Current date: 2026-09-04
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Datestamp limit: 2026-09-04 (0 days ago)
Created/updated limit: 2026-08-28 (7 days ago)
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Suggested sets: physics, physics:astro-ph, physics:gr-qc, physics:physics
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Scoring abstracts
Number of records retrieved: 802
Keyword score statistics
score 11 -- 2 abstracts
score 9 -- 1 abstracts
score 7 -- 2 abstracts
score 6 -- 2 abstracts
score 5 -- 4 abstracts
score 4 -- 5 abstracts
score 3 -- 12 abstracts
score 2 -- 14 abstracts
in total -- 42 abstracts
Articles that appeared on 2026-09-04
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[abstract 1 / 42] Wow! (score: 11)
- Title: Are JET speeds governed by accretion modes?Authors: Hong Tu, Xinwu Cao, Andrzej A. Zdziarski,Comments: 11 pages, 3 figures, accepted by MNRASSubjects: astro-ph.HECreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
Relativistic JETs are observed in both stellar-mass BLACK HOLE X-ray binaries (BHXRBs) and ACTIVE GALACTIC NUCLEi (AGNs), yet their bulk Lorentz factors differ systematically---those in BLACK HOLE X-ray binaries are typically below $\sim2$, whereas AGN JETs can reach $\sim50$. The origin of this discrepancy remains unclear. Searching the literature, we compile a sample of 333 AGNs with well-measured JET component motions, consisting of 270 QUASARs, 47 BL Lac objects, 10 FRI, and 6 FRII galaxies. We find that QUASARs/FRIIs exhibit minimal bulk Lorentz factors ranging from $\sim$1.0 to 41.5, with a mean of 11.5 (median 9.5). In contrast, BL Lac objects/FRIs show $Γ_{\rm JET}\sim$1.0--21.9, averaging 4.2 (median 1.5). These values, particularly the median, closely resemble those of BHXRBs, implying a strong correlation between JET speed and accretion mode. The Lorentz factor of a MAGNETically driven JET is mainly determined by the ratio of the MAGNETic pressure to rest mass energy density at the JET base. In BL Lacs/FRIs/BHXRBs, the field is maintained by the advection-dominated accretion flow (ADAF), and the gas at the ADAF surface is MAGNETically driven into the JETs. In QUASARs/FRIIs, the field is maintained by the disc, while the JET base is connected to the corona. Our model calculations show that the disc field is always much stronger than that of the ADAF, and therefore leads to a larger $Γ_{\rm JET}$, which can explain the systematic difference in $Γ_{\rm JET}$ between these two types of sources.
[abstract 2 / 42] Wow! (score: 11) - Title: The Jet Properties and Accretion Regime for the Blazar SequenceAuthors: Qingchen Long,Comments: 19 pages, 4 figures, and 3 tables; accepted for publication in ApJ. Comments are welcomeSubjects: astro-ph.HECreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
The puzzling bimodality displayed by BLAZARs on the broad-band spectral indices ($α_{\rm ro}-α_{\rm ox}$) plane is still an open question. To investigate its physical origin, we compiled a sample comprising 136 flat-spectrum radio QUASARs (FSRQs), 64 low-SYNCHROTRON-peaked BL Lac objects (LBLs), 39 intermediate-SYNCHROTRON-peaked BL Lac objects (IBLs), and 105 high-SYNCHROTRON-peaked BL Lac objects (HBLs). Our results show that (FSRQs+LBLs)$\rightarrow$IBLs$\rightarrow$HBLs follow a \reflectbox{$\angle$}-shaped evolutionary sequence on the $α_{\rm ro}-α_{\rm ox}$ plane, with the average 5\,GHz radio Doppler factor, JET power, and accretion Eddington ratio decreasing along this \reflectbox{$\angle$}-shaped track. Additionally, the distributions of $α_{\rm ox}$ exhibit only slight differences among BLAZAR subclasses, whereas those of $α_{\rm ro}$ and $α_{\rm rx}$ differ significantly. Our results can be naturally explained if the distribution of BLAZARs on the $α_{\rm ro}-α_{\rm ox}$ plane is regulated by the accretion rates and the Doppler beaming effect across different bands ($δ_i^{q_i}/δ_j^{q_j}$). However, $δ_i/δ_j$ plays a pivotal role in the distribution, while JET shape ($q=2(3)+α_ν$) and spectral indices ($α_ν$) play a minor role. Our results suggest that FSRQs+LBLs are strong-JET sources coupled with radiatively efficient accretion, and their JETs are accelerated to a larger distance from the core and still maintain RELATIVISTIC speeds down to the radio region; HBLs are weak-JET sources coupled with radiatively inefficient accretion, and their JETs may begin to decelerate in the optical region and exhibit sub-RELATIVISTIC speeds as they propagate to the radio region. IBLs are regarded as transitional objects between FSRQs+LBLs and HBLs.
[abstract 3 / 42] Wow! (score: 9) - Title: Magnetized accretion onto rapidly spinning binary BLACK HOLEs: mini-disk thermodynamics, MAGNETic transport, and dual JETsAuthors: Luciano Combi, Manuela Campanelli, Sean M. Ressler, Alexander J. Dittmann, Federico Cattorini,Comments: 26 pages, 20 figures. Comments welcome!Subjects: astro-ph.HE gr-qcCreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
Supermassive binary BLACK HOLEs embedded in gas-rich environments are promising multi-messenger sources for pulsar timing arrays and future space-borne gravitational-wave interferometers. Their electroMAGNETic emission is governed by nonlinear plasma dynamics around the binary and is expected to inherit variability associated with the orbital motion thereof. Because ACTIVE GALACTIC NUCLEi are intrinsically stochastic, identifying robust binary signatures requires predictive models that connect large-scale circumbinary flows to the BLACK HOLEs. Previous RELATIVISTIC simulations of accreting binaries have mostly focused on smaller separations and lower spins. We perform three-dimensional general RELATIVISTIC MAGNETohydrodynamic simulations of a relaxed, MAGNETized circumbinary disk accreting onto an equal-mass binary BLACK HOLE with a separation of $30$ gravitational radii and dimensionless spin $χ=0.9$. At these separations, the mini-disks around each BLACK HOLE are persistent mass reservoirs but still show pronounced amplitude modulations governed by the eccentric circumbinary disk and the sloshing gas between the mini-disks. We analyze how the MAGNETic flux is transported from the circumbinary disk to the horizons, launching powerful dual JETs with energy extraction efficiencies reaching $\approx 40\%$. The horizon-threading flux and JET luminosity alternate between the two BLACK HOLEs, producing an on-off dual-JET state. The wide JET funnels interact above the binary and form a persistent current sheet favorable to RECONNECTion. We explore the influence of mini-disk thermodynamics, comparing efficient and inefficient cooling inside the cavity. Hotter mini-disks are less massive, exhibit weaker coherent periodicity, and launch less luminous JETs despite comparable horizon-threading MAGNETic flux.
[abstract 4 / 42] Wow! (score: 7) - Title: How similar are narrow-line Seyfert 1 galaxies and high-z type 1 AGN?Authors: Marco Berton, Emilia Järvelä, Alessia Tortosa, Chiara Mazzucchelli,Comments: 18 pages, 8 figures. Published in the Open Journal of AstrophysicsSubjects: astro-ph.GA astro-ph.HECreated: 2026-09-01; Updated: 2026-09-04; Datestamp: 2026-09-04
The recent observations of highly accreting supermassive BLACK HOLEs (SMBH) at very high redshift ($z>$4) with the James Webb Space Telescope (\textit{JWST}) allowed us to shed light for the very first time on the early evolutionary phases of ACTIVE GALACTIC NUCLEi (AGN). Perhaps unsurprisingly, several of the physical properties observed in these new objects, including those known as little red dots (LRDs), are closely reminiscent of the low-mass and high-Eddington AGN in the local Universe, and in particular of the class of narrow-line Seyfert 1 (NLS1) galaxies. However, some differences also emerged, likely due to the radically different evolutionary path and the environment where LRDs and NLS1s live. In this work, we review the multiwavelength properties of local NLS1s and briefly compare them with type 1 AGN found at high-$z$, showing that despite some differences, the study of NLS1s can be extremely useful to better understand the extreme accretion physics of high-$z$ QUASARs and the early stages of AGN evolution. The goal of this review is to provide the high-z community a handbook to compare their new sources with those already known in the local Universe, and to give the low-z community a starting point to venture in the early phases of AGN evolution.
[abstract 5 / 42] Wow! (score: 7) - Title: Multiwavelength View of Black Hole X-ray Binary SWIFT J151857.0-572147Authors: Manoj Mandal, Sachindra Naik, Souvik Manik, Sabyasachi Pal,Comments: Accepted for publication in ApJSubjects: astro-ph.HECreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
We investigate multiwavelength timing and spectral properties of the newly discovered BLACK HOLE X-ray binary SWIFT J151857.0-572147 during its 2024 outburst using observations from AstroSat, NUSTAR, NICER, SWIFT, and MeerKAT. The AstroSat/LAXPC20 power density spectrum reveals a $\sim$8 Hz low-frequency QPO with a quality factor of $\sim2.8$. The broadband X-ray spectrum of the source exhibits prominent reflection features, which are modeled to constrain the geometry and physical properties of the accretion disk. The spectral analysis indicates that the source was in the soft/intermediate spectral state, characterized by a steep power law with a photon index of $Γ\approx 2.6$ and a relatively high disk temperature of $\sim0.9$ keV. The reflection modeling suggests a disk inclination of $23-31^{\circ}$ and a highly ionized accretion disk with $\logξ\sim 3.3$-4.0. The MeerKAT monitoring revealed a strong radio variability that closely tracked the hard X-ray evolution, including a bright radio flare during the hard-to-soft state transition, supporting close coupling between the accretion flow and JET activity. Using the quasi-simultaneous AstroSat, SWIFT/XRT and MeerKAT observations, we investigated the radio/X-ray correlation and found that SWIFT J151857.0-572147 follows the established $L_{\rm X}$-$L_{\rm R}$ relation for Galactic BLACK HOLE X-ray binaries. Its location in the $L_{\rm X}$-$L_{\rm R}$ plane is consistent with that of Galactic BLACK HOLE X-ray binaries, further supporting its BLACK HOLE nature.
[abstract 6 / 42] Yes (score: 6) - Title: Expanding the Population of Short Gamma-Ray Transients with a Coherent FERMI/GBM Search. A 13-year catalog of short GRBsAuthors: Ariel Perera, Barak Zackay, Tejaswi Venumadhav,Comments:Subjects: astro-ph.HECreated: 2026-09-02; Updated: 2026-09-04; Datestamp: 2026-09-04
In this paper, we present an archival search for short GAMMA-RAY BURSTs (sGRBs) over 13 years (2013-2025) of FERMI/GBM data using a Poisson matched-filter pipeline that performs a fully coherent analysis across all detectors and energy channels, significantly improving sensitivity relative to the onboard triggering algorithms. A central component of the analysis is the empirical estimation of trigger significance using 'timeslided' data, allowing each candidate to be assigned a probability of astrophysical origin. We also developed a new parameter-estimation framework based on the Poisson matched filter, which uses the global structure of the detected event across spectral, temporal, and spatial parameter spaces. This enables us to systematically classify bursts and distinguish between GRBs, soft gamma repeaters, terrestrial gamma-ray flashes, and solar flares. We identify 568 new GRB candidates with $p_{\text{astro}}\geq0.9$ and thousands of MAGNETar bursts, significantly expanding the known short-transient population in GBM data. To further strengthen the significance of the GRB candidates, we performed a targeted follow-up search in SWIFT/BAT rate data. Applying the followup to all of our triggers - including triggers below the detection threshold yielded 1736 temporally coincident events with association probability above $90\%$. The resulting probabilistically ranked catalog substantially expands the population of short GRBs and MAGNETar flares detected in GBM data and provides a statistically robust framework for multimessenger searches.
[abstract 7 / 42] Yes (score: 6) - Title: Thermal and non-thermal emission from supermassive BLACK HOLE circumbinary disks: Disks, Coronae, Streams, and CavitiesAuthors: Chris Nagele, Julian H. Krolik, Brooks E. Kinch, Jeremy D. Schnittman, Scott Noble,Comments: Submitted to ApJ Comments welcome!Subjects: astro-ph.HECreated: 2026-09-02; Updated: 2026-09-04; Datestamp: 2026-09-04
The search for electroMAGNETic signals from supermassive BLACK HOLE (SMBH) binary systems is one of the cornerstones of multi-messenger astrophysics, complementing gravitational wave observations of such systems by pulsar timing arrays and LISA. Although extensive simulations have been run to understand the time variability of the bolometric luminosity from accreting binary SMBH systems, comparatively few spectral predictions have been made, and none that go beyond simple emission models. In this paper, we post-process a \texttt{HARM3D} simulation snapshot of a binary at $20 M$ separation accreting at 0.01 Eddington. For BLACK HOLE masses $10^6$, $10^7$, and $10^8\, M_\odot$, we self-consistently solve for the radiated spectrum on the basis of time-steady radiation transfer, thermal balance, and ionization equilibrium, including all relevant RELATIVISTIC effects as well as emission and absorption processes. Although most of the bolometric luminosity is radiated thermally by the disk, the low density regions evacuated by the binary's quadrupole moment produce copious X-rays, with $\sim40\%$ of the observed luminosity in a soft X-ray power law ($Γ= 2.3$). We identify two modes of observed azimuthal variation. The X-ray continuum varies by $\sim10\%$ due to an underlying asymmetry in the gas temperature of spiral shocks in the disk. The Fe~K$α$ equivalent width dips by $\sim25\%$ when the line of sight to the inner disk is partially obscured by the lump. These two effects share the same period and are $\sim π/2$ out of phase; the period is order days to weeks for typical AGN masses and a 20$M$ separation.
[abstract 8 / 42] Yes (score: 5) - Title: The propagation-induced circular POLARIZATION of fast radio bursts in RELATIVISTIC plasmaAuthors: Z. Y. Zhao, F. Y. Wang,Comments: 12 pages, 11 figures, 2 tables, accepted for publication in A&ASubjects: astro-ph.HECreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
Although the physical origin of fast radio bursts (FRBs) remains unknown, MAGNETars are the most likely candidates. The POLARIZATION properties of FRBs offer crucial insights into their origins and radiation mechanisms. Significant circular POLARIZATION (CP) has been observed in some FRBs. CP may result from intrinsic radiation or propagation effects, both within and outside the MAGNETosphere. Recent observations indicate that POLARIZATION properties of FRB 20201124A can change over short timescales (about tens of milliseconds), challenging models that attribute CP to out-of-MAGNETosphere emission and propagation. Additionally, some MAGNETospheric radiation models predict that bursts with high CP produced by off-axis emission will be systematically fainter, which contradicts the observations. We propose that CP arises from MAGNETospheric propagation effects caused by RELATIVISTIC plasma. We identify the conditions under which high CP occurs, finding it to be rare. Moreover, our model accounts for the more commonly observed low CP and the varying handedness of CP.
[abstract 9 / 42] Yes (score: 5) - Title: Multi-epoch Detection of an Ultra-fast Inflow in ESP 39607: Evidence for an Accretion CascadeAuthors: Alessandro Peca, Michael J. Koss, Roberto Serafinelli, C. Megan Urry, Claudio Ricci, Keigo Fukumura, Massimo Gaspari, Elias Kammoun, Alessia Tortosa, Giulia Cerini, Peter G. Boorman, Richard Mushotzky, Quirino D'Amato,Comments: Resubmitted to ApJ after addressing a positive referee reportSubjects: astro-ph.HE astro-ph.GACreated: 2026-09-02; Updated: 2026-09-04; Datestamp: 2026-09-04
We present simultaneous XRISM, XMM-Newton, and NUSTAR observations of ESP 39607, a Seyfert 2 galaxy at $z = 0.201$. XRISM/Resolve reveals two absorption features near 4.7 and 4.9 keV in the observed frame, consistent with redshifted Fe XXV He-$α$/Fe XXVI Ly-$α$ absorption from gas inflowing at $v_{\rm in} \simeq 0.16c$. The high velocity identifies the absorber as an ultra-fast inflow (UFI), which is detected at $\sim 3$-$3.7σ$ across different methods and continuum models. Photoionization modeling yields $\log ξ/{\rm erg\,s^{-1}\,cm} \simeq 3.7$-$3.8$ and a column density $\log N_{\rm H,abs}/{\rm cm^{-2}} \simeq 23.2$-$23.8$, the latter depending on the assumed metallicity. The inflow velocity and line properties are consistent with those reported from two earlier NUSTAR epochs, indicating that similar inflowing material was present over a baseline of at least 2.2 yr in the source rest frame. Across all three epochs, the combined detection significance of the UFI is $5.3σ$. Given the dynamical timescale of a few days at the inferred radius, $R \simeq 49$-$77\,R_{\rm g}$, the multi-year evidence favors a scenario in which the inflow is continuously replenished, forming an accretion "cascade", rather than a single long-lived cloud. With an estimated mass inflow rate of $\dot{M}_{\rm in} \simeq 0.3$-$1.4\,M_\odot$ yr$^{-1}$, depending on metallicity, and a ratio $\dot{M}_{\rm in}/\dot{M}_{\rm acc} \simeq 0.2$-$1.0$, the inflow could supply a substantial fraction of the accretion needed to power the central ACTIVE GALACTIC NUCLEus.
[abstract 10 / 42] Yes (score: 5) - Title: Radiative Efficiency Enhancement by ElectroMAGNETic Energy Dissipation in Strongly Magnetized Supercritical Accretion Flows around Kerr Black HolesAuthors: Hiroyuki R. Takahashi, Ken Ohsuga, Ryohei Kobayashi, Akihiro Inoue, Yuta Asahina, Akira Nukada, Taisuke Boku,Comments: 18 pages, 10 figures, 1 table. Accepted for publication in ApJSubjects: astro-ph.HECreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
We investigate how BLACK HOLE spin and the amount of MAGNETic flux affect electroMAGNETic energy dissipation and radiation transport in supercritical accretion flows. For this purpose, we perform general RELATIVISTIC radiation MAGNETohydrodynamic simulations of MAD and SANE accretion flows with different BLACK HOLE spins. In the high-spin MAD model, we find that a fraction of the electroMAGNETic energy extracted by the Blandford--Znajek mechanism is dissipated near the disk surface in the vicinity of the BLACK HOLE. This dissipation significantly contributes to the generation of radiative energy and enhances the luminosity. The time-averaged radiative efficiency reaches $η_{\rm rad}=0.60$, which is much larger than $0.088$ for the non-spinning BLACK HOLE case and $0.21$ for the weak-MAGNETic-flux case, corresponding to the SANE state. As a result, the effective trapping radius, defined as the radius at which the outward radiative luminosity becomes equal to the inward radiative luminosity, is $r_{\rm trap}=2.5r_{\rm g}$, comparable to the ISCO radius. This value is significantly smaller than $12r_{\rm g}$ for the non-spinning case and $8.5r_{\rm g}$ for the SANE state. These results suggest that the amount of MAGNETic flux accumulated on the BLACK HOLE can affect the radiative properties of supercritical accretion flows and should therefore be considered, in addition to BLACK HOLE mass, spin, and mass accretion rate, when interpreting observed luminosities and spectra.
[abstract 11 / 42] Yes (score: 5) - Title: KM3NeT/ARCA stacking search for high-energy neutrino point sources: the case of ultra-luminous infrared galaxies and BLAZARsAuthors: The KM3NeT Collaboration,Comments: 26 pages, 11 figuresSubjects: astro-ph.HECreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
A stacking search for high-energy astrophysical neutrino emission is presented using three candidate source populations: ultra-luminous infrared galaxies and two categories of BLAZARs, specifically high-SYNCHROTRON-peaked BL Lacs and extreme BLAZARs. The analysis is based on 336 days of data from the Astroparticle Research with Cosmics in the Abyss component of the KM3NeT research infrastructure (KM3NeT/ARCA), collected with detector configurations comprising 19-21 detection units, yielding 1544 selected track-like neutrino candidates. The sample of ultra-luminous infrared galaxies consists of 75 sources, for which conventional power-law spectra are assumed in modelling their signal emission. The BLAZAR samples comprise 232 high-SYNCHROTRON-peaked BL Lac objects and 88 extreme SYNCHROTRON-peaked emitters, respectively. Their expected neutrino fluxes are obtained from numerical tools constrained by multi-wavelength observational data. No statistically significant excess above the atmospheric background is found for the three catalogues and 90% confidence level upper limits are set.
[abstract 12 / 42] Yes (score: 4) - Title: Unlocking the QPE Mystery: Star-Disk Collisions in Realistic AGN DisksAuthors: Zhaohuan Zhu, Xiaoshan Huang, Yan-Fei Jiang, Shunquan Huang,Comments: 11 pages, 6 figures. Revised after the first referee reportSubjects: astro-ph.HECreated: 2026-09-02; Updated: 2026-09-04; Datestamp: 2026-09-04
Quasi-periodic eruptions (QPEs) are luminous, recurring soft X-ray outbursts observed in the nuclei of low-mass galaxies. They display two remarkable trends: outburst durations are $\sim$10-20% of the recurrence timescale, and longer bursts are more luminous. A promising theory that naturally explains the quasi-periodicity invokes collisions between a star on an extreme mass-ratio inspiral (EMRI) orbit and the accretion disk around the supermassive BLACK HOLE. However, it remains unclear how this model reproduces the observed trends. We therefore carry out two-dimensional, multi-frequency radiation hydrodynamic (RH) simulations of star--disk collisions. Crucially, we adopt a more realistic circumnuclear disk structure from previous Radiation MHD simulations of sub-Eddington accretion disks. We find that the thick, puffed-up disk atmosphere, extending to $z/r\sim1$, causes different portions of the bow shock to break out at different times, producing prolonged thermal emission as the shock emerges through the breakout surface at $z/r\sim0.7$. The X-ray flare duration is set by the shock propagation time through the optically thick disk--a $\sim$10% of the orbital timescale, reproducing the observed duty cycle. A more oblique star-disk interaction yields a longer, more luminous flare. The realistic AGN disk models also exhibit a surface density $Σ\propto r^2$, giving a collisional energy $E\propto P^{2/3}$ that may explain the luminosity--period trend, especially for the weaker QPEs. Overall, we suggest that a more realistic circumnuclear disk structure can explain several observed QPE trends-and QPEs may, in turn, constrain the disk structure.
[abstract 13 / 42] Yes (score: 4) - Title: CLAS+: A large catalog of Changing-Look AGN candidates selected through S-PLUS narrow-band photometryAuthors: L. Nakazono, L. L. Oliveira, R. R. Valença, P. Sánchez-Sáez, G. Oliveira-Schwarz, N. M. Cardoso, A. L. O'Mill, S. Panda, E. Telles, R. Demarco, W. Schoenell, T. Ribeiro, A. Kanaan, C. Mendes de Oliveira,Comments: Accepted in ApJ. Crossmatch of CLAS+ with LSST is available in https://marixko.github.io/CLAS_lsst_fup/Subjects: astro-ph.GACreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
Changing-look ACTIVE GALACTIC NUCLEi (CLAGN) exhibit rapid spectral transitions on timescales of months to years, challenging standard AGN unification models and providing unique insight into accretion-disk variability and obscuration processes. Despite their scientific importance, systematic searches for CLAGN remain limited by the scarcity of multi-epoch spectroscopy and the difficulty of constructing large samples efficiently. We introduce CLAS+, a catalog constructed by comparing synthetic photometry derived from DESI DR1 and SDSS DR17 spectra with contemporaneous narrow-band imaging from the S-PLUS survey. Applying our pipeline to a parent sample of 98,139 QUASARs, we select high-confidence CLAGN candidates above a threshold of reduced chi-squared $χ_r^2 > 15$. We identify 3,554 strong CLAGN candidates, corresponding to 3.6\% of the parent sample. This selected fraction is conditional on the adopted criterion and should not be interpreted as an intrinsic CLAGN occurrence rate. Cross-matching with existing CLAGN compilations shows that CLAS+ identifies a large population of previously unreported high-priority candidates (3,481). Among the spectroscopic--photometric comparisons with reliable temporal classification, 40\% are classified as photometric turn-on, 41\% as intermediate, and 19\% as turn-off. We also find an apparent redshift dependence in the relative fractions, with photometric turn-on candidates becoming more common at higher redshifts within the CLAS+ selected sample. Therefore, narrow-band photometry provides a powerful and efficient alternative to purely spectroscopic searches for identifying CLAGN candidates at scale. CLAS+ substantially expands the known CLAGN candidate population and provides a valuable target list for future spectroscopic follow-up and time-domain studies with facilities such as Rubin/LSST.
[abstract 14 / 42] Yes (score: 4) - Title: NUSTAR View of the 2025 Mini-Outburst of the Black Hole X-ray Binary GRS 1739-278: Spectral and Timing Evolution in the Soft StateAuthors: Arshad Hussain, Umananda Dev Goswami,Comments: 17 pages, 10 figuresSubjects: astro-ph.HECreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
We present a dedicated timing and spectral analysis of three NUSTAR observations of the Galactic BLACK HOLE candidate GRS 1739-278 obtained during the decay of its 2025 mini-outburst (September 18-30, 2025). The source is found in a soft, disk-dominated state throughout, with a declining $3$-$79$ keV count rate (from $112.4$ to $99.4$ cts s$^{-1}$), a low and only mildly evolving hardness ratio ($\approx0.14$-$0.16$) and a fractional variability that drops from $3.2\%$ to $1.1\%$; no periodic or quasi-periodic signal is detected in the power spectrum or the Lomb-Scargle periodogram of any observation. Joint FPMA+FPMB spectral fits with an absorbed disk-blackbody plus thermal-Comptonization continuum, together with a broad, high-significance ($11.7$-$15.0σ$) curvature feature near $10$-$12$ keV (an empirical proxy for a strong disk-reflection/returning-radiation component) describe the $4$-$30$ keV spectra well ($χ^2/{\rm dof}=1.04$-$1.15$). The inner-disk temperature cools steadily from $1.021\pm0.001$ to $1.002^{+0.003}_{-0.002}$ keV while the disk normalization and hence the derived inner radius, $R_{\rm in}\simeq27.7$ km $\simeq0.95\,R_{ISCO}$ remains constant to within $0.3\%$, consistent with a disk anchored at the innermost stable circular orbit throughout. The unabsorbed $4$-$30$ keV luminosity declines from $1.35\times10^{37}$ to $1.15\times10^{37}$ erg s$^{-1}$ ($0.67\%$ to $0.57 L_{Edd}$). These results of the spectral-timing characterization of the 2025 mini-outburst are broadly consistent with a high-spin BLACK HOLE accreting at a low, steadily declining rate in the canonical soft state.
[abstract 15 / 42] Yes (score: 4) - Title: Sgr A* as a Galactic PeVatron: Multimessenger Signatures of the Magnetic Penrose ProcessAuthors: Marina Cermeño, Pedro De la Torre Luque, Cristina Fernández-Suárez, Viviana Gammaldi, Enrique Mier-Alonso, María J. Rodríguez, Miguel Á. Sánchez-Conde, Jaume Zuriaga-Puig,Comments: 27 pages, 12 figures and 2 tables. Comments welcomeSubjects: astro-ph.HE astro-ph.GA gr-qcCreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
The MAGNETic Penrose process (MPP) is one of the most efficient mechanisms for extracting rotational energy from a MAGNETized Kerr BLACK HOLE (BH), enabling charged particles to reach very-high energies. We investigate this process in Sagittarius A* (Sgr A*), the supermassive BH at the Galactic center (GC), focusing on its ultra-high-efficiency regime, in which neutrons undergo beta decay inside the BH ergosphere. As a key novelty, we compute the neutron production spectrum in the accretion flow directly from the nuclear reaction kinematics and follow neutron trajectories in the Kerr spacetime to determine the population that reaches the ergosphere and undergoes the MPP. From this population, we derive the spectrum of accelerated protons and show that Sgr A* can accelerate them up to PeV energies, strengthening its interpretation as a candidate Galactic PeVatron. We further compute the gamma-ray and neutrino emission produced through hadronic interactions of the escaping protons in the Central Molecular Zone. The predicted gamma-ray fluxes exhibit distinctive spectral features that could provide an observational signature of the MPP and may constitute a non-negligible contribution to the very-high-energy emission detected by H.E.S.S. and HAWC. The associated neutrino fluxes remain below the diffuse Galactic component inferred by IceCube, but may still contribute to the high-energy emission from the GC. Remarkably, the predicted signals lie within the projected sensitivity of SWGO for all scenarios considered here and, for some models, only a factor of a few below the nominal CTAO sensitivity, while KM3NeT/ARCA and IceCube-Gen2 will provide complementary tests. Our results establish the MPP as an observable mechanism for extracting BH rotational energy, providing a direct connection between horizon-scale physics and multimessenger observations that can be extended to other MAGNETized BHs.
[abstract 16 / 42] Yes (score: 4) - Title: Fundamental differences in the X-ray accretion properties of low and high-excitation RADIO GALAXiesAuthors: R. Kondapally, T. Holc, P. N. Best, J. Aird, K. J. Duncan, L. K. Morabito, D. M. Alexander, D. J. B. Smith, S. Shenoy, S. Das,Comments: Submitted to Monthly Notices of the Royal Astronomical Society (MNRAS). 10 pages, 5 figuresSubjects: astro-ph.GA astro-ph.HECreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
We characterise the accretion rate properties of radio-detected AGN by combining deep radio and X-ray observations of the Boötes field. We used deep international LOFAR telescope observations to identify 2840 radio-AGN across $0.3 < z \leq 2$, divided into samples that are complete in radio luminosity. We further split this sample into four different classes: radio-quiet AGN (RQ-AGN), high-excitation RADIO GALAXies (HERGs), and low-excitation RADIO GALAXies (LERGs) hosted by star-forming (SF-LERGs) and quiescent galaxies (Q-LERGs). Through performing X-ray stacking, we determined the average X-ray luminosities, $L_{\rm{X, 2-10\,keV}}$ and average specific X-ray luminosities, $λ_{sL_{X}}$ (X-ray luminosity scaled by the stellar mass; a proxy for the accretion rate). We studied how these X-ray properties depend on radio luminosity, stellar mass, and redshift for each of the four AGN classes. We found that the LERGs, regardless of their star-formation activity, show significantly lower $L_{\rm{X, 2-10\,keV}}$ and $λ_{sL_{X}}$ than both HERGs and RQ-AGN across all redshifts. The average X-ray luminosities for the HERGs, RQ-AGN, and SF-LERGs typically increase with redshift, which may be associated with the increased cold gas fractions at earlier times, resulting in more enhanced BLACK HOLE accretion. The average X-ray luminosities show weak-to-no correlation with radio luminosity at a given redshift, suggesting that the physical processes producing the X-ray and radio emission may not be coupled on spatial and/or temporal scales.
[abstract 17 / 42] (score: 3) - Title: Remnant recoil and host environments of GWTC-4.0 binary black-hole mergersAuthors: Joan Llobera-Querol, Eleanor Hamilton, Neha Singh, Marta Colleoni, Felip A. Ramis Vidal, Abbas Askar, Tomasz Bulik, Aleksandra Olejak, Sascha Husa, Yumeng Xu, Jorge Valencia,Comments: 21 pages, 12 figures, 6 tablesSubjects: astro-ph.HE gr-qcCreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
Determining the astrophysical origin of binary BLACK HOLEs and whether merger remnants are retained in their birth environments is essential for understanding hierarchical mergers and the growth of intermediate-mass BLACK HOLEs. We identified gravitational-wave events most consistent with dense-cluster origin and assessed whether their merger remnants are retained in globular clusters, nuclear star clusters, or galactic potentials. We considered 84 events consistent with binary-black-hole mergers from the first part of the fourth observing run (O4a) of the LIGO-Virgo-KAGRA detector network, and 3 selected events from the second part (O4b). We compared parameter-estimation posteriors with synthetic population models for field and cluster binaries using Bayes factors, accounting for the relative abundances of these formation channels. We computed recoil-velocity posteriors for all events using the IMRPhenomXPNR waveform model. We identified five events whose intrinsic parameters show preference for the adopted dense-cluster models over the considered field-binary populations, including the most massive O4a event GW231123_135430, while finding no robust preference for a dense-cluster origin for the high-spinning O4b event GW241011_233834. Typical recoil velocities are a few hundred km/s, with extended high-velocity tails. These kicks suggest merger remnants are likely ejected from typical globular clusters, while retention in nuclear star clusters remains possible but not guaranteed. Within the adopted models, efficient hierarchical growth may be challenging in typical globular clusters, whereas nuclear star clusters remain viable environments for repeated mergers. Although results depend on the adopted population models, this analysis highlights the importance of improved population models and higher-quality detections enabled by future GW detectors.
[abstract 18 / 42] (score: 3) - Title: Tidally-enhanced resonances in extreme-mass-ratio inspirals: A tertiary path to chaosAuthors: Kyriakos Destounis, Takuya Katagiri, Sajal Mukherjee, Kostas D. Kokkotas,Comments: 22 pages, 11 figuresSubjects: gr-qc astro-ph.HE hep-ph hep-th nlin.CDCreated: 2026-09-02; Updated: 2026-09-04; Datestamp: 2026-09-04
Extreme-mass-ratio inspirals (EMRIs) provide a unique laboratory for probing strong-field gravity and complex RELATIVISTIC dynamics. We study a tidally deformed EMRI composed of a stellar-mass secondary orbiting a supermassive (non-)rotating BLACK HOLE embedded in an external, adiabatically varying tidal environment. These systems provide a restricted, yet astrophysically motivated, realization of the RELATIVISTIC three-body problem, expected to appear in ACTIVE GALACTIC NUCLEi, with a clear hierarchy of masses and radiation-reaction timescales. The external tidal deformation breaks the axisymmetry of the Kerr spacetime, rendering the geodesic dynamics non-integrable and giving rise to chaotic motion. The resulting signature of non-integrability is characterized through Poincaré maps and rotation curves constructed from the ratios of the fundamental frequencies of bound radial, polar, and azimuthal motion. We identify two prominent plateaus whose widths increase with the tidal field amplitude, signaling a transition from weak to strong chaos. We then demonstrate the sensitivity of the chaotic dynamics to the orientation of the orbit relative to the tidal field. We further analyze the proper-time evolution of the action-angle variables, showing that the angle combinations associated with the dominant commensurabilities are phase locked, thereby allowing the associated tidal contributions to induce secular changes in the constants of motion, whereas off-plateau angle combinations circulate. These results clarify the dynamical significance of the prominent plateaus and provide a novel phase-space characterization of tidal resonances in EMRIs. Finally, we discuss the potential role of radiation-reaction effects in driving EMRIs through tidal island crossings and the implications for gravitational-wave inference with future detectors.
[abstract 19 / 42] (score: 3) - Title: Direct Four-Spacecraft Measurement of Reconnection Exhaust Thickness in the Solar WindAuthors: Mani K Chettri, Rupak Mukherjee, Hemam D. Singh,Comments: 9 pages, 3 figures, 1 tableSubjects: physics.space-ph astro-ph.SRCreated: 2026-09-02; Updated: 2026-09-04; Datestamp: 2026-09-04
The thickness of a RECONNECTing solar wind current sheet is normally inferred from a single spacecraft as the product of the boundary-normal speed and the crossing duration. Multipoint measurements have tested this method for generic solar wind current sheets and constrained the geometry of RECONNECTion exhausts, but a direct comparison with single-spacecraft thickness estimates for the same RECONNECTion-associated crossings is still lacking. We analyze four current-sheet crossings observed by Magnetospheric Multiscale in the pristine solar wind on 2017 November 10 the two boundaries of a confirmed RECONNECTion exhaust and two nearby current sheets. The tetrahedron separation was $\approx 16$ km. Cross-correlation of the MAGNETic-field ramps gives millisecond-level lag uncertainties, boundary normals to $4^\circ-8^\circ$ and speeds to $5\%-8\%$, while single-threshold timing at these separations is noise dominated. The exhaust edges are 29-31 ion inertial lengths ($d_i$) thick. The two edge normals differ by $22^\circ$ (68% interval [$19^\circ,26^\circ$]), resolving a nonparallel exhaust geometry. At the exhaust edges, the measured boundary speeds agree with three standard single-spacecraft estimates to 4%-15% and remain within about one Alfvén speed of the plasma motion. Estimating the normal from one spacecraft is the larger source of error, though the thickness is still recovered to within tens of percent when a degenerate minimum-variance solution is rejected. At the actively RECONNECTing sheet, the boundary speed exceeds the local plasma speed along the normal by $29\% \pm 10\%$.
[abstract 20 / 42] (score: 3) - Title: The Accretion Explorer Interferometer (AEI) Phase I NASA Innovative Advanced Concepts Final ReportAuthors: Kimberly A. Weaver, Jenna M. Cann, Kenneth Carpenter, Maurice Leutenegger, Takashi Okajima, Scott Rohrbach, Liz Matson, Craig Stevens, George Bussey, Jean-Etienne Dongmo, David Kim, Jess Lewis, Khashayar Parsay, Sharon Peabody, Alison Rao, Sara Riall, Marta Shelton, Kan Yang, Isabella Carlton, Webster Cash, Kaylee DeGennaro, Emma Kleiner, John Krizmanic, Erini Lambrides, Miranda McCarthy, Jeffrey McKaig, Atul Mohan, Teresa Monsue, Ryan Pfeifle, Mainak Singha, Melville Ulmer, Laura D. Vega, Kelly E. Whalen,Comments: 39 pages plus appendicesSubjects: astro-ph.IMCreated: 2026-09-02; Updated: 2026-09-04; Datestamp: 2026-09-04
We must create superb X-ray images to understand the detailed physical processes behind some of the most powerful astronomical objects. The need to achieve this capability has been known for decades. But as time proceeds, X-ray astronomy falls further behind other wavebands that are steadily increasing their imaging capacity. Radio astronomy in particular has reached an angular resolution on the order of micro arcseconds via aperture synthesis interferometry, using the interference of electroMAGNETic waves from many small telescopes together to simulate having a much larger telescope. Developing an equivalent high-resolution capability in the X-ray band would be a game changer for high-energy astrophysics. We will understand how supermassive BLACK HOLEs grow and evolve. We will learn what powers astrophysical JETs. We will learn how young, active stars affect the habitability of their planets. Technologically, our NIAC study has shown that the Accretion Explorer Interferometer (AEI) concept, unlike the original MAXIM concept, is more feasible in operation, being only 2 km long, versus approximately 450 km. Our study has also shown that satellite station keeping is possible, leveraging from LISA pathfinder technology, and using large mirror flats plus an X-ray beamsplitter for enabling technology is feasible.
[abstract 21 / 42] (score: 3) - Title: Hall-MHD in driven turbulence FLASH simulationsAuthors: A. Mohapatra, E. C. Hansen, A. Reyes, A. F. A. Bott, E. G. Blackman, P. Tzeferacos,Comments: 28 pages, 14 figures, 2 tablesSubjects: physics.plasm-phCreated: 2026-09-02; Updated: 2026-09-04; Datestamp: 2026-09-04
The origin of MAGNETic fields in turbulent astrophysical systems has long been a central problem in plasma astrophysics. Fluctuation dynamos are a class of field amplification mechanisms that occur in turbulent MAGNETohydrodynamics whereby stochastically forced motions of plasma at sufficiently high MAGNETic Reynolds numbers exponentially amplify MAGNETic energy. For steady forcing, such dynamos saturate with MAGNETic energies at a sizable fraction of the turbulent kinetic energy. Although fluctuation dynamo is widely studied within the framework of resistive MAGNETohydrodynamics (MHD) and driven-turbulence numerical simulations, this work explores the difference when the Hall term is included in the MAGNETo-fluid's generalized Ohm's law. The inclusion is motivated in part by recent high energy-density plasma experiments studying fluctuation dynamo that are governed by an extended MAGNETohydrodynamics (xMHD) ansatz, which includes the Hall term. We first discuss the details of the Hall-MHD implementation in the FLASH code, the tool we use to model xMHD fluctuation dynamo. We then investigate the influence of the Hall term on the fluctuation dynamo in a three-dimensional periodic box, driven with stochastic forcing at the box scale. We compare cases with a Hall term of varying magnitude to no-Hall cases with respect to the MAGNETic field growth rate, saturation level, and MAGNETic field structure. The Hall-MHD fluctuation dynamo is found to saturate at lower MAGNETic energies and with fewer small-scale MAGNETic structures than the no-Hall cases. Both findings are consistent with the interpretation that the Hall term acts as an additional, non-linear transport term, akin to an enhanced turbulent diffusivity.
[abstract 22 / 42] (score: 3) - Title: Search for intranight optical variability in a large sample of intermediate-mass BLACK HOLEsAuthors: Himanshu Sharma, Gopal-Krishna, Vibhore Negi, Hum Chand, Krishan Chand, Anshul Kumar Sharma,Comments: 14 pages, 9 figures, 2 tables. Submitted to MNRASSubjects: astro-ph.GACreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
Using the extensive archival database of the Zwicky Transient Facility (ZTF) survey, we have investigated intranight optical variability (INOV) in a large sample of low-mass ACTIVE GALACTIC NUCLEi (LMAGN) powered by intermediate-mass BLACK HOLEs (IMBHs). After applying a sequence of well-motivated selection filters, we constructed an unbiased, representative sample of 62 IMBHs for which $r$-band intranight photometric sequences are available in the ZTF database, yielding 167 sessions with a minimum duration of 2 h. By performing aperture photometry on the sequence of exposures in each session, we derived differential light curves (DLCs) of the target LMAGN relative to two carefully selected non-varying comparison stars monitored simultaneously with the LMAGN in the same exposure sequence. Application of the widely used test based on $F$-statistics to all these DLCs revealed no case of statistically significant INOV. We discuss this result for the present large sample of LMAGN in the context of an earlier report of INOV detections in another, albeit much smaller and differently selected, sample of LMAGN that had been monitored in targeted observations.
[abstract 23 / 42] (score: 3) - Title: Gamma-Ray Bursts and Optical Brightness: Insights from SWIFT SatelliteAuthors: Istvan I. Racz, Yasmin Nehme, Lajos G. Balazs,Comments: 9 pages, 5 figures, accepted for publicationSubjects: astro-ph.HE astro-ph.IMCreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
During the examination of optical properties of GAMMA-RAY BURSTs (GRBs) measured during the life of the Neil Gehrels SWIFT Observatory satellite, significant discoveries were made. While the satellite measures gamma, X-ray, and optical data simultaneously, in many cases, only an upper limit is established in the optical domain. Hence, survival analysis, a.k.a. dependability modelling, was necessary, serving as a tool for studying samples where some cases are bound only by the upper limit, as mentioned earlier. This method is used to analyse datasets that may have upper or lower bounds rather than precise observations, but nevertheless contain relevant information. It was previously established that the duration, gamma fluence, and peak flux all have a substantial effect on the optical brightness distribution, probably due to the energy of the beam from the GRB's central engine. However, after analysing more than 200 data points, we no longer see this association. This disagreement shows that the previously reported impact may not be as significant as previously derived, needing more research to better understand the underlying processes that determine the optical brightness in connection to gamma-ray properties.
[abstract 24 / 42] (score: 3) - Title: Computing high-order mixed derivatives in physics-informed neural networks using multi-index Bell polynomialsAuthors: Fumihiro Imoto,Comments:Subjects: physics.comp-ph physics.plasm-phCreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
Physics-informed neural networks for high-order partial differential equations require mixed input derivatives and their gradients with respect to the network parameters. Standard implementations obtain an order-$K$ derivative by repeated automatic differentiation. We instead organize the forward recursion of the multivariate Faà di Bruno formula and its explicit backpropagation over a prescribed downward-closed set of multi-indices, with the Bell-polynomial convolutions tabulated once. The forward pass carries only the derivatives the differential operator requires. The backward pass propagates gradients from losses formed from any subset of them, including nonlinear products and coupled fields. Both recursions are exact up to roundoff and avoid nested computational graphs. An independent Taylor-JET implementation, symbolic checks of the test problems, and finite differences verify derivatives and loss gradients through order seven. On one CPU core, the method evaluates 330 mixed derivatives with respect to four inputs through order seven and the corresponding loss gradient without the memory failures observed for several nested implementations. Numerical tests include third-, fifth-, and seventh-order dispersive equations, incompressible flow, and a manufactured five-field electrohydrodynamic system. The seventh-order Zakharov-Kuznetsov test in $3+1$ dimensions has a relative solution error of $6\times10^{-4}$.
[abstract 25 / 42] (score: 3) - Title: Eight Local Couplings of Gravitational Waves from Unified Field EquationsAuthors: Hong-Bo Jin, Yue-Liang Wu,Comments: 10 pages, 3 tablesSubjects: gr-qc astro-ph.HECreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
A gravitational-wave (GW) detector records a linear mixture of local couplings under the assumption that extra POLARIZATIONs enter geodesic deviation. Vacuum general relativity (GR) admits two transverse-traceless (TT) amplitudes. It remains to determine the largest set of couplings that can sit in that mixture, and whether a tensor-only arm-length result selects GR uniquely. The little group \(E(2)\) of a null four-momentum classifies the strain amplitudes \(\mathbf{p}=(p_{+},p_{\times},p_{x},p_{y},p_{b},p_{\ell})\), commonly written \(h_{P}\), which determine the electric tidal tensor along a ray. Geodesic deviation, recorded as differential arm length, therefore contains only those \(p_{P}\) that enter that tensor. Lorentz mixing at helicity \(\pm1\) supplies a gravito-MAGNETic (GEM) field that does not enter the tidal tensor. if GEM field is static, that does not propagate as a wave. A time-varying helicity-\(\pm1\) current sources a GEM wave that enters the mixture as a coupling, to be isolated by its measured quantity. For a radiation-zone wave that depends only on retarded time, \(\betag_{\perp}=\hat{\mathbf{k}}\times\partial_{t}(p_{x},p_{y})\), and the eight couplings are \(\Pvec=(\mathbf{p},\betag_{\perp})\). Here we adopt unified field equations on \(\mathbf{p}\) to clarify the origin of each component of \(\Pvec\); the measured quantity of each coupling then isolates the POLARIZATIONs in that mixture, which favors identification of distinct POLARIZATIONs and model tests.
[abstract 26 / 42] (score: 3) - Title: Absolute Motion of the Infrared Counterpart to Sagittarius A* in the Gaia Celestial Reference Frame 3 and Limits on an Intermediate-mass Black Hole CompanionAuthors: Rebecca A. Lewis-Merrill, Tuan Do, Matthew W. Hosek, Gregory David Martinez, Shoko Sakai, Kelly Kosmo O'Neil, Grant Weldon, Abhimat Gautam, Zoë Haggard, Andrea M. Ghez, Jessica R. Lu, Keith Matthews,Comments: 22 pages, 10 figures, Accepted to ApJSubjects: astro-ph.GA astro-ph.IMCreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
We report the first proper motion and acceleration measurements of the infrared (IR) counterpart to Sagittarius A* (Sgr A*-IR), the supermassive BLACK HOLE (SMBH) at the center of our Galaxy, in the Gaia-Celestial Reference Frame (Gaia-CRF3). This reference frame realizes the International Celestial Reference System (ICRS), which is an absolute reference coordinate system defined by QUASARs. A combination of Gaia and Hubble Space Telescope data was used to transform Keck adaptive optics (AO) observations into Gaia-CRF3. We developed a method for selecting reference stars that minimizes astrometric transformation errors (statistical error = $0.10-0.63$ mas) and drift of the coordinate system (systematic error $\sim 0.01$ mas/yr). We find the proper motion of Sgr A*-IR in Gaia-CRF3 to be $μ_{α^{*}} = -3.093 \pm 0.085$ mas yr$^{-1}$ and $μ_δ= -5.62 \pm 0.13$ mas yr$^{-1}$ with the initial position at $t_{0} = 2016.0$ of R.A. = 266.41680848 $\pm$ 0.00000029 deg and DEC = -29.00783947 $\pm$ 0.00000050 deg, which translates to a precision of 1.05 mas in R.A. and 1.79 mas DEC. This is consistent with the astrometric measurements of the radio counterpart to Sgr A* by \citet{Xu_2022}. We also place a $2σ$ upper constraint of the acceleration of Sgr A*-IR on the sky at 0.061 mas yr$^{-2}$. This acceleration limit on Sgr A*-IR excludes any intermediate-mass BLACK HOLE companion with mass $\gtrsim 4\times 10^{4}$ $M_{\odot}$ within a distance of $\sim$0.01 pc, consistent with previous studies. With the release of Gaia Data Release 4, we predict these limits will be improved by at least a factor of two.
[abstract 27 / 42] (score: 3) - Title: A targeted search for fast radio bursts from MAGNETars in elliptical galaxiesAuthors: S. Paine, D. R. Lorimer, S. Sirota, G. M. Doskoch, S. Tabassum, M. Flanagan, J. Lituchy, A. Stone, J. W. Kania, M. Bhardwaj, S. Mehta, M. A. McLaughlin, B. Kharel, D. Agarwal, M. P. Surnis,Comments: 12 pages, 8 figuresSubjects: astro-ph.HE astro-ph.GACreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
Motivated by predictions that globular clusters associated with nearby giant elliptical galaxies are prime environments for detecting fast radio bursts (FRBs) from MAGNETars, we report on a targeted high-sensitivity search across five local massive elliptical galaxies. We utilized the GREENBURST single-pulse search pipeline and the VEGAS backend on the Green Bank Telescope (GBT) to conduct an L-band (1.4 GHz) survey for FRBs in each target environment. We discovered FRB 20240817A in the direction of M49 (NGC 4472) which has a pulse width of 15 ms, a signal-to-noise ratio of 13, and a dispersion measure (DM) of $983~\rm{cm}^{-3}$ pc. Although a Bayesian spatial association framework initially flags M49 as the host, carefully accounting for the foreground electron column contributions from the Milky Way and both the Virgo intracluster medium and M49's hot gaseous halo ($\sim300-400~\rm{cm}^{-3}$ pc combined) strongly disfavours a physical connection. We conclude that FRB 20240817A is a background event. We also identified a repeating cluster of three low-significance pulses from the direction of M49 at a physically plausible DM of $150-160~\rm{cm}^{-3}$ pc. Accounting for the fraction of each target's extended globular cluster distribution observed, the absence of unambiguous, host-localized bursts allows us to place a joint upper limit on the intrinsic burst rate of a single active source within these systems of $R_0 < 0.028~\rm{hr}^{-1}$ (and an integrated rate limit of $<1.0$~hr$^{-1}$ for M49), lowering previous upper limits and suggesting that MAGNETar formation within dynamical clusters is less efficient than previously assumed.
[abstract 28 / 42] (score: 3) - Title: Low-angular-momentum accretion shocks can power weak-to-moderate X-ray flares from SgrA*Authors: Samik Mitra, Bożena Czerny, Michal Zajaček, Zach Sumners,Comments: 12 pages, 4 figures. Accepted for publication in The Astrophysical JournalSubjects: astro-ph.HECreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
X-ray flares from Sgr~A* span broad ranges in duration, fluence, and luminosity, but their origin remains unsettled. We test whether standing shocks in low-angular-momentum MAGNETized accretion flows can provide a viable energy reservoir to account for these events. Using semi-analytic trans-MAGNETosonic shock solutions, we estimate the kinetic energy available in the downstream post-shock flow and compare it with the 25-year \textit{Chandra} X-ray flare catalog. For each theoretical solution, we compute the required efficiency $ε=E_{\rm data}/E_{\rm sh}$, where $E_{\rm data}$ is the observed radiated energy for each flare and $E_{\rm sh}$ is the available energy in the shocked flow. Notably, the weak flares require $ε\sim10^{-3}$--$10^{-2}$, while moderate flares require a few percent. We perform the analyses for weakly and highly spinning cases, and the resulting weak-to-moderate flare energy budget remains unchanged. For the fiducial accretion rate and bolometric correction, the kinetic energy reservoir in standing shock is sufficient for the observed weak-to-moderate flare population, whereas the strongest events likely require higher efficiency which can be mediated via additional MAGNETic energy dissipation channel.
[abstract 29 / 42] (score: 2) - Title: From Feedback-Free Star Clusters to Little Red Dots via CompactionAuthors: Avishai Dekel, Dhruba Dutta Chowdhury, Sharon Lapiner, Zhiyuan Yao, Shmuel Gilbaum, Daniel Ceverino, Joel Primack, Rachel Somerville, Romain Teyssier,Comments: 24 pages, 8 figures, accepted for publication in ApJSubjects: astro-ph.GACreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
We address the origin of the Little Red Dots (LRDs) seen by JWST at cosmic morning ($z \!=\! 4 \!-\! 8$) as compact stellar systems with over-massive BLACK HOLEs (BHs). We propose that LRDs form naturally after feedback-free starbursts (FFB) in thousands of star clusters and following wet compaction. Analytically, we show how the clusters enable efficient dry migration of stars and BHs to the galaxy center by two-body segregation and dynamical friction against the disk. The clusters merge to form compact central stellar systems as observed. Mutual tidal stripping does not qualitatively affect the analysis. The young, rotating clusters are natural sites for the formation of BH seeds via rapid core collapse. The migrating clusters carry the BH seeds, which merge into central super-massive BHs (SMBHs). Compactions are required to deepen the potential wells such that the SMBHs are retained after post-merger gravitational-wave recoils, locked to the galaxy centers. Using cosmological simulations at different epochs, with different codes and physical recipes, we evaluate the additional growth of LRD-matching compact central stellar systems by global compaction events. Adding to the dry growth by cluster mergers, the compactions can increase the escape velocities to retain the SMBHs. The LRDs appear at $z \!\sim\! 8$, after the formation of FFB clusters, and disappear after $z \!\sim\! 4$ when the stellar mass is above $10^9 M_\odot$ by growing post-compaction blue disks around the nuclear LRDs. The LRD abundance is expected to be $\sim\! 10^{-5} \!-\! 10^{-4}\,{\rm Mpc}^{-3}$, increasing from $z \!\sim\! 4$ to $z\!\sim\! 8$.
[abstract 30 / 42] (score: 2) - Title: A unified model of active repeating fast radio bursts associated with persistent radio sourcesAuthors: F. Y. Wang, H. T. Lan, Z. Y. Zhao, Q. Wu, Y. Feng, S. X. Yi, Z. G. Dai, K. S. Cheng,Comments: title changed, 16 pages, 6 figures, 1 table, accepted for publication in ApJSubjects: astro-ph.HECreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
Fast radio bursts (FRBs) are intense pulses with unknown origins. A subclass of repeating FRBs show some common features, such as associated compact persistent radio sources (PRSs), high burst rates, and large host-galaxy dispersion measures (DMs). Meanwhile, they show diverse DM and rotation measure (RM) variations, which cannot be explained by current models. A unified model urgently needs to be established. Here we show the first evidence for a SUPERNOVA remnant surrounding the FRB 20190520B source. We then demonstrate that the five active repeating FRB sources associated with PRSs can be understood within a single model in which central objects are young MAGNETars in massive binary systems embedded in SUPERNOVA remnants. This model naturally predicts distinct variations of DM and RM for repeating FRBs. Crucially, young MAGNETar wind nebulae can generate bright PRSs. As a MAGNETar becomes older, the luminosity of a PRS will fade, which can naturally explain less-luminous PRSs for some active FRBs. Our results support a unified population of active FRBs in dynamic MAGNETized environments.
[abstract 31 / 42] (score: 2) - Title: Mapping the nuclear environments of extreme coronal line emitting galaxiesAuthors: Daniel Kynoch, Or Graur, Peter Clark, J. N. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, T. Claybaugh, A. de la Macorra, P. Doel, J. E. Forero-Romero, S. Gontcho A Gontcho, G. Gutierrez, R. Joyce, S. Juneau, M. Landriau, L. Le Guillou, A. Meisner, R. Miquel, J. Moustakas, S. Panda, W. J. Percival, F. Prada, I. Pérez-Ràfols, G. Rossi, E. Sanchez, D. Schlegel, J. Silber, D. Sprayberry, G. Tarlé, B. A. Weaver, R. Zhou, H. Zou,Comments: 27 pages (main paper), 6 figures. Revised version accepted by MNRASSubjects: astro-ph.GACreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
Extreme coronal line emitters (ECLEs) are a rare class of galactic nuclei exhibiting unusually strong high-ionisation forbidden emission lines, and several ECLEs have been linked to tidal disruption events (TDEs). In this work, we compile and analyse optical spectra of 33 ECLEs, dividing them into variable, TDE-linked sources and non-variable, AGN-linked systems. Using multi-epoch spectroscopy from the Sloan Digital Sky Survey, Dark Energy Spectroscopic Instrument, and other facilities, we investigate the evolution of the emission line spectra and measure emission line profiles. Many variable ECLEs have changing spectra in which the highest-ionisation lines (e.g., [Fe X]-[Fe XIV]) appear and fade first, followed by [Fe VII], accompanied by brightening of [O III]. These changes may reflect a softening ionising continuum, the outward propagation of the ionisation front following the TDE flare, or both. Assuming virial motion, we translate line widths into characteristic radial distances, reconstructing the spatial distribution of line-emitting gas. Coronal lines are generally emitted at radii intermediate between the broad line region and the low-ionisation narrow line region. This ionisation stratification is seen in many sources, with similar incidence in variable and non-variable ECLEs, suggesting no apparent difference in circumnuclear gas distributions between active and quiescent nuclei. We find positive correlations between gas distance and BLACK HOLE mass for both [O III] and [Fe VII]: the log(Distance)-log(Mass) relations have slopes $0.63\pm0.08$ and $0.69\pm0.12$, respectively, broadly consistent with a Mass$^{0.5}$ dependence and with characteristic radii set primarily by photoionisation.
[abstract 32 / 42] (score: 2) - Title: Isochrones in primordial MAGNETic field evolutionAuthors: Axel Brandenburg, Mattia Cielo, Oksana Iarygina, Franco Vazza,Comments: 12 pages, 14 figures, 2 tables, resubmitted to A&ASubjects: astro-ph.COCreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
In the early universe, a primordial MAGNETic field undergoes a turbulent decay while its length scale increases due to an inverse cascade. The size of the largest processed eddy scales with the Alfvén speed and grows with time. In a diagram of Alfvén speed vs.\ length scale, all possible solutions must lie on a line through the origin with a slope proportional to the inverse of the present time. In principle, however, such lines can also be defined for earlier times. The lines for earlier times form isochrones that may be observationally accessible, for example through the MAGNETically driven stochastic gravitational wave background. However, the position and slope of these isochrones is sensitive to the zero point of the time. Here, we show that for any initial MAGNETic field, a proper time can be determined such that the resulting isochrones at early times are nearly parallel to those at late times, i.e., they have the same slope. We use two-dimensional numerical simulations of decaying MHD turbulence and vary the initial position of the peak of the MAGNETic energy spectrum. In this case, the evolution is governed by the conservation of anastrophy. A fit to the Alfvén time yields an accurate estimate of the factor by which the decay time is longer than the Alfvén time, while the offset in the fit provides an estimate of the proper time that needs to be added to the nominal time since the beginning of each simulation. We also find that the presence of an initial velocity field of realistic strength helps producing a more straight track from the beginning. The MAGNETic field parameters lie on universal isochrones even for early times. They provide a testable framework for MAGNETic fields generated at times as early as the end of inflation, starting with the time of reheating.
[abstract 33 / 42] (score: 2) - Title: A Suppressed Volumetric Rate of High-Luminosity Mid-Infrared Selected Tidal Disruption EventsAuthors: Prajna Nair, Christos Panagiotou, Megan Masterson, Kishalay De, Erin Kara, Eleanor Winkler, M. Subhi Abo Rdan,Comments: 11 pages, 4 figures (+ 4 pages, 4 figures in appendix); Accepted for publication in ApJSubjects: astro-ph.HECreated: 2026-09-02; Updated: 2026-09-04; Datestamp: 2026-09-04
Tidal Disruption Events (TDEs) serve as direct probes of the population of supermassive BLACK HOLEs in the center of galaxies and are nowadays regularly detected in optical wide-field time-domain sky surveys. Recent studies have demonstrated that a large fraction of TDEs can be uniquely identified in the infrared (IR) waveband, but these studies have to date been limited to relatively nearby events. In this work, we searched for highly luminous IR-bright TDEs that are rare and thus missed by searches in the local universe. We performed a systematic search of the NEOWISE archive and developed a new selection criterion based on the evolution of the W1-W2 color to select TDE candidates. We identified 10 IR bright TDEs with peak luminosities above $L_{\rm peak\, W2} \simeq 3 \times 10^{43}$ erg s$^{-1}$ and estimated an event rate of $1.2^{+0.5}_{-0.4}\times10^{-10}$ Mpc$^{-3}$year$^{-1}$ for the luminosity range of our sample. Compared to the existing local luminosity function of lower luminosity events, we detect a suppressed rate for these highly luminous events. This turn-over in the luminosity function can be naturally explained by the suppressed amount of TDEs taking place in systems with larger BLACK HOLE masses, thereby confirming the TDE nature of our sources.
[abstract 34 / 42] (score: 2) - Title: Inelastic Dark Photon Dark Matter for the LUX-ZEPLIN High-Recoil Event and the Galactic Halo Gamma-Ray ExcessAuthors: Kimiko Yamashita,Comments: 4 pages, 1 figure, 2 tablesSubjects: hep-ph astro-ph.HECreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
We show that a dark-photon DARK MATTER framework can simultaneously account for two recently reported anomalies: the halo-like Galactic gamma-ray excess identified by Totani in 15 years of FERMI-LAT data, and the $E_{\rm nr}=248\pm23\,({\rm stat})\pm23\,({\rm sys})$ keV nuclear-recoil event of interest reported by the LUX-ZEPLIN Collaboration. The DARK MATTER is a $U(1)_X$ dark photon $X$ with mass $m_X=420$ GeV, stabilized by a dark parity that forbids kinetic mixing with the Standard Model photon. A light scalar mediator $ϕ$, required to explain the Totani excess via Sommerfeld enhancement, is joined by a second light scalar $ϕ'$ that couples a nearly degenerate heavier vector partner $V$ to $X$. The resulting inelastic transition $X+N\to V+N$, with mass splitting $δ\simeq316$ keV close to the kinematic endpoint for $m_X=420$ GeV, naturally reproduces the localized LZ event once the detector energy resolution is included, while leaving the relic abundance and the halo phenomenology of the original Totani-motivated benchmark essentially unchanged.
[abstract 35 / 42] (score: 2) - Title: Sub-TeV Singlino Dark Matter in light from Sagittarius A$^\ast$ and LUX-ZEPLIN Nuclear-Recoil EventAuthors: Utpal Chattopadhyay, Debottam Das, Rahul Puri, Joydeep Roy,Comments: 24 pages, 9 figures, 3 tablesSubjects: hep-ph astro-ph.HECreated: 2026-09-02; Updated: 2026-09-04; Datestamp: 2026-09-04
We investigate the impact of a DARK MATTER density spike surrounding the Milky Way's supermassive BLACK HOLE (SMBH) on the detectability of Singlino-dominated neutralino DARK MATTER within the Next-to-Minimal Supersymmetric Standard Model (NMSSM). Similar density enhancements, or mini-spikes, around stellar-mass BLACK HOLEs (sBHs), have also been considered. Such a DARK MATTER (DM) candidate typically produces weak indirect detection signals in conventional DARK MATTER halos. Additionally, a Singlino-like lightest supersymmetric particle (LSP) is very difficult to probe at the LHC or through the direct DM search experiments. On top of that, recent observation of the LUX-ZEPLIN 248 keV Nuclear-Recoil Event may hint towards a DM that can be accommodated by a Singlino with mass more than 200 GeV. Keeping these in consideration, we examine the prospects for detecting these sub-TeV DARK MATTER scenarios through gamma-ray observations of the regions surrounding the SMBH Sgr A$^\ast$ and the sBH in the low-mass X-ray binary XTE J1118+480.
[abstract 36 / 42] (score: 2) - Title: Strong Constraints for Line Signals from Dark Matter Annihilation in Sub-haloAuthors: Asier Salces Pérez, Thong T. Q. Nguyen, Pedro De la Torre Luque, Tim Linden,Comments: 10 pages, 9 figuresSubjects: hep-ph astro-ph.HECreated: 2026-09-02; Updated: 2026-09-04; Datestamp: 2026-09-04
We present a dedicated search for monochromatic gamma-ray emission from a recently proposed nearby DARK MATTER subhalo candidate. Using nearly 15 years of FERMI-LAT Pass 8 data, we perform a sliding-window search for gamma-ray lines between 10 and 300 GeV. We do not find any statistically significant evidence for a line signal. The largest excess occurs at $E_γ\simeq 28 \, {\rm GeV}$ with a local significance of $2.5σ$. We therefore derive 95% confidence level upper limits on the annihilation cross section for $χχ\rightarrow γγ$. Under the assumed NFW subhalo model, the resulting constraints are stronger than existing Galactic Center line limits over much of the explored mass range. We further translate these line constraints into bounds on well-motivated WIMP models, such as Higgs-portal and Wino DARK MATTER scenarios, restricting previously open parameter regions consistent with thermal freeze-out as well as models associated with DARK MATTER interpretations of the Galactic Center Excess.
[abstract 37 / 42] (score: 2) - Title: Energy-Energy Correlators in $Z$-Tagged Jets in $pp$ CollisionsAuthors: João Barata, Zhong-Bo Kang, Xoán Mayo López, Jani Penttala, Yiyu Zhou,Comments: 10 pages, 5 figuresSubjects: hep-ph hep-exCreated: 2026-09-02; Updated: 2026-09-04; Datestamp: 2026-09-04
We present predictions for the collinear energy-energy correlator (EEC) measured inside $Z$-tagged JETs in proton-proton collisions across the confinement transition. Our framework combines transverse-momentum-dependent factorization for back-to-back $Z+$JET production with an exclusive differential EEC JET function incorporating perturbative evolution and flavor-dependent non-perturbative fragmentation. The EEC JET function is evaluated at $\mathrm{NLL}^{\prime}$ accuracy, with separate QUARK and gluon non-perturbative scales constrained by existing $e^+e^-$ and inclusive-JET data. We provide predictions for forward $Z+$JET production at $\sqrt{s}=8~\mathrm{TeV}$ and $13~\mathrm{TeV}$ in the JET transverse-momentum intervals $(20, 30)$, $(30, 50)$ and $(50, 100) \, \mathrm{GeV}$. The EEC distributions as functions of $z_χ$ exhibit finite plateaus at small $z_χ$, while the corresponding angular distributions display the characteristic turnover associated with the confinement transition. A flavor decomposition shows that this transition becomes increasingly dominated by QUARK-initiated JETs as the JET transverse momentum increases. Forward $Z$-tagged JETs therefore provide a clean probe of non-perturbative QUARK fragmentation and offer a direct test of whether the characteristic confinement scale extracted from $e^+e^-$ collisions remains universal in a hadronic environment.
[abstract 38 / 42] (score: 2) - Title: TDCOSMO XXIX: JWST/NIRSpec IFU Spatially Resolved Kinematics of Three Time-delay LensesAuthors: Shawn Knabel, Pritom Mozumdar, Anowar J. Shajib, Tommaso Treu, Devon M. Williams, Michele Cappellari, David Law, Simon Birrer, Takahiro Morishita, William Sheu, Massimo Stiavelli,Comments: 23 pages, 18 figures, 6 tables; submitted to Physical Review DSubjects: astro-ph.CO astro-ph.GACreated: 2026-09-02; Updated: 2026-09-04; Datestamp: 2026-09-04
Spatially resolved stellar kinematics are critical to the high precision achieved by cosmological probes utilizing time delays of strongly lensed QUASARs. Combined with high-resolution imaging and lens modeling, dynamical models of the 2D resolved kinematics of the deflector galaxy tightly constrain the mass profile and break the mass-sheet degeneracy, in turn providing tight constraints on the Hubble constant when the time delays are included. We extract stellar kinematics of the deflector galaxies in the quadruply lensed QUASAR systems HE0435-1223, PG1115+080, and WFI2033-4723 from James Webb Space Telescope Near-Infrared Spectrograph (JWST-NIRSpec) integral field spectroscopy. The kinematic maps reach average per-bin total (statistical and systematic) uncertainties of 6-11%, with average bin-to-bin correlated errors of only $\sim 1.2\%$. The aperture-integrated velocity dispersions are statistically consistent with the values used in the previous TDCOSMO analysis (all within $0.9σ$), with their average uncertainty reduced from 3.7% to 2.4% owing to improvements in the data reduction and kinematic-extraction methodology. We classify PG1115+080 as a fast rotator, HE0435-1223 and WFI2033-4723 as slow rotators within the probed radii, and we refine the source redshifts from the kinematics of the lensed host galaxies. Kinematic maps will be combined with time delays, lens models, and line-of-sight convergence estimates to measure cosmological parameters in the upcoming TDCOSMO 2026 milestone publication.
[abstract 39 / 42] (score: 2) - Title: Bifurcations in the Heliosphere: Global-scale Coronal Pseudostreamer Evolution and the Creation of Secondary Heliospheric Current SheetsAuthors: Lizet S. Casillas, Benjamin J. Lynch, Victor Réville, Olga A. Panasenco, Marco Velli,Comments: 16 pages 8 figures Accepted for publication in ApJSubjects: astro-ph.SR physics.space-phCreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
The heliospheric current sheet (HCS) is the boundary between open MAGNETic fields of opposite polarity in the solar wind that connect back to their respective open flux regions in the corona. The HCS is often described as a disc-like sheet warped by the combined effects of the inclination of the MAGNETic equator on the Sun, solar rotation, and solar wind expansion. The HCS is an extension of the helmet streamer belt-the closed-flux region resulting from the global dipole component of the observed photospheric MAGNETic field. In the absence of a strong dipole, a dominant quadrupole can result in two separate HCSs. Here we report on a set of idealized, axisymmetric solar wind simulations designed to study the transition of the single-HCS corona and inner heliosphere into a multiple-HCS configuration, run with the WindPredict-AW PLUTO MHD code. We systematically vary the relative strengths of the dipole/quadrupole contributions to the global field and show this results in the formation of a large-scale, closed-flux pseudostreamer that interacts with the ambient solar wind. We find that when the dipole and quadrupole magnitudes are approximately equal, our model corona can oscillate between a one- and two-HCS configuration on the timescale of days-to-weeks. We characterize the plasma dynamics of the transition of a global-scale pseudostreamer into a localized, secondary helmet-streamer belt with its own HCS surrounding a newly-opened, opposite-polarity coronal hole. We discuss the implications of our results for solar cycle evolution and the dynamic coupling of the highly structured corona and inner heliosphere.
[abstract 40 / 42] (score: 2) - Title: Rapid Growth of Intermediate-Mass Black Holes through Disk-induced Stellar DisruptionsRapid Growth of Intermediate-Mass Black Holes through Disk-induced Stellar DisruptionsAuthors: Mengye Wang, Yiqiu Ma, Qingwen Wu, Boyuan Liu, Zijian Wang, Zhili Wang,Comments: 13 pages, 8 figures. Submitted to ApJSubjects: astro-ph.GA astro-ph.HECreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
Dense nuclear star clusters provide unique environments for studying the dynamical interactions between stars and massive BLACK HOLEs. When an accretion disk is present, dissipative star--disk interactions can capture surrounding stars, drive their inward migration, and ultimately lead to disk-induced tidal disruption events\,(dTDEs). The long-term feeding rate from this process, however, cannot be inferred from single-orbit migration estimates alone, as it depends on the coupled evolution of disk capture, collisional relaxation, stellar depletion and replenishment, and physical mergers within the star cluster. In this work, we use high-performance direct $N$-body simulations combined with analytic prescriptions for star--disk interactions to follow this coupled evolution for intermediate-mass BLACK HOLEs\,(IMBHs) with accretion disks embedded in dense stellar clusters. The simulations track the formation of the stellar cusp, the capture of stars by repeated disk crossings, their subsequent orbital damping and migration, and their eventual consumption by the central IMBH. We find that dTDEs can sustain stellar mass supply rates of $\sim10^{-3}\,M_\odot \,\mathrm{yr}^{-1}$, which exceeds the Eddington-limited gas accretion rate for IMBHs with $M_\bullet<10^5\,M_\odot$. These results identify dTDEs as an efficient stellar feeding channel for IMBHs in gas-rich dense stellar systems. As one possible application, this mechanism may help transform $\sim10^3\,M_\odot$ IMBHs into more massive black-hole seeds, provided that compact stellar clusters and accretion disks persist for $>30$ Myr.
[abstract 41 / 42] (score: 2) - Title: The Physics of the Nebular Phase in Black Hole X-ray Binaries: Modelling V404 CygniAuthors: A. Ambrifi, T. Muñoz-Darias, J. A. Fernández-Ontiveros, J. Casares, D. Mata Sánchez, J. H. Matthews,Comments: Accepted for publication in A&ASubjects: astro-ph.HECreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
Some of the most extreme galactic BLACK HOLE transients exhibit a nebular phase at the end of their outbursts. This stage was first identified in the 2015 outburst of V404 Cygni, when it dominated the optical spectrum for ~4 days. It is characterised by exceptionally strong optical emission lines, together with a significant increase in the Balmer decrement. The emission features show broad wings reaching velocities consistent with outflow speeds derived from prominent P-Cygni profiles that preceded the nebular phase. They are thus interpreted as arising from previously launched ejecta that expand and recombine as X-ray irradiation declines. In this work, we modelled this phase using the photoionisation code Cloudy. Adopting simple assumptions for the irradiating continuum and emitting gas, we quantitatively reproduced key observables, such as the Balmer decrement and the H$α$ equivalent width, and qualitatively reproduced the observed spectra. Our simulations show that the Balmer decrement remains roughly stable within the observed range across orders-of-magnitude changes in the density and ionisation parameter, spanning $n_\mathrm{H} \sim 10^{10.5}-10^{12.5}\,\text{cm}^{-3}$ and $-1.5 \lesssim \logξ\lesssim 1$. This supports the scenario in which the nebular phase can persist through moderate ejecta expansion and cooling, consistent with observations. Finally, we used different approaches to constrain the general properties of the nebular phase, which we propose is produced by clumpy, partially ionised ejecta whose total mass likely exceeds the mass accreted during the outburst.
[abstract 42 / 42] (score: 2) - Title: Ionized Nebulae Around Two New Symbiotic Stars: GR Cygni and [D75] 141Authors: Howard E. Bond, Calvin Carter, Sven E. Eklund, Peter Goodhew, Ulisse Munari, Jonathan Talbot, Gregory R. Zeimann,Comments: Accepted by PASPSubjects: astro-ph.SR astro-ph.GACreated: 2026-09-03; Updated: 2026-09-04; Datestamp: 2026-09-04
In the course of selecting targets for a spectroscopic survey of faint planetary-nebula nuclei, we encountered two anomalous cases of late-type variable stars surrounded by nebulosities discovered by amateur astronomers. We obtained follow-up deep narrow-band images of the two nebulae: StDr ObJET 14 (diameter 1.5 arcmin) and StDr 4 (diameter 2.5 arcmin). StDr ObJET 14 is found to be a low-excitation nebula, bright only in Ha+[N II], and showing a unique double-ring "bull's-eye" morphology. StDr 4 exhibits a bow-shock structure, bright in Halpha and [S II], embedded in an extended emission nebula. Both central stars, respectively GR Cygni and [D75] 141, are found to be pulsating semiregular variable stars. Our spectroscopic observations show GR Cyg to be a cool carbon star of type C9,2, with emission lines of the Balmer series, [O II] and [O III], [Ne III], [S II], and Fe II. A synthetic narrow-band image of GR Cyg shows that the source of its strong [O II] 3727 A emission line is a knot displaced from the star by about 1.6 arcsec, indicative of a recent collimated ejection event. [D75] 141 is a M6 III red giant, with weak Balmer-series emission. Both stars show a blue excess, and GR Cyg was detected in the near-UV by the GALEX spacecraft. These data establish both stars as new symbiotic binaries, containing a late-type red giant and a hot companion accreting from its stellar wind. We speculate that the double rings surrounding GR Cyg were ejected during helium-shell thermal pulses (or conceivably from recurring nova outbursts), while the nebula around [D75] 141 may be the result of a collision of the symbiotic star's ejecta with an interstellar cloud. Our accidental discoveries of these two binaries because they are surrounded by faint nebulae supports the view that there is a significant population of "missing" symbiotic stars yet to be discovered.
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