Current date: 2025-10-14
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Number of records retrieved: 1046
Keyword score statistics
score 8 -- 1 abstracts
score 7 -- 1 abstracts
score 6 -- 5 abstracts
score 5 -- 6 abstracts
score 4 -- 8 abstracts
score 3 -- 15 abstracts
score 2 -- 27 abstracts
in total -- 63 abstracts
Articles that appeared on 2025-10-14
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[abstract 1 / 63] Wow! (score: 8)
- Title: Quasi-Periodic Oscillations in Gamma-Ray Bursts' Prompt Light CurvesAuthors: Mariusz Tarnopolski,Comments: Published https://www.pta.edu.pl/proc/v13p87Subjects: astro-ph.HE astro-ph.COCreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
I report on the discovery of 34 new quasi-periodic oscillations (QPOs) in the prompt light curves of long GAMMA-RAY BURSTs (GRBs) from the SWIFT/BAT catalog: with one or more constant leading periods, as well as several chirping signals. This is the largest homogenously identified sample or GRB QPOs to date. The presence of QPOs suggests the existence of characteristic time scales that at least in some GRBs might be related to the dynamical properties of plasma trajectories in the accretion disks powering the RELATIVISTIC JETs. Several scenarios for their origin were examined. We identify non-planar orbits around Kerr BLACK HOLEs, the Lense-Thirring effect, and shock oscillations as plausible mechanisms for the QPO generation.
[abstract 2 / 63] Wow! (score: 7) - Title: Second Discovery of GeV-TeV Connection from the Globular Cluster UKS 1Authors: Jiwon Shin, C. Y. Hui, Sangin Kim, Kwangmin Oh, Ellis R. Owen,Comments: To appear in the proceedings of IAU symposium 398 & MODEST-25: Compact objects and Binaries in Dense Stellar SystemsSubjects: astro-ph.HECreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
Using 16 years of data collected by FERMI Large Area Telescope and 1523 days of survey data from High Altitude Water Cherenkov (HAWC) Observatory, we discovered the long-sought second GeV-TeV connection towards the globular cluster (GC) UKS 1 (Shin et al. 2025). Gamma-ray spectroscopy suggests that the GeV emission can be attributed to both the pulsar MAGNETosphere and inverse Compton scattering (ICS) by the pulsar wind. In particular, the TeV peak is displaced from the cluster center by several tidal radii in the trailing direction of the proper motion of UKS 1. This alignment supports a scenario in which RELATIVISTIC leptons, likely driven by a millisecond pulsar population, produce very-high-energy (VHE) gamma-rays via ICS within a bow shock tail. Our findings not only highlights GCs as potential sources of VHE gamma-rays, but also offers a rare opportunity to probe COSMIC RAY transport in the Milky Way by studying particle propagation and anisotropic gamma-ray production associated with the extended, offset TeV feature of UKS 1.
[abstract 3 / 63] Yes (score: 6) - Title: The Cygnus X-1 Puzzle: Implications of X-ray Polarization Measurements in the Soft and Hard States on the Properties of the Accretion Flow and the Emission MechanismsAuthors: Henric Krawczynski, Kun Hu,Comments: ApJ, in press, 15 pages, 5 figuresSubjects: astro-ph.HECreated: 2025-10-12; Updated: 2025-10-14; Datestamp: 2025-10-14
In this paper, we summarize key observational constraints of the accretion flow on the BLACK HOLE X-ray binary Cygnus X-1 (Cyg X-1). The discussion highlights the flows of energy close to the BLACK HOLE and the importance of the distance range from which the radiating zone draws its energy. For the hard state, we examine compact and extended corona models. We find that compact corona models are energetically favored, but extended models cannot be fully excluded. We discuss the high linear POLARIZATION of the Cyg X-1 X-rays in the soft and hard states, parallel to the direction of the radio JET. We propose the presence of a pair layer enveloping the accretion disk moving at approximately half the speed of light away from the disk for both the soft and the hard state. In the soft state, the pairs cool to the Compton temperature of the disk emission. In the hard state, the pairs acquire thermal and bulk motion allowing them to Comptonize the emission to produce the observed power law emission. In both emission states, the bulk motion away from the disk leads to a net POLARIZATION parallel to the radio JET. We emphasize that the geometry of the accretion flow in the hard state is still not well constrained, and that observed spectral (including the RELATIVISTICally broadened Fe K-$α$ line) and spectro-polarimetric signatures depend strongly on the plasma processes responsible for energy dissipation in the plasma.
[abstract 4 / 63] Yes (score: 6) - Title: Extracting energy from plunging region of a Kerr-Taub-NUT BLACK HOLE by MAGNETic RECONNECTionAuthors: Zhengwei Cheng, Songbai Chen, Jiliang Jing,Comments: 21 pages, 9 figures, Accepted by EPJCSubjects: gr-qcCreated: 2025-10-09; Updated: 2025-10-14; Datestamp: 2025-10-14
We have studied the energy extraction from a Kerr-Taub-NUT BLACK HOLE via MAGNETic RECONNECTion occurring in the plunging region. Our results show that the gravitoMAGNETic charge suppresses the energy extraction process through MAGNETic RECONNECTion and reduces the corresponding extraction efficiency, which is opposite to the effects of the BLACK HOLE spin and the MAGNETization parameter. Finally, we treat the energy extraction process through MAGNETic RECONNECTion as a mechanism to revisit the problem of the observed JET power and radiative efficiency of GRS 1915+105. Our results show that the allowed BLACK HOLE parameter region originating from the JET power has an intersection with the region from the radiative efficiency. This means that with this mechanism related to MAGNETic RECONNECTion the Kerr-Taub-NUT metric can simultaneously explain the observed JET power and radiative efficiency for GRS 1915+105, which is not explained by other mechanisms in previous studies.
[abstract 5 / 63] Yes (score: 6) - Title: A Late-time Radio Search for Highly Off-axis Jets from PTF Broad-lined Ic Supernovae in GRB-like Host Galaxy EnvironmentsAuthors: Genevieve Schroeder, Anna Y. Q. Ho, Ranadeep G. Dastidar, Maryam Modjaz, Alessandra Corsi, Paul C. Duffell,Comments: 20 pages, 8 figures, acceptedSubjects: astro-ph.HECreated: 2025-10-10; Updated: 2025-10-14; Datestamp: 2025-10-14
Hydrogen/Helium-poor stripped-envelope core-collapse SUPERNOVAe with broad lines (SNe Ic-bl) almost always accompany the nearby ($z < 0.3$) JETted RELATIVISTIC explosions known as long duration GAMMA-RAY BURSTs (GRBs). However, the majority of SNe Ic-bl have no detected GRB counterpart. At least some of these SNe should harbor off-axis JETs, whose afterglow may become detectable at late times, particularly at radio wavelengths. Here, we present Karl G. Jansky Very Large Array radio observations (rest frame times of $\sim 3$-$4\times10^{3}$ days post SN discovery) of a sample of 14 SNe Ic-bl discovered by the Palomar Transient Factory (PTF) that have been demonstrated to originate from the same host environments as the SNe Ic-bl associated with nearby GRBs. Of the 14 SNe, we identify three that are radio detected, one of which (PTF10tqv, $z = 0.0795$) is consistent with an off-axis JET with energy similar to classical GRBs (${\sim 10^{51}}$-${10^{51.7}~}$erg). Using recently developed SYNCHROTRON radiation code, we find that for our 11 non-detections, which are among the deepest limits obtained for Ic-bl, we rule out an off-axis JET with an energy of $\gtrsim 10^{51}~{\rm erg}$ in circumburst densities of $\gtrsim 10^{-1}~{\rm cm}^{-3}$. We predict that well-spaced monitoring of newly discovered SNe Ic-bl from $\sim 10~$days to $\sim 10~$years (rest frame) to luminosities of $\sim 10^{27}~{\rm erg~s}^{-1}~{\rm Hz}^{-1}$ will constrain the existence of highly off-axis JETs ($\gtrsim60^\circ$) with classical GRB energies. The VLA Sky Survey will probe JETs that are $\lesssim 60^\circ$ off-axis, whereas the Deep Synpotic Array 2000 will probe JETs out to $\sim 90^\circ$ off-axis, demonstrating the importance of utilizing radio surveys to supplement targeted observations.
[abstract 6 / 63] Yes (score: 6) - Title: Studying the properties of RECONNECTion-driven turbulenceAuthors: Shi-Min Liang, Jian-Fu Zhang, Na-Na Gao, Nian-Yu Yi,Comments: 9 pages, 6 figures and 1 table. Accepted for publication in A&ASubjects: astro-ph.HE physics.plasm-phCreated: 2025-10-11; Updated: 2025-10-14; Datestamp: 2025-10-14
Magnetic RECONNECTion, often accompanied by turbulence interaction, is a ubiquitous phenomenon in astrophysical environments. However, the current understanding of the nature of turbulent MAGNETic RECONNECTion remains insufficient. We investigate the statistical properties of RECONNECTion turbulence in the framework of the self-driven RECONNECTion. Using the open-source software package AMUN, we first perform numerical simulations of turbulent MAGNETic RECONNECTion. We then obtain the statistical results of RECONNECTion turbulence by traditional statistical methods such as the power spectrum and structure function. Our numerical results demonstrate: (1) the velocity spectrum of RECONNECTion turbulence follows the classical Kolmogorov type of $E\propto k^{-5/3}$, while the MAGNETic field spectrum is steeper than the Kolmogorov spectrum, which are independent of limited resistivity, guide field, and isothermal or adiabatic fluid states; (2) most of the simulations show the anisotropy cascade, except that the presence of a guide field leads to an isotropic cascade; (3) RECONNECTion turbulence is incompressible in the adiabatic state, with energy distribution dominated by the velocity solenoidal component; (4) different from pure MAGNETohydrodynamic (MHD) turbulence, the intermittency of the velocity field is stronger than that of the MAGNETic field in RECONNECTion turbulence. The steep MAGNETic field spectrum, together with the velocity spectrum of Kolmogorov type, can characterize the feature of the RECONNECTion turbulence. In the case of the presence of the guide field, the isotropy of the RECONNECTion turbulence cascade is also different from the cascade mode of pure MHD turbulence. Our experimental results provide new insights into the properties of RECONNECTion turbulence, which will contribute to advancing the self-driven RECONNECTion theory.
[abstract 7 / 63] Yes (score: 6) - Title: Coherence of Supermassive Black Hole Binary Demographics with the nHz Stochastic Gravitational Wave BackgroundAuthors: Katsunori Kusakabe, Yoshiyuki Inoue, Daisuke Toyouchi,Comments:Subjects: astro-ph.HECreated: 2025-10-12; Updated: 2025-10-14; Datestamp: 2025-10-14
We present a refined estimation of the stochastic gravitational wave background (SGWB) based on observed dual ACTIVE GALACTIC NUCLEi (AGNs) together with AGN X-ray luminosity functions, in light of recent Pulsar Timing Array detections of an nHz SGWB. We identify a characteristic luminosity dependence in dual AGN fractions by compiling recent observational datasets, providing crucial constraints on supermassive BLACK HOLE binary (SMBHB) populations. Our AGN-based model reproduces the current SGWB measurements within PTA observational uncertainties of $2 - 4 σ$ uncertainties, demonstrating consistency between electroMAGNETic and gravitational wave observations. These findings establish SMBHBs as the dominant source of the nHz gravitational wave signal, providing crucial insights into their demographics and evolution.
[abstract 8 / 63] Yes (score: 5) - Title: Utilizing Maximum Variability to Discern TDE Emission from AGN FlaresAuthors: Samaresh Mondal, K. Decker French,Comments: 15 pages, 13 figures, accepted for publication in ApJSubjects: astro-ph.HECreated: 2025-10-11; Updated: 2025-10-14; Datestamp: 2025-10-14
X-ray emission arising from ACTIVE GALACTIC NUCLEus (AGN) activity may potentially mimic the expected emission of tidal disruption events (TDEs). Ongoing and upcoming wide-field X-ray surveys will detect thousands of TDE-like sources, and classifying them securely as TDEs or AGNs is a challenging task. To this aim, we measure the average X-ray variability of AGNs and derive a threshold of maximum variation as a function of time separating the TDEs from AGN flares. For the comparison between TDE and AGN X-ray variability, we cross-match the publicly available XMM-Newton and SWIFT-XRT point source catalogs with the Million Quasars Catalog and optically selected TDEs. Then we compute the X-ray structure function (SF) and maximum variability of the AGN and TDE samples. The X-ray SF of AGNs has a power-law index $γ\sim0.11-0.14$ when fitted with a simple power-law model. However, the SF of AGNs is best described by a broken power-law or a power exponential model with a damping time scale $τ=950\pm300$ days. The maximum variability comparison between TDE and simulated AGN light curves indicates they have a similar order of variation on a time scale of less than 20 days. However, at a longer time scale of $\sim20$ days or more, the large-scale variations expected from power-law-like decay in TDEs become less frequent in AGNs. Furthermore, we compare the maximum variability of eROSITA TDE candidates with AGN, finding that many of the eROSITA-DE TDE candidates are consistent with flares from AGNs, and may not be TDEs.
[abstract 9 / 63] Yes (score: 5) - Title: Characterizing Power Spectra of Density Fluctuations in GRMHD Simulations of Black Hole Accretion Using Taylor's Frozen-in HypothesisAuthors: Pravita Hallur, Lia Medeiros, Pierre Christian, George N. Wong,Comments: 12 pages, 7 figures. Submitted to ApJSubjects: astro-ph.HECreated: 2025-10-10; Updated: 2025-10-14; Datestamp: 2025-10-14
We characterize the spatial power spectrum of density fluctuations in MAGNETohydrodynamic flows in a suite of high-resolution, long-time-span general RELATIVISTIC MAGNETohydrodynamic (GRMHD) simulations. Extracting the local spatial power spectrum in curved spacetime directly from GRMHD simulations can be challenging for several conceptual and mechanical reasons, including choices of the reference frame, the non-uniform co-ordinate grid of the outputs and limited resolution. Taylor's frozen-in hypothesis describes a mapping between the temporal and spatial power spectrum of turbulence, which we apply to density fluctuations. We explore the validity of the assumptions underlying Taylor's hypothesis and evaluate its applicability in extracting spatial power spectra of density fluctuations of BLACK HOLE accretion flows. Using outputs from the GRMHD code KORAL, we explore models with strong and ordered MAGNETic fields (MAD, Magnetically Arrested Disks) as well as weak and disordered MAGNETic fields (SANE, Standard and Normal Evolution). We explore the effects of BLACK HOLE spin on the power spectra and characterize their spectral properties as a function of distance from the BLACK HOLE. The observed power spectra follow a broken power law with two slopes separated by a break frequency. Our analysis shows a decrease in break frequency with increasing radius, with distinct trends between SANE and MAD flows. We also observe the first slope to be steeper for SANE flows and some notable distinctions between prograde and retrograde spins.
[abstract 10 / 63] Yes (score: 5) - Title: Revisiting FRB 20121102A: milliarcsecond localisation and a decreasing dispersion measureAuthors: M. P. Snelders, J. W. T. Hessels, J. Huang, N. Sridhar, B. Marcote, A. M. Moroianu, O. S. Ould-Boukattine, F. Kirsten, S. Bhandari, D. M. Hewitt, D. Pelliciari, L. Rhodes, R. Anna-Thomas, U. Bach, E. K. Bempong-Manful, V. Bezrukovs, J. D. Bray, S. Buttaccio, I. Cognard, A. Corongiu, R. Feiler, M. P. Gawroński, M. Giroletti, L. Guillemot, R. Karuppusamy, M. Lindqvist, K. Nimmo, A. Possenti, W. Puchalska, D. Williams-Baldwin,Comments: Submitted. Comments welcomeSubjects: astro-ph.HECreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
FRB 20121102A is the original repeating fast radio burst (FRB) source and also the first to be localised to milliarcsecond precision using very-long-baseline interferometry (VLBI). It has been active for over 13 years and resides in an extreme MAGNETo-ionic environment in a dwarf host galaxy at a distance of ~1 Gpc. In this work, we use the European VLBI Network (EVN) to (re-)localise FRB 20121102A and its associated persistent radio source (PRS). We confirm that the two are co-located -- improving on previous results by a factor of ~4 and constraining the FRB and PRS co-location to ~12 pc transverse offset. Over a decade, the PRS luminosity on milliarcsecond scales remains consistent with measurements on larger angular scales, showing that the PRS is still compact. We also present the detection of 18 bursts with the Nancay Radio Telescope (NRT) as part of our ÉCLAT monitoring program. These bursts, together with previously published results, show that the observed dispersion measure (DM) of FRB 20121102A has dropped by ~25 pc/cc in the past five years, highlighting a fractional decrease in the local DM contribution of >15%. We discuss potential physical scenarios and highlight possible future observations that will help reveal the nature of FRB 20121102A, which is one of only a few known FRBs with a luminous PRS.
[abstract 11 / 63] Yes (score: 5) - Title: ElectroMAGNETic Observables of Weakly Collisional Black Hole AccretionAuthors: Vedant Dhruv, Ben Prather, Mani Chandra, Abhishek V. Joshi, Charles F. Gammie,Comments: 13 pages, 9 figures. AcceptedSubjects: astro-ph.HE physics.plasm-phCreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
The BLACK HOLEs in the Event Horizon Telescope sources Messier 87* and Sagittarius A* (SgrA*) are embedded in a hot, collisionless plasma that is fully described in kinetic theory yet is usually modeled as an ideal, MAGNETized fluid. In this Letter, we present results from a new set of weakly collisional fluid simulations in which leading order kinetic effects are modeled as viscosity and heat conduction. Consistent with earlier, lower-resolution studies, we find that overall flow dynamics remain very similar between ideal and non-ideal models. For the first time, we synthesize images and spectra of SgrA* from weakly collisional models -- assuming an isotropic, thermal population of electrons -- and find that these remain largely indistinguishable from ideal fluid predictions. However, most weakly collisional models exhibit lower light curve variability, with all MAGNETically dominated models showing a small but systematic decrease in variability.
[abstract 12 / 63] Yes (score: 5) - Title: Observational study of chromospheric JETs in and around a sunspot observed by NVST and SDOAuthors: Guotang Wu, Xiaoli Yan, Zhike Xue, Jincheng Wang, Zhe Xu, Liheng Yang, Yian Zhou, Liping Yang, Xinsheng Zhang, Qifan Dong, Zongyin Wu,Comments: 18 pages, 11 figures, accepted for publication in ApJSubjects: astro-ph.SR physics.space-phCreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
To better understand the characteristics, driving mechanisms, and potential heating contributions of chromospheric JETs, we analyze two contrasting types: one originating from within the sunspot penumbra (inside JETs), and the other originating from outside the penumbra (outside JETs). Statistical analysis of 100 JETs (50 inside JETs and 50 outside JETs) reveals that inside JETs have a projected velocity range of 4--14~km\,s$^{-1}$, a length range of 1--4~Mm, a width range of 0.2--0.6~Mm, and a lifetime range of 135--450~s, with mean values of 7.90~km\,s$^{-1}$, 2.61~Mm, 0.41~Mm, and 260~s, respectively. About 52\% of inside JETs are associated with brightenings in H$α$ blue wing images, and some show high-temperature signatures, suggesting a connection with localized energy release. In contrast, outside JETs have higher velocities (8--50~km\,s$^{-1}$, average 19.04~km\,s$^{-1}$), greater lengths (average 6.26~Mm, up to 27.27~Mm), slightly larger widths (average 0.46~Mm), and longer lifetimes (135--630~s, average 327~s). They typically originate from regions of opposite MAGNETic polarities and are associated with MAGNETic flux emergence and EUV brightenings. Some outside JETs correspond to coronal JETs with inverted Y-shaped structures and temperatures exceeding one million Kelvin. Our results suggest that both JET types are driven by MAGNETic RECONNECTion occurring in distinct MAGNETic field configurations and contribute to chromospheric and coronal heating.
[abstract 13 / 63] Yes (score: 5) - Title: Probing spectral variability in NGC 4490 ULX-8 over 24 years of XMM-Newton, Chandra and SWIFT-XRT observationsAuthors: Tarang Vashisht, Aru Beri, Tanuman Ghosh, Aman Upadhyay, Vikram Rana,Comments:Subjects: astro-ph.HECreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
We present comprehensive spectral and timing results of 14 Chandra, 6 XMM-Newton and 19 SWIFT-XRT observations of the ultraluminous X-ray source NGC 4490 ULX-8, spanning from 2000 to 2024. We model the source spectra using absorbed power-law and absorbed multicolour disc blackbody models. The best-fit photon indices span 0.92-2.68, with typical uncertainties ranging from $\pm$0.1 to $\pm$1 depending on data quality. The inner disk temperature range from 0.97 to 1.69 keV, consistent with blackbody emission from an accretion disk. Our results reveal significant long-term variability in intrinsic X-ray source fluxes while the source remains relatively stable within individual observations. A Hardness-Intensity Diagram of the source shows no clear transition between hard and soft states, but an increase in brightness during two recent observations taken on 2022 December 1 and 2024 May 4. We find a positive correlation of X-ray luminosity and photon index that persists even when the hydrogen column density is tied across observations, suggesting a physical origin. The X-ray luminosity-inner disk temperature relation yields a weakly constrained slope owing to large temperature uncertainties, but a simpler fixed-slope test indicates consistency with a standard thin-disk. Using the derived disk parameters, we estimate the BLACK HOLE mass to lie in the range of 16-75 $M_{\odot}$, under the assumption of a geometrically thin accretion flow, where the lower and upper bounds correspond to a Schwarzchild and a Kerr BLACK HOLE respectively. Alternatively, we consider the scenario of ULX-8 hosting an accreting neutron star and estimate the corresponding MAGNETic field strength required to explain the observed properties.
[abstract 14 / 63] Yes (score: 4) - Title: No Sign of a Magnetar Remnant Following the Kilonova-Producing Long GRB 211211A $\sim 1.7~$Years LaterAuthors: Genevieve Schroeder, Ben Margalit, Brian D. Metzger, Wen-fai Fong, Benjamin P. Gompertz, Kate D. Alexander, Edo Berger, Tanmoy Laskar, Gavin P. Lamb, Andrew Levan, Charles D. Kilpatrick, Jillian C. Rastinejad,Comments: 15 pages, 4 figures, submitted to ApJSubjects: astro-ph.HECreated: 2025-10-10; Updated: 2025-10-14; Datestamp: 2025-10-14
In addition to a $γ$-ray burst (GRB), the merger of two neutron stars may produce a temporarily or indefinitely stable neutron star remnant with a strong MAGNETic field (a "MAGNETar"). As this MAGNETar remnant spins down, it can deposit its rotational energy into the surrounding kilonova ejecta, producing SYNCHROTRON emission that peaks in the radio bands $\sim$months-years after the merger ("boosted kilonova"). The nearby ($z=0.0763$) long-duration GRB 211211A, which has an apparent kilonova counterpart and likely neutron star merger progenitor, may have produced such a remnant. We observed the location of GRB 211211A at 6 GHz with the NSF's Karl G. Jansky Very Large Array (VLA) spanning $\approx 0.54$-$1.7~$years after the burst. We do not detect any radio emission, placing strong limits on the energy deposited into the ejecta by any remnant to $\lesssim 4.4 \times 10^{52}~{\rm erg}$. Due to the proximity of the event, we are also able to place limits on a kilonova afterglow that did not receive any additional energy deposition, though it is possible such emission will be suppressed until $\sim 4~{\rm years}$ after the burst, when the kilonova is expected to overtake the forward shock of the GRB. Future observations with the VLA and next-generation radio facilities will be able to further constrain the MAGNETar-boosted kilonova and kilonova afterglow scenarios, as well as directly constrain models in the scenario that GRB 211211A was instead produced by a collapsar.
[abstract 15 / 63] Yes (score: 4) - Title: Luminous Fast Blue Optical Transients as "Failed" Gravitational Wave Sources: Helium Core$-$Black Hole Mergers Following Delayed Dynamical InstabilityAuthors: Jakub Klencki, Brian D. Metzger,Comments: 20 pages, 11 figures + AppendixSubjects: astro-ph.HE astro-ph.SR gr-qcCreated: 2025-10-10; Updated: 2025-10-14; Datestamp: 2025-10-14
Binaries in which a massive donor star undergoes an extended ($\gtrsim$ kyr) phase of stable mass transfer onto a BLACK HOLE (BH) accretor offer a promising channel for creating LIGO gravitational wave sources. However, in many systems the mass transfer terminates prematurely in a dynamical instability at orbital periods of a few days, culminating in the BH plunging into the donor and potentially disrupting and accreting its helium core at highly super-Eddington rates. Combining a suite of binary evolution models with analytic estimates and population synthesis, we predict the population of luminous transients from delayed dynamical instability (DDI) and attribute them to the "luminous" class of fast blue optical transients (LFBOTs). The initial plunge of the BH into the partially stripped envelope typically ejects $\sim 10M_{\odot}$ of H/He-enriched material at speeds $\sim 10^{2}-10^{3}$ km s$^{-1}$, generating a compact circumstellar medium (CSM) of radius $\lesssim 1000R_{\odot}$ by the time the BH meets and tidally disrupts the HeC. Rapid BH accretion generates a highly aspherical wind-driven explosion into the environment, powering UV/optical emission via CSM interaction and X-ray reprocessing that rises over a few days to a luminosity $\sim 10^{44}-10^{45}$ erg s$^{-1}$ before fading as the disk spreads outwards and accretion rate drops. Luminous radio/sub-mm emission is generated over several months as the JET collides with the slow quasi-spherical binary outflow, generated by the stable mass transfer preceding DDI, extending to radii $\sim 10^{17}$ cm, in agreement with the inferred CSM environments of LFBOTs. We estimate local rates of DDI merger transients $5-300$ Gpc$^{-3}$ yr$^{-1}$, with a preference for low-metallicities, in agreement with LFBOT demographics. Taken together, our results support LFBOTs as being luminous signposts of "failed" gravitational wave sources.
[abstract 16 / 63] Yes (score: 4) - Title: BEES: Quasar lifetime measurements from extended rest-optical emission line nebulae at $z\sim6$Authors: Dominika Ďurovčíková, Anna-Christina Eilers, Yuzo Ishikawa, Minghao Yue, Marianne Vestergaard, Frederick B. Davies, Jan-Torge Schindler, Xiaohui Fan, Fabrizio Arrigoni Battaia, Marta Volonteri, Robert A. Simcoe, Joseph F. Hennawi, Laura Blecha, Irham T. Andika, Sarah E. I. Bosman, Rebekka Bieri,Comments: 22 pages, 10 figures, 4 tablesSubjects: astro-ph.GA astro-ph.COCreated: 2025-10-10; Updated: 2025-10-14; Datestamp: 2025-10-14
Measurements of QUASAR lifetimes at high redshift indicate that the earliest billion-solar-mass supermassive BLACK HOLEs (SMBHs) have only been active as luminous QUASARs for less than a million years. Recently, extended Ly$α$ nebulae around $z\sim6$ QUASARs have revealed that these short observed lifetimes are unlikely a sightline-dependent effect. However, the interpretation of Ly$α$ emission is not straightforward due to its resonant nature. In this work, we use rest-frame optical emission lines, which more directly trace photoionization by the QUASAR, to unambiguously validate the short line-of-sight QUASAR lifetimes observed at early cosmic epochs. We use deep James Webb Space Telescope/NIRSpec IFU observations of five $z\sim 6$ QUASARs with small proximity zones to search for their extended emission line nebulae in H$α$ and [O III]$5007$, and detect extended emission in both emission lines around four QUASARs in our sample. We then use the light-crossing time of these nebulae to measure QUASAR lifetimes along transverse sightlines. Using their H$α$ nebulae, we also confirm that recombination is likely the dominant emission mechanism behind their previously detected Ly$α$ nebulae. Our results confirm the existence of high-redshift QUASARs with extremely short lifetimes, $t_{\rm Q} \lesssim 10^{5}\ {\rm yr}$, hosting billion-solar-mass BLACK HOLEs, indicating that rapid accretion is likely responsible for the assembly of SMBHs in the early Universe.
[abstract 17 / 63] Yes (score: 4) - Title: QPOs in a highly MAGNETized ultra-compact X-ray binary 4U 1626-67Authors: Zi-Yi Zhou, Long Ji, Ling-Da Kong, Sergey S. Tsygankov, Qing-Cang Shui, Lian Tao,Comments: Accepted for publication in APJSubjects: astro-ph.HECreated: 2025-10-11; Updated: 2025-10-14; Datestamp: 2025-10-14
We report the detection of mHz quasi-periodic oscillations (QPOs) in four NUSTAR observations of 4U 1626-67 during its recent spin-down episode. By using a novel method based on the Hilbert-Huang Transform (HHT), we present the first QPO-phase-resolved timing and spectral analysis of accreting X-ray pulsars in low mass X-ray binaries. Broadband QPO waveforms have been reconstructed and exhibit approximately sinusoidal shapes, with fractional amplitudes that vary with energy. In addition, we find that spin pulse profiles exhibit stable shapes between different QPO phases with different instantaneous fluxes, while the fractional root-mean-square (rms) is distinct for different observations. In this source, both QPO-phase-resolved and averaged spectra can be modeled with a negative and positive powerlaws exponential (NPEX) model, and their spectral evolutions show a similar trend, suggesting that the QPO modulation is caused by accretion rate variability instead of a geometric obscuration. These results provide new constraints on accretion physics in strongly MAGNETized neutron stars and the underlying mechanisms of QPOs.
[abstract 18 / 63] Yes (score: 4) - Title: Black-hole X-ray binary SWIFT J1727.8$-$1613 shows Type-B quasi-periodic oscillations across the hard-intermediate and soft-intermediate statesAuthors: Pei Jin, Mariano Méndez, Federico García, Diego Altamirano, Federico M. Vincentelli,Comments: 14 pages, 14 figures, under the third round of review for A&ASubjects: astro-ph.HECreated: 2025-10-11; Updated: 2025-10-14; Datestamp: 2025-10-14
We present a timing analysis of \textit{Insight}-HXMT observations of the black-hole X-ray binary SWIFT J1727.8$-$1613 across a bright soft X-ray flare on 2023 September 19 (MJD 60206). At the peak of the flare, the source undergoes a brief transition from the hard-intermediate state (HIMS) into the soft-intermediate state (SIMS), marked by the simultaneous appearance of three discrete radio JET ejections, a drop in broadband noise in the 2$-$10 keV band, and the presence of a narrow quasi-periodic oscillation (QPO) with a characteristic ``U''-shaped phase-lag spectrum and a quality factor of $Q \geq 6$, features that robustly identify it as a Type-B QPO. The Type-C QPO, which was clearly detected in the HIMS prior to the flare, is not observed at the flare's peak and only reappears afterward. Most notably, we find that the Type-B QPO is not restricted to the SIMS: it is present throughout all our observations, including those taken in the HIMS, where it appears as a broad shoulder of the Type-C QPO. During the flare, the Type-B and Type-C QPOs exhibit distinct evolutionary trends in frequency, fractional rms amplitude, and phase lag. These results challenge the traditional view that Type-B QPOs are exclusive to the SIMS, a state that is, in fact, defined by their appearance in the power spectrum, and directly linked to discrete JET ejections. Instead, our findings suggest that the physical conditions giving rise to Type-B QPOs occur more broadly within the inner accretion flow.
[abstract 19 / 63] Yes (score: 4) - Title: Characterizing IceTop Response to Low-Energy Air ShowersAuthors: Yanee Tangjai, Agnieszka Leszczynska, Tatphicha Promfu, Achara Seripienlert, Serap Tilav,Comments: Presented at the 39th International Cosmic Ray Conference (ICRC2025)Subjects: astro-ph.HECreated: 2025-10-12; Updated: 2025-10-14; Datestamp: 2025-10-14
This study evaluates the response of the IceTop tanks to low-energy air showers in the GeV to TeV energy range based on simulated and measured count rates. Correlating this response with primary COSMIC RAYs provides a tool to study Galactic and solar cosmic-ray flux modulations, particularly for solar particle events. We present long-term behavior of the IceTop scaler rates for a range of discriminator thresholds to better understand and calibrate the detector's response to changing environmental conditions.
[abstract 20 / 63] Yes (score: 4) - Title: State-Dependent X-ray Variability in Cygnus X-1: A 12-Year NUSTAR Timing Study of Accretion Flow GeometryAuthors: Kshitij Duraphe, Kartik Mandar, Chooda Khanal, Abha Pareek, Tejaswi Kondhiya, V Sree Suswara, Deeksha Dinesh, Vidyasagar Bhat, Gopal Bhatta,Comments: 18 pages, 8 figures, 2 tablesSubjects: astro-ph.HECreated: 2025-10-12; Updated: 2025-10-14; Datestamp: 2025-10-14
We present a comprehensive timing analysis of the BLACK HOLE X-ray binary Cygnus X-1 using 26 NUSTAR observations spanning 2012-2024, providing the most detailed characterization to date of its accretion flow variability across spectral states. Our analysis reveals fundamental insights into the physics governing state transitions in stellar-mass BLACK HOLEs. We discover distinct bimodal flux distributions in the 8-79 keV band with well-separated peaks, contrasting with overlapping distributions in the 3-8 keV band. This energy-dependent bimodality establishes hard X-rays as the optimal diagnostic for state classification, directly tracing the geometric transformation between corona-dominated and disk-dominated configurations. Power spectral analysis uncovers state-dependent characteristic frequencies shifting from 0.050 Hz (hard) to 0.074 Hz (intermediate), with featureless red noise in soft states. These frequencies correspond to disk truncation radii evolving from $\sim$5.5 $R_g$ to $\sim$2 $R_g$, providing direct observational evidence for the inward progression of the accretion disk during state transitions. Frequency-dependent time lags evolve systematically from $\sim$50 ms hard lags at 0.1 Hz in hard states to near-zero in soft states, quantifying the collapse of the Comptonizing corona. Linear rms-flux relations persist across all states with parameters that precisely track the relative contributions of thermal versus non-thermal emission components. Most remarkably, we identify a failed state transition (observation 30302019006) exhibiting anticorrelated band behavior, suppressed variability ($F_{var}$ < 1.38\%), and apparent sub-ISCO truncation. This discovery challenges standard transition models and suggests new pathways for accretion flow evolution in wind-fed systems.
[abstract 21 / 63] Yes (score: 4) - Title: Gamma-ray Orbital Modulation in Spider Pulsars: Three Discoveries and a Universal Modulated FractionAuthors: Maksat Satybaldiev, Manuel Linares, Vittoria Vecchiotti,Comments: 23 pages, 15 figures, 4 tables. Submitted to ApJSubjects: astro-ph.HECreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
Compact binary millisecond pulsars (also known as spiders) allow us to probe pulsar winds in their innermost regions, between the light cylinder (radius $\sim10^{7}$ cm) and the companion star (at $\sim10^{11}$ cm). Their flux is known to vary along the orbit, from radio to X-rays. During the past decade, gamma-ray orbital modulation (GOM) has been discovered in a handful of spiders, but its origin remains largely unknown. We present the results of a systematic search for GOM among 43 systems, selecting pulsed 0.1-1 GeV photons and using spin and orbital ephemeris from FERMI's Third Pulsar Catalog. We discover GOM from three spiders - PSR J1124-3653, PSR J1946-5403 and PSR J2215+5135 - and confirm four previous detections. In all seven cases so far, the GOM peaks near the pulsar's superior conjunction. The X-ray orbital light curves are usually in anti-phase, peaking when the pulsar is at inferior conjunction, but we find one case where both gamma-rays and X-rays peak around superior conjunction: PSR J1946-5403. We measure the modulated fractions of the GOM and find consistent values for all seven spiders, with an average $22.0\pm2.6\%$. Including eclipsing systems seen edge-on, we find no clear dependence of the modulated fraction on the orbital inclination (within $\simeq$45-90$^\circ$). Our results challenge previous models proposed to explain GOM in spiders, based on inverse Compton and SYNCHROTRON emission close to the companion, since these predict a clear dependence with orbital inclination (stronger modulation at high inclinations). We nearly double the number of GOM detections in spiders, showing that it is more common than previously thought.
[abstract 22 / 63] (score: 3) - Title: Kilonova emission from GW230529 and mass gap neutron star-BLACK HOLE mergersAuthors: Keerthi Kunnumkai, Antonella Palmese, Mattia Bulla, Tim Dietrich, Amanda M. Farah, Peter T. H. Pang,Comments: 13 pages, 5 figures, 2 tablesSubjects: astro-ph.HECreated: 2025-10-11; Updated: 2025-10-14; Datestamp: 2025-10-14
The detection of the gravitational wave event GW230529, presumably a neutron star-BLACK HOLE (NSBH) merger, by the LIGO-Virgo-KAGRA (LVK) Collaboration marks an exciting discovery for multimessenger astronomy. The BLACK HOLE (BH) has a high probability of falling within the "mass gap" (mg) between the neutron star (NS) and the BH mass distributions. Because of the relatively low primary mass, this system has a higher likelihood of producing an electroMAGNETic counterpart than previously detected NSBH mergers. We analyze the potential kilonova (KN) emission from GW230529 and find that, if the source was an NSBH merger, there is a $\sim $2-$28\%$ probability (depending on the assumed equation of state) that it produced a KN peaking at $\sim 1$ day post-merger with $g \lesssim 23.5$ and $i < 23$. Hence, it could have been detected by ground-based telescopes. If instead the event was a binary neutron star (BNS) merger, the probability of KN production drops to $\sim $0-$10\%$. Motivated by these results, we simulate a broader population of mgNSBH mergers expected during the fifth LIGO/Virgo/KAGRA observing run (O5) and find a $2$-$3\%$ chance of KN production per event. Such KNe would typically be fainter than GW230529, with $g \lesssim 26$ and $i \lesssim 25$. Based on these findings, DECam-like instruments may be able to detect up to $\sim 70\%$ of future mgNSBH KNe, corresponding to $1-2$ multimessenger mgNSBH per year in O5.
[abstract 23 / 63] (score: 3) - Title: Detecting electroMAGNETic counterparts to LIGO/Virgo/KAGRA gravitational wave events with DECam: Neutron Star MergersAuthors: Keerthi Kunnumkai, Antonella Palmese, Amanda M Farah, Mattia Bulla, Tim Dietrich, Peter T H Pang, Shreya Anand, Igor Andreoni, Tomas Cabrera, Brendan O Connor,Comments: 24 pages, 12 figures, 10 tablesSubjects: astro-ph.HE gr-qcCreated: 2025-10-11; Updated: 2025-10-14; Datestamp: 2025-10-14
With GW170817 being the only multimessenger gravitational wave (GW) event with an associated kilonova detected so far, there exists a pressing need for realistic estimation of the GW localization uncertainties and rates, as well as optimization of available telescope time to enable the detection of new kilonovae. We simulate GW events assuming a data-driven distribution of binary parameters for the LIGO/Virgo/KAGRA (LVK) fourth and fifth observing runs (O4 and O5). We map the binary neutron star (BNS) and neutron star-BLACK HOLE (NSBH) properties to the kilonova optical light curves. We use the simulated population of kilonovae to generate follow-up observing plans, with the primary goal of optimizing detection with the Gravitational Wave Multi-Messenger Astronomy DECam Survey (GW-MMADS). We explore the dependence of kilonova detectability on the mass, distance, inclination, and spin of the binaries. Assuming that no BNS was detected during O4 until the end of 2024, we present updated GW BNS (NSBH) merger detection rates. We expect to detect BNS (NSBH) kilonovae with DECam at a per-year rate of: $0$-$2.0$ ($0$) in O4, and $2.0$-$19$ ($0$-$1.0$) in O5. We expect the majority of BNS detections and also those accompanied by a detectable kilonova to produce a hypermassive NS remnant, with a significant fraction of the remaining BNSs promptly collapsing to a BH. We release GW simulations and depths required to detect kilonovae based on our predictions to support the astronomical community in their multimessenger follow-up campaigns and analyses.
[abstract 24 / 63] (score: 3) - Title: A Time-Dependent Solution for GSN 069 Disk Evolution and the Nature of Long-Lived Tidal Disruption EventsAuthors: M. Guolo, A. Mummery, A. Ingram, M. Nicholl, S. Gezari, E. Nathan,Comments: 25 pages, 13 Figs, +Appendix. Published ApJ. Accepted versionSubjects: astro-ph.HE astro-ph.GACreated: 2025-10-10; Updated: 2025-10-14; Datestamp: 2025-10-14
We present the implementation of a fully \textit{time-dependent} RELATIVISTIC disk model-based on the light curve fitting package FitTeD-into the X-ray spectral fitting environment, pyXspec. This implementation enables simultaneous fitting of multi-epoch and multi-wavelength spectral data, where the only free parameters are those describing the BLACK HOLE and the initial conditions, while the subsequent evolution is governed by the dynamical equations of an evolving accretion flow. We use it fit seven epochs of X-ray spectra and two epochs of UV spectra of the 'long-lived' tidal disruption event (TDE) and quasi-periodic eruption (QPE) source GSN 069, from 2010 through late-2019. Our results show that such 'long-lived', X-ray-bright TDEs-of which GSN 069 is a prime, but not unique, example-can naturally be explained within the same framework as events with shorter-lived X-ray emission, like ASASSN-14li and AT2019dsg. Their distinction lies in the `viscous' timescale parameter-tied to the disk's angular momentum transport efficiency-which should be treated as a free parameter when modeling the disk evolution of transient events. We examine the implications for QPE models by tracking the time evolution of disk properties such as mass surface density and accretion rate. We argue that existing QPE models may not be able to reproduce the observed connection between the presence (2018) or absence (2014) of eruptions and the disk properties. In the context of orbiter-disk collision models, the change in mass surface density appears insufficient to explain the needed variation in the eruption's temperature. The absence of eruptions in GSN 069 in 2014 remains a challenge for QPE models.
[abstract 25 / 63] (score: 3) - Title: Uncertainties in the Estimation of Air Shower Observables from Monte Carlo Simulation of Radio EmissionAuthors: Carlo S. Cruz Sanchez, Patricia M. Hansen, Matias Tueros, Jaime Alvarez-Muñiz, Diego G. Melo,Comments: 24 pages, 11 figures, version accepted in Astroparticle PhysicsSubjects: astro-ph.HECreated: 2025-10-12; Updated: 2025-10-14; Datestamp: 2025-10-14
The detection of extensive air showers (EAS) induced by COSMIC RAYs via radio signals has undergone significant advancements in the last two decades. Numerous ultra-high energy COSMIC RAY experiments routinely capture radio pulses in the MHz to GHz frequency range emitted by EAS. The Monte Carlo simulation of these radio pulses is crucial to enable an accurate reconstruction of the primary COSMIC RAY energy and to infer the composition of the primary particles. In this work, a comprehensive comparison of the predicted electric field in EAS simulated with CoREAS and ZHAireS was conducted to estimate the systematic uncertainties arising from the use of different simulation packages in the determination of two key shower observables namely, the electroMAGNETic energy of the EAS and the depth of maximum development ($X_{\rm max}$). For this comparison, input parameters and settings as similar as possible were used in both simulations, along with the same realistic atmospheric refractive index depending on altitude, which is crucial for the prediction of radio emission properties of EAS. In addition, simulated EAS with very similar values of depth of maximum development were selected. Good agreement was found between CoREAS and ZHAireS, with discrepancies in the dominant electric field components generally remaining below 10\% across the frequency range of a few MHz to hundreds of MHz, relevant for most radio detection experiments, translating into uncertainties in the determination of energy below $5\%$ and $\simeq 10\,\mathrm{g/cm^2}$ in $X_{\rm max}$. Our work underscores the need for further studies to clarify their origin and impact on $X_{\rm max}$ inference in composition analyses.
[abstract 26 / 63] (score: 3) - Title: An Accurate Modeling of Nano-hertz Gravitational Wave Signal from Eccentric Supermassive Binary Black Holes: An Essential Step Toward a Robust DiscoveryAuthors: Mohit Raj Sah, Akash Maurya, Suvodip Mukherjee, Prayush Kumar, Vida Saeedzadeh, Arif Babul, Chandra Kant Mishra, Kaushik Paul, Thomas R. Quinn, Michael Tremmel,Comments: 24 pages, 12 figures. Accepted for publication in ApJSubjects: astro-ph.CO astro-ph.HE gr-qcCreated: 2025-10-11; Updated: 2025-10-14; Datestamp: 2025-10-14
The stochastic gravitational wave background (SGWB) in the nanohertz (nHz) regime, detectable by pulsar timing arrays (PTAs), provides a promising probe of the cosmic population of supermassive BLACK HOLE binaries (SMBHBs). These binaries are expected to retain significant eccentricity throughout their evolution. We present a new technique to model the nHz SGWB by incorporating eccentricity into a multi-scale adaptive simulation framework. Using the time-domain eccentric waveform model ESIGMAHM, we generate realistic GW signals from astrophysical populations of SMBHBs. Unlike circular binaries, eccentric systems emit across multiple frequencies, introducing spectral correlations between frequency bins. These correlations provide a novel observational signature of the eccentricity distribution of the SMBHB population. In this work, we adopt simplified power-law models for the eccentricity distribution. While this does not capture the full complexity of galactic environments, it effectively highlights the key features of GW emission from eccentric binaries and their imprint on the SGWB. Our approach advances nHz GW signal modeling by incorporating eccentricity at small scales, enabling more realistic predictions and offering a new avenue for probing SMBHB astrophysics with future PTA observations.
[abstract 27 / 63] (score: 3) - Title: A RELATIVISTIC treatment of accretion disk torques on extreme mass ratio inspirals around spinning BLACK HOLEsAuthors: Abhishek Hegade K. R., Charles F. Gammie, Nicolás Yunes,Comments: Minor change. 12 pages, 5 figures. Supplementary material available in the source file and at https://github.com/AbhiHegade/Supplementary-Material-for-Disc-Torques-in-Schwarzschild-Background. Comments are welcome!Subjects: gr-qcCreated: 2025-10-10; Updated: 2025-10-14; Datestamp: 2025-10-14
We model the motion of a small compact object on a nearly circular orbit around a spinning supermassive BLACK HOLE, which is also interacting with a thin equatorial accretion-disk surrounding the latter, through tools from self-force and Hamiltonian perturbation theory. We provide an analytical and RELATIVISTICally-accurate formalism to calculate the rate of energy and angular momentum exchanged at Lindblad resonances. We show that strong RELATIVISTIC effects can potentially cause a reversal in the direction of the torque on the small compact object if the surface density gradient is not too large. We analytically explore the dependence of the torque reversal location on the spin of the supermassive BLACK HOLE and demonstrate that the ratio of the reversal location to the innermost stable circular orbit is approximately insensitive to the spin of the supermassive BLACK HOLE. Our results show that RELATIVISTIC torques can be 1--2 order of magnitude larger than the Newtonian torque routinely used in the literature to model disk/small-compact-object interactions close to the supermassive BLACK HOLE. Our results highlight the importance of including RELATIVISTIC effects when modeling environmental effects in extreme mass-ratio inspirals.
[abstract 28 / 63] (score: 3) - Title: The Gravitational Wave Memory from Binary Neutron Star MergersAuthors: Jamie Bamber, Antonios Tsokaros, Milton Ruiz, Stuart L. Shapiro, Marc Favata, Matthew Karlson, Fabrizio Venturi Piñas,Comments: 8 pages, 5 figures. Movies and additional visualizations available at https://tinyurl.com/shapiromoviesSubjects: gr-qcCreated: 2025-10-10; Updated: 2025-10-14; Datestamp: 2025-10-14
The gravitational wave signal produced by the merger of two compact objects includes both an oscillatory transient and a non-oscillatory part, the so-called memory effect. This produces a permanent displacement of test masses and has not yet been measured. We use general RELATIVISTIC MAGNETohydrodynamic simulations, including neutrinos, with several representative viable equations of state, to quantify--for the first time--the effects of the neutron star MAGNETic field, neutrino emission, and the ejected mass on the linear and nonlinear displacement memory in binary neutron star mergers. We find that the additional contributions due to the emission of electroMAGNETic radiation, neutrinos and baryonic ejecta can be ~15% of the total memory for moderate MAGNETic fields and up to ~50% for extreme MAGNETic fields. The memory is most affected by changes in the equation of state, the binary mass, and the MAGNETic field. In particular, for moderate premerger field strengths, the dominant impact of the electroMAGNETic field is the change in the gravitational wave luminosity, and the associated gravitational wave null memory, due to the unstable growth of the MAGNETic field and the resulting redistribution of angular momentum it induces in the remnant. While the direct electroMAGNETic contribution to the null memory is additive, the change in the gravitational wave null memory can--in some cases--result in the total memory being smaller than that from the corresponding nonMAGNETized binary. Furthermore, in contrast to binary BLACK HOLE mergers, the growth of the memory in binary neutron star mergers is extended due to the long emission timescale of electroMAGNETic fields, neutrinos, and ejecta. These results necessitate the consideration of the MAGNETic field, as well as the equation of state, for accurate parameter estimation in future analyses of gravitational wave memory data.
[abstract 29 / 63] (score: 3) - Title: Elusive Plunges and Heavy Intermediate-mass-ratio Inspirals from Single and Binary Supermassive Black HolesAuthors: Lazaros Souvaitzis, Antti Rantala, Thorsten Naab,Comments: 21 pages, 11 figuresSubjects: astro-ph.GA gr-qcCreated: 2025-10-10; Updated: 2025-10-14; Datestamp: 2025-10-14
The most massive galaxies in the Universe also host the largest supermassive BLACK HOLEs (SMBHs), with masses of $10^9 \: \mathrm{M_{\odot}}$ and above. During their hierarchical assembly, these galaxies have experienced only a few major mergers at low redshift, but have accreted many low-mass galaxies across cosmic time, possibly hosting intermediate mass BLACK HOLEs (IMBHs). If some of these IMBHs migrate to the galactic center, they may form compact subsystems around the central SMBH. We investigate the evolution of such subsystems, consisting of ten $10^5 \: \mathrm{M_{\odot}}$ IMBHs at three different concentrations around a $10^9 \: \mathrm{M_{\odot}}$ SMBH. We evolve these systems both in isolation and in the presence of a companion SMBH, using \texttt{MSTAR}, a regularized integration method including RELATIVISTIC effects up to post-Newtonian order 3.5PN. Our analysis focuses on gravitational--wave--driven intermediate--mass--ratio inspirals (heavy IMRIs) and direct plunges. We show that perturbations from a secondary SMBH enhance the number of IMBH direct plunges by more than a factor of two, making them the dominant merger channel. These plunges and IMRIs with a central $10^9 \: \mathrm{M_{\odot}}$ SMBH will contribute to SMBH growth but will likely evade detection with future gravitational-wave interferometers and pulsar timing arrays (PTAs). However, for galaxies with lower--mass SMBHs ($M_\bullet \lesssim 10^8 \:\mathrm{M_{\odot}}$), heavy IMRIs will be detectable with the Laser Interferometer Space Antenna (LISA) and can provide direct observational constraints on the existence of IMBHs, while the more numerous plunges will still remain hidden.
[abstract 30 / 63] (score: 3) - Title: MaNGA AGN dwarf galaxies (MAD) -- IV. Revealing hidden AGN in dwarf galaxies with radio observationsAuthors: I. Flores, M. Mezcua, V. Rodríguez Morales,Comments:Subjects: astro-ph.GACreated: 2025-10-10; Updated: 2025-10-14; Datestamp: 2025-10-14
Low-mass BLACK HOLEs hosted by dwarf galaxies offer valuable insights into galaxy formation and the growth of the massive BLACK HOLEs found in massive galaxies. Their detection as AGN is challenging due to their low luminosity and compact size. This can be circumvented employing multi-wavelength observational strategies, such as combining optical and radio observations, which enables the detection of AGN features that may be hidden in single-wavelength analyses We aim to detect any JET-like emission indicative of the presence of an AGN in a sample of four dwarf galaxies with AGN signatures based on spatially resolved emission line diagnostic diagrams with SDSS MaNGA. Confirming the presence of an AGN will prove IFU spectroscopy to be a resourceful tool for identifying hidden or switched-off AGN. Using VLA radio observations, we image the radio emission of the four dwarf galaxies and derive their integrated radio flux and luminosity. We compare these to that expected from STAR FORMATION processes to determine the origin of the radio emission and probe if it is consistent with the results of the emission line diagnostic diagrams. We find that one out of the four galaxies shows AGN radio emission consistent with the analysis of the MaNGA IFU data. The kinetic JET power of this source is QJET ~ 1e42 erg / s, indicating that dwarf galaxies can host radio JETs as powerful as those of massive RADIO GALAXies. This galaxy exhibits an AGN outflow able to escape the gravitational bound produced by the DARK MATTER halo, along with a decrease in the STAR FORMATION rate of the central region. This suggests the presence of negative feedback from the AGN, which could be suppressing STAR FORMATION. The other three galaxies exhibit regions of radio emission consistent with a stellar origin and overlapping with the star-forming regions found in the IFU spectroscopy.
[abstract 31 / 63] (score: 3) - Title: FLAMINGO: Baryonic effects on the weak lensing scattering transformAuthors: Mariia Marinichenko, Marcel P. van Daalen, Elena Sellentin, Jeger C. Broxterman, Matthieu Schaller, Joop Schaye,Comments: 17 pages; 9 figuresSubjects: astro-ph.COCreated: 2025-10-10; Updated: 2025-10-14; Datestamp: 2025-10-14
The scattering transform is a wavelet-based statistic capable of capturing non-Gaussian features in weak lensing (WL) convergence maps and has been proven to tighten cosmological parameter constraints by accessing information beyond two-point functions. However, its application in cosmological inference requires a clear understanding of its sensitivity to astrophysical systematics, the most significant of which are baryonic effects. These processes substantially modify the matter distribution on small to intermediate scales ($k\gtrsim 0.1\,h\,\mathrm{Mpc}^{-1}$), leaving scale-dependent imprints on the WL convergence field. We systematically examine the impact of baryonic feedback on scattering coefficients using full-sky WL convergence maps with Stage IV survey characteristics, generated from the FLAMINGO simulation suite. These simulations include a broad range of feedback models, calibrated to match the observed cluster gas fraction and galaxy stellar mass function, including systematically shifted variations, and incorporating either thermal or JET-mode AGN feedback. We characterise baryonic effects using a baryonic transfer function defined as the ratio of hydrodynamical to dark-matter-only scattering coefficients. While the coefficients themselves are sensitive to both cosmology and feedback, the transfer function remains largely insensitive to cosmology and shows a strong response to feedback, with suppression reaching up to $10\%$ on scales of $k\gtrsim 0.1\,h\,\mathrm{Mpc}^{-1}$. We also demonstrate that shape noise significantly diminishes the sensitivity of the scattering coefficients to baryonic effects, reducing the suppression from $\sim 2 - 10 \;\%$ to $\sim 1\;\%$, even with 1.5 arcmin Gaussian smoothing. This highlights the need for noise mitigation strategies and high-resolution data in future WL surveys.
[abstract 32 / 63] (score: 3) - Title: Accretion onto Reissner-Nordström naked singularitiesAuthors: Tomasz Krajewski, Włodek Kluźniak,Comments: 29 pages, 49 figuresSubjects: astro-ph.HE gr-qcCreated: 2025-10-11; Updated: 2025-10-14; Datestamp: 2025-10-14
Nearly every galactic core contains a supermassive compact object, hypothesized to be a Kerr BLACK HOLE. It was only with the advent of Event Horizon Telescope observations that the predictions of this hypothesis could be observationally tested for our own Galaxy, and the nearby elliptical M87, on spatial scales comparable to the gravitational radius. At the same time it became possible to test whether alternatives such as naked singularities in general relativity, or similar objects in alternative theories of gravity, are excluded by the data. These and other observational developments renewed interest in non-Kerr spacetime metrics, also in the context of ACTIVE GALACTIC NUCLEi at cosmological distances. Recently, we have shown that accreting naked singularities in the Reissner-Nordström metric of general relativity tend to produce strong outflows. The geometry and origin of these winds is studied here, and their parameter dependence is investigated. To this end we performed numerical GR hydrodynamical simulations of accretion of electrically neutral matter in the Reissner-Nordström metric and discussed the results in the context of analytic predictions of fluid motion in this spacetime.
[abstract 33 / 63] (score: 3) - Title: Possible Quasi-Period Oscillation Signals in the Unique Event of GRB 250702DBE/EP250702a?Authors: Fei-Fan Song, Jirong Mao,Comments: ApJ acceptedSubjects: astro-ph.HECreated: 2025-10-11; Updated: 2025-10-14; Datestamp: 2025-10-14
GRB 250702DBE was time-consequently triggered by GBM onboard the FERMI satellite. It is uncertain which celestial catalog is suitable for this special ultra-long event to belong to. In this paper, we comprehensively investigate the lightcurves obtained by FERMI-GBM detectors. In the energy band of 8-1000 keV, no Quasi-Period Oscillation (QPO) signals are found in the lightcurve of the first burst 250702D, a possible QPO signal of 0.046 Hz corresponding to a period of 21.7 s is found in the lightcurve of the second burst 250702B, and a possible QPO signal of 0.024 Hz corresponding to a period of 41.7 s is found in the lightcurve of last burst 250702E. The significance level of the possible QPO signals is comprehensively examined. In addition, we examine the spectral properties of the sources. In general, a broken power law is suitable for modeling the spectral data from 8 keV to 40 MeV. We qualitatively suggest some kinds of celestial object with the periodic characteristic that might be the progenitors of this unique event.
[abstract 34 / 63] (score: 3) - Title: Investigation for binary characteristics of LS I+61303 with optical POLARIZATIONAuthors: Jiaxin Liu, Haoyu Yuan, Xiangli Lei, Wenlong Xu, Jumpei Takata, Weihua Lei,Comments: 20 pages, 12 figuresSubjects: astro-ph.HECreated: 2025-10-12; Updated: 2025-10-14; Datestamp: 2025-10-14
We investigate the optical linear POLARIZATION caused by Thomson scattering of the stellar radiation for gamma-ray binary \lsi61, which likely contains a young pulsar. Based on the pulsar binary scenario, we model the interaction between the pulsar wind and stellar wind from the massive companion star, which creates a shock. To accurately compute the resulting POLARIZATION of the stellar wind, we develop a method for the Thomson scattering that accounts for the finite size of the companion star. By fitting the optical POLARIZATION data, we constrain the system parameters, such as eccentricity, the momentum ratio of the two winds, and mass-loss rate from the companion star. We find that (i) the predicted eccentricity $e\sim 0.1$ is smaller than the values derived from the radial velocity curve and (ii) the orbital phase of the periastron is $ν_{\rm p}=0.5-0.6$, which is consistent with the previous POLARIZATION study of Kravtsov et al. Additionally, we estimate the mass-loss rate from the companion star and the momentum ratio of two winds as $\dot{M}\sim 2\times 10^{-6}\rm M_{\odot}~{\rm year^{-1}}$ and $η>0.1$, respectively. Assuming that the pulsar wind carries the spin-down energy, the spin-down MAGNETic field of the putative pulsar inferred from these parameters is of the order of $B\sim 10^{14}\mathrm{G}$, which may support the highly-B pulsar or MAGNETar scenario for the compact object of $\rm{LS\ I} +61^{\circ}303$. We also discuss the dispersion measure under the predicted orbital geometry and provide a corresponding interpretation of the pulsed radio signal detected by FAST.
[abstract 35 / 63] (score: 3) - Title: Black Holes in the Shadow: The Missing High-Ionization Lines in the Earliest JWST AGNsAuthors: Greta Zucchi, Xihan Ji, Piero Madau, Roberto Maiolino, Ignas Joudzbalis, Francesco D'Eugenio, Sophia Geris, Yuki Isobe,Comments: 16 pages, 15 figures, submitted to A&ASubjects: astro-ph.GACreated: 2025-10-12; Updated: 2025-10-14; Datestamp: 2025-10-14
Observations with the James Webb Space Telescope (JWST) have uncovered a substantial population of high-redshift, broad-line ACTIVE GALACTIC NUCLEi (AGNs), whose properties challenge standard models of BLACK HOLE growth and AGN emission. We analyze a spectroscopic sample of 34 Type 1 AGNs from the JWST Advanced Deep Survey (JADES) survey, spanning redshifts 1.7 < z < 9, to constrain the physical nature of the accretion flows powering these sources with broad-line diagnostics statistically for the first time. At z > 5, we find a marked suppression of high-ionization emission lines (HeII, CIV, NV) relative to prominent broad Halpha and narrow [OIII] features. This contrast places strong constraints on the shape of the ionizing spectral energy distribution (SED) and on the physical conditions in the broad-line region (BLR). By comparing the observations to photoionization models based on SEDs of BLACK HOLEs accreting at sub-Eddington ratios, we show that standard AGN continua struggle to reproduce the observed broad line ratios and equivalent widths across a wide ionization parameter range. These results suggest the need for modified SEDs -- either intrinsically softened due to super-Eddington accretion or radiative inefficiencies in the innermost disk, or externally filtered by intervening optically thick gas that absorbs or scatters the highest-energy photons before they reach the BLR.
[abstract 36 / 63] (score: 3) - Title: The Relation Between AGN and Host Galaxy Properties in the JWST Era: II. The merger-driven evolution of Seyferts at Cosmic NoonAuthors: Nina Bonaventura, Jianwei Lyu, George H. Rieke, Andrew J. Bunker, Chris J. Willott, Christopher N. A. Willmer,Comments:Subjects: astro-ph.GACreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
In Paper I, we exploited the unsurpassed resolution and depth of JWST/NIRCam imagery to investigate the relationship between AGN and host-galaxy properties in the JWST era, finding a correlation between the level of spatial disturbance (as measured by shape asymmetry, $A_S$) and obscuration ($N_H$). Here in Paper II, we report an expansion of our X-ray and infrared analysis of Seyfert-luminosity host galaxies with four additional metrics to the single-metric morphology analysis of Paper I, as well as new samples of inactive control galaxies. This expanded study of one of the largest and most complete, multi-wavelength samples of AGN detected at $0.6
[abstract 37 / 63] (score: 2) - Title: The Phase Space of Low-Mass Binary Compact Objects from LIGO-Virgo-KAGRA Catalog: Hints on the Chances of Different Formation ScenariosAuthors: Samsuzzaman Afroz, Suvodip Mukherjee,Comments: 13 Pages, 5 figures, Accepted for publication in MNRASSubjects: astro-ph.HE astro-ph.CO gr-qcCreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
Gravitational wave (GW) observations have significantly advanced our understanding of binary compact object (BCO) formation, yet directly linking these observations to specific formation scenarios remains challenging. The BCO phase space provides a robust and data-driven approach to discover the likely formation scenarios of these binaries. In this study, we expand the previously introduced binary BLACK HOLE phase space technique to encompass low-mass compact objects (LMCOs), establishing a novel framework to investigate their diverse formation mechanisms. Applying this approach to selected low-mass events $(\lesssim 5 M_\odot)$ from the GWTC-3 catalog and the recently observed GW230529 event, we show for the first time the phase space demonstration of the LMCOs and find the associated probabilities for different formation scenarios including neutron star, astrophysical BLACK HOLE, or primordial BLACK HOLE. Our analysis includes the astrophysical modelling uncertainties in and how it causes degeneracy between different formation scenarios. In future, with improvements in GW detector sensitivity and with detection of more GW events, the LMCO phase space framework will significantly strengthen our capacity to associate more likely formation scenarios over the other, thereby refining our understanding of compact object formation for both astrophysical and primordial scenarios, and its evolution across the cosmic redshift.
[abstract 38 / 63] (score: 2) - Title: Sagittarius A* near-infrared flares POLARIZATION as a probe of space-time I: Non-rotating exotic compact objectsAuthors: Nicolas Aimar, João Luís Rosa, Hanna Liis Tamm, Paulo Garcia,Comments: 14 pages, 9 figures, 7 tables; submitted to A&A; minor changesSubjects: astro-ph.HE gr-qcCreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
The center of our galaxy hosts Sagittarius~A*, a supermassive compact object of $\sim 4.3\times 10^6$ solar masses, usually associated with a BLACK HOLE. Nevertheless, BLACK HOLEs possess a central singularity, considered unphysical, and an event horizon, which leads to loss of unitarity in a quantum description of the system. To address these theoretical inconsistencies, alternative models, collectively known as exotic compact objects, have been proposed. In this paper, we investigate the potential detectability of signatures associated with non-rotating exotic compact objects within the Sgr~A* polarized flares dataset, as observed through GRAVITY and future instruments. We examine a total of eight distinct metrics, originating from four different categories of static and spherically symmetric compact objects: Black Holes, Boson stars, Fluid spheres, and Gravastars. Our approach involves utilizing a toy model that orbits the compact object in the equatorial plane, at the Schwarzschild-Keplerian velocity. Using simulated astrometric and polarimetric data with present GRAVITY and future GRAVITY+ uncertainties, we fit the datasets across all metrics examined. We evaluated the detectability of the metric for each dataset based on the resulting $χ^2_\mathrm{red}$ and BIC-based Bayes factors. Plunge-through images of ECOs affect POLARIZATION and astrometry. With GRAVITY's present uncertainties, only a compact BOSON-star model is discernible. GRAVITY+'s improved sensitivity allows detection of most exotic compact object models. However, enhancing the astrophysical complexity of the hot spot model diminishes these outcomes. Presently, GRAVITY's uncertainties limit us to detecting just one exotic compact object metric. With GRAVITY+'s enhanced sensitivity, we can expect to uncover additional exotic compact object models and use Sgr~A* as a laboratory for fundamental physics.
[abstract 39 / 63] (score: 2) - Title: A binary model of long period radio transients and white dwarf pulsarsAuthors: Csanád Horváth, Nanda Rea, Natasha Hurley-Walker, Samuel J. McSweeney, Richard A. Perley, Emil Lenc,Comments: 43 pages, 7 figures, submittedSubjects: astro-ph.HE astro-ph.SRCreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
Long-period radio transients (LPTs) represent a recently uncovered class of Galactic radio sources exhibiting minute-to-hour periodicities and highly polarised pulses of second-to-minute duration. Their phenomenology does not fit exactly in any other class, although it might resemble that of radio MAGNETars or white dwarf (WD) radio emitting binary systems. Notably, two LPTs with confirmed multi-wavelength counterparts have been identified as WD -- M dwarf binaries. Meanwhile, systems such as AR Scorpii and J1912-44 exhibit short-period pulsations in hrs-tight orbits, with polarised radio emission proposed to be generated by the interaction of the WD MAGNETosphere with the low-mass companion wind. Here, we investigate the longest-lived LPT known, GPM J1839-10, demonstrating that it has a ~8.75 hr orbital period. We show that its radio pulses can be modelled in the same geometric framework as WD binary pulsars, in which radio emission is triggered when the MAGNETic axis of a rotating WD intersects its companion's wind in the binary orbital plane. We use a 36-year timing baseline to infer the orbital period and binary geometry from radio data alone. The model naturally predicts its intermittent emission and double-pulse structure. Crucially, we show that the beat period between the spin and the orbit matches the observed pulse substructure and polarisation signatures, providing strong support for the model. Applying it to the WD pulsar J1912-44, it successfully reproduces the emission profile and geometry as well. Our results suggest analogous emission-site geometries in these related classes of binary system -- a possibility we extend to the broader LPT / WD pulsar population.
[abstract 40 / 63] (score: 2) - Title: Prospects for DARK MATTER observations in dwarf spheroidal galaxies with the Cherenkov Telescope Array ObservatoryAuthors: K. Abe, S. Abe, J. Abhir, A. Abhishek, F. Acero, A. Acharyya, R. Adam, A. Aguasca-Cabot, I. Agudo, A. Aguirre-Santaella, J. Alfaro, R. Alfaro, C. Alispach, R. Alves Batista, J. -P. Amans, E. Amato, G. Ambrosi, D. Ambrosino, F. Ambrosino, L. Angel, L. A. Antonelli, C. Aramo, C. Arcaro, K. Asano, Y. Ascasibar, L. Augusto Stuani, M. Backes, C. Balazs, M. Balbo, A. Baquero Larriva, V. Barbosa Martins, J. A. Barrio, L. Barrios-Jiménez, C. Bartolini, P. I. Batista, I. Batković, R. Batzofin, J. Becerra González, G. Beck, J. Becker Tjus, W. Benbow, D. Berge, E. Bernardini, J. Bernete, A. Berti, B. Bertucci, V. Beshley, P. Bhattacharjee, S. Bhattacharyya, C. Bigongiari, A. Biland, E. Bissaldi, O. Blanch, J. Blazek, G. Bonnoli, A. Bonollo, Z. Bosnjak, E. Bottacini, M. Böttcher, T. Bringmann, E. Bronzini, R. Brose, G. Brunelli, J. Buces Sáez, M. Bunse, L. Burmistrov, M. Burton, P. G. Calisse, A. Campoy-Ordaz, B. K. Cantlay, G. Capasso, A. Caproni, R. Capuzzo-Dolcetta, P. Caraveo, S. Caroff, R. Carosi, E. Carquin, M. -S. Carrasco, E. Cascone, G. Castignani, A. J. Castro-Tirado, D. Cerasole, M. Cerruti, A. Cerviño Cortínez, P. M. Chadwick, Y. Chai, S. Chaty, A. W. Chen, Y. Chen, M. Chernyakova, A. Chiavassa, G. Chon, J. Chudoba, G. M. Cicciari, A. Cifuentes, C. H. Coimbra Araujo, M. Colapietro, V. Conforti, J. L. Contreras, B. Cornejo, J. Cortina, A. Costa, H. Costantini, G. Cotter, P. Cristofari, O. Cuevas, Z. Curtis-Ginsberg, G. D'Amico, F. D'Ammando, L. David, F. Dazzi, A. De Angelis, M. de Bony de Lavergne, F. De Frondat Laadim, E. M. de Gouveia Dal Pino, B. De Lotto, M. de Naurois, G. De Palma, V. de Souza, R. Del Burgo, L. del Peral, M. V. del Valle, C. Delgado, D. della Volpe, D. Depaoli, T. Di Girolamo, A. Di Piano, F. Di Pierro, R. Di Tria, L. Di Venere, S. Diebold, A. Dinesh, J. Djuvsland, A. Donini, J. Dörner, M. Doro, C. Duangchan, L. Ducci, V. V. Dwarkadas, J. Ebr, C. Eckner, K. Egberts, D. Elsässer, G. Emery, C. Escañuela Nieves, P. Escarate, M. Escobar Godoy, P. Esposito, S. Ettori, D. Falceta-Goncalves, E. Fedorova, S. Fegan, Q. Feng, G. Ferrand, F. Ferrarotto, E. Fiandrini, A. Fiasson, M. Filipovic, V. Fioretti, L. Foffano, G. Fontaine, F. Frías García-Lago, Y. Fukazawa, Y. Fukui, A. Furniss, G. Galanti, G. Galaz, S. Gallozzi, V. Gammaldi, S. García Soto, M. Garczarczyk, C. Gasbarra, D. Gasparrini, M. Gaug, S. Germani, A. Ghalumyan, F. Gianotti, J. G. Giesbrecht Formiga Paiva, N. Giglietto, F. Giordano, R. Giuffrida, J. -F. Glicenstein, J. Glombitza, P. Goldoni, J. M. González, J. Goulart Coelho, T. Gradetzke, J. Granot, L. Gréaux, D. Green, J. G. Green, G. Grolleron, L. M. V. Guedes, O. Gueta, D. Hadasch, P. Hamal, W. Hanlon, S. Hara, V. M. Harvey, T. Hassan, K. Hayashi, B. Heß, L. Heckmann, M. Heller, N. Hiroshima, B. Hnatyk, R. Hnatyk, D. Hoffmann, W. Hofmann, D. Horan, P. Horvath, D. Hrupec, S. Hussain, M. Iarlori, T. Inada, F. Incardona, S. Inoue, Y. Inoue, F. Iocco, A. Iuliano, Jahanvi, M. Jamrozy, P. Janecek, F. Jankowsky, C. Jarnot, I. Jaroschewski, P. Jean, I. Jiménez Martínez, W. Jin, J. Jurysek, O. Kalekin, V. Karas, J. Kataoka, S. Kaufmann, D. Kazanas, T. Keita, D. Kerszberg, D. B. Kieda, R. Kissmann, W. Kluźniak, K. Kohri, D. Kolar, N. Komin, P. Kornecki, G. Kowal, H. Kubo, J. Kushida, A. La Barbera, N. La Palombara, B. Lacave, M. Láinez, A. Lamastra, J. Lapington, S. Lazarević, J. -P. Lenain, F. Leone, E. Leonora, Y. Li, E. Lindfors, M. Linhoff, S. Lombardi, F. Longo, R. López-Coto, M. López-Moya, A. López-Oramas, S. Loporchio, J. Lozano Bahilo, H. Luciani, P. L. Luque-Escamilla, E. Lyard, O. Macias, J. Mackey, P. Majumdar, D. Malyshev, D. Mandat, S. Mangano, G. Manicò, A. Marchetti, M. Mariotti, I. Márquez, G. Marsella, D. Martín Domínguez, G. A. Martínez, M. Martínez, O. Martinez, D. Mazin, A. J. T. S. Mello, J. Mé ndez Gallego, S. Menon, S. Mereghetti, D. M. -A. Meyer, M. Meyer, D. Miceli, M. Miceli, M. Michailidis, T. Miener, J. M. Miranda, A. Mitchell, M. Molero, C. Molfese, M. Molina Delicado, E. Molina, T. Montaruli, A. Moralejo, A. Moreno Ramos, A. Morselli, E. Moulin, V. Moya Zamanillo, K. Munari, T. Murach, A. Muraczewski, H. Muraishi, T. Nakamori, R. Nemmen, J. P. Neto, J. Niemiec, D. Nieto, M. Nievas Rosillo, M. Nikołajuk, K. Nishijima, K. Noda, D. Nosek, V. Novotny, S. Nozaki, A. Okumura, J. -F. Olive, R. A. Ong, R. Orito, M. Orlandini, E. Orlando, S. Orlando, J. Otero-Santos, I. Oya, M. Ozlati Moghadam, A. Pagliaro, M. Palatiello, A. Pandey, G. Panebianco, D. Paneque, F. R. Pantaleo, R. Paoletti, J. M. Paredes, N. Parmiggiani, B. Patricelli, M. Pech, M. Pecimotika, M. Peresano, A. Pérez Aguilera, J. Pé rez-Romero, G. Peron, F. Perrotta, M. Persic, O. Petruk, F. Pfeifle, E. Pietropaolo, L. Pinchbeck, F. Pintore, G. Pirola, C. Pittori, F. Podobnik, M. Pohl, V. Poireau, V. Pollet, G. Ponti, C. Pozo González, E. Prandini, G. Principe, M. Prouza, E. Pueschel, G. Pühlhofer, M. L. Pumo, A. Quirrenbach, S. Rainò, R. Rando, S. Recchia, M. Regeard, A. Reimer, O. Reimer, I. Reis, A. Reisenegger, W. Rhode, M. Ribó, C. Ricci, T. Richtler, J. Rico, F. Rieger, L. Riitano, C. Ríos, V. Rizi, E. Roache, G. Rodríguez-Fernández, M. D. Rodríguez Frías, J. J. Rodríguez-Vázquez, P. Romano, G. Romeo, J. Rosado, A. Rosales de Leon, G. Rowell, A. Roy, B. Rudak, A. Ruina, E. Ruiz-Velasco, F. S. Queiroz, I. Sadeh, L. Saha, H. Salzmann, M. Sánchez-Conde, P. Sangiorgi, H. Sano, R. Santos-Lima, V. Sapienza, S. Sarkar, F. G. Saturni, S. Savarese, V. Savchenko, A. Scherer, F. Schiavone, P. Schipani, F. Schussler, D. Sengupta, O. Sergijenko, V. Sguera, H. Siejkowski, G. Silvestri, A. Simongini, C. Siqueira, V. Sliusar, I. Sofia, H. Sol, D. Spiga, S. Spinello, A. Stamerra, S. Stanič, T. Starecki, R. Starling, T. Stolarczyk, Y. Suda, H. Tajima, M. Takahashi, R. Takeishi, S. J. Tanaka, L. A. Tejedor, M. Teshima, V. Testa, W. W. Tian, L. Tibaldo, O. Tibolla, S. J. Tingay, F. Tombesi, D. Tonev, F. Torradeflot, D. F. Torres, N. Tothill, A. Tramacere, P. Travnicek, A. Trois, S. Truzzi, A. Tutone, M. Vacula, C. van Eldik, J. Vandenbroucke, V. Vassiliev, M. Vázquez Acosta, M. Vecchi, S. Ventura, S. Vercellone, G. Verna, I. Viale, A. Viana, N. Viaux, A. Vigliano, J. Vignatti, C. F. Vigorito, E. Visentin, V. Vitale, V. Voitsekhovskyi, S. Vorobiov, G. Voutsinas, R. Walter, M. Wechakama, M. White, A. Wierzcholska, F. Wohlleben, F. Xotta, R. Yamazaki, Y. Yao, T. Yoshikoshi, D. Zavrtanik, M. Zavrtanik, A. Zech, W. Zhang, V. I. Zhdanov, M. Živec, J. Zuriaga-Puig,Comments: 40 pages, 19 figures, 10 tables, accepted for publication on MNRASSubjects: astro-ph.HE astro-ph.GA astro-ph.IMCreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
The dwarf spheroidal galaxies (dSphs) orbiting the Milky Way are widely regarded as systems supported by velocity dispersion against self-gravity, and as prime targets for the search for indirect DARK MATTER (DM) signatures in the GeV-to-TeV $γ$-ray range owing to their lack of astrophysical $γ$-ray background. We present forecasts of the sensitivity of the forthcoming Cherenkov Telescope Array Observatory (CTAO) to annihilating or decaying DM signals in these targets. An original selection of candidates is performed from the current catalogue of known objects, including both classical and ultra-faint dSphs. For each, the expected DM content is derived using the most comprehensive photometric and spectroscopic data available, within a consistent framework of analysis. This approach enables the derivation of novel astrophysical factor profiles for indirect DM searches, which are compared with results from the literature. From an initial sample of 64 dSphs, eight promising targets are identified -- Draco I, Coma Berenices, Ursa Major II, Ursa Minor and Willman 1 in the North, Reticulum II, Sculptor and Sagittarius II in the South -- for which different DM density models yield consistent expectations, leading to robust predictions. CTAO is expected to provide the strongest limits above $\sim$10 TeV, reaching velocity-averaged annihilation cross sections of $\sim$5$\times$10$^{-25}$ cm$^3$ s$^{-1}$ and decay lifetimes up to $\sim$10$^{26}$ s for combined limits. The dominant uncertainties arise from the imprecise determination of the DM content, particularly for ultra-faint dSphs. Observation strategies are proposed that optimise either deep exposures of the best candidates or diversified target selections.
[abstract 41 / 63] (score: 2) - Title: The orbital period and inclination of the neutron star X-ray transient MAXI J1807+132Authors: E. A. Saavedra, T. Muñoz-Darias, M. A. P. Torres, I. V. Yanes-Rizo, M. Armas Padilla, A. Álvarez-Hernández, J. Casares, D. Mata Sánchez, S. K. Rout, S. Navarro,Comments: Published in Astronomy & AstrophysicsSubjects: astro-ph.HECreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
The neutron star X-ray transient MAXI J1807+132 has undergone outbursts in 2017, 2019, and 2023. We conducted an $R$-band time series photometry campaign using the Isaac Newton Telescope during the 2022 quiescent state. We detected a periodic variation in the light curve, consistent with ellipsoidal modulation, which allowed us to determine an orbital period of $P_{\rm orb} = 4.258 \pm 0.008$ hr. By modelling the light curve, we obtained a binary inclination of $ i = 72\pm5 \, °$ and a mass ratio $q = 0.24^{+0.19}_{-0.14}$ ($68$ per cent confidence level). Furthermore, our analysis supports an early M-dwarf companion that contributes between 30 and 50 per cent to the total flux in the $R$-band. We extend the previously established absolute magnitude versus orbital period correlation for BLACK HOLE X-ray transients to neutron star systems. We applied the correlation to MAXI J1807+132, estimating its distance as $6.3 \pm 0.7$ kpc and its height above the Galactic plane to be $1.6 \pm 0.2$ kpc.
[abstract 42 / 63] (score: 2) - Title: Broadband interferometry-based searches for photon-axion conversion in vacuumAuthors: Josep Maria Batllori, Dieter Horns, Marios Maroudas,Comments: 13 pages, 4 figures, 2 tablesSubjects: hep-exCreated: 2025-10-11; Updated: 2025-10-14; Datestamp: 2025-10-14
A novel experiment is introduced to detect photon-axion conversion independent of the dark-matter hypothesis in a broad mass-range called WISP Interferometer (WINTER). The setup consists of a free-space Mach-Zehnder-type interferometer incorporating an external MAGNETic field and vacuum in one of the arms, where photon-axion mixing occurs via the Primakoff effect and is detected through changes in amplitude. The expected axion-induced signal is then modulated by POLARIZATION changes. The experiment is designed to integrate a Fabry-Pérot cavity with a finesse of $10^{5}$ that will be operated in a vacuum environment, significantly enhancing the sensitivity. The setup is sensitive to photon-axion coupling strengths values $g_{aγγ}\gtrsim 5.5\times10^{-15}$ $\text{GeV}^{-1}$ for axion masses up to 84.8 $μ$eV
[abstract 43 / 63] (score: 2) - Title: Long Living Hot and Dense Plasma from Relativistic Laser-Nanowire Array InteractionAuthors: Ehsan Eftekhari-Zadeh, Mikhail Gyrdymov, Parysatis Tavana, Robert Loetzsch, Ingo Uschmann, Thomas Siefke, Thomas Käsebier, Uwe Zeitner, Adriana Szeghalmi, Alexander Pukhov, Dmitri Serebryakov, Evgeni Nerush, Igor Kostyukov, Olga Rosmej, Christian Spielmann, Daniil Kartashov,Comments:Subjects: physics.plasm-ph hep-ex physics.opticsCreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
Long-living, hot and dense plasmas generated by ultra-intense LASER beams are of critical importance for LASER-driven nuclear physics, bright hard X-ray sources, and laboratory astrophysics. We report the experimental observation of plasmas with nanosecond-scale lifetimes, near-solid density, and keV-level temperatures, produced by irradiating periodic arrays of composite nanowires with ultra-high contrast, RELATIVISTICally intense femtosecond LASER pulses. Jet-like plasma structures extending up to 1~mm from the nanowire surface were observed, emitting K-shell radiation from He-like Ti$^{20+}$ ions. High-resolution X-ray spectra were analyzed using 3D Particle-in-Cell (PIC) simulations of the LASER-plasma interaction combined with collisional--radiative modeling (FLYCHK). The results indicate that the JETs consist of plasma with densities of $10^{20}$-$10^{22}$ cm$^{-3}$ and keV-scale temperatures, persisting for several nanoseconds. We attribute the formation of these JETs to the generation of kiloTesla-scale global MAGNETic fields during the LASER interaction, as predicted by PIC simulations. These fields may drive long-timescale current instabilities that sustain MAGNETic fields of several hundred tesla, sufficient to confine hot, dense plasma over nanosecond durations.
[abstract 44 / 63] (score: 2) - Title: Time-Dilation Methods for Extreme Multiscale Timestepping ProblemsAuthors: Philip F. Hopkins, Elias R. Most,Comments: 15 pages, 4 figures, 3 appendices. Submitted to the Open Journal of Astrophysics. Comments welcome. Example implementation in the public GIZMO code at: http://www.tapir.caltech.edu/~phopkins/Site/GIZMO.htmlSubjects: astro-ph.IM astro-ph.GA astro-ph.HE astro-ph.SR physics.comp-phCreated: 2025-10-10; Updated: 2025-10-14; Datestamp: 2025-10-14
Many astrophysical simulations involve extreme dynamic range of timescales around 'special points' in the domain (e.g. BLACK HOLEs, stars, planets, disks, galaxies, shocks, mixing interfaces), where processes on small scales couple strongly to those on large scales. Adaptive resolution, multi-physics, and hybrid numerical methods have enabled tremendous progress on the spatial, physics, and numerical challenges involved. But often the limiter for following the long timescales of global evolution is the extremely short numerical timestep required in some subdomains (which leads to their dominating simulation costs). Recently several approaches have been developed for tackling this in problems where the short timescale solution is sampled and then projected as an effective subgrid model over longer timescales (e.g. 'zooming in and out'). We generalize these to a family of models where time evolution is modulated by a variable but continuous in space-and-time dilation/stretch factor $a({\bf x},\,t)$. This extends previous well-studied approaches (including reduced-speed-of-light and binary orbital dynamics methods), and ensures that the system comes to correct local steady-state solutions, and derive criteria that the dilation factor/timesteps/resolution must obey to ensure good behavior. We present a variety of generalizations to different physics or coupling scales. Compared to previous approaches, this method makes it possible to avoid imprinting arbitrary scales where there is no clear scale-separation, and couples well to Lagrangian or Eulerian methods. It is flexible and easily-implemented and we demonstrate its validity (and limitations) in test problems. We discuss the relationship between these methods and physical time dilation in GRMHD. We demonstrate how this can be used to obtain effective speedup factors exceeding $\gtrsim 10^{4}$ in multiphysics simulations.
[abstract 45 / 63] (score: 2) - Title: GMIMS-DRAGONS: A Faraday Depth Survey of the Northern Sky Covering 350 to 1030 MHzAuthors: Anna Ordog, Rebecca A. Booth, T. L. Landecker, Ettore Carretti, Alex S. Hill, Jo-Anne C. Brown, Artem Davydov, Leonardo Moutinho Caffarello, Luca B. Galler, Jonas Flygare, Jennifer L. West, A. G. Willis, Mehrnoosh Tahani, G. J. Hovey, Dustin Lagoy, Stephen Harrison, Mike Smith, Charl Baard, Rob H. Messing, D. A. Del Rizzo, Benoit Robert, Timothy Robishaw, John M. Dickey, George Morgan, Ian R. Kennedy, Marijke Haverkorn, Andrea Bracco, John Conway,Comments: Submitted to Astrophysical Journal Supplement (ApJS)Subjects: astro-ph.IMCreated: 2025-10-10; Updated: 2025-10-14; Datestamp: 2025-10-14
Polarized SYNCHROTRON emission at meter to centimeter wavelengths provides an effective tracer of the Galactic MAGNETic field. Calculating Faraday depth, the most useful parameter for mapping the line-of-sight MAGNETic field, requires observations covering wide frequency bands with many channels. As part of the Global Magneto-Ionic Medium Survey we have observed polarized emission spanning 350-1030 MHz over the Northern sky, in the declination range ${-20^{\circ}}\leqδ\leq{90^{\circ}}$. We used the 15 m telescope at the Dominion Radio Astrophysical Observatory (DRAO), equipped to receive orthogonal circular POLARIZATIONs, with the Onsala Space Observatory band-1 feed developed for the Square Kilometre Array. Angular resolution varies across the band from $1.3^{\circ}$ to $3.6^{\circ}$. A digital spectrometer provided 42 kHz frequency resolution. Data were taken with the telescope moving rapidly in azimuth and are absolutely calibrated in intensity. Approximately 20% of the band was obscured by radio-frequency interference. Resolution in Faraday depth is $\sim6$ rad m$^{-2}$, and features as wide as $\sim38$ rad m$^{-2}$ are represented. The median sensitivity of the Faraday depth cube is 11 mK. Approximately 55% of sight-lines in this survey show Faraday complexity. This dataset, called ``DRAO GMIMS of the Northern Sky'' (DRAGONS), is the first to probe Faraday depth of the Northern sky in its frequency range and will support many scientific investigations. The data will be used to calibrate surveys with higher angular resolution, particularly Galactic foreground maps from the Canadian Hydrogen Intensity Mapping Experiment, and to provide information on large structures for aperture-synthesis telescopes, particularly the DRAO Synthesis Telescope. The data are available through the Canadian Astronomy Data Centre.
[abstract 46 / 63] (score: 2) - Title: GATOS IX: A Detailed Assessment and Treatment of Emission Line Contamination in JWST/MIRI Images of Nearby Seyfert GalaxiesAuthors: Steph Campbell, David J. Rosario, Houda Haidar, Enrique López Rodríguez, Dan Delaney, Erin Hicks, Ismael García-Bernete, Miguel Pereira-Santaella, Almudena Alonso Herrero, Anelise Audibert, Enrica Bellocchi, Donaji Esparza-Arredondo, Santiago García-Burillo, Omaira González Martín, Sebastian F. Hönig, Nancy A. Levenson, Chris Packham, Cristina Ramos Almeida, Dimitra Rigopoulou, Lulu Zhang,Comments: 20 pages (3 appendix), 15 figures (8 appendix). Accepted in MNRASSubjects: astro-ph.GA astro-ph.HECreated: 2025-10-10; Updated: 2025-10-14; Datestamp: 2025-10-14
Broadband mid-infrared (MIR) imaging with high spatial resolution is useful to study extended dust structures in the circumnuclear regions of nearby AGN. However, broadband imaging filters cannot distinguish dust continuum emission from emission lines, and so accounting for the emission line contamination becomes crucial in studying extended dust in these environments.This paper uses Cycle 1 MIR imaging from JWST/MIRI and spectroscopy from JWST/MRS for 11 local Seyfert galaxies, as part of the Galactic Activity, Torus and Outflow Survey (GATOS). Three of the objects (NGC 3081, NGC 5728, and NGC 7172) exist in both datasets, allowing direct measurement of the line emission using the spectroscopy for these objects. We find that extended MIR emission persists on scales of 100s of parsecs after the removal of contamination from emission lines. Further, the line contamination levels vary greatly between objects (from 5% to 30% in the F1000W filter), and across filters, so cannot be generalised across a sample and must be carefully treated for each object and band. We also test methods to estimate the line contamination when only MRS spectroscopy or MIRI imaging is available, using pre-JWST ancillary data. We find that these methods estimate the contamination within 10 percentage points. This paper serves as a useful guide for methods to quantify and mitigate for emission line contamination in MIRI broadband imaging
[abstract 47 / 63] (score: 2) - Title: Chandra/HETG and NUSTAR Observations of V750 Ara, a $γ\,$Cas-type StarAuthors: David P. Huenemoerder, Sean J. Gunderson, Richard Ignace, Joy S. Nichols, A. M. T. Pollock, Pragati Pradhan, Norbert S. Schulz, Dustin K. Swarm, José M. Torrejón,Comments: Accepted for publication in the Astrophysical Journal. 9 pages, 3 figures, 3 tablesSubjects: astro-ph.SRCreated: 2025-10-11; Updated: 2025-10-14; Datestamp: 2025-10-14
We present 197 ks HETG and 95 ks NUSTAR spectra of the $γ\,$Cas-type object V750 Ara. The high-resolution X-ray spectra show that the target is similar to other objects of this class. Data are interpreted under the assumption that the X-rays come from an accreting white dwarf, and our analysis implies an accretion rate of about $3\times10^{-11}M_\odot\mathrm{yr}^{-1}$. Emission lines are weak, and predominantly from hydrogen-like ions: Mg XII, Si XIV, and S XVI. H-like and He-like Fe are both present, but Fe K$α$ fluorescence is weak, being significantly detected only in the NUSTAR spectrum, but was not obviously detected in the HETG dispersed or zeroth-order spectra. The flux was variable above a level expected by Poisson statistics. There were no significant changes in the spectral hardness, though we are limited by lack of soft signal below 1 keV. Emission lines of Mg and Si were strong enough to measure velocity offsets and widths which were found to be marginally inconsistent. The H-like Mg line is consistent with instrumental broadening only, but shows a 300 km/s blueshift. He-like Mg and H-like Si lines have no significant shift in velocity but are broadened by about 1000 km/s. This suggests either different physical origins or velocity structure differing with plasma temperature.
[abstract 48 / 63] (score: 2) - Title: Comprehensive X-ray Spectral-timing Analysis of GRS 1915+105 Based on Insight-HXMT ObservationsAuthors: Xiao Chen, Weiping Liu, Wei Wang,Comments: 12 pages, 12 figures, accepted by MNRASSubjects: astro-ph.HECreated: 2025-10-11; Updated: 2025-10-14; Datestamp: 2025-10-14
GRS 1915+105 has been well studied since its discovery, and is well-known for its complex light curve variability. Using the full currently available Insight-HXMT dataset from July 2017 to June 2023, we make a comprehensive spectral-timing analysis of this source and report four main findings. First, we uncover a QPO frequency rising branch between MJD 58206 and 58230, where the centroid frequency increases from $\sim$2 Hz to $\sim$6 Hz, consistent with a spectral state transition from the hard to intermediate state. This rising branch completes the full QPO frequency evolution cycle when combined with the subsequent frequency decay phase, and had been missed in prior NICER and Insight-HXMT studies. Second, we identify a previously unreported Flare 3 during the obscured state, which shows distinct spectral and timing properties compared to the earlier flares. Third, we detect sub-Hz QPOs (<1 Hz) in all three flares, specifically at $\sim$0.01 Hz in Flare 1 and $\sim$0.2 Hz in both Flares 2 and 3. In particular, the weak $\sim$0.2 Hz signals observed in Flare 3 indicate ongoing coronal activity despite strong obscuration. Finally, a comparison between QPOs above and below 1 Hz suggests distinct origins, with the former likely arising from Lense-Thirring precession of the inner hot flow and the latter from MAGNETic perturbations driving a failed disk wind. These findings offer new insights into the unique accretion geometry and variability behaviors of GRS 1915+105.
[abstract 49 / 63] (score: 2) - Title: New Evidence for Extragalactic Einstein Probe Transients associated with Long Gamma-ray BurstsAuthors: Qin-Mei Li, Qi-Bin Sun, Sheng-Bang Qian, Fu-Xing Li,Comments: 8 pages,3 figures and 1 tableSubjects: astro-ph.HE hep-phCreated: 2025-10-11; Updated: 2025-10-14; Datestamp: 2025-10-14
The origin of extragalactic fast X-ray transients (EFXTs) remains a fundamental open question in high-energy astrophysics. The Einstein Probe (EP) mission provides a transformative opportunity to investigate their nature. While mounting observations of EP-discovered EFXTs (EP-EFXTs) suggest a possible connection to long GAMMA-RAY BURSTs (lGRBs), an in-depth comparative analysis between them remains lacking. Here, we present a comparative analysis of their cosmic formation histories, revealing that EP-EFXTs and lGRBs share a similar evolutionary trend-showing a marked decline at $z<1.0$ and a plateau beyond $1.0
[abstract 50 / 63] (score: 2) - Title: Microlensing of non-singular BLACK HOLEs at finite size: a ray tracing approachAuthors: Jens Boos, Hao Hu,Comments: 21 pages, 14 figures, comments welcomeSubjects: gr-qc astro-ph.CO astro-ph.GACreated: 2025-10-11; Updated: 2025-10-14; Datestamp: 2025-10-14
We study the gravitational microlensing of various static and spherically symmetric non-singular BLACK HOLEs (and horizonless, non-singular compact objects of similar size). For pointlike sources we extend the parametrized post-Newtonian lensing framework to fourth order, whereas for extended sources we develop a ray tracing approach via a simple radiative transfer model. Modelling non-RELATIVISTIC proper motion of the lens in front of a background star we record the apparent brightness as a function of time, resulting in a photometric lightcurve. Taking the star radius to smaller values, our numerical results approach the theoretical predictions for point-like sources. Compared to the Schwarzschild metric in an otherwise unmodified lensing geometry, we find that non-singular BLACK HOLE models (and their horizonless, non-singular counterparts) at finite size tend to feature larger magnifications in microlensing lightcurves, contrary to the point-source prediction.
[abstract 51 / 63] (score: 2) - Title: Water Maser Disk and a Supermassive Black Hole at the Nucleus of the Active Galaxy NGC 7738Authors: Rinka Ito, Yusuke Miyamoto, Naomasa Nakai, Aya Yamauchi, Yuichi Terashima,Comments: 11 pages, 8 figuresSubjects: astro-ph.GACreated: 2025-10-11; Updated: 2025-10-14; Datestamp: 2025-10-14
We present the results of very long baseline interferometry (VLBI) observations of water vapor masers in the nucleus of the LINER galaxy NGC 7738. The red- and blue-shifted and newly detected systemic maser features show an almost edge-on disk located at a distance of ${0.031}\mbox{-}{0.222}$ pc from the galactic center and rotating with a velocity of $324\mbox{-}454$ km s$^{-1}$ . The velocity field of the disk indicates sub-Keplerian rotation, suggesting a non-negligible disk mass. The Mestel disk model reveals the central and disk masses to be $(1.2 \pm 0.4) \times 10^6$ $M_{\odot}$ and $(4.7 \pm 1.5) \times10^6$ $M_{\odot}$, respectively. The mean volume density within the inner radius of the disk [$(1.2 \pm 0.5) \times 10^{10}$ $M_{\odot}$ $\mathrm{pc^{-3}}$] strongly suggests the existence of a supermassive BLACK HOLE at the center.
[abstract 52 / 63] (score: 2) - Title: Thermal Deformations in Super-Eddington Magnetized Neutron Stars: Implications for Continuous Gravitational-Wave DetectabilityAuthors: Hong-Bo Li, Yacheng Kang, Ren-Xin Xu,Comments: 11 pages, 3 figures, and 1 tableSubjects: astro-ph.HE gr-qcCreated: 2025-10-12; Updated: 2025-10-14; Datestamp: 2025-10-14
Rapidly rotating neutron stars (NSs) are promising targets for continuous gravitational-wave (CGW) searches with current and next-generation ground-based GW detectors. In this Letter, we present the first study of thermal deformations in super-Eddington MAGNETized NSs with column accretion, where MAGNETic fields induce anisotropic heat conduction that leads to crustal temperature asymmetries. We compute the resulting mass quadrupole moments and estimate the associated CGW strain amplitudes. Our results show that Galactic MAGNETized NSs undergoing super-Eddington column accretion can emit detectable CGWs in upcoming observatories. Assuming a 2-yr coherent integration, the Einstein Telescope and Cosmic Explorer could detect such CGW signals from rapidly spinning NSs with spin periods $P \lesssim 20\,\rm ms$, while the LIGO O5 run may detect systems with $P \lesssim 6 \,{\rm ms}$. These findings suggest that super-Eddington MAGNETized NSs could represent a new class of CGW sources, providing a unique opportunity to probe the NS crust and bridge accretion physics with GW astronomy.
[abstract 53 / 63] (score: 2) - Title: Multimodal axion emissions from Abelian-Higgs cosmic stringsAuthors: Naoya Kitajima, Michiru Uwabo-Niibo,Comments: 6 pages, 5 figuresSubjects: hep-ph astro-ph.CO hep-thCreated: 2025-10-12; Updated: 2025-10-14; Datestamp: 2025-10-14
We show that axions can be produced from Abelian-Higgs cosmic strings due to the axion-gauge coupling. The strong MAGNETic field is confined in the string, and the electric field is induced around the moving string, allowing axion productions from the dynamics of cosmic strings. Our numerical analysis on the string collision shows that a sizable number of axions can be produced at the RECONNECTion, and further emissions occur from moving kinks afterward. Furthermore, the simulation on the string network shows multimodal axion emissions in the sense that axions are produced in both the low-energy and high-energy regimes. The former can contribute to the cold DARK MATTER and the latter can be regarded as dark radiation. We found that the axion with sub-GeV mass can explain the current relic DARK MATTER abundance and simultaneously predicts a sizable amount of dark radiation which can be probed by future observations.
[abstract 54 / 63] (score: 2) - Title: Mass-Centered GCM Framework in Perturbations of Kerr(-Newman)Authors: Allen Juntao Fang, Elena Giorgi, Jingbo Wan,Comments:Subjects: gr-qc math.APCreated: 2025-10-12; Updated: 2025-10-14; Datestamp: 2025-10-14
The nonlinear stability problem for BLACK HOLE solutions of the Einstein equations critically depends on choosing an appropriate geometric gauge. In the vacuum setting, the use of Generally Covariant Modulated (GCM) spheres and hypersurfaces has played a central role in the proof of stability for slowly rotating Kerr spacetime. In this work, we develop an alternative GCM framework, that we call mass-centered, designed to overcome the breakdown of the standard GCM construction in the charged case, where electroMAGNETic-gravitational coupling destroys the exceptional behavior of the $\ell=1$ mode of the center-of-mass quantity used in the vacuum analysis. This construction is aimed at the nonlinear stability of Reissner-Nordström and Kerr-Newman spacetimes. Our approach replaces transport-based control of the center-of-mass quantity with a sphere-wise vanishing condition on a renormalized $\ell=1$ mode, yielding mass-centered GCM hypersurfaces with modified gauge constraints. The resulting elliptic-transport system remains determined once an $\ell=1$ basis is fixed via effective uniformization and provides an alternative construction in vacuum in the uncharged limit.
[abstract 55 / 63] (score: 2) - Title: Einstein-Maxwell Equations on Mass-Centered GCM HypersurfacesAuthors: Allen Juntao Fang, Elena Giorgi, Jingbo Wan,Comments:Subjects: gr-qc math.APCreated: 2025-10-12; Updated: 2025-10-14; Datestamp: 2025-10-14
The resolution of the nonlinear stability of BLACK HOLEs as solutions to the Einstein equations relies crucially on imposing the right geometric gauge conditions. In the vacuum case, the use of Generally Covariant Modulated (GCM) spheres and hypersurfaces has been successful in the proof of stability for slowly rotating Kerr spacetime. For the charged setting, our companion paper introduced an alternative mass-centered GCM framework, adapted to the additional difficulties of the Einstein-Maxwell system. In this work, we solve the Einstein-Maxwell equations on such a mass-centered spacelike GCM hypersurface, which is equivalent to solving the constraint equations there. We control all geometric quantities of the solution in terms of some seed data, corresponding to the gauge-invariant fields describing coupled gravitational-electroMAGNETic radiation in perturbations of Reissner-Nordström or Kerr-Newman, first identified by the second author and expected to be governed by favorable hyperbolic equations. This provides the first step toward controlling gauge-dependent quantities in the nonlinear stability analysis of the Reissner-Nordström and Kerr-Newman families.
[abstract 56 / 63] (score: 2) - Title: Co-evolution of Nuclear Star Clusters and Massive Black Holes: Extreme Mass-Ratio InspiralsAuthors: Fupeng Zhang, Pau Amaro Seoane,Comments: 30 pages, 15 figures, submitted to Astrophysical JournalSubjects: astro-ph.GA astro-ph.HECreated: 2025-10-12; Updated: 2025-10-14; Datestamp: 2025-10-14
We explore extreme mass-ratio inspirals (EMRIs) in the co-evolution of massive BLACK HOLEs (MBHs) and nuclear star clusters (NSCs), which host diverse stellar populations across a wide range of masses. The dynamics are simulated self-consistently with GNC, which we have updated to incorporate gravitational wave orbital decay, the loss cone of a spinning MBH, and stellar evolution. Over $12$ Gyr, we investigate the evolution of the NSC with a mass-growing MBH, as well as the EMRIs of stellar BLACK HOLEs, neutron stars, white dwarfs, brown dwarfs (BDs), and low-mass main-sequence stars (MSs), along with tidal disruption events (TDEs) involving MSs, BDs, and post-MSs. The mass growth of the MBH contributed by TDEs is typically $\sim 10^7\,M_{\odot}$, $\sim 10^6\,M_{\odot}$, and $\sim 5\times10^4\,M_{\odot}$ for massive, Milky-Way-like, and smaller NSCs, respectively. Between $40\%$ and $70\%$ of the stellar mass is lost during stellar evolution, which dominates the mass growth of the MBH if a significant fraction of the lost mass is accreted. The evolution of EMRI rates is generally affected by the cluster's size expansion or contraction, stellar population evolution, MBH mass growth, and the stellar initial mass function. The EMRI rates for compact objects peak at early epochs ($\lesssim 1$ Gyr) and then gradually decline over cosmic time. LISA-band ($0.1$ mHz) EMRIs involving compact objects around Milky-Way-like MBHs tend to have high eccentricities, while those around spinning MBHs preferentially occupy low-inclination (prograde) orbits. In contrast, MS- and BD-EMRIs usually have eccentricity and inclination distributions that are distinct from those of compact objects.
[abstract 57 / 63] (score: 2) - Title: Resonant W and Z Boson Production in FSRQ Jets: Implications for Diffuse Neutrino FluxesAuthors: J. -H. Ha, I. Alikhanov,Comments: 7 figures, 1 table, submitted to JCAPSubjects: astro-ph.HE hep-phCreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
Blazars, particularly Flat Spectrum Radio Quasars (FSRQs), are well-known for their ability to accelerate a substantial population of electrons and positrons, as inferred from multiwavelength radiation observations. Therefore, these astrophysical objects are promising candidates for studying high-energy electron--positron interactions, such as the production of $W^{\pm}$ and $Z$ BOSONs. In this work, we explore the implications of electron--positron annihilation processes in the JET environments of FSRQs, focusing on the resonant production of electroweak BOSONs and their potential contribution to the diffuse neutrino flux. By modeling the electron distribution in the JET of the FSRQ 3C~279 during a flaring state, we calculate the reaction rates for $W^{\pm}$ and $Z$ BOSONs and estimate the resulting diffuse fluxes from the cosmological population of FSRQs.We incorporate the FSRQ luminosity function and its redshift evolution to account for the population distribution across cosmic time, finding that the differential flux contribution exhibits a pronounced peak at redshift $z \sim 1$. While the expected fluxes remain well below the detection thresholds of current neutrino observatories such as IceCube, KM3NeT, or Baikal-GVD, the expected flux from the $Z$ BOSON production could account for approximately $10^{-3}$ of the total diffuse astrophysical neutrino flux. These results provide a theoretical benchmark for the role of Standard Model electroweak processes in extreme astrophysical environments and emphasize the interplay between particle physics and astrophysics, illustrating that even rare high-energy interactions can leave a subtle but quantifiable imprint on the diffuse astrophysical neutrinos.
[abstract 58 / 63] (score: 2) - Title: Tuning Layer Orbital Hall Effect via Spin Rotation in FerroMAGNETic Transition Metal DichalcogenidesAuthors: Shilei Ji, Jianping Yang, Li Gao, Xing'ao Li,Comments:Subjects: physics.comp-phCreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
Orbitronics, which leverages the angular momentum of atomic orbitals for information transmission, provides a novel strategy to overcome the limitations of electronic devices. Unlike electron spin, orbital angular momentum (OAM) is strongly influenced by crystal field effects and band topology, making its orientation difficult to manipulate with external fields. In this work, by using first principle calculations, we investigate quantum anomalous Hall insulators (QAHIs) as a model system to study the layer orbital Hall effect (OHE). Due to band inversion, only one valley remains orbital POLARIZATION, and thus the OHE originates from a single valley. Based on stacking symmetry analysis, we investigated both AA and AB stacking configurations, which possess mirror and inversion symmetries, respectively. The excitation of OAM exhibits valley selectivity, determined jointly by valley POLARIZATION and orbital POLARIZATION. In AA stacking, the absence of inversion center gives rise to intrinsic orbital POLARIZATION, leading to OAM excitations from different valleys in the two layers. In contrast, AB stacking is protected by inversion symmetry, which enforces valley POLARIZATION and
[abstract 59 / 63] (score: 2) - Title: Survival of the accretion disk in LMC Recurrent Nova 1968-12a: UV--X-ray case study of the 2024 eruptionAuthors: Judhajeet Basu, G. C. Anupama, Jan-Uwe Ness, Kulinder Pal Singh, Sudhanshu Barway, Shatakshi Chamoli,Comments: 10 pages, 4 figures, 1 table. Accepted for publication in ApJSubjects: astro-ph.HECreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
We report on UV and X-ray observations of the 2024 eruption of the recurrent nova LMCN 1968-12a, a rapidly recurring extragalactic system with a $\sim$4.3 year recurrence period and a massive white dwarf (WD). The eruption was discovered on 2024 August 1.8 by \textit{SWIFT}, and subsequently monitored using \textit{AstroSat}'s UVIT and SXT, along with SWIFT/UVOT and XRT. The multi-wavelength light curves reveal a rapid UV-optical decline, followed by a plateau phase exhibiting 1.26-day modulations consistent with the orbital period. The Supersoft (SSS) X-ray emission, that emerged by day 5, exhibited a double peak, suggesting variable obscuration that could be due to an inhomogeneous nova ejecta or due to a nova super-remnant along the line of sight. Time-resolved X-ray spectroscopy shows a blackbody component with T $\approx 10^6$ K. The SEDs obtained concurrently in the UV, peaking at T $\approx$ 20,000 K and with a source radius $\sim$2-3 R$_\odot$, are inconsistent with emission from the secondary star or nova photosphere alone. Instead, the UV emission is attributed to an irradiated accretion disk that survived the eruption. The persistent UV plateau and its temperature suggest that the accretion disk was not completely disrupted and resumed activity within days, consistent with recent findings in other rapidly recurring novae such as U~Sco and M31N~2008-12a.
[abstract 60 / 63] (score: 2) - Title: Unveil A Peculiar Light Curve Pattern of Magnetar Burst with GECAM observations of SGR J1935+2154Authors: Yue Wang, Chen-Wei Wang, Shaolin Xiong, Xiao Xiao, Yanqiu Zhang, Sheng-Lun Xie, Lin Lin, Yuan-Pei Yang, Haoxuan Guo, Ce Cai, Yue Huang, Cheng-Kui Li, Bing Li, Xiaobo Li, Jiacong Liu, Xiang Ma, Liming Song, Wen-Jun Tan, Ping Wang, Wang-Chen Xue, Shu-Xu Yi, Yun-Wei Yu, Zheng-Hang Yu, Jin-Peng Zhang, Peng Zhang, Shuang-Nan Zhang, Wen-Long Zhang, Zhen Zhang, Xiao-Yun Zhao, Chao Zheng, S. J. Zheng,Comments: 13 pages, 5 figures, accepted to publication on ApJSubjects: astro-ph.HECreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
Magnetar X-ray Burst (MXB) is usually composed of a single pulse or multiple pulses with rapid rise and brief duration mostly observed in hard X-ray (soft gamma-ray) band. Previous work studied the temporal behavior of some MAGNETar bursts and employed the Fast Rise Exponential Decay (FRED) model to fit pulses of MXB. However, whether there is other kind of pulse shape has not been explored. In this study, we systematically examined light curve of MXBs from SGR J1935+2154 detected by GECAM between 2021 and 2022. We find that there are different light curve morphologies. Especially, we discover a peculiar and new pattern, Exponential Rise and Cut-Off Decay (ERCOD), which is significantly different from FRED and could be well described by a mathematical function we proposed. We find that MXBs with ERCOD shape are generally longer in duration, brighter in the peak flux, and harder in spectrum. We note that the ERCOD shape is not unique to SGR J1935+2154 but also present in other MAGNETars. This new light curve pattern may imply a special burst and radiation mechanism of MAGNETar.
[abstract 61 / 63] (score: 2) - Title: Lyα Intensity Mapping in HETDEX: Galaxy-Lyα Intensity Cross-Power SpectrumAuthors: Maja Lujan Niemeyer, Eiichiro Komatsu, José Luis Bernal, Chris Byrohl, Robin Ciardullo, Olivia Curtis, Daniel J. Farrow, Steven L. Finkelstein, Karl Gebhardt, Caryl Gronwall, Gary J. Hill, Matt J. Jarvis, Donghui Jeong, Erin Mentuch Cooper, Deeshani Mitra, Shiro Mukae, Julian B. Muñoz, Masami Ouchi, Shun Saito, Donald P. Schneider, Lutz Wisotzki,Comments: 26 pages, 13 figuresSubjects: astro-ph.COCreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
We present a measurement of the Lyman-$α$ (Ly$α$) intensity mapping power spectrum from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). We measure the cross-power spectrum of the Ly$α$ intensity and Ly$α$-emitting galaxies (LAEs) in a redshift range of $1.9 < z < 3.5$. We calculate the intensity from HETDEX spectra that do not contain any detected LAEs above a signal-to-noise ratio of $5.5$. To produce a power spectrum model and its covariance matrix, we simulate the data using lognormal mocks for the LAE catalog and Ly$α$ intensity in redshift space. The simulations include the HETDEX sensitivity, selection function, and mask. The measurements yield the product of the LAE bias, the intensity bias, the mean intensity of undetected sources, and the ratio of the actual and fiducial redshift-space distortion parameters, $b_\mathrm{g} b_I \langle I \rangle \bar{F}_{\rm RSD} / \bar{F}^{\rm fid}_{\rm RSD}= (6.7 \pm 3.1)$, $(11.7 \pm 1.4)$, and $(8.3 \pm 1.5) \times 10^{-22} \, \text{erg}\, \text{s}^{-1} \, \text{cm}^{-2} \, \text{arcsec}^{-2} \, \text{Å}^{-1}$ in three redshift bins centered at $\bar z=2.1$, 2.6, and 3.2, respectively. The results are reasonably consistent with cosmological hydrodynamical simulations that include Ly$α$ radiative transfer. They are, however, significantly smaller than previous results from cross-correlations of QUASARs with Ly$α$ intensity. These results demonstrate the statistical power of HETDEX for Ly$α$ intensity mapping and pave the way for a more comprehensive analysis. They will also be useful for constraining models of Ly$α$ emission from galaxies used in modern cosmological simulations of galaxy formation and evolution.
[abstract 62 / 63] (score: 2) - Title: A framework for realisable data-driven active flow control using model predictive control applied to a simplified truck wakeAuthors: Alberto Solera-Rico, Carlos Sanmiguel Vila, Stefano Discetti,Comments: 28 pages, 15 figuresSubjects: physics.flu-dynCreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
We present an efficient and realisable active flow control framework with few non-intrusive sensors. The method builds upon data-driven, reduced-order predictive models based on Long-Short-Term Memory (LSTM) networks and efficient gradient-based Model Predictive Control (MPC). The model uses only surface-mounted pressure probes to infer the wake state, and is trained entirely offline on a dataset built with open-loop actuations, thus avoiding the complexities of online learning. Sparsification of the sensors needed for control from an initially large set is achieved using SHapley Additive exPlanations. A parsimonious set of sensors is then deployed in closed-loop control with MPC. The framework is tested in numerical simulations of a 2D truck model at Reynolds number 500, with pulsed-JET actuators placed in the rear of the truck to control the wake. The parsimonious LSTM-MPC achieved a drag reduction of 12.8%.
[abstract 63 / 63] (score: 2) - Title: Revisiting the limits on DARK MATTER annihilation cross-section and decay lifetime in light of electron and positron fluxesAuthors: Nagisa Hiroshima, Kazunori Kohri, Partha Kumar Paul, Narendra Sahu,Comments: 8 pages, 4 captioned figuresSubjects: hep-ph astro-ph.CO astro-ph.HECreated: 2025-10-13; Updated: 2025-10-14; Datestamp: 2025-10-14
We revisit the upper bound on the annihilation cross-section, $\langleσv\rangle$ of a stable DARK MATTER (DM) of mass $5\times10^2-10^{14}$ GeV by considering five different channels: $W^+W^-$, $b\bar{b}$, $μ^+μ^-$, $τ^+τ^-$, and $e^+e^-$. We use the observed electron and positron fluxes from CALET, DAMPE, HESS, positron flux from AMS-02, and gamma-ray flux from HAWC, GRAPES-3, CASA-MIA to constrain the annihilation cross-section. We also consider unstable DM of mass $10^3-10^{16}$~GeV decaying to $W^+W^-$, $b\bar{b}$, $μ^+μ^-$, $τ^+τ^-$, and $e^+e^-$ and derive the corresponding lower bound on the DM lifetime, $τ_{\rm DM}$. We find that the latest data from CALET gives a stringent constraint on $\langleσv\rangle$ in the low DM mass regime. For a typical DM mass of 1 TeV, we show that $\langleσv\rangle_{{\rm DM~DM}\rightarrowμ^+μ^-}\gtrsim\mathcal{O}(10^{-24})~\rm cm^3/s$ is disfavored. On the other hand in the low mass regime, the AMS-02 gives a much stringent limit on the DM lifetime, excluding $τ_{\rm DM\rightarrowμ^+μ^-}\lesssim\mathcal{O}(10^{27})$ s for a 1 TeV mass of DM. In the high mass regime, typically $M_{\rm DM}\gtrsim\mathcal{O}(10^5)$ GeV, HAWC and CASA-MIA give the strongest constraints on $\langleσv\rangle$ and $τ_{\rm DM}$.
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