Current date: 2026-05-19

Setting default datestamp limit: 0

Datestamp limit: 2026-05-19 (0 days ago)

Created/updated limit: 2026-05-12 (7 days ago)

Suggested sets: physics, physics:astro-ph, physics:gr-qc, physics:physics

Setting default set: physics

OAI-PMH request: http://export.arxiv.org/oai2?verb=ListRecords&from=2026-05-19&until=2026-05-19&set=physics&metadataPrefix=arXiv

Scoring abstracts

Number of records retrieved: 195

Keyword score statistics

score 9 -- 1 abstracts

score 5 -- 2 abstracts

score 4 -- 1 abstracts

score 3 -- 2 abstracts

score 2 -- 10 abstracts

in total -- 16 abstracts

Articles that appeared on 2026-05-19

[abstract 1 / 16] Wow! (score: 9)
arXiv:2605.16495 [pdf, ps, other]

Title: A 14-year-old Mystery: The Peculiar Case of the Engine-driven SN 2012ap

Authors: Itai Sfaradi, Raffaella Margutti, Ryan Chornock, A. J. Nayana, Eli Wiston, Fabio De Colle, Tracy E. Clarke, Wendy M. Peters, Paz Beniamini, Wenbin Lu, Rodolfo Barniol Duran, Michael Bietenholz, Collin T. Christy, Deanne L. Coppejans, Maria R. Drout, Dina Ibrahimzade, Michal J. Michalowski, Dan Milisavljevic, Conor M. B. Omand, Yihan Wang, Kate D. Alexander, Carles Badenes, Joe Bright, Jonathan Granot, Erica Hammerstein, Wynn V. Jacobson-Galan, Natalie LeBaron, Kohta Murase, Gitika Rameshan, Huei Sears, Michael Stroh, Giacomo Terreran,

Comments: 24 pages, 8 figures, 5 tables; Submitted to ApJ

Subjects: astro-ph.HE

Created: 2026-05-15; Updated: 2026-05-19; Datestamp: 2026-05-19

We present late-time ($δt > 3000$ d) optical (Keck), X-ray (Chandra and NUSTAR), and radio (VLA, ALMA, and the uGMRT) observations of the Type Ic-BL SN 2012ap. Previous studies of this SN suggested that it stands out as a key example of a weak engine-driven explosion due to the lack of GAMMA-RAY BURST detection and a mildly RELATIVISTIC ejecta. Recently, radio sky surveys revealed the rebrightening of the radio emission from this SN, highlighting the possibilities of a density enhancement at large radii or the existence of an off-axis RELATIVISTIC JET. While the late-time optical spectra does not exhibit the broad emission lines seen in other interacting SNe, our analysis of the broadband radio and X-ray emission implies that both scenarios are plausible. If a density enhancement is responsible for the radio rebrightening, it has to result from a change in the mass-loss rate and/or wind velocity, possibly due to the transition of the progenitor from a red supergiant to a Wolf-Rayet star. If the late-time radio component is a result of an off-axis RELATIVISTIC JET, we find that an energetic narrow JET viewed at $θ_{\rm obs} \geq 80^{\circ}$ is needed. In this scenario, SN 2012ap is not a result of a weak engine-driven explosion, and, instead, it is similar to other GRBs. However, radio rebrightenings of Type Ic-BL SNe are not enough on their own to determine the existence of off-axis JETs and our planned VLBA observation will help reveal the true nature of this SN.

[abstract 2 / 16] Yes (score: 5)
arXiv:2603.28666 [pdf, ps, other]

Title: Variable ADAF disk as the origin of Changing-Look AGN

Authors: Chun Xu,

Comments: Preprint. 8 pages, 1 figure. Two additional examples are added: GSN 069 with QPE and PG1211+143 with UFO/Fe lines

Subjects: astro-ph.HE

Created: 2026-05-16; Updated: 2026-05-19; Datestamp: 2026-05-19

We propose that changing-look AGN transitions arise from variations in the size of the inner ADAF disk. The AGN accretion disk consists of an outer thin disk and an inner thick ADAF component, whose size is intrinsically unstable and evolves over time. The size variations of the ADAF are governed by a parameter η, which represents the turbulence strength within the accretion flow. ηalso determines the accretion rate onto the central BLACK HOLE and controls JET formation and outflow rate, with the latter regulating the line-of-sight absorption. From the perspective of a variable ADAF, changing-state and changing-observation AGN are two sides of the same coin. We further discuss gigahertz-peaked and compact steep-spectrum radio sources as possible manifestations of intermediate-to-large scale ADAFs. Finally, we propose that AGN unification models should include both orientation and ADAF size as key parameters.

[abstract 3 / 16] Yes (score: 5)
arXiv:2605.16698 [pdf, ps, other]

Title: Multiwavelength Probes of Cosmic Ray Transport in Molecular Cloud Structures

Authors: Hayden P. H. Ng, Ellis R. Owen, Naomi Tsuji, Szu-Ting Chen,

Comments: 21 pages, 11 figures, 3 tables. Accepted for publication in PASJ

Subjects: astro-ph.HE astro-ph.GA

Created: 2026-05-15; Updated: 2026-05-19; Datestamp: 2026-05-19

We investigate how COSMIC RAY (CR) transport in molecular clouds and their substructures can be probed using multi-wavelength observations. The detailed microphysics regulating the penetration and coupling of CRs in dense molecular structures is unsettled. Self-generated turbulence can produce scattering and diffusive transport, while ion-neutral damping in cold, dense gas promotes ballistic CR propagation. We construct a self-consistent framework for CR transport and interactions in MAGNETized molecular clouds, considering three limiting propagation scenarios: ballistic transport, diffusion, and a hybrid configuration with a diffusive envelope and quasi-ballistic core. By forward-modeling pion-decay $γ$-ray emissivities, CR-driven ionization-rate profiles, and electron SYNCHROTRON emission in the hard X-ray band, we connect GeV attenuation and propagation signatures to independent diagnostics of secondary production and CR penetration. As an illustrative example, we apply our framework to the Taurus molecular cloud complex and selected embedded clumps. We show that CR scattering may be substantially enhanced on clump scales, with inferred CR diffusion coefficients suppressed relative to canonical interstellar medium (ISM) values at GeV energies. In this interpretation, CRs are more closely coupled with dense gas in the ISM, and a diffusive envelope boosts the effective gas column density encountered by the CRs. This increases the hadronic interaction rate in the cloud. In turn, the secondary CR electron injection is also increased, and CR ionization rates are elevated at higher densities. We show that a hard X-ray SYNCHROTRON emission component is also generated, which may be detectable with near-future facilities. Finally, we discuss how future $γ$-ray, X-ray, and ionization constraints will provide firm tests of CR propagation theories in molecular cloud environments.

[abstract 4 / 16] Yes (score: 4)
arXiv:2605.16766 [pdf, ps, other]

Title: XRISM detection of the 6.4 keV Fe K$α$ line in the RADIO GALAXy Cygnus A

Authors: Anwesh Majumder, T. Heckman, L. Gu, A. Simionescu, B. R. McNamara, A. Ptak, E. Hodges-Kluck, M. Yukita, M. W. Wise, N. Roy,

Comments: 10 pages, 4 figures. Submitted in ApJ

Subjects: astro-ph.HE astro-ph.CO

Created: 2026-05-16; Updated: 2026-05-19; Datestamp: 2026-05-19

We detail the spectral analysis of a 170 ks XRISM Resolve observation of the core of Cygnus A. The high spectral resolution of Resolve have enabled us to probe the inner accretion region of Cygnus A by analyzing the 6.4 keV Fe K$α$ line complex. We find that it consists of two Keplerian broadened components. (1) A broad component with a velocity dispersion of $3400^{+800}_{-600}$ km s$^{-1}$ and (2) a narrow component of $440^{+60}_{-50}$ km s$^{-1}$. For an inclination of $50^{\circ}-85^{\circ}$, constrained by VLBI, we find that the broad component arises from a distance of $\sim 0.1-0.17$ pc ($800-1400$ gravitational radii) and the narrow component from $\sim 6-10$ pc ($50,000-80,000$ gravitational radii) from the central BLACK HOLE depending on the inclination angle. Our result suggests that the origin of the broad component is consistent with the broad line region and the narrow component from the torus of Cygnus A. We also find a potential emission line possibly from intermediate ionized Fe XVII with a very low dispersion ($<80$ km s$^{-1}$) that originates from either the outer edge of the torus or the narrow line region. Finally, we find that the Fe K edge is redshifted compared to the Fe K$α$ line components, suggesting a line of sight bulk velocity of $470 \pm 100$ km s$^{-1}$. Such a shift may be due to an inflowing wind or relative motion between the two components originating from the near and far side of an inflowing torus, respectively.

[abstract 5 / 16] (score: 3)
arXiv:2605.16485 [pdf, ps, other]

Title: Halo-driven Origin and Suppression of Over-massive Black Holes and Little Red Dots

Authors: Ritik Sharma, Mahavir Sharma,

Comments: 9 pages, 5 figures, submitted, comments welcome

Subjects: astro-ph.GA astro-ph.CO astro-ph.HE

Created: 2026-05-15; Updated: 2026-05-19; Datestamp: 2026-05-19

We present a theoretical model in which the recently detected over-massive BLACK HOLEs (OBHs), and possibly Little Red Dots (LRDs), arise during a halo-driven transient phase preceding the established coevolution of supermassive BLACK HOLEs (SMBHs) and their host galaxies. In this model, halo gravity drives an early phase of rapid BLACK HOLE growth, leading to systems in high-redshift haloes that lie above the local scaling relations. As the halo evolves, a transition in halo thermodynamics leads to the onset of a hot, pressure-supported medium that suppresses accretion, reducing the BLACK HOLE growth rate and driving the system toward the local BLACK HOLE mass$-$stellar mass relation. LRDs may represent an observational manifestation of the rapid, halo-driven growth phase, while OBHs trace its direct mass signature. Our model thus provides a unified framework in which these systems form and evolve toward the regulated coevolution observed in the local Universe.

[abstract 6 / 16] (score: 3)
arXiv:2605.16734 [pdf, ps, other]

Title: FIRM3D: Fast ion reduced models in 3D

Authors: Elizabeth Paul, Alexey Knyazev, Michael Czekanski, Alexandra Lachmann, Abdullah Hyder, Christopher Albert, Matt Landreman,

Comments:

Subjects: physics.plasm-ph

Created: 2026-05-16; Updated: 2026-05-19; Datestamp: 2026-05-19

The dynamics of energetic particle (EP) species, born from fusion reactions or plasma heating schemes, are critical for predicting the behavior of MAGNETic confinement fusion experiments and future fusion reactors. Because energetic particles are largely collisionless, the orbits of Monte Carlo samples drawn from a given distribution function can be efficiently integrated in prescribed electroMAGNETic fields. In addition to the static MAGNETo-hydrodynamic (MHD) equilibrium fields produced by the electroMAGNETic coils of a fusion device, MHD waves can be excited by -- and resonantly transport -- energetic particle populations. FIRM3D is an open-source Python/C++/CUDA software suite for modeling energetic particle dynamics in 3D MAGNETic fields, available at https://github.com/ColumbiaStellaratorTheory/firm3d. The core guiding-center integration routines grew out of SIMSOPT (Landreman et al., 2021), but have been extended to include additional physics and diagnostics not typically required in the stellarator optimization context. This standalone framework enables focused development of energetic particle physics capabilities with minimal dependencies, making it accessible to the broader stellarator and plasma physics community. Components of FIRM3D include interfaces with MHD equilibrium and wave stability software (BOOZ_XFORM, AE3D, FAR3D); CPU and GPU parallelized integration of the guiding center orbit equation, with symplectic and Runge-Kutta integrator options; and orbit visualization and transport diagnostics, including Poincare maps, orbit classification, and weighted Birkhoff averaging.

[abstract 7 / 16] (score: 2)
arXiv:2408.04878 [pdf, ps, other]

Title: Modelling DSA, FAST and CRAFT surveys in a z-DM analysis and constraining a minimum FRB energy

Authors: Jordan Hoffmann, Clancy W. James, Marcin Glowacki, Jason X. Prochaska, Alexa C. Gordon, Adam T. Deller, Ryan M. Shannon, Stuart D. Ryder,

Comments: 17 pages, 7 figures, submitted to PASA

Subjects: astro-ph.CO astro-ph.HE

Created: 2026-05-16; Updated: 2026-05-19; Datestamp: 2026-05-19

Fast radio burst (FRB) science primarily revolves around two facets: the origin of these bursts and their use in cosmological studies. This work follows from previous redshift-dispersion measure ($z$-DM) analyses in which we model instrumental biases and simultaneously fit population parameters and cosmological parameters to the observed population of FRBs. This sheds light on both the progenitors of FRBs and cosmological questions. Previously, we have completed similar analyses with data from the Australian Square Kilometer Array Pathfinder (ASKAP) and the Murriyang (Parkes) Multibeam system. With this manuscript, we additionally incorporate data from the Deep Synoptic Array (DSA) and the Five-hundred-meter Aperture Spherical Telescope (FAST), invoke a Markov chain Monte Carlo (MCMC) sampler and implement uncertainty in the Galactic DM contributions. The latter leads to larger uncertainties in derived model parameters than previous estimates despite the additional data. We provide refined constraints on FRB population parameters and derive a new constraint on the minimum FRB energy of log$\,E_{\mathrm{min}}$(erg)=39.49$^{+0.39}_{-1.48}$ which is significantly higher than bursts detected from strong repeaters. This result may indicate a low-energy turnover in the luminosity function or may suggest that strong repeaters have a different luminosity function to single bursts. We also predict that FAST will detect 25-41% of their FRBs at $z \gtrsim 2$ and DSA will detect 2-12% of their FRBs at $z \gtrsim 1$.

[abstract 8 / 16] (score: 2)
arXiv:2605.16425 [pdf, ps, other]

Title: Polarization Birefringence and Waveform Systematics in GW231123

Authors: Tonghua Liu, Chenggang Shao, Kai Liao,

Comments: 9 pages, 4 figures, comments are welcome

Subjects: astro-ph.HE

Created: 2026-05-14; Updated: 2026-05-19; Datestamp: 2026-05-19

GW231123 is a short, massive binary-black-hole event whose source properties show strong waveform dependence. We use this event to test gravitational-wave POLARIZATION birefringence, modeled as a frequency-dependent rotation of the tensor-POLARIZATION basis. Instead of sampling a distance-normalized coefficient directly, we sample the band-differential rotation $δ_{\rm br}=Δ(448\,\mathrm{Hz})-Δ(20\,\mathrm{Hz})$ with prior $[-π,π]$, and report the derived coefficient $β_{\rm br}^{\rm derived}$ for comparison with standard propagation parametrizations. We analyze three waveform families: IMRPhenomXPHM (XPHM), IMRPhenomXO4a (XO4a), and NRSur7dq4. The derived posteriors are consistent with the general relativity value, giving $90\%$ upper limits $|β_{\rm br}^{\rm derived}|_{90}=0.378,\,0.097,\,0.273$ for XPHM, XO4a, and NRSur7dq4, respectively. The directly sampled $δ_{\rm br}$ posterior remains broad, with $|δ_{\rm br}|_{90}\simeq2.8\,\mathrm{rad}$, so the accumulated rotation across the analysis band is weakly constrained. The Bayes factors are waveform dependent: $\ln\mathcal{B}_{\rm br/GR}=-1.26\pm0.30$, $+3.64\pm0.28$, and $-0.86\pm0.29$, respectively. We therefore find no waveform-robust evidence for parity-violating propagation. The positive XO4a result is better interpreted as a waveform-dependent birefringence-like response associated with the mass-ratio--distance--spin degeneracy of this short high-mass event.

[abstract 9 / 16] (score: 2)
arXiv:2605.16461 [pdf, ps, other]

Title: Particle Dynamics, Shadow and Hawking Sparsity of a Kalb-Ramond Black Hole Coupled to Nonlinear Electrodynamics

Authors: Faizuddin Ahmed, Ahmad Al-Badawi, İzzet Sakallı,

Comments: 12 pages. Comments are welcome

Subjects: gr-qc astro-ph.HE hep-th

Created: 2026-05-15; Updated: 2026-05-19; Datestamp: 2026-05-19

We study the timelike and null geodesic structure of a static, spherically symmetric BLACK HOLE sourced by a Kalb--Ramond (KR) field coupled to nonlinear electrodynamics (NED). The geometry is characterized by the mass $M$, the MAGNETic monopole charge $q$, and the Lorentz-violating parameters $(γ,λ)$. Closed-form expressions are derived for the effective potential, as well as the specific energy and angular momentum of massive particles on circular orbits. We further analyze the photon sphere, BLACK HOLE shadow, and the Lyapunov exponent associated with unstable null circular geodesics. The latter determines the eikonal quasinormal-mode frequencies through $ω_{\rm eik}=(\ell+1/2)\,Ω_c-i(n+1/2)\,|λ_L|$. The shadow radius is compared with the Event Horizon Telescope (EHT) observations of M87$^\ast$ and Sgr~A$^\ast$, allowing us to identify the viable region in the $(q,γ)$ parameter space. Finally, we compute the Hawking temperature, horizon area, and the Gray--Visser sparsity parameter. We demonstrate that the combined effects of the KR field and MAGNETic monopole charge increase the sparsity parameter from the Schwarzschild value $16π^3 \simeq 496$ to nearly $1.7\times10^3$. This indicates a significantly sparser Hawking cascade compared to the Schwarzschild case, while the photon ring remains consistent with the EHT $1σ$ observational bounds across most of the physically allowed parameter range.

[abstract 10 / 16] (score: 2)
arXiv:2605.16483 [pdf, ps, other]

Title: The limits of feedback from ACTIVE GALACTIC NUCLEi

Authors: Andrew Pontzen, Hiranya V. Peiris, Joop Schaye, Matthieu Schaller,

Comments: 17 pages, 8 figures. Companion letter (Peiris et al.) in this listing

Subjects: astro-ph.GA astro-ph.CO

Created: 2026-05-15; Updated: 2026-05-19; Datestamp: 2026-05-19

We use FLAMINGO to investigate why feedback from ACTIVE GALACTIC NUCLEi (AGN) significantly depletes gas in galaxy groups but is ineffective in clusters. We delineate three radial zones: an inner zone where AGN feedback heats halo gas via shocks; an intermediate buoyancy zone where the heated halo gas rises; and an outer zone where the outflow may stall in a termination shock. Heating in the inner zone self-limits because, once the gas is sufficiently hot, shocks become too weak to deposit further entropy. Consequently, outflows have a ceiling entropy value ($360\, {\rm keV\, cm^2}$) that is nearly independent of halo mass. These values (and trends with redshift and feedback variants) are explained using an argument based on the Rankine-Hugoniot relations. Outflows rise at fixed entropy through the buoyancy zone, escaping the halo if the ceiling value is sufficiently elevated over that of the inflowing gas. This condition is satisfied only for halo masses $M_{\rm 200m}<10^{13.7}\,{\rm M_\odot}$, because inflow entropy tracks the virial relation. Variants with stronger (or weaker) feedback have a higher (or lower) entropy ceiling and a correspondingly modified critical mass of $M_{\rm 200m}=10^{14.0}\,{\rm M_\odot}$ (or $10^{13.5}\,{\rm M_\odot}$). In clusters above the critical mass, the increased inflow entropy causes the outflow to stall and potentially shock at the 'splashback' radius. We derive an expression for the time evolution of the virial gas fraction, which shows how lingering gas is reincorporated as the halo virial radius expands. This effect dominates over outflows unless they rejoin the Hubble flow; as a result, virial gas fractions rise as a function of mass starting at $M_{\rm 200m} = 10^{13.0}\,{\rm M_\odot}$. These effects explain why groups have depleted gas, while clusters have close to the cosmic baryon fraction.

[abstract 11 / 16] (score: 2)
arXiv:2605.16488 [pdf, ps, other]

Title: Thermostats, Not Engines: A New Picture of Halo Gas Regulation

Authors: Hiranya V. Peiris, Andrew Pontzen, Madalina N. Tudorache, Anik Halder, Stephen Thorp, Sinan Deger, Joop Schaye, Matthieu Schaller,

Comments: 7 pages, 3 figures, 1 table. Comments welcome. Companion paper Pontzen et al. in this arxiv listing

Subjects: astro-ph.CO astro-ph.GA

Created: 2026-05-15; Updated: 2026-05-19; Datestamp: 2026-05-19

We propose that BLACK HOLE feedback regulates gas in massive halos by establishing an entropy ceiling; the resulting buoyant gas migrates to the virial radius with no additional energy input required. The FLAMINGO simulations support this picture: at the virial radius, outflow entropy is mass-independent for isotropic thermal feedback but depends on the solid angle of directly heated gas for JET feedback. Above a critical halo mass $M_\rm{crit} \approx 10^{13.5\text{--}14}\, M_\odot$, virial shocks overwhelm the ceiling, predicting rejuvenation of STAR FORMATION in the most massive galaxies, supported by new low-redshift evidence from STAR FORMATION rates and morphologies.

[abstract 12 / 16] (score: 2)
arXiv:2605.16498 [pdf, ps, other]

Title: Searching for the Third Wheel: High-Contrast Imaging Constraints on Tertiaries to Black Hole and Neutron Star Binaries

Authors: Pranav Nagarajan, Kareem El-Badry, Aniket Sanghi,

Comments: 20 pages, 12 figures, Submitted to PASP

Subjects: astro-ph.SR astro-ph.HE

Created: 2026-05-15; Updated: 2026-05-19; Datestamp: 2026-05-19

Hierarchical triple evolution provides a promising alternative to isolated binary formation models for BLACK HOLEs (BHs) and neutron stars (NSs) with low-mass stellar companions. To search for tertiaries, we perform deep, adaptive optics-assisted, near-infrared imaging of five quiescent BH low-mass X-ray binaries (LMXBs), Gaia BH1, and twelve Gaia NSs. We detect several faint stars previously unresolved in survey imaging, but none are close enough to robustly rule out a chance alignment. To achieve high contrast sensitivity at close separations, we use the reference star differential imaging strategy with the Karhunen-Loéve Image Processing algorithm to model and subtract the point-spread function of each target. We identify tertiary candidates in the speckle-dominated regime, but injection-recovery tests suggest most 5$σ$ detections are likely artifacts. We derive $5σ$ contrast curves and convert these to limits on the mass of main sequence (MS) tertiaries and the effective temperature of white dwarf (WD) tertiaries consistent with a non-detection. We rule out plausible MS tertiaries and young, hot WD tertiaries at projected separations $\gtrsim 500$ au for the Gaia compact object binaries and $\gtrsim 2000$ au for the more distant BH LMXBs. While the recent discovery of a $1.2\,M_{\odot}$ tertiary to V404 Cygni supports triple formation scenarios for BH LMXBs, our results suggest such companions are relatively rare. Our observations remain consistent with intermediate-mass tertiaries that have since evolved into cool WDs, detectable with deeper JWST imaging. Follow-up observations are required to measure proper motions and confirm or rule out physical association of tertiary candidates.

[abstract 13 / 16] (score: 2)
arXiv:2605.16506 [pdf, ps, other]

Title: Rapidly Rotating Neutron Star Collapse in Massive Scalar-Tensor Theories

Authors: José Carlos Olvera M., Daniela D. Doneva, Pablo Cerdá-Durán, José A. Font, Stoytcho S. Yazadjiev,

Comments: 25 pages, 20 figures

Subjects: gr-qc astro-ph.HE

Created: 2026-05-15; Updated: 2026-05-19; Datestamp: 2026-05-19

We present a full 3D numerical evolution code to study neutron stars in massive-scalar-tensor theories. The code is embedded in the Einstein Toolkit framework and its implementation constitutes a modified version of the Baumgarte-Shapiro-Shibata-Nakamura formalism with an additional nonminimally coupled scalar field. The approach we follow preserves the standard hydrodynamic evolution for matter fields, allowing eventually for a straightforward inclusion of more microphysical effects and better flexibility. Using this code, we examine the gravitational collapse of rapidly rotating, scalarized neutron stars to a BLACK HOLE by exploring the influence of the scalar field on the dynamical features of the process and on the gravitational-wave emission. We find that for the configurations studied in this work, there is an observational degeneracy in the tensorial gravitational-wave emission between collapsing scalarized stars and their counterparts in general relativity. However, this degeneracy can be broken through the emission of scalar radiation, which carries an energy of ~10^-3 M_sun c^2. This is orders of magnitude higher than the quadrupolar emission (~10^-7 M_sun c^2) and might be used as an observational probe of modified gravity. We also find that rapid rotation can enhance this signal, since fast rotating stars can sustain larger scalar field amplitudes.

[abstract 14 / 16] (score: 2)
arXiv:2605.16670 [pdf, ps, other]

Title: The Torques Acting on Accreting Millisecond X-Ray Pulsars in the Outburst and Quiescent States, and During the Long-Term Evolution

Authors: Fatmanur Ertugrul, Ali Arda Gencali, Unal Ertan, Ndiogou Niang,

Comments: 10 pages, 6 figures, accepted for publication in MNRAS

Subjects: astro-ph.HE

Created: 2026-05-15; Updated: 2026-05-19; Datestamp: 2026-05-19

Accreting millisecond X-ray pulsars (AMXPs) are transient X-ray sources likely to be in the final evolutionary phases of low-mass X-ray binaries (LMXBs). In this work, we have investigated the torque and X-ray luminosity variations of five AMXPs during outburst and quiescence, using a model previously employed to explain some typical behaviours of LMXBs. Most of these systems spin up in the outburst state and spin down in quiescence, while they slow down on the long term. We have obtained reasonable results with the model in agreement with these observations. We have found that the torques produced by the disc-MAGNETosphere interaction, the MAGNETic dipole radiation, and the mass accretion are compatible with the X-ray luminosity and rotational properties of the sources in their outburst and quiescent states, and during the resultant long-term evolution. Nevertheless, our results are not sufficient to rule out the spin-down contribution of the gravitational radiation torques due to significant timing noise and uncertainties about the bolometric corrections for X-ray luminosity during the outbursts of some sources.

[abstract 15 / 16] (score: 2)
arXiv:2605.16760 [pdf, ps, other]

Title: A Rare Population of Intermediate-mass Helium Stars Between Hot Subdwarfs and Wolf-Rayet Stars

Authors: Gui-Yu Wang, Yong Shao, Jian-Guo He, Yu-Dong Nie, Xiao-Jie Xu, Xiang-Dong Li,

Comments: 18 pages, 15 figures, accepted by ApJ

Subjects: astro-ph.SR astro-ph.HE

Created: 2026-05-16; Updated: 2026-05-19; Datestamp: 2026-05-19

Helium stars stripped of their hydrogen envelopes represent pivotal phases in binary evolution, yet their origins, particularly within the intermediate-mass range of $2-8\, M_{\odot}$, still remain poorly understood. This population bridges the gap between low-mass hot subdwarfs and massive Wolf-Rayet stars, but has remained largely unobserved. In this study, we employ binary population synthesis to systematically investigate the formation and properties of intermediate-mass helium stars (IMHeS) across various galactic metallicities. Our results indicate that metallicity and common-envelope ejection efficiency are the dominant factors shaping the IMHeS population. We estimate that several thousand IMHeS exist in the Milky Way, with several hundred more in the Magellanic Clouds. The vast majority of IMHeS reside in binaries, with fewer than $10\%$ appearing as single stars. Among IMHeS binaries, $\gtrsim 50\%$ are expected to have main-sequence companions, and the remainder host compact companions (including helium stars, white dwarfs, neutron stars, or BLACK HOLEs). The former systems form mainly through stable mass transfer, whereas the latter arise predominantly from common envelope evolution. Our work provides quantitative predictions for the populations of these elusive stars formed through binary interactions and offers guidance for future observational searches.

[abstract 16 / 16] (score: 2)
arXiv:2605.16792 [pdf, ps, other]

Title: Static electroMAGNETic Love tensors of 5-dimensional Myers-Perry BLACK HOLEs

Authors: Boyang Yu,

Comments: 24 pages

Subjects: hep-th gr-qc

Created: 2026-05-16; Updated: 2026-05-19; Datestamp: 2026-05-19

We study the separable master equations for the electroMAGNETic and gravitational perturbations in five-dimensional Myers-Perry BLACK HOLEs. In the static limit, while the master equation for the electric POLARIZATION of the Maxwell field reduces to that of a massless scalar field, the MAGNETic POLARIZATION and gravitational perturbation yield Heun equations for both its angular and radial components. Remarkably, these Heun equations fall into a special class that admits exact analytic solutions in terms of hypergeometric functions. We reconstruct the gauge field using master fields and study its asymptotic behavior. When expanding the result in the basis of modified spherical harmonics, we find modes with higher angular momentum arise in response to the excitation of sources with lower angular momentum. The static tidal Love tensor that characterizes such mixing structure of the response can be computed iteratively. We also discuss the possible near zone approximation of the master equations for the MAGNETic POLARIZATION.