-1}$) to a mildly relativistic ultra-fast outflow ($-9800~\rm km~s^{-1}$). Despite their diversity, the components exhibit relatively small broadening ($\lesssim$$400~\rm km~s^{-1}$), implying comparable internal dynamics within a medium of a complex structure. Time-resolved spectroscopy reveals pronounced variability in three highly ionized absorbers, with Fe XXV$-$Fe XXVI features that appear and disappear on timescales of tens of kiloseconds. This behavior likely reflects a combination of geometrical transits of clumpy gas and ionization-state changes driven by continuum variability. An additional temporary absorption feature in the red wing of the Fe K$α$ line, consistent with Fe XXV absorption, indicates a possible transient ultra-fast inflow at $\sim$$15\,000~\rm km~s^{-1}$ ($\sim$5% $c$). Finally, the continuum light curve exhibits a tentative $\sim$40 ks oscillatory pattern, accompanied by correlated shifts of a weak, narrow Fe K$α$ emission feature, suggesting dynamic coupling between the continuum and the line-emitting region. Together, these results reveal that the nuclear environment of NGC 3516 is dominated by rapidly evolving, multi-phase gas flows, where accretion, ejection, and ionization processes are tightly coupled on sub-parsec scales.

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arXiv2025

XRISM Spectroscopy of the Stellar-mass Black Hole GRS 1915+105

GRS 1915$+$105 was the stellar-mass black hole that best reproduced key phenomena that are also observed in Type-1 active galactic nuclei. In recent years, however, it has evolved to resemble a Type-2 or Compton-thick AGN. Herein, we report on the first XRISM observation of GRS 1915$+$105. The high-resolution Resolve calorimeter spectrum reveals that a sub-Eddington central engine is covered by a layer of warm, Compton-thick gas. With the obscuration acting as a coronagraph, numerous strong, narrow emission lines from He-like and H-like charge states of Si, S, Ar, Ca, Cr, Mn, Fe, and Ni dominate the spectrum. Radiative recombination continuum (RRC) features are also observed, signaling that much of the emitting gas is photoionized. The line spectrum can be fit by three photoionized emission zones, with broadening and bulk velocities suggestive of an origin in the outer disk atmosphere and/or a slow wind at $r \simeq 10^{6}~GM/c^{2}$. The Fe XXV He-$α$ and Fe XXVI Ly-$α$ lines have a broad base that may indicate some emission from $r \sim 3\times 10^{3}~GM/c^{2}$. These results broadly support a picture wherein the current state in GRS 1915$+$105 is due to obscuration by the irradiated outer disk. This could arise through disk thickening if the Eddington fraction is higher than inferred, but it is more likely due to a warped, precessing disk that has brought the outer disk into the line of sight. We discuss the strengths and weaknesses of this interpretation and our modeling, and possible explanations of some potentially novel spectral features.

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arXiv2025

A Sharper View of the X-ray Spectrum of MCG--6-30-15 with XRISM, XMM-Newton and NuSTAR

We present a time-averaged spectral analysis of the 2024 XRISM observation of the narrow-line Seyfert-1 galaxy MCG--6-30-15, taken contemporaneously with XMM-Newton and NuSTAR. Our analysis leverages a unique combination of broadband and high-resolution X-ray spectroscopy to definitively isolate and characterize both broad and narrow emission and absorption features in this source. The best-fitting model for the joint spectral analysis is very well described by reflection from the inner accretion disk illuminated by a compact corona, modified by multi-zone ionized absorption from an outflowing wind along the line of sight. The XRISM/Resolve data confirm that a strong, relativistically-broadened Fe K$α$ emission line is required in order to obtain an adequate model fit. The Resolve data additionally verify the presence of a $v_{\rm out} \sim 2300$ km/s component of this outflowing wind, find tentative evidence for a $v_{\rm out} \sim 20,000$ km/s wind component, and indicate that the reflection from distant, neutral material may originate in a non-uniform structure rather than the traditional torus of AGN unification schemes. Though a rapid prograde black hole spin is statistically preferred by the best-fitting model, consistent with previous results, the AGN flux variability over the course of the observation complicates the interpretation of the time-averaged spectra. This insight, clarified by the combination of high signal-to-noise and high spectral resolution in the joint dataset, emphasizes the importance of time-resolved, high-resolution spectral analysis in unambiguously measuring the physical properties of variable AGN.

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