arXiv subjects

Laura Brenneman

Publications and source records attributed to Laura Brenneman.

At least 37 records · Page 2Linked to original sources

arXiv2025

The population of NuSTAR Black Hole X-ray Binaries

The spin of a black hole (BH) encodes information about its formation and evolution history. Yet the understanding of the distribution of BH spins in X-ray binaries (XBs), of the models used to measure spin, and of their impact on systematic uncertainties remains incomplete. In this work, we expand on previous analyses of the entire NuSTAR archive of accreting BH XBs. Prior work compiled a sample of 245 spectral fits using the relativistic reflection method for NuSTAR observations of 36 BH systems. Here, we aim to probe two aspects: the connection between BH spin and binary system properties, and the relationships between parameters in the spectral fits. We identify moderate negative correlations between spin uncertainty and both BH mass and system inclination, and a moderate positive correlation with distance. We also point out tentative multidimensional degeneracies between inclination, disk density, Fe abundance, ionization, and the presence or absence of absorption features from ionized outflows linked to disk winds. Lastly, we provide a comprehensive view of the observed distribution of BH spins in XBs, in comparison to spins inferred from gravitational waves. We find that the distribution of BH spins in XBs can be described by a beta distribution with $α=5.66$ and $β=1.09$. This data set is highly complex, and the analysis presented here does not fully explore all potential parameter correlations. We make the full data set available in Zenodo to the community to encourage further exploration.

astro-ph.HE↗

arXiv2025

XRISM/Resolve View of Abell 2319: Turbulence, Sloshing, and ICM Dynamics

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 ($\sim$11 keV) in the northwest. The average gas velocity in the 3 arcmin $\times$ 4 arcmin region around the brightest cluster galaxy (BCG) covered by two Resolve pointings is consistent with that of the BCG to within 40 km s$^{-1}$ and we found modest average velocity dispersion of 230-250 km s$^{-1}$. On the other hand, spatially-resolved spectroscopy reveals interesting variations. A blueshift of up to $\sim$230 km s$^{-1}$ 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 400 km s$^{-1}$, 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.

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arXiv2025

XRISM Spectroscopy of Accretion-Driven Wind Feedback in NGC 4151

The hottest, most ionized, and fastest winds driven by accretion onto massive black holes have the potential to reshape their host galaxies. Calorimeter-resolution X-ray spectroscopy is the ideal tool to understand this feedback mode, as it enables accurate estimates of physical characteristics needed to determine the wind's kinetic power. We report on a photoionization analysis of five observations of the Seyfert-1.5 galaxy NGC 4151, obtained with XRISM/Resolve in 2023 and 2024. In the Fe K band, individual spectra require as many as six wind absorption components. Slow "warm absorbers" (WAs, $v_{\mathrm{out}} \sim 100 - 1000~\mathrm{km~s^{-1}}$), very fast outflows (VFOs, $v_{\mathrm{out}} \sim 10^3~{\rm km}~{\rm s}^{-1} - 10^4~{\rm km}~{\rm s}^{-1}$), and ultra-fast outflows (UFOs, $v_{\mathrm{out}} \sim 10^4~{\rm km}~{\rm s}^{-1} - 10^5~{\rm km}~{\rm s}^{-1}$ or $0.033 - 0.33~c$) are detected simultaneously, and indicate a stratified, multiphase wind. Fast and variable emission components suggest that the wind is axially asymmetric. All of the wind components have mass flow rates comparable to or in excess of the mass accretion rate, though the slowest zones may be "failed" winds that do not escape. Two UFO components have kinetic luminosities that exceed the theoretical threshold of $L_{kin} \geq 0.5\% L_{Edd}$ necessary to strip the host bulge of gas and halt star formation, even after corrections for plausible filling factors. The bulk properties of the observed winds are consistent with magnetocentrifugal driving, where the density depends on radius as $n \propto r^{-1.5}$, but radiative driving and other mechanisms may also be important. Numerous complexities and variability require further analysis.

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arXiv2025

X-Ray Reflection Signatures of Supermassive Black Hole Binaries

We investigate the presence of supermassive black hole (SMBH) binary signatures and the feasibility of identifying them through X-ray reflection spectra. The X-ray emitting region is modeled as a set of two mini-disks bound to the individual SMBHs separated by 100 $GM/c^2$ and the spectra calculated as a function of the mass, mass ratio, and total accretion rate of the binary. The X-ray reflection features are strongly influenced by the accretion-inversion phenomenon expected in SMBH binaries, which results in a wide range of ionization conditions in the two mini-disks. These are imprinted in the resulting composite spectra and the double-peaked and time-variable relativistic Fe K$α$ line profiles. To test whether these features can be used as evidence for the presence of an SMBH binary, we fit mock 100 ks observations with a single AGN model. For a $10^9$ $M_\odot$ binary targeted by Pulsar Timing Arrays (PTAs), at $z=0.1$ the single AGN model clearly fails to fit the data, while at $z=1$ the fit is acceptable but unable to converge on the SMBH spin. For a $10^6$ $M_\odot$ binary, a progenitor of a Laser Interferometer Space Antenna (LISA) source, spectral fitting is only possible at $z=0.1$, with the outcomes similar to the PTA binary at $z=1$. We also find that PTA binaries can be expected to show a distinct X-ray spectral variability in multi-epoch observations, whereas for LISA precursors, orbital averaging results in the loss of spectral variability signatures.

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arXiv2025

Constraining gas motion and non-thermal pressure beyond the core of the Abell 2029 galaxy cluster with XRISM

We report a detailed spectroscopic study of the gas dynamics and hydrostatic mass bias of the galaxy cluster Abell 2029, utilizing high-resolution observations from XRISM Resolve. Abell 2029, known for its cool core and relaxed X-ray morphology, provides an excellent opportunity to investigate the influence of gas motions beyond the central region. Expanding upon prior studies that revealed low turbulence and bulk motions within the core, our analysis covers regions out to the scale radius $R_{2500}$ (670~kpc) based on three radial pointings extending from the cluster center toward the northern side. We obtain accurate measurements of bulk and turbulent velocities along the line of sight. The results indicate that non-thermal pressure accounts for no more than 2% of the total pressure at all radii, with a gradual decrease outward. The observed radial trend differs from many numerical simulations, which often predict an increase in non-thermal pressure fraction at larger radii. These findings suggest that deviations from hydrostatic equilibrium are small, leading to a hydrostatic mass bias of around 2% across the observed area.

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arXiv2025

XRISM forecast for the Coma cluster: stormy, with a steep power spectrum

The XRISM Resolve microcalorimeter array measured the velocities of hot intracluster gas at two positions in the Coma galaxy cluster: 3'x3' squares at the center and at 6' (170 kpc) to the south. We find the line-of-sight velocity dispersions in those regions to be sigma_z=208+-12 km/s and 202+-24 km/s, respectively. The central value corresponds to a 3D Mach number of M=0.24+-0.015 and the ratio of the kinetic pressure of small-scale motions to thermal pressure in the intracluster plasma of only 3.1+-0.4%, at the lower end of predictions from cosmological simulations for merging clusters like Coma, and similar to that observed in the cool core of the relaxed cluster A2029. Meanwhile, the gas in both regions exhibits high line-of-sight velocity differences from the mean velocity of the cluster galaxies, Delta v_z=450+-15 km/s and 730+-30 km/s, respectively. A small contribution from an additional gas velocity component, consistent with the cluster optical mean, is detected along a sightline near the cluster center. The combination of the observed velocity dispersions and bulk velocities is not described by a Kolmogorov velocity power spectrum of steady-state turbulence; instead, the data imply a much steeper effective slope (i.e., relatively more power at larger linear scales). This may indicate either a very large dissipation scale resulting in the suppression of small-scale motions, or a transient dynamic state of the cluster, where large-scale gas flows generated by an ongoing merger have not yet cascaded down to small scales.

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arXiv2023

Fierce Feedback in an Obscured, Sub-Eddington State of the Seyfert 1.2 Markarian 817

Markarian 817 is a bright and variable Seyfert-1.2 active galactic nucleus (AGN). X-ray monitoring of Mrk 817 with the Neil Gehrels Swift Observatory in 2022 revealed that the source flux had declined to a lower level than recorded at any prior point in the then-19-year mission. We present an analysis of deep XMM-Newton and NuSTAR observations obtained in this low flux state. The spectra reveal a complex X-ray wind consisting of neutral and ionized absorption zones. Three separate velocity components are detected as part of a structured ultra-fast outflow (UFO), with v/c = 0.043 (+0.007,-0.003), v/c = 0.079 (+0.003,-0.0008), and v/c = 0.074 (+0.004,-0.005). These projected velocities suggest that the wind likely arises at radii that are much smaller than the optical broad line region (BLR). In order for each component of the outflow to contribute significant feedback, the volume filling factors must be greater than f ~ 0.009, f ~ 0.003, and f ~ 0.3, respectively. For plausible, data-driven volume filling factors, these limits are passed, and the total outflow likely delivers the fierce feedback required to reshape its host environment, despite a modest radiative Eddington fraction of lambda ~ 0.008-0.016 (this range reflects plausible masses). UFOs are often detected at or above the Eddington limit; this result signals that black hole accretion has the potential to shape host galaxies even at modest Eddington fractions, and over a larger fraction of a typical AGN lifetime. We discuss our findings in terms of models for disk winds and black hole feedback in this and other AGN.

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arXiv2023

Redshifted iron emission and absorption lines in the Chandra X-ray spectrum of Centaurus A

Cen A hosts the closest active galactic nucleus to the Milky Way, which makes it an ideal target for investigating the dynamical processes in the vicinity of accreting supermassive black holes. In this paper, we present 14 Chandra HETGS spectra of the nucleus of Cen A that were observed throughout 2022. We compared them with each other, and contrasted them against the two previous Chandra HETGS spectra from 2001. This enabled an investigation into the spectral changes occurring on timescales of months and 21 years. All Chandra spectra could be well fitted by an absorbed power law with a strong and narrow Fe K$α$ line, a leaked power law feature at low energies, and Si and S K$α$ lines that could not be associated with the central engine. The flux of the continuum varied by a factor of $2.74\pm0.05$ over the course of the observations, whereas the Fe line only varied by $18.8\pm8.8\%$. The photon index increased over 21 years, and the Hydrogen column density varied significantly within a few months as well. The Fe K$α$ line was found at a lower energy than expected from the Cen A redshift, amounting to an excess velocity of $326^{+84}_{-94}~\mathrm{km}~\mathrm{s}^{-1}$ relative to Cen A. We investigated warped accretion disks, bulk motion, and outflows as possible explanations of this shift. The spectra also featured ionized absorption lines from Fe XXV and Fe XXVI, describing a variable inflow.

astro-ph.HE↗

arXiv2020

Measuring Supermassive Black Hole Spin in the Chandra COSMOS-Legacy Survey

Spin measurements of supermassive black holes (SMBHs) provide crucial constraints on the accretion processes that power active galactic nuclei (AGN), fuel outflows, and trigger black hole growth. However, spin measurements are mainly limited to a few dozen nearby sources for which high quality, high S/N spectra (e.g., from Chandra, XMM-Newton, Suzaku, NuSTAR) are available. Here we measure the average SMBH spin of $\sim$1900 AGN in the Chandra COSMOS-Legacy survey using spectral stacking analysis. We find broad Fe K$α$ line emission in the average COSMOS spectrum (Gaussian width $σ=0.27\pm0.05$ keV), and by fitting this emission line profile with relativistic line models, we measure the average black hole spin parameter $a=0.62~\substack{+0.07 \\ -0.17}$. The sample size, availability of multiwavelength data, and spatial resolution of the COSMOS Legacy field also provide a unique environment to investigate the average SMBH spin as a function of other observables (e.g., redshift, luminosity) up to $z\sim5.3$. We find that optically classified Type 1 sources have broader Fe K$α$ line emission than Type 2 sources. X-ray unobscured and obscured sources, as defined by their column densities, have widths that are consistent with the optically defined unobscured and obscured sources, respectively. There is some evidence for evolution of the Fe K$α$ width and black hole spin parameter with luminosity, but not conclusively with redshift. The results of this work provide insights into the average spins of SMBHs in AGN, shedding light on their growth mechanisms and observed co-evolution with their host galaxies.

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arXiv2019

A Survey of Hot Gas in the Universe

A large fraction of the baryons and most of the metals in the Universe are unaccounted for. They likely lie in extended galaxy halos, galaxy groups, and the cosmic web, and measuring their nature is essential to understanding galaxy formation. These environments have virial temperatures >10^5.5 K, so the gas should be visible in X-rays. Here we show the breakthrough capabilities of grating spectrometers to 1) detect these reservoirs of hidden metals and mass, and 2) quantify hot gas flows, turbulence, and rotation around the Milky Way and external galaxies. Grating spectrometers are essential instruments for future X-ray missions, and existing technologies provide 50-1500-fold higher throughput compared to current orbiting instruments.

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arXiv2019

High-Energy Astrophysics in the 2020s and Beyond

With each passing decade, we gain new appreciation for the dynamic, connected, and often violent nature of the Universe. This reality necessarily places the study of high-energy processes at the very heart of modern astrophysics. This White Paper illustrates the central role of high-energy astrophysics to some of the most pressing astrophysical problems of our time, the formation/evolution of galaxies, the origin of the heavy elements, star and planet formation, the emergence of life on exoplanets, and the search for new physics. We also highlight the new connections that are growing between astrophysicists and plasma physicists. We end with a discussion of the challenges that must be addressed to realize the potential of these connections, including the need for integrated planning across physics and astronomy programs in multiple agencies, and the need to foster the creativity and career aspirations of individual scientists in this era of large projects.

astro-ph.HE↗

arXiv2019

Probing the Black Hole Engine with Measurements of the Relativistic X-ray Reflection Component

Over the last decades X-ray spectroscopy has proven to be a powerful tool for the estimation of black hole spin and several other key parameters in dozens of AGN and black hole X-ray binaries. In this White Paper, we discuss the observational and theoretical challenges expected in the exploration, discovery, and study of astrophysical black holes in the next decade. We focus on the case of accreting black holes and their electromagnetic signatures, with particular emphasis on the measurement of the relativistic reflection component in their X-ray spectra.

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arXiv2019

STROBE-X: X-ray Timing and Spectroscopy on Dynamical Timescales from Microseconds to Years

We present the Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X), a probe-class mission concept selected for study by NASA. It combines huge collecting area, high throughput, broad energy coverage, and excellent spectral and temporal resolution in a single facility. STROBE-X offers an enormous increase in sensitivity for X-ray spectral timing, extending these techniques to extragalactic targets for the first time. It is also an agile mission capable of rapid response to transient events, making it an essential X-ray partner facility in the era of time-domain, multi-wavelength, and multi-messenger astronomy. Optimized for study of the most extreme conditions found in the Universe, its key science objectives include: (1) Robustly measuring mass and spin and mapping inner accretion flows across the black hole mass spectrum, from compact stars to intermediate-mass objects to active galactic nuclei. (2) Mapping out the full mass-radius relation of neutron stars using an ensemble of nearly two dozen rotation-powered pulsars and accreting neutron stars, and hence measuring the equation of state for ultradense matter over a much wider range of densities than explored by NICER. (3) Identifying and studying X-ray counterparts (in the post-Swift era) for multiwavelength and multi-messenger transients in the dynamic sky through cross-correlation with gravitational wave interferometers, neutrino observatories, and high-cadence time-domain surveys in other electromagnetic bands. (4) Continuously surveying the dynamic X-ray sky with a large duty cycle and high time resolution to characterize the behavior of X-ray sources over an unprecedentedly vast range of time scales. STROBE-X's formidable capabilities will also enable a broad portfolio of additional science.

astro-ph.IM↗

arXiv2016

The Quiescent Intracluster Medium in the Core of the Perseus Cluster

Clusters of galaxies are the most massive gravitationally-bound objects in the Universe and are still forming. They are thus important probes of cosmological parameters and a host of astrophysical processes. Knowledge of the dynamics of the pervasive hot gas, which dominates in mass over stars in a cluster, is a crucial missing ingredient. It can enable new insights into mechanical energy injection by the central supermassive black hole and the use of hydrostatic equilibrium for the determination of cluster masses. X-rays from the core of the Perseus cluster are emitted by the 50 million K diffuse hot plasma filling its gravitational potential well. The Active Galactic Nucleus of the central galaxy NGC1275 is pumping jetted energy into the surrounding intracluster medium, creating buoyant bubbles filled with relativistic plasma. These likely induce motions in the intracluster medium and heat the inner gas preventing runaway radiative cooling; a process known as Active Galactic Nucleus Feedback. Here we report on Hitomi X-ray observations of the Perseus cluster core, which reveal a remarkably quiescent atmosphere where the gas has a line-of-sight velocity dispersion of 164+/-10 km/s in a region 30-60 kpc from the central nucleus. A gradient in the line-of-sight velocity of 150+/-70 km/s is found across the 60 kpc image of the cluster core. Turbulent pressure support in the gas is 4% or less of the thermodynamic pressure, with large scale shear at most doubling that estimate. We infer that total cluster masses determined from hydrostatic equilibrium in the central regions need little correction for turbulent pressure.

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arXiv2014

The ASTRO-H X-ray Astronomy Satellite

The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions developed by the Institute of Space and Astronautical Science (ISAS), with a planned launch in 2015. The ASTRO-H mission is equipped with a suite of sensitive instruments with the highest energy resolution ever achieved at E > 3 keV and a wide energy range spanning four decades in energy from soft X-rays to gamma-rays. The simultaneous broad band pass, coupled with the high spectral resolution of Delta E < 7 eV of the micro-calorimeter, will enable a wide variety of important science themes to be pursued. ASTRO-H is expected to provide breakthrough results in scientific areas as diverse as the large-scale structure of the Universe and its evolution, the behavior of matter in the gravitational strong field regime, the physical conditions in sites of cosmic-ray acceleration, and the distribution of dark matter in galaxy clusters at different redshifts.

astro-ph.IM↗

arXiv2014

The Broad-band X-ray Spectrum of IC 4329A from a Joint NuSTAR/Suzaku Observation

We have obtained a deep, simultaneous observation of the bright, nearby Seyfert galaxy IC 4329A with Suzaku and NuSTAR. Through a detailed spectral analysis, we are able to robustly separate the continuum, absorption and distant reflection components in the spectrum. The absorbing column is found to be modest at $N_H = 6 \times 10^{21}$ cm$^2$, and does not introduce any significant curvature in the Fe K band. We are able to place a strong constraint on the presence of a broadened Fe Kα line: $E = 6.46^{+0.08}_{-0.07}$ keV rest frame with $σ = 0.33^{+0.08}_{-0.07}$ keV and $EW = 34^{+8}_{-7}$ eV, though we are not able to constrain any of the parameters of a relativistic reflection model. These results highlight the range in broad Fe Kα line strengths observed in nearby, bright AGN (roughly an order of magnitude), and imply a corresponding range in the physical properties of the inner accretion disk in these sources. We have also updated our previously reported measurement of the high-energy cutoff of the hard X-ray emission using both observatories rather than just NuSTAR alone: $E_{cut} = 186 \pm 14$ keV. This high-energy cutoff acts as a proxy for the temperature of the coronal electron plasma, enabling us to further separate this parameter from the optical depth of the plasma and to update our results for these parameters as well. We derive $kT = 50^{+6}_{-3}$ keV with $τ = 2.34^{+0.16}_{-0.11}$ using a spherical geometry, $kT = 61 \pm 1$ keV with $τ = 0.68 \pm 0.02$ for a slab geometry, with both having an equivalent goodness-of-fit.

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arXiv2013

Measuring Supermassive Black Hole Spins in Active Galactic Nuclei

Measuring the spins of supermassive black holes (SMBHs) in active galactic nuclei (AGN) can inform us about the relative role of gas accretion vs. mergers in recent epochs of the life of the host galaxy and its AGN. Recent advances in theory and observation have enabled spin measurements for a handful of SMBHs thus far, but this science is still very much in its infancy. Herein, I discuss how and why we seek to measure black hole spin in AGN, using recent results from long X-ray observing campaigns on three radio-quiet AGN (MCG-6-30-15, NGC 3783 and Fairall 9) to illustrate this process and its caveats. I then present our current knowledge of the distribution of SMBH spins in the local universe. I also address prospects for improving the accuracy, precision and quantity of these spin constraints in the next decade and beyond with instruments such as NuSTAR, Astro-H and a future generation large-area X-ray telescope.

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arXiv2013

The Hot and Energetic Universe: A White Paper presenting the science theme motivating the Athena+ mission

This White Paper, submitted to the recent ESA call for science themes to define its future large missions, advocates the need for a transformational leap in our understanding of two key questions in astrophysics: 1) How does ordinary matter assemble into the large scale structures that we see today? 2) How do black holes grow and shape the Universe? Hot gas in clusters, groups and the intergalactic medium dominates the baryonic content of the local Universe. To understand the astrophysical processes responsible for the formation and assembly of these large structures, it is necessary to measure their physical properties and evolution. This requires spatially resolved X-ray spectroscopy with a factor 10 increase in both telescope throughput and spatial resolving power compared to currently planned facilities. Feedback from supermassive black holes is an essential ingredient in this process and in most galaxy evolution models, but it is not well understood. X-ray observations can uniquely reveal the mechanisms launching winds close to black holes and determine the coupling of the energy and matter flows on larger scales. Due to the effects of feedback, a complete understanding of galaxy evolution requires knowledge of the obscured growth of supermassive black holes through cosmic time, out to the redshifts where the first galaxies form. X-ray emission is the most reliable way to reveal accreting black holes, but deep survey speed must improve by a factor ~100 over current facilities to perform a full census into the early Universe. The Advanced Telescope for High Energy Astrophysics (Athena+) mission provides the necessary performance (e.g. angular resolution, spectral resolution, survey grasp) to address these questions and revolutionize our understanding of the Hot and Energetic Universe. These capabilities will also provide a powerful observatory to be used in all areas of astrophysics.

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