arXiv subjects

Daniel Stern

Publications and source records attributed to Daniel Stern.

At least 37 records · Page 2Linked to original sources

arXiv2026

Transient Relativistic Iron Emission Line from an X-ray Flaring Supermassive Black Hole

We report the discovery of the first transient relativistic iron Kα line in an Active Galactic Nucleus (AGN) J1047+5907. The line was detected 21.5 days (rest-frame) after an X-ray coronal flare observed in 2008 and it exhibits significant broadening consistent with relativistic reflection from the accretion disk in the vicinity of the central supermassive black hole (SMBH). The line has a width of ~300 eV, corresponding to a Keplerian velocity of 14,000 km s-1, at a distance of 5-41 light-days from the SMBH, strongly implying that the observed coronal flare triggered the emergence of the line. This event provides rare direct evidence of the response of the accretion disk to impulsive coronal illumination and offers a new method to probe the SMBH and disk physics. The relativistic modeling favors a broadened line produced by distant reflection from an accretion disk around a rapidly spinning black hole viewed at an intermediate inclination, consistent with other observations. Systematic monitoring of type 1 AGN following strong X-ray flares may open a new observational window into the innermost regions of AGN, enabling constraints on the physics of SMBH and its accretion disk at different radii that are otherwise challenging to access.

astro-ph.HE↗

arXiv2026

The Massive and Distant Clusters of WISE Survey 2: Splashback Radii to z=1.65 from Galaxy Density Profiles

The Massive and Distant Clusters of WISE Survey 2 (MaDCoWS2) is a WISE-selected catalog of galaxy clusters at $0.1 6000$ deg$^2$. In this paper, we derive splashback radii for this cluster ensemble from galaxy density profiles and constrain the mass threshold of the survey as a function of redshift. We use MaDCoWS2 cluster candidates at $0.4\leq z \leq 1.65$ divided into subsamples with different signal-to-noise (S/N$_{\rm P}$) and redshifts, cross-correlated with galaxies from the CatWISE2020 catalog, to obtain average surface density profiles. We perform a Markov Chain Monte Carlo analysis to derive parameter estimates for theoretical models consisting of orbiting and infalling terms. A distinct splashback feature is detected in all subsamples. The measured splashback radii span from $0.89^{+0.02}_{-0.02}h^{-1}$ comoving Mpc/cMpc ($0.61^{+0.02}_{-0.02}h^{-1}$ proper Mpc/pMpc) at $\overline{z}=0.45$ to $1.27^{+0.05}_{-0.05}h^{-1}$ cMpc ($0.53^{+0.04}_{-0.04}h^{-1}$ pMpc) at $\overline{z}=1.54$. We also find that splashback radii increase with $S/N_{\rm P}$ at fixed redshift. The resultant splashback radii constrain the redshift dependence of the mass of MaDCoWS2 clusters at fixed $S/N_{\rm P}$. We calculate $M_{\rm 200m}$ from the radii using a relation based on a cosmological simulation. MaDCoWS2 $M_{\rm 200m}$ values derived from the simulation-based relation are lower than the expected values based on weak-lensing observations. More robust mass constraints will come from calibrating splashback radii derived from galaxy density profiles with weak lensing shear profiles from facilities such as $\textit{Euclid}$, Rubin, and $\textit{Roman}$.

astro-ph.CO↗

arXiv2026

The Tantalizing Case of the Quasar J0950+5128 -- I. Presentation of the Data and Detailed Exploration of the Binary Supermassive Black Hole Scenario

Spectroscopic observations of the quasar J0950$+$5128 spanning 22 years reveal monotonic radial velocity variations in its broad H$β$ emission line. Moreover, the line profile becomes broader over time, necessitating careful measurements. We present robust H$β$ velocity shift measurements obtained via cross correlation, applied to both the full spectra and to isolated broad H$β$ components derived from spectral decomposition. We also examine the light curves for variability consistent with the spectroscopic trends. Using Lomb-Scargle periodogram analysis we find no significant periodic signal. We consider several interpretations for the observed changes, including a binary supermassive black hole, dust-cloud obscuration, outflows, a recoiling black hole, and a single perturbed, disk-like broad-line region. We deem the binary and perturbed broad-line region scenarios to be physically plausible. The binary interpretation is the only one for which we can immediately compare a physical model to the available data. Thus, we incorporate radial velocity ''jitter'' to emulate typical quasar variability and fit the radial velocity curve with a Keplerian model to examine whether it can reproduce the observations. In this context, the available observations trace only a segment of the putative orbit. The fit yields a period of 33 years (observed frame) and an eccentricity of 0.65, with lower limits on the semi-major axis and black hole mass of $10^{-2}\;$pc and $10^7\;{\rm M}_\odot$, respectively. Thus, J0950$+$5128 is a binary candidate deserving further study. The single, perturbed broad-line region interpretation remains viable but requires additional observations and modeling for further evaluation. Continued monitoring is, therefore, essential.

astro-ph.GA↗

arXiv2026

Fast X-ray transients in NuSTAR data

Fast X-ray transients (FXTs) are flashes of X-rays that last for a few hundreds of seconds to a few hours. An enigmatic population of these transients that did not have a clear origin has been known for several decades, mostly found serendipitously in soft X-ray imaging observations. Recent progress in this field by Einstein Probe has found that many FXTs are associated with gamma-ray bursts and the collapse of massive stars. Motivated by this, we searched the NuSTAR archive in the harder 3--79 keV band for $\sim1000$ s duration transients. From 204 Ms of exposure we present five candidate FXTs, four of which are spectrally hard, with power-law indices $-3<Γ<0$, standing them apart from FXTs discovered in the soft band. Three have potential associations with galaxies at $z=0.1-2$, implying 3--79 keV luminosities of $10^{43}$ to $10^{48}$ erg s$^{-1}$ and volumetric event rates of 125--2900 Gpc$^{-3}$ yr$^{-1}$. The properties of these NuSTAR FXTs most resemble low-luminosity gamma-ray bursts, and would be much more common than their higher-luminosity counterparts in this redshift range.

astro-ph.HE↗

arXiv2026

Reducing the Dimensions of AGN Lightcurve Manifolds

The Active Galactic Nuclei (AGN) glossary is vast and complex. Depending on selection method, observing wavelength, and brightness, AGNs are assigned distinct labels, yet the relationship between different selection methods and the diversity of time-domain behavior within and across classes remains difficult to characterize in a unified framework. Changing-look AGNs (CLAGNs), which transition between classifications over time, further complicate this picture. In this work, we learn a data-driven, low-dimensional representation of multi-wavelength photometric light curves of AGNs, in which the structure of the projected manifold correlates with AGN class and independent spectroscopic properties. Using the NASA Fornax Science Platform, we assemble light curves from ZTF, Pan-STARRS, Gaia, and WISE/NEOWISE for two samples: (1) a heterogeneous set of $\sim$2000 AGNs spanning $z \lesssim 1$, including SDSS quasars, variability-selected sources, and CLAGNs; and (2) a homogeneous sample of $\sim$65000 narrow-line AGNs at $z \approx 0.1$ with well-characterized optical emission-line measurements. Without using class labels during training, the learned manifolds organize variability-selected AGNs into coherent regions of the low-dimensional space, distinguish between turn-on and turn-off CLAGNs, and place tidal disruption events in distinct regions. Manifold coordinates correlate with key spectroscopic and host-galaxy properties, including stellar mass, [OIII] luminosity, and D$_n$(4000), demonstrating that heterogeneous multi-band variability can be combined in a purely data-driven manner to recover correlations with independent physical diagnostics, without requiring explicit physical modeling. These results show that manifold learning offers a practical, assumption-light approach for integrating time-domain surveys and prioritizing spectroscopic follow-up.

astro-ph.GA↗

arXiv2026

A comprehensive search for high-velocity X-ray sources: New compact object binary candidates in the Gaia era

We perform a comprehensive search for high-velocity X-ray sources with large X-ray/optical flux ratios ($F_\mathrm{X}/F_\mathrm{G}$), identifying candidates for interacting black hole or neutron star binaries potentially accelerated by supernova natal kicks. We cross-match X-ray points sources from a variety of catalogues (Chandra, XMM-Newton, Swift and eROSITA) with Gaia DR3. Using Gaia coordinates, parallaxes, and proper motions, we compute peculiar velocities ($\upsilon_\mathrm{pec}$) relative to Galactic disc rotation. Remaining agnostic about radial velocities (RVs), we vary RVs to find the minimum possible $\upsilon_\mathrm{pec}$ values ($\upsilon_\mathrm{pec, min}$). Uncertainties on $\upsilon_\mathrm{pec, min}$ are estimated via Monte Carlo resampling, and we select X-ray sources that have $1\,σ$ lower limits on $\upsilon_\mathrm{pec, min}\geq 200\,\mathrm{km~s^{-1}}$ and high $F_\mathrm{X}/F_\mathrm{G}$ values. We show that this velocity threshold excludes most contaminants (e.g., cataclysmic variables and active binaries) while retaining a sensible fraction of compact object binaries, demonstrating that $\upsilon_\mathrm{pec}$ could serve as an effective indicator for the presence of a neutron star or black hole companion. Our selection yields a sample of 2372 sources, from which we construct a gold sample of 7 sources that have relatively well-constrained astrometry and confident optical counterparts. Follow-up is necessary to confirm and characterise their high-energy emission, as well as a Galactic disc vs. halo origin.

astro-ph.HE↗

arXiv2025

BASS.L. Near-infrared Data Release 3: A Spectral Atlas and Characterization of AGN

We present an analysis of near-infrared (NIR) emission-line properties, AGN diagnostics, and circumnuclear gas dynamics for 453 hard X-ray selected (14$-$195 keV) AGN from the BAT AGN Spectroscopic Survey (BASS) NIR Data Release 3 (DR3; $\langle z \rangle=0.036$, $z<1.0$). This dataset is the largest compilation of rest-frame NIR spectroscopic observations of hard-X-ray-selected AGN and includes the full DR2 sample. Observations were obtained with VLT X-shooter, a multiwavelength (0.3$-$2.5$μ$m) spectrograph ($R$ = 4,000$-$18,000), using a $\geq 2 σ$ detection threshold, enabling broad analysis of emission features. We find that NIR coronal lines, particularly SiVI $\lambda1.964$, are more reliable tracers of AGN luminosity than optical [OIII], showing a tighter correlation with hard X-ray luminosity ($σ=0.25$dex) than [OIII] $\lambda5007$ ($σ=0.55$dex). Broad Paschen lines (Pa$α$ and Pa$β$) are detected in 12% of Seyfert 2 and 57% of Seyfert 1.9, consistent with previous hidden BLR studies. We introduce a refined NIR diagnostic diagram (FeII $\lambda1.257$$μ$m/Pa$β$ and H$_2$ $λ2.122$$μ$m/Br$γ$) that effectively distinguishes AGN, star-forming, and composite sources even when contamination limits individual diagnostics or only upper limits are available. Additionally, we find a moderate correlation ($p \approx 7.4 \times 10^{-3}$) between hot molecular gas mass (traced by H$_2$ 2.121$μ$m) and X-ray luminosity, while its relation with Eddington ratio is weaker. The hot-to-cold gas mass ratio spans four orders of magnitude, averaging $\sim 3 \times 10^{-7}$, indicating diverse molecular gas excitation processes likely driven by star formation and AGN feedback. Our results underscore the value of NIR spectroscopy in probing AGN activity, obscured BLRs, and the complex interactions between AGN and their circumnuclear environments.

astro-ph.GA↗

arXiv2025

SN 2021ukt: A Transitional Supernova with a Short Plateau and Persistent Interaction

We present spectroscopic and photometric observations of supernova (SN) 2021ukt, a peculiar short-plateau object that was originally identified as a Type IIn SN and later underwent an unprecedented transition to a Type Ib (possibly Type IIb) SN. The early-time light curves of SN 2021ukt exhibit a ~25 day plateau. Such a short phase of hydrogen recombination suggests a rather thin H-rich outer envelope of the progenitor star. The relatively narrow Balmer emission lines in spectra of SN 2021ukt during the first week indicate the interaction between the expanding ejecta and the immediate circumstellar material (CSM). This Hα line is observed throughout its helium-rich ejecta-dominated phase and nebular phase, suggesting persistent interaction with a radially extended CSM profile. We explore the synthetic light-curve model among grids of parameters generated by MESA+STELLA. We also compare the spectrophotometric evolution of SN 2021ukt with several well-sampled supernovae that exhibit a short plateau and persistent ejecta-CSM interaction. An estimate of the progenitor mass of SN 2021ukt is made based on the flux ratio between [Ca II] λλ 7291, 7324 and [O I] λλ 6300, 6364 during its nebular phase. Our analysis suggests that the progenitor star of SN 2021ukt has a zero-age main-sequence (ZAMS) mass of about 12 solar masses, a mass of radioactive nickel-56 synthesized in the SN ejecta of about 0.04 solar masses, and a mass of the H-rich envelope of about 0.5 solar masses. This study adds to the growing sample of transitional supernovae, reinforcing evidence for a continuum of underrepresented progenitors whose evolutionary pathways lie between those of standard SN models.

astro-ph.SR↗

arXiv2025

Chandra and HST Observations of Radio-Selected (Wandering) Massive Black Hole Candidates in Dwarf Galaxies

We present Chandra X-ray Observatory and Hubble Space Telescope (HST) follow-up observations of 12 dwarf galaxies from Reines et al. (2020) that are potential hosts of radio-selected active galactic nuclei (AGNs), eight of which are non-nuclear and possible ``wandering" black holes (BHs). Our multi-wavelength analysis indicates a heterogeneous sample with five radio sources detected at both X-ray and optical wavelengths within positional uncertainties and non-detections for the remaining objects. Of the radio objects detected in the X-ray/optical, three have multi-wavelength evidence for hosting nuclear massive BHs and one object is consistent with an extreme compact starburst. Only one of the off-nuclear radio sources has a significant optical counterpart and we present Palomar spectroscopy that identifies this object as a background AGN. We cannot definitively determine if the seven remaining off-nuclear radio sources are wandering massive BHs in the target dwarf galaxies or background AGNs, although the three sources with the largest offsets have compact radio cores detected with the Very Large Baseline Array and are consistent with expectations for background AGNs (Sargent et al 2022). Our HST sensitivity limits also allow for wandering massive BHs in the target dwarf galaxies that are hosted by stellar clusters with masses $\lesssim 10^6 M_\odot$.

astro-ph.GA↗

arXiv2025

An Extremely Luminous Flare Recorded from a Supermassive Black Hole

Since their discovery more than 60 years ago, accreting supermassive black holes in active galactic nuclei (AGN) were recognized as highly variable sources, requiring an extremely compact, dynamic environment. Their variability traces to multiple phenomena, including changing accretion rates, temperature changes, foreground absorbers, and structural changes to the accretion disk. Spurred by a new generation of time-domain surveys, the extremes of black hole variability are now being probed. We report the discovery of an extreme flare by the AGN J224554.84+374326.5, which brightened by more than a factor of 40 in 2018. The source has slowly faded since then. The total emitted UV/optical energy to date is $\sim10^{54}$ erg, i.e., the complete conversion of approximately one solar mass into electromagnetic radiation. This flare is 30 times more powerful than the previous most powerful AGN transient. Very few physical events in the Universe can liberate this much electromagnetic energy. We discuss potential mechanisms, including the tidal disruption of a high mass $(>30\, M_\odot)$ star, gravitational lensing of an AGN flare or supernova, or a supermassive (pair instability) supernova in the accretion disk of an AGN. We favor the tidal disruption of a massive star in a prograde orbit in an AGN disk.

astro-ph.GA↗

arXiv2025

Hard X-ray Emission in AU Mic Flares: A Minor Contributor to Planetary Atmospheric Escape

Stellar flares are potent drivers of atmospheric evolution on orbiting exoplanets, primarily through extreme ultraviolet (EUV) and soft X-ray (XUV) irradiation. However, the contribution of hard X-rays (HXR; 3--20 keV)-which penetrate deeper into planetary atmospheres-to mass loss and particle acceleration has remained poorly understood. To quantify the HXR share of the total radiative budget, we conducted quasi-simultaneous observations of the active M-dwarf AU Mic using NuSTAR, Swift, and the Einstein Probe. Our analysis detected two major flares, and we performed an empirical check by deriving a quiescent-phase soft X-ray (SXR; 0.3--3 keV)-HXR relation and then applying it to the flares. By combining this with the quiescent coronal SXR-EUV relations conversion of J. Sanz-Forcada et al. (2011), we computed the total high-energy flux (EUV + SXR + HXR) and assessed the relative role of HXR in atmospheric escape. We find that HXR accounts for only a few percent of the total radiative energy budget during both quiescent and flaring states. While a high-energy spectral tail is detected in the second flare, time-resolved spectroscopy reveals a dominant chromospheric-evaporation signature, indicating that the flare energetics are primarily thermal.

astro-ph.SR↗

arXiv2025

The 2025 Failed Outburst of IGR J17091-3624: Spectral Evolution and the Role of Ionized Absorbers

IGR J17091-3624 is the only black hole X-ray binary candidate, aside from the well-studied black hole system GRS 1915+105, observed to exhibit a wide range of structured variability patterns in its light curves. In 2025, the source underwent a ``failed'' outburst: it brightened in the hard state but did not transition to the soft state before returning to quiescence within a few weeks. During this period, IGR J17091-3624 was observed by multiple ground- and space-based facilities. Here, we present results from six pointed NuSTAR observations obtained during the outburst. None of the NuSTAR light curves showed the exotic variability classes typical of the soft state in this source; however, we detected, for the first time, strong dips in the count rate during one epoch, with a total duration of $\sim4\,\mathrm{ks}$ as seen by NuSTAR. Through spectral and timing analysis of all six epochs, we investigate the hard-state spectral evolution and the nature of the dips. A clear evolution of the coronal properties with luminosity is observed over all six epochs, with clear signatures of relativistic disk reflection which remain largely unchanged across the first five epochs. The first five epochs also show a strong and stable quasi-periodic oscillation (QPO) feature in the power spectra. The dips observed in Epoch 5 are consistent with partial obscuration by ionized material with a column density $N_{\mathrm{H}} \approx 2.0 \times 10^{23}\,\mathrm{cm^{-2}}$. We discuss possible origins for this material and place constraints on the orbital parameters and distance of the system.

astro-ph.HE↗

arXiv2025

Probing the Physics of Dusty Outflows through Complex Organic Molecules in the Early Universe

Galaxy-scale outflows are of critical importance for galaxy formation and evolution. Dust grains are the main sites for the formation of molecules needed for star formation but are also important for the acceleration of outflows that can remove the gas reservoir critical for stellar mass growth. Using the MIRI medium-resolution integral field spectrograph aboard the James Webb Space Telescope (JWST), we detect the 3.28 $μ$m aromatic and the 3.4 $μ$m aliphatic hydrocarbon dust features in absorption in a redshift 4.601 hot dust-obscured galaxy, blue-shifted by $Δ$V=$-5250^{+276}_{-339}$ kms$^{-1}$ from the systemic redshift of the galaxy. The extremely high velocity of the dust indicates that the wind was accelerated by radiation pressure from the central quasar. These results pave a novel way for probing the physics of dusty outflows in active galaxies at early cosmic time.

astro-ph.GA↗

arXiv2025

Hot Diggity Dog: Simultaneous CO and Dust Modeling of the Most Luminous WISE Hot Dust-Obscured Galaxy Unveils Extreme Molecular Gas Excitation

Hot dust-obscured galaxies (Hot DOGs), the most infrared (IR) luminous objects selected by the WISE all-sky mid-IR survey, have yielded a sample of intrinsically luminous quasars (QSOs) with obscured nuclear activity and hot dust temperatures. The molecular gas excitation properties have yet to be examined in detail under such extreme conditions. Here we study the most far-IR luminous \textit{WISE} Hot DOG W2246-0526, focusing on ALMA observations of the central host galaxy. Multi-J CO transition measurements at J=2-1, 5-4, 7-6, 12-11, and 17-16 provide the first self-consistent modeling constraints on the molecular gas and dust properties of any WISE Hot DOG to date, providing a benchmark for future studies of dust-obscured QSOs. We implement a state-of-the-art TUrbulent Non-Equilibrium Radiative transfer model (TUNER) that simultaneously models both the line and dust continuum measurements. The extreme CO spectral line energy distribution seems to turnover around the CO(12-11) transition, likely making this among the most highly excited galaxies ever reported. The model infers a molecular gas mass $\sim 8\times10^{10}$\,\Msun, and we conclude that J$\ge$3 CO line luminosities trace the bulk of the molecular gas mass for this extreme system unlike low-excitation conditions calibrated locally. W2246-0526 is a rapidly evolving system, with a high mean value of the molecular gas kinetic temperature versus dust temperature $T_\mathrm{k}$ / $T_\mathrm{d} \sim 4.3$. This may be due to the shocks and outflows injecting kinetic energy within the central kpc of this host that have previously been reported. These signs of highly excited molecular gas in W2246-0526 motivates obtaining well-sampled CO ladders in larger samples to better understand the conditions within these short-lived episodes associated with the most obscured supermassive black hole activity.

astro-ph.GA↗

arXiv2025

Minimal surface doublings and electrostatics for Schrödinger operators

Twenty years ago, N. Kapouleas introduced a singular perturbation construction known as "doubling", which produces sequences of high-genus minimal surfaces converging to a given minimal surface with multiplicity two. Doubling constructions have since been implemented successfully in several settings, with deep work of Kapouleas-McGrath reducing their existence theory to the problem of finding suitable families of ansatz data on the initial minimal surface. In this paper, we introduce a variational approach to the existence of minimal doublings, relating the Kapouleas-McGrath construction to the study of nondegenerate critical points for a Coulomb-type interaction energy. By analyzing the minimizers of this energy, we prove that, in a generic closed 3-manifold, every two-sided, embedded minimal surface of index one admits a sequence of minimal doublings. As a corollary, we find that a generic 3-manifold contains an infinite sequence of embedded minimal surfaces with bounded area and arbitrarily large genus, whose geometry can be described with some precision.

math.DG↗

arXiv2025

Investigating Little Red Dots with UV Excess: Are They the High-Redshift Siblings of Blue Hot DOGs?

Little Red Dots (LRDs), newly identified compact and dusty galaxies with an unexpectedly high number density observed by JWST, have an unusual "V-shaped" rest-frame UV to near-infrared spectral energy distribution (SED). A group of hyper-luminous, obscured quasars with excess blue emission, called Blue-excess Hot Dust-Obscured Galaxies (BHDs), also exhibit qualitatively similar SEDs to those of LRDs. They represent a rare population of galaxies hosting supermassive black holes (SMBHs) accreting near the Eddington limit at redshifts z \sim 1--4. In this study, we compare their multi-wavelength SEDs to investigate whether LRDs, or a subset of them, could be high-redshift analogs of BHDs. Our analysis reveals that despite their similar "V-shape" SEDs, LRDs appear to be a different population than BHDs. The "V-shape" of BHDs appear at longer wavelengths compared to LRDs due to different selection strategies, suggesting LRDs have much less dust attenuation than typical BHDs. The bluer colors in the rest-frame infrared (continuum) emission of LRDs suggest the absence of hot dust heated by AGN accretion activities. We also argue that the blue excess in LRDs is unlikely from AGN scattered light. The compact morphologies and lower X-ray detection frequencies of LRDs suggest a distinct formation pathway from BHDs -- which are thought to be powered by super-Eddington accretion onto central SMBHs following major galaxy mergers.

astro-ph.GA↗

arXiv2025

BASS LII: The prevalence of double-peaked broad lines at low accretion rates among hard X-ray selected AGN

A fraction of active galactic nuclei (AGN) have double-peaked H$α$, H$β$ and Mg II broad lines attributed to emission from rotating gas in the accretion disk. Using optical spectroscopy of a flux-limited sample of AGN selected via ultrahard X-rays from the BAT AGN Spectroscopic Survey (BASS), we systematically identify 71 double-peaked emitters amongst 343 broad-line AGN with redshifts $0.004<z<0.297$ and 2-10 KeV X-ray luminosities of log 40-45.7 (erg/s), and provide their best-fit accretion disk geometry parameters. We find that ~21% of X-ray selected broad-line AGN are double-peaked emitters (DPEs), consistent with rates previously reported for $z<0.2$ broad-line AGN selected for strong optical variability in ZTF. 11 of 71 DPEs (15%) exhibited a single-peaked Gaussian component to the broad line profile in addition to the double-peaked disk profile. In this sample, DPEs have intrinsically higher masses by ~0.4 dex and lower Eddington ratios by ~0.3 dex than other broad-line AGN, and have a preference for elliptical host galaxies, higher X-ray luminosities, and higher [OI] $λ$6302 to narrow H$α$ flux ratios than other broad-line AGN. We find that DPEs are not segregated from other broad-line AGN in the $L_{\rm bol}$ vs $M_{\rm BH}$ relation or their X-ray to radio luminosity ratios, and do not show a preference for intermediate Seyfert types over Seyfert 1s. We do not find differences in a wide range of multi-wavelength properties when comparing DPEs to other broad-line AGN, including optical and mid-IR variability levels, and the rate of changing-look events. We discuss the two populations in the context of multi-component disk-wind models of the AGN broad line region and consider how unrecognized contributions of disk emission to the broad lines introduce biases in virial SMBH mass estimates.

astro-ph.GA↗

arXiv2025

BASS LIII: The Eddington Ratio as the Primary Regulator of the Fraction of X-ray Emission in Active Galactic Nuclei

Active galactic nuclei (AGN) emit radiation via accretion across the entire energy spectrum. While the standard disk and corona model can somewhat describe this emission, it fails to predict specific features such as the soft X-ray excess, the short-term optical/UV variability, and the observed UV/X-ray correlation in AGN. In this context, the fraction of AGN emission in different bands (i.e., bolometric corrections) can be useful to better understand the accretion physics of AGN. Past studies have shown that the X-ray bolometric corrections are strongly dependent on the physical properties of AGN, such as their luminosities and Eddington ratios. However, since these two parameters depend on each other, it has been unclear which is the main driver of the X-ray bolometric corrections. We present here results from a large study of hard X-ray-selected (14-195 keV) nearby ($z<0.1$) AGN. Based on our systematic analysis of the simultaneous optical-to-X-ray spectral energy distributions of 236 unobscured AGN, we found that the primary parameter controlling the X-ray bolometric corrections is the Eddington ratio. Our results show that while the X-ray bolometric correction increases with the bolometric luminosity for sources with intermediate Eddington ratios ($0.01-1$), this dependence vanishes for sources with lower Eddington ratios ($<0.01$). This could be used as evidence for a change in the accretion physics of AGN at low Eddington ratios.

astro-ph.GA↗