Current date: 2026-07-15

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Datestamp limit: 2026-07-15 (0 days ago)

Created/updated limit: 2026-07-08 (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=2026-07-15&until=2026-07-15&set=physics&metadataPrefix=arXiv

Scoring abstracts

Number of records retrieved: 701

Keyword score statistics

score 8 -- 1 abstracts

score 7 -- 1 abstracts

score 6 -- 2 abstracts

score 5 -- 5 abstracts

score 4 -- 2 abstracts

score 3 -- 7 abstracts

score 2 -- 24 abstracts

in total -- 42 abstracts

Articles that appeared on 2026-07-15

[abstract 1 / 42] Wow! (score: 8)
arXiv:2607.08657 [pdf, ps, other]

Title: VAPOLA -- A multi-year, multi-band POLARIZATION survey of AGN and Sgr A* at mm wavelengths with ALMA I. Survey Overview and Science-Ready Archival Products

Authors: Alejandro Mus, Ciriaco Goddi, Douglas Carlos, Vincenzo Galluzzi, Ezequiel Albentosa-Ruiz, Ivan Martí-Vidal, Hugo Messias, Kazi L. J. Rygl, Geoffrey B. Crew, Lynn D. Matthews, Elisabetta Liuzzo, Nicola Marchili, Raphael P. Rolim, Mariafelicia De Laurentis, Rocco Lico, Cristiano Urban,

Comments: Accepted in A&A, 07/06/2026

Subjects: astro-ph.GA astro-ph.IM

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

The Atacama Large Millimeter/submillimeter Array (ALMA) is the most sensitive interferometric array at millimeter and submillimeter wavelengths. Through the ALMA Phasing System (APS), it can participate in global Very Long Baseline Interferometry (VLBI) arrays, enhancing their sensitivity and resolution. However, processing and analzing the ALMA data obtained in APS mode during VLBI observations remains a complex task, requiring specialized expertise and time-consuming calibration and imaging procedures. In this paper, we present VAPOLA-the first online, multi-epoch, multi-band repository of high-level data products from ALMA observations of ACTIVE GALACTIC NUCLEi (AGN) and Sgr A* during global VLBI campaigns. Built on an automated pipeline that processes fully calibrated ALMA (QA2) data, generates science-ready products with minimal user intervention. The repository includes fully calibrated interferometric visibilities, full-Stokes images across individual and combined spectral windows, polarimetric and spectral index maps, as well as tabulated polarimetric parameters from visibility-domain POLARIZATION fitting. By offering ready-to-use data through a user-friendly web portal, VAPOLA enables non-expert users to perform advanced science analyses without needing in-depth knowledge of ALMA procedures. This resource will facilitate a broad range of scientific investigations, including the characterization of MAGNETic field properties in accretion flows and RELATIVISTIC JETs, the structure and kinematics of dusty and molecular tori in AGN, and absorption studies of the interstellar medium toward the Galactic Center. In addition, the dataset provides source-integrated parameters and calibration metadata essential for refining VLBI calibration and imaging workflows as well as for placing robust observational constraints on theoretical models of supermassive BLACK HOLEs and their environments.

[abstract 2 / 42] Wow! (score: 7)
arXiv:2607.13019 [pdf, ps, other]

Title: Gamma-ray Modes in a Transitional Pulsar

Authors: Maksat Satybaldiev, Manuel Linares,

Comments: 11 pages, 4 figures, 2 tables

Subjects: astro-ph.HE

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

Transitional millisecond pulsars (tMSPs) exhibit a unique sub-luminous disk state, at the cross-roads between accretion and rotation power, where they switch between two distinct X-ray modes. We present the discovery of gamma-ray modes in PSR J1023+0038, the first confirmed tMSP, from stacking FERMI-LAT data during the modes (which we identify using simultaneous X-ray observations). Surprisingly, we find that gamma-rays and X-rays are anti-correlated during this mode switching: the gamma-ray flux is higher in the X-ray low mode, and vice versa. This contradicts the state-of-the-art model, which predicts bright gamma-rays from the interaction between the pulsar wind and surrounding disk via SYNCHROTRON and inverse Compton processes. Because the pulsar wind is likely absent in the gamma-ray high (X-ray low) mode, which is also brighter in the radio band, we suggest that JET emission is dominant in GeV gamma-rays.

[abstract 3 / 42] Yes (score: 6)
arXiv:2607.12731 [pdf, ps, other]

Title: An internal shock model calibrated with real GAMMA-RAY BURST light curves using a genetic algorithm

Authors: Manuele Maistrello, Cristiano Guidorzi, Shiho Kobayashi, Romain Maccary,

Comments: 11 pages, 8 figures, A&A accepted for publication

Subjects: astro-ph.HE

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

The origin of GAMMA-RAY BURST (GRB) prompt emission remains an open question. The internal shock (IS) model is a leading scenario for converting RELATIVISTIC ejecta kinetic energy into gamma rays, but its parameters have not yet been fully calibrated against observed GRB light curves (LCs) to reproduce their diversity. We adopt a machine-learning framework to optimise the IS model by comparing simulated and observed LC properties from three GRB catalogues (SWIFT/BAT, FERMI/GBM, CGRO/BATSE). Assuming a redshift-dependent GRB formation rate, we employ a genetic algorithm to minimise a loss function based on six independent metrics capturing both average behaviours and statistical distributions. The optimised model reproduces several key observational properties, including the average post-peak temporal profile, autocorrelation function, and the distributions of duration, signal-to-noise ratio, number of peaks, peak flux, and fluence. We also derive constraints on the central engine activity: (i) the number of emitted shells is well described by a generalised Zipf distribution, analogous to the Gutenberg-Richter law for earthquakes, and (ii) the rest-frame shell-emission times follow a negative exponential distribution, indicating a stochastic process with a constant ejection probability. This calibrated IS model provides a physically grounded framework for interpreting GRB variability and predicting GRB populations detectable by future missions.

[abstract 4 / 42] Yes (score: 6)
arXiv:2607.12967 [pdf, ps, other]

Title: High-Resolution Numerical Calculations of GRB Afterglow Plateaus arising from Stratified Ejecta

Authors: Paul C. Duffell, Ranadeep Ghosh Dastidar,

Comments: ApJ Submitted

Subjects: astro-ph.HE

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

Since the discovery of plateaus in GRB afterglows by SWIFT, they have been modeled predominantly by late-time energy injection. However, many studies have suggested that the plateau may be modeled by an early phase before reverse shock crossing (either coasting with constant Lorentz factor or decelerating very slowly as the reverse shock crosses the ejecta). The slope of the early plateau provides some constraints the stratification of the fastest-moving ejecta, which could be the ejecta responsible for the prompt emission. However, numerical studies typically do not model the JET as a stratified outflow; the reason being the extremely high resolution required in order to accurately evolve this tiny amount of highly RELATIVISTIC material. In this study, we perform high-resolution numerical calculations ($Δr/r \lesssim 10^{-5}$) verifying that a stratified ejecta structure can indeed produce an afterglow plateau in both wind ($k=2$) and ISM ($k=0$) environments, and computing break times explicitly. We evolve the RELATIVISTIC hydrodynamics using the JET code, and post-process this to compute the afterglow using the Firefly code. Our results show that a stratified ejecta structure (which should generically be present in GRB JETs) is sufficient to explain GRB afterglows, and the plateau slopes can be used to constrain the ejecta stratification. We additionally provide precise measured scalings for the plateau duration as a function of the characteristic Lorentz factor of the ejecta. The long duration of typical plateaus requires a very modest characteristic Lorentz factor for the ejecta ($γ_0 \sim 10-50$), in agreement with other afterglow plateau models.

[abstract 5 / 42] Yes (score: 5)
arXiv:2602.23417 [pdf, ps, other]

Title: Universality of the Blandford-Znajek emission in stationary and axisymmetric spacetimes

Authors: Filippo Camilloni, Luciano Rezzolla,

Comments: v2: matches published version in PRD

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

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

The Blandford-Znajek (BZ) mechanism is widely recognised as the most compelling process to extract rotational energy from an accreting BLACK HOLE and power the emission of RELATIVISTIC JETs. We explore the universality of this process for generic black-hole spacetimes within the Konoplya-Rezzolla-Zhidenko formalism and find that the lowest-order contribution to the BZ power is invariant across different black-hole spacetimes. We also show that at the next-leading-order, different black-hole spacetimes will lead to different BZ luminosities. As a result, while slowly rotating BLACK HOLEs cannot be distinguished via measurements of their JET power, rapidly rotating ones have the potential of providing information on the strong-field properties of the spacetime when independent measurements of the BZ luminosity and of the black-hole angular velocity are available.

[abstract 6 / 42] Yes (score: 5)
arXiv:2607.11805 [pdf, ps, other]

Title: HAMCOR: A physics-driven Hamiltonian framework for inferring AGN coronal geometry from X-ray reverberation lags

Authors: Buffoli Fabio,

Comments: 11 pages, 7 figures, 5 tables

Subjects: astro-ph.HE

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

We present HAMCOR (Hamiltonian-based AGN Multi-constraint CORonal inference framework), a geometry-agnostic method for inferring the X-ray coronal structure of accreting BLACK HOLEs using reverberation-lag measurements. Unlike conventional template-fitting approaches, HAMCOR reframes coronal geometry inference as the ground-state selection of a physical Hamiltonian. The corona is represented as a discrete emissivity distribution over a cylindrical grid, and its geometry emerges from five competing physical constraints: MAGNETic coherence, lag consistency, illumination consistency, pair-production stability, and energy budget feasibility. Minimisation is performed via projected gradient descent with Armijo backtracking line search on the probability simplex. We validate HAMCOR on three synthetic geometries (lamppost, column, ring) using the same grid as the real-data fits, recovering spatial correlations rho = 0.24, 0.50, 0.12 and fractional lag errors below 24 per cent. A hyperparameter sensitivity analysis confirms robustness over more than one order of magnitude in the coupling constants. We apply HAMCOR to five sources spanning seven orders of magnitude in BLACK HOLE mass: four AGN observed with XMM-Newton (Mrk 335, 1H 0707-495, IRAS 13224-3809, MCG-6-30-15) and the stellar-mass BLACK HOLE binary Cyg X-1 (M_bh = 14.8 M_sun), recovering consistent extended disc-corona geometries across the full mass range. We further present a multi-epoch analysis of Mrk 335 across five XMM-Newton observations (2006-2019), revealing that the coronal centroid remains stable at (R_c, z_c) ~ (6.3, 0.5) r_g across flux states spanning a factor of ~15 in reverberation lag amplitude, arguing against a collapsing or expanding lamppost. Schwarzschild-Shapiro delay corrections amount to ~79 per cent of the flat-spacetime lag on average; the recovered spatial morphology is robust to this correction.

[abstract 7 / 42] Yes (score: 5)
arXiv:2607.12776 [pdf, ps, other]

Title: Identifying potentially missed extended sources in the FERMI-LAT 4FGL Catalog using clustering analysis

Authors: Giovanni Cozzolongo, Alison M. W. Mitchell, Samuel T. Spencer, Dmitry V. Malyshev, Tim Unbehaun,

Comments: Accepted for publication in Astronomy & Astrophysics (A&A)

Subjects: astro-ph.HE

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

Context. Since its launch in 2008, the FERMI Large Area Telescope (LAT) has detected thousands of sources, many of which remain unassociated. Some may be extended sources represented in the catalog by multiple point-like entries. The reinterpretation of HESS J1813-178 as a single extended source motivates a systematic search for further missed extended sources. Aims. We search for clusters of unassociated FERMI-LAT sources and test whether single extended-source models describe them better than multiple catalog sources. Methods. We apply the DBSCAN (Density-Based Spatial Clustering of Applications with Noise) algorithm to 4FGL sources with a linking scale of $ε= 0.3^\circ$ over the 5 GeV to 1 TeV energy range. Each cluster contains at least one unassociated source and up to one extended or point-like associated source from selected categories, including pulsars, pulsar wind nebulae, and SUPERNOVA remnants. Using FERMIpy, we compare extended- and multiple-source models and characterize each candidate spectrally and morphologically, focusing on the Galactic plane. Results. We identify 48 clusters containing 124 sources, each with at least one unassociated source. For all eight clusters passing our quality selection, an extended-source model is statistically preferred. At linking scales of $0.4^\circ$ and $0.5^\circ$, all eight retain their core sources. Cross-matches with the Second FERMI Galactic Extended Sources Catalog (2FGES) and the HESS Galactic Plane Survey (HGPS) show that five overlap known extended sources. The other three, including one with morphology dependent on the interstellar emission model, have no counterpart in either catalog and are new extended-source candidates. Conclusions. Spatial clustering combined with likelihood-based model comparison can uncover extended sources missed in the FERMI-LAT catalog and complements existing searches.

[abstract 8 / 42] Yes (score: 5)
arXiv:2607.12952 [pdf, ps, other]

Title: SMA Observations of the Archetypal Compact Steep-spectrum Radio Source 3C 303.1

Authors: Rushikesh Bhutkar, Mark Gurwell, Christopher O'Dea, Mojegan Azadi, Belinda Wilkes, Stefi Baum, D. J. Saikia, Grant Tremblay,

Comments: 17 pages, 3 figures. Published in the Astrophysical Journal. This is the accepted manuscript version

Subjects: astro-ph.GA

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

AGN (ACTIVE GALACTIC NUCLEi) feedback plays a crucial role in shaping galaxy evolution. Numerical simulations show that the kinetic energy transfer efficiency from radio JETs to interstellar medium (ISM) is relatively high, suggesting a significant role of radio JETs in the feedback. We investigate AGN feedback on cold gas in the compact steep-spectrum (CSS) radio source 3C 303.1. CSS sources are largely young RADIO GALAXies evolving through dense environments of their host galaxies. This early evolutionary phase likely represents a critical stage in which the radio source has maximum impact on host galaxy evolution. 3C 303.1 is the only CSS source so far showing alignment in optical, X-ray and UV with the radio structure, making it an interesting source to investigate JET-feedback. We present continuum and spectral line observations of the J=3-2 transition of carbon monoxide ($^{12}$CO) of 3C 303.1, obtained with the Submillimeter Array. We detect continuum emission at 221.1 and 271.2 GHz. We do not detect the $^{12}$CO(J=3-2) line and derive an upper limit on the molecular gas mass of $\sim 2.3 \times 10^{9}\ \mathrm{M_\odot}$. The gas to-dust mass (G/D) ratio is found to be at the lower end of typical Galactic values, and the star-formation rate (SFR) derived is moderate but declining likely due to a recent quenching event. Therefore, $^{12}$CO(J=3-2) non-detection, relatively low G/D ratio, and the moderate but declining SFR point to the shock-heating and/or removal of CO gas by AGN, consistent with the AGN feedback signatures observed in 3C 303.1.

[abstract 9 / 42] Yes (score: 5)
arXiv:2607.12964 [pdf, ps, other]

Title: Dynamical modelling of giant radio QUASARs in the HETDEX Spring Field

Authors: T. M. O. Franzen, J. Machalski, M. Jamrozy, R. Morganti, D. A. Green, Y. C. Perrott, T. W. Shimwell,

Comments: Accepted for publication in MNRAS

Subjects: astro-ph.GA

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

Giant radio sources are defined as extragalactic radio sources, hosted by galaxies or QUASARs, with linear sizes $\geq 0.7$ Mpc. They are thought to represent the final stage of the evolution of RADIO GALAXies whose sizes range from pc to Mpc scales. We analyse in detail the radio morphology and spectra between 54 MHz and 4.85/15.5 GHz of 15 giant radio QUASARs (GRQs) in the HETDEX Spring Field, and fit dynamical evolution models to the sources' observational properties to study their physical parameters (age of the lobes, JET power, ambient medium density etc.). We compare the physical parameters of the GRQs with published results for a compiled sample of Fanaroff-Riley type II radio sources. We find that the GRQs evolve in significantly lower medium densities, both at the central core radius and in front of the lobes, than smaller-sized radio QUASARs (RQs) with similar JET powers. The derived central core densities for both populations are, however, highly sensitive to the assumed ambient medium density profile. For both populations combined, the JET power, $Q_{\text{j}}$, is anti-correlated with the age of the lobes, $t_l$ ($R = -0.67$, where $R$ is the Pearson correlation coefficient), as well as the linear size, $D_l$ ($R=-0.32$), but $t_l$ is a much stronger indicator of $Q_{\text{j}}$ than $D_l$. Using a Spearman partial rank correlation analysis, we demonstrate that there is a fundamental relation between $Q_{\text{j}}$, $t_l$, and $D_l$, despite the strong underlying correlation between age and size.

[abstract 10 / 42] Yes (score: 4)
arXiv:2605.20779 [pdf, ps, other]

Title: A MINOT-based Study of Gamma-ray emission from SPT-CL J2012-5649/Abell 3667

Authors: Siddhant Manna, Shantanu Desai,

Comments: Accepted for publication in Phys. Dark Univ . ( 21 pages, 10 Figures, 5 Tables)

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

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

We present an analysis of the non-thermal properties of the merging galaxy cluster SPT-CL J2012-5649/Abell~3667 ($z = 0.0556$, $M_{500} = 7.16 \times 10^{14}\ M_\odot$) using the MINOT non-thermal emission modeling framework. The predicted hadronic gamma-ray flux from $pp$ interactions in the $1$--$300\ \mathrm{GeV}$ band is $2.82 \times 10^{-11}\ \mathrm{cm^{-2}\ s^{-1}}$ within $R_{500}$, rising to $1.15 \times 10^{-10}\ \mathrm{cm^{-2}\ s^{-1}}$ at the truncation radius ($3.7\,R_{500}$), in broad agreement with the FERMI-LAT reported flux of $1.3 \times 10^{-10}\ \mathrm{cm^{-2}\ s^{-1}}$. Approximately $76\%$ of the predicted hadronic flux originates from beyond $R_{500}$. The Inverse Compton contribution from cosmic-ray electrons is subdominant relative to the hadronic $π^0$-decay gamma-ray component by a factor of ${\sim}20$ in the $1$--$300\ \mathrm{GeV}$ energy band, and therefore does not contribute significantly to the observable signal. The best fit of the observed FERMI-LAT data is achieved with a hadronic emission assuming a proton spectrum $\propto E^{-3.5}$ and a proton energy density almost in equipartition with the thermal energy density. Even though those parameters may look extreme, they could well be explained by the particle acceleration by low Mach number accretion shocks.

[abstract 11 / 42] Yes (score: 4)
arXiv:2607.11316 [pdf, ps, other]

Title: Search for GeV gamma-ray emission from PSZ G181.06+48.47 galaxy cluster using FERMI-LAT data

Authors: Anuja Deshpande, Siddhant Manna, Shantanu Desai,

Comments: 24 pages, 6 figures, 6 tables

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

Created: 2026-07-13; Updated: 2026-07-15; Datestamp: 2026-07-15

We present a search for high energy gamma rays in the energy range from 1--300~GeV from the galaxy cluster PSZ2~G181.06+48.47 using 17.9~years of FERMI-LAT data. A binned likelihood analysis employing the 16-year source catalog reveals a significant $γ$-ray excess at the cluster position. Modelling the emission as a point source yields a detection with $\mathrm{TS}=19.0 (4.3 σ)$, a photon index of $Γ=3.20 \pm 0.62$, and an integrated photon flux of $(9.75\pm2.74)\times10^{-11}\,\mathrm{ph\,cm^{-2}\,s^{-1}}$, but leaves statistically significant residual emission at the cluster center. Replacing the point-source hypothesis with a RadialGaussian spatial template significantly improves the fit, with a preferred width of $σ=0.4^{\circ}$ and an extension significance of $\mathrm{TS}_{\rm ext}=36.8 (6.0σ)$. The adopted Gaussian model yields a source detection significance of $\mathrm{TS}=55.0 (7.4σ)$, a photon index of $Γ=2.62\pm0.26$, and an integrated photon flux of $(3.22\pm0.50)\times10^{-10}\,\mathrm{ph\,cm^{-2}\,s^{-1}}$, while reducing the residual emission at the cluster position to a level consistent with zero. The cluster spectral energy distribution shows significant emission only in the lowest energy interval (1.0--3.13~GeV), while all higher-energy bins are consistent with upper limits, indicating a soft $γ$-ray spectrum with no evidence for emission above $\sim5$~GeV. These results provide strong evidence that the $γ$-ray emission associated with PSZ2~G181.06+48.47 is spatially extended on a scale of $σ\approx0.4^{\circ}$ and is more consistent with diffuse intracluster emission than with a single unresolved point source.

[abstract 12 / 42] (score: 3)
arXiv:2511.21786 [pdf, ps, other]

Title: Parity violating spectral dynamics of BLACK HOLEs in dynamical Chern-Simons gravity

Authors: Han-Wen Hu, Chen Lan, Zong-Kuan Guo,

Comments: 10 pages, 5 figures

Subjects: gr-qc

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

We study how environmentally driven spectral instabilities of quasinormal modes respond to parity violating gravito-scalar coupling in BLACK HOLEs. Focusing on dynamical Chern-Simons gravity as a paradigm for parity violation, we perturb the Schwarzschild background with a localized potential bump. Our analysis reveals three distinctive phenomena absent in general relativity: 1) branch RECONNECTions in the complex frequency plane, 2) a counterintuitive mode stabilization that delays overtaking transitions, and 3) scalar mode dominance emerging at intermediate coupling strengths. These frequency domain features show how comparatively weak static sector differences manifest as distinct dynamical signatures, thereby linking parity violating BLACK HOLE perturbations with non-Hermitian spectral physics. Our results provide a frequency domain characterization of parity violating coupling and motivate future targeted ringdown studies of modified gravity.

[abstract 13 / 42] (score: 3)
arXiv:2606.22595 [pdf, ps, other]

Title: Radio spectral properties and aging of two tailed RADIO GALAXies in a galaxy group at z=0.35

Authors: Paula Vulić, Vernesa Smolčić, Alexis Finoguenov, Ghassem Gozaliasl, Hiddo Algera, Ivan Delvecchio,

Comments:

Subjects: astro-ph.CO

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

We present a study of two tailed RADIO GALAXies in the core of a massive, dynamically young galaxy group - an early group-group merger. Using VLA (3 GHz and 1.4 GHz), MeerKAT (1.35 GHz), and GMRT (610 and 325 MHz) observations, we investigate their radio spectral properties, spectral and dynamical ages. Radio morphologies show clear evidence of interaction with the intragroup medium (IGM). One galaxy is a wide-angle tail (WAT) source, while the other is most likely a head-tail (HT) galaxy. Both galaxies exhibit high radio luminosities, and we find spectral indices of $α=0.8\pm 0.1$ (WAT) and $α=0.6\pm 0.2$ (HT). Spectral index analysis reveals spectral steepening with distance from the core in both galaxies, with localized flattening in the WAT lobes and hotspots along the northern JET, and indications of such flattening in the middle of the HT tail. Spectral ages derived using Jaffe-Perola model are $33.80\substack{+7.63 \\ -7.23}$ Myr (WAT) and $20.86\substack{+10.07 \\ -17.17}$ Myr (HT), significantly lower than dynamical ages of $420\pm60$ to $700\pm100$ Myr (WAT) and $140\pm20$ Myr (and possibly up to $280\pm40$ Myr, for HT), yielding dynamical-to-spectral age ratios of $\sim12-20$ and $\sim7$ (and up to $\sim14$), respectively. The discrepancy may be reduced by using more complex dynamical age models, incorporating interactions with the IGM, which requires deeper X-ray observations of the group. Spectral age estimates may be affected by mixing of electron populations, and could be better constrained with future deep, high-resolution broad-band radio observations at both MHz and frequencies above 3 GHz. The combination of extended radio structures, spectral signatures of radiative aging with localized re-acceleration, and activity timescales up to hundreds of Myr indicates that galaxies are actively interacting with, and likely depositing energy into their environment.

[abstract 14 / 42] (score: 3)
arXiv:2607.12291 [pdf, ps, other]

Title: Nonlinear Tearing Modes in Current-Vortex Sheets

Authors: D. Urbanski, F. L. Waelbroeck, A. Tenerani,

Comments:

Subjects: physics.plasm-ph

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

The linear and nonlinear development of instabilities and Alfvén resonances in a plane current-vortex sheet is presented here for sheared equilibrium profiles $\boldsymbol{B_{y0}} = \tanh(z)\boldsymbol{\hat{y}}$ and $\boldsymbol{V_{y0}} = M_0\tanh(z/r)\boldsymbol{\hat{y}}$. We extend Rutherford's nonlinear model for constant-psi MAGNETic islands to account for a sheared equilibrium flow and determine the flow's impact on the MAGNETic island's size. We find that the POLARIZATION current induced by the equilibrium flow slows the nonlinear growth of the tearing mode. The saturation of the MAGNETic island is hastened somewhat for $r > 1$, slowed for $r < 1$, and unmodified for $r=1$. Finally, we find that, in the presence of Alfvén resonances, the MAGNETic island's growth in the nonlinear regime is no longer adequately characterized by constant-psi, and the dynamics of such islands are not captured by the model.

[abstract 15 / 42] (score: 3)
arXiv:2607.12664 [pdf, ps, other]

Title: Discovery of a star sensitive to the spin of Sgr A*

Authors: K. Abd El Dayem, R. Abuter, N. Aimar, P. Amaro-Seoane, A. Berdeu, J. -P. Berger, G. Bourdarot, W. Brandner, A. Burkert, D. Calderon, C. Correia, J. Cuadra, R. Davies, D. Defrere, L. Delit, A. Drescher, F. Eisenhauer, L. Esteras Otal, M. Fabricius, H. Feuchtgruber, N. M. Foerster Schreiber, A. Foschi, P. Garcia, R. Garcia Lopez, A. Generozov, R. Genzel, S. Gillessen, F. Gonte, X. Haubois, S. F. Hoenig, M. Houlle, S. Joharle, A. Kaufer, J. Kammerer, P. Kervella, J. Kolb, L. Kreidberg, L. Labadie, S. Lacour, O. Lai, R. Laugier, J. -B. Le Bouquin, J. Leftley, B. Lopez, D. Lutz, F. Mang, A. Merand, F. Millour, M. Montarges, N. Morujao, H. Nowacki, M. Nowak, S. Oberti, J. Osorno, T. Ott, T. Paumard, C. Paladini, H. B. Perets, K. Perraut, G. Perrin, R. Petrov, P. O. Petrucci, T. Piran, N. Pourre, S. Rabien, D. C. Ribeiro, S. Robbe-Dubois, M. Sadun Bordoni, J. Sanchez Bermudez, D. Santos, R. Sari, J. Sauter, S. Scheithauer, J. Scigliuto, J. Shangguan, T. T. Shimizu, F. Soulez, J. Stadler, C. Straubmeier, E. Sturm, M. Subroweit, C. Sykes, L. J. Tacconi, P. Thevenet, I. Urso, F. Vincent, J. Woillez, G. Zins,

Comments: accepted for publication in Nature

Subjects: astro-ph.GA gr-qc

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

Residing in the center of the Milky Way, Sgr A* is the closest massive BLACK HOLE (MBH). Its vicinity has allowed measuring individual stellar orbits around it. The stars act as test particles and probe the gravitational potential around the $4.3 \times 10^6 M_\odot$ MBH. These observations have determined the central mass to sub-percent precision, and the mildly RELATIVISTIC motions of stars have given access to the dominant RELATIVISTIC corrections, the gravitational redshift, the transverse Doppler effect, and the prograde precession imposed by the Schwarzschild metric nature of the potential. These effects are of order $β^2 = (v/c)^2$ (for velocity $v$ and speed of light $c$). The Kerr metric for a rotating BLACK HOLE leads to corrections of order $β^3$. Here, we report the discovery of a faint main-sequence star ($m_K = 19.3$), S301, on a 8.7-year orbit and with small enough a pericenter distance, such that the star's peak velocity reaches $25000\,$km/s. Within the measurement capabilities of current near-infrared interferometry and future spectroscopy on an extremely large telescope, S301's motion is directly sensitive to the spin of Sgr A*. The high eccentricity of S301 suggests that it is the captured component of a binary that was torn apart via the Hills mechanism.

[abstract 16 / 42] (score: 3)
arXiv:2607.12682 [pdf, ps, other]

Title: On the transition to large fluxes and access to second stability in gyrokinetic simulations of electroMAGNETic turbulence in STEP

Authors: Daniel Kennedy, Yujia Zhang, Toby Adkins, Plamen Ivanov, Francis Casson, Harry Dudding, Bhavin Patel, Colin Roach, Howard Wilson,

Comments:

Subjects: physics.plasm-ph

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

This work investigates the nonlinear transition to large heat fluxes observed in local gyrokinetic simulations of electroMAGNETic turbulence in STEP. Using the stress-balance framework of Zhang et al. (arXiv:2606.04616, arXiv:2607.11789), we confirm that the onset of extreme transport correlates with a critical value of $q^{2}β_{e}$, where $q$ is the safety factor and $β_{e}$ is the ratio of electron thermal pressure to MAGNETic pressure, and relate this to a limit on the poloidal beta $β_{\mathrm{pol}}$. Crucially, this critical value lies below any relevant linear stability limit in the ($q$, $β_{e}$) space (e.g., the onset of ideal or kinetic ballooning modes). Using an extensive set of nonlinear gyrokinetic simulations, we demonstrate that the transition to large fluxes in STEP is governed by a balance between the electrostatic and MAGNETic-flutter stresses. We argue, and also show numerically, that larger-major-radius tokamaks reach the electroMAGNETic non-zonal regime at lower $β_{e}$, making this MHD-controlled saturation limit more accessible in reactor-scale devices than in small spherical tokamaks. We also demonstrate that access to a second-stable regime enables re-saturation at larger values of $β^{\prime}$. We further show that the ideal ballooning mode (IBM) threshold serves as a useful proxy for delineating this second-stable region and also as a qualitative guide for the onset of large fluxes. These results provide a predictive framework for identifying no-go zone predictions from local gyrokinetics and offer new insight into the electroMAGNETic saturation physics relevant to STEP and other high-$β_{e}$ devices.

[abstract 17 / 42] (score: 3)
arXiv:2607.12904 [pdf, ps, other]

Title: Investigating the Periodic X-ray Behaviour in the Eclipsing AGN NGC 6814

Authors: T. O. Hodd, L. C. Gallo, A. G. Gonzalez, J. M. Miller, D. Rogantini,

Comments: 17 pages, 15 figures, 2 tables. Accepted for publication in ApJ

Subjects: astro-ph.HE

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

A 2016 XMM-Newton X-ray light curve of the Seyfert 1.5 galaxy NGC 6814 exhibited clear eclipsing behaviour, with distinct ingress and egress, during half of the observation. Here, we report on the periodic behaviour in the light curve prior to the eclipse. We use timing and spectral analysis techniques to quantify the behaviour and examine the characteristics of the periodic signal. A superlet transform of the X-ray light curve reveals a period of ~45-50 $μ$Hz in the initial 60 ks of the observation with a detection significance at the >90% level in both the broad (0.3-10 keV) and soft (0.3-1.0 keV) bands. The period is confirmed by fitting a sinusoid, and is also evident in the highest energy bands with diminished significance because of reduced signal-to-noise. There appear to be distinct changes in the variability behaviour during the eclipse as the measured period is modulated (stretched) at all energies. From phase-resolved spectra, we investigate possible physical causes of this periodic behaviour and find that it can be interpreted as changes in the covering fraction or a non-standard inner accretion flow (e.g. truncated disc and misaligned flow). The non-standard inner flow appears consistent with previous reports of a truncated inner disc and compact corona in NGC 6814.

[abstract 18 / 42] (score: 3)
arXiv:2607.13023 [pdf, ps, other]

Title: Simulating the convection in red super-giant stars: wobbling JETs in common envelope evolution

Authors: Shlomi Hillel, Ron Schreier, Noam Soker,

Comments: It will be submitted in two days to allow for comments (including missing references)

Subjects: astro-ph.SR

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

We use our newly constructed three-dimensional red supergiant (RSG) stellar model, which also mimics nuclear energy production and photospheric emission, to calculate the stochastic component of the angular momentum of the mass that a companion spiraling within the RSG's envelope accretes during common envelope evolution (CEE). The accreted mass has a fixed-direction angular-momentum component arising from the density gradient in the RSG envelope and orbital motion. The angular momentum component with a stochastically varying direction results from vigorous envelope convection. We do not include the companion's influence on the RSG envelope during the CEE and consider an undisturbed, non-rotating RSG stellar model. We find that the fluctuating angular momentum amplitude can be several times the fixed-axis angular momentum. The total specific angular momentum of the accreted mass easily forms intermittent accretion disks around neutron stars and BLACK HOLEs, but it is only marginally sufficient, or not at all, to form accretion disks around main-sequence stellar companions. The intermittent accretion disks we expect to form will launch wobbling JETs with varying axes. We discuss aspects of wobbling JETs in the CEE and the grazing envelope evolution (GEE), which might precede the CEE or replace it altogether. Studies have claimed that JETs are a crucial ingredient in many cases of CEE, and the standard CEE should include JETs that the companion launches, before (like the GEE), during, and/or at the exit from the CEE. Our study supports this claim and emphasizes the importance of wobbling JETs.

[abstract 19 / 42] (score: 2)
arXiv:2411.00532 [pdf, ps, other]

Title: Cross-Correlating the Universe: The Gravitational Wave Background and Large-Scale Structure

Authors: Federico Semenzato, J. Andrew Casey-Clyde, Chiara M. F. Mingarelli, Alvise Raccanelli, Nicola Bellomo, Nicola Bartolo, Daniele Bertacca,

Comments: 14 pages, 7 figures. Matches the published version

Subjects: astro-ph.CO

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

The nature of the gravitational wave background (GWB) is a key question in modern astrophysics and cosmology, with significant implications for understanding the structure and evolution of the Universe. We demonstrate how cross-correlating large-scale structure (LSS) tracers with the GWB spatial anisotropies can extract a clear astrophysical imprint from the GWB signal. Focusing on the unresolved population of supermassive BLACK HOLE binaries (SMBHBs) as the primary source for the GWB at nHz frequencies, we construct full-sky maps of galaxy distributions and characteristic strain of the GWB to explore the relationship between GWB anisotropies and the LSS. We find that at current pulsar timing array (PTA) sensitivities, few loud SMBHBs act as Poisson-like noise. This results in anisotropies dominated by a small number of sources, making GWB maps where SMBHBs trace the LSS indistinguishable from a GWB from a uniform distribution of SMBHBs. In contrast, we find that the bulk of the unresolved SMBHBs produce anisotropies which mirror the spatial distribution of galaxies, and thus trace the LSS. Importantly, we show that cross-correlations are required to retrieve a clear LSS imprint in the GWB. Specifically, we forecast the distinguishability of this LSS signature at a $3σ$ level in near-future PTA experiments that probe angular scales of $\ell_{\text{max}} \geq 42$, and $5σ$ for $\ell_{\text{max}} \geq 72$ in optimistic settings. These values assume that GWB anisotropy maps can be reconstructed at these angular resolutions and that loud sources above a resolvability threshold can be identified and removed. Our approach opens new avenues to employ the GWB as an LSS tracer, providing unique insights into SMBHB population models and the nature of the GWB itself. Our results motivate further exploration of synergies between next-generation PTAs and LSS tracers.

[abstract 20 / 42] (score: 2)
arXiv:2506.08341 [pdf, ps, other]

Title: A discussion on the symmetry of RELATIVISTIC Vlasov gas and its accretion in Kerr-Newman BLACK HOLE

Authors: Yongqiang Liu,

Comments: Accepted for publication in Class. Quantum Grav. https://doi.org/10.1088/1361-6382/ae8a0c

Subjects: gr-qc

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

We investigate the kinetic properties of collisionless Vlasov gas in Kerr-Newman spacetime, analyzing how spacetime symmetries constrain the distribution functions. The distribution function is shown to depend on the constants of motion ($m, E, L_z, L$) and a configuration variable $Q^{3}$. Furthermore, we discuss in detail the different scenarios of charged particles being captured or scattered by the BLACK HOLE in Kerr-Newman spacetime, and analytically derive the boundaries of the absorption and scattering domains in phase space. Within the Locally Non-Rotating Frame, we compute particle number density, energy density, principal pressures, and construct a set of diagnostic parameters to quantitatively measure the anisotropy information of the Vlasov gas (relative to a perfect fluid), and provide the analytic results of these physical quantities at spatial infinity. In addition, we discuss the accretion rates of the Kerr-Newman BLACK HOLE and obtain their analytic expressions. Numerical results for the relative (normalized) mass and energy accretion rates reveal an identical parametric dependence: both are suppressed as the BLACK HOLE's rotation $a$ and charge $Q$ increase. Conversely, the absolute value of the normalized angular momentum accretion rate (which is negative) increases with $a$, and $Q$ also moderately influences the angular momentum accretion rate through its effect on spacetime geometry. Accretion of weakly charged plasma drives charged BLACK HOLEs toward electrical neutrality while reducing angular momentum, ultimately favoring evolution toward Schwarzschild configurations. These findings provide new insights into kinetic accretion processes in spacetime geometries.

[abstract 21 / 42] (score: 2)
arXiv:2601.04961 [pdf, ps, other]

Title: FERMI Acceleration Mechanisms Beyond Lorentz Symmetry

Authors: Gilson A. Ferreira, Erick Aguiar, A. A. Araújo Filho, Edson Otoniel, Valdir B. Bezerra, Iarley P. Lobo,

Comments: 23 pages. Added a section with comparison with data

Subjects: gr-qc

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

We construct models for first- and second-order FERMI acceleration of particles, incorporating generic frame transformations, dispersion relations, and conservation laws. Within this framework, we study deformations of Lorentz symmetry via the $κ$-Poincaré algebra in the bicrossproduct and classical bases, which respectively deform and preserve the RELATIVISTIC dispersion relation. We also examine explicit Lorentz symmetry violation and compare the results with deformed relativity and special relativity. The energy spectra present different shapes when one considers deformation or violation of Lorentz symmetry in superluminal or subluminal scenarios. One of the possible outcomes is an intense decay of the spectrum for higher energies. We compare our results with Pierre Auger data.

[abstract 22 / 42] (score: 2)
arXiv:2601.05117 [pdf, ps, other]

Title: Divide and conquer complex flows. Part I: cluster and manifold-based local analysis

Authors: Qihong L. Li-Hu, Guy Y. Cornejo Maceda, Andrea Ianiro, Stefano Discetti,

Comments:

Subjects: physics.flu-dyn

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

This work is a two-part study on the description and prediction of complex fluid flows through the partitioning of the flow domain. In this first part, we propose a framework for a global description of the dynamics of complex flows via clustered spatial representations of the flow, isolating and identifying local dynamics, retrieving different \acp{ST-CNM}. The key enabler is the partitioning of the domain based on a nonlinear manifold learning approach, in which spatial points are clustered based on the similarity of their dynamics, as observed in their compact embedding in manifold coordinates. The method receives as input time-resolved flow fields. The spatial manifold is computed through isometric mapping applied to the vorticity time histories at each spatial location. An unsupervised clustering method, applied in the manifold space, partitions the full flow domain into subdomains. The dynamics of each subdomain are then described with cluster-based modelling. The method is demonstrated on two flow-field datasets obtained with a direct numerical simulation of a fluidic pinball under periodic forcing and with two-dimensional particle image velocimetry measurements of a transitional JET flow. The spatial manifold-based flow partitioning identifies regions with similar dynamics in an automated way. For both cases, \ac{ST-CNM} identifies local dynamics that are not captured by a global approach. In particular, vortex shedding and vortex pairing dynamics are isolated in the JET flow experiment. The proposed fully automated domain partitioning method will benefit the structural description of controlled flows and unveil the actuation mechanisms at play.

[abstract 23 / 42] (score: 2)
arXiv:2601.15198 [pdf, ps, other]

Title: Revealing massive BLACK HOLE astrophysics: The potential of hierarchical inference with extreme mass-ratio inspiral observations

Authors: Shashwat Singh, Christian E. A. Chapman-Bird, Christopher P. L. Berry, John Veitch,

Comments: 19 pages, 6 figures, 3 tables

Subjects: astro-ph.HE gr-qc

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

Gravitational waves from extreme mass-ratio inspirals (EMRIs) will enable sub-percent measurements of massive BLACK HOLE parameters and provide access to the demographics of compact objects in galactic nuclei. During the LISA mission, multiple EMRIs are expected to be detected, allowing statistical studies of massive BLACK HOLE populations and their formation pathways. We perform hierarchical Bayesian inference on simulated EMRI catalogues to assess how well LISA could constrain the astrophysical population using parametrised population models. We test our inference framework on a variety of populations, including heterogeneous and homogeneous mixtures of parametrised subpopulations, and scenarios in which the assumed model is deliberately misspecified. Our results show that population parameters governing distributions with sharp features can be tightly constrained. Mixed populations can be disentangled with as few as $\sim20$ detections, and even with model misspecification, the inference retains sensitivity to key population features. These results demonstrate the capabilities and limitations of EMRI population inference, providing guidance for constructing realistic astrophysical population models for LISA analysis.

[abstract 24 / 42] (score: 2)
arXiv:2605.08068 [pdf, ps, other]

Title: Magnetar field dynamics driven by chiral anomalies without MAGNETic helicity

Authors: Clara Dehman,

Comments: 18 pages, 9 figures. In press, Phys. Rev. D

Subjects: astro-ph.HE hep-ph hep-th physics.plasm-ph

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

The chiral MAGNETic effect (CME), arising from the chiral anomaly and enabling a mutual conversion between MAGNETic topology and fermionic chirality, is a key mechanism in MAGNETar field evolution. Previous work by Dehman & Pons (2025) demonstrated that the CME can efficiently generate dipolar fields $\left(B_{\rm dip} \gtrsim 10^{14}\,\mathrm{G}\right)$, consistent with MAGNETar timing measurements, provided that the initial MAGNETic field carries net helicity. However, whether neutron stars are born with MAGNETic helicity remains uncertain. In this work, we investigate the CME across a range of initial helicity configurations, including non-helical initial conditions. We find that the CME efficiently generates MAGNETar-strength dipoles on timescales of decades, independently of the initial helicity content. The chiral instability is driven by localized helical structures that induce a residual chiral asymmetry and is primarily governed by the maximum chiral chemical potential, requiring $μ_5^{\rm max} \gtrsim \mathrm{few}\times10^{-11}\,\mathrm{MeV}$ for onset in the MAGNETar regime. Our results further show that these dipoles may either remain stable and subsequently evolve through standard Ohmic decay, or become unstable if they acquire sufficient helicity, in which case they decay through the chiral anomaly, transferring energy to less helical modes. This outcome depends sensitively on the initial helicity distribution. These findings extend the applicability of the CME to more realistic MAGNETic-field configurations and underscore the importance of the helicity distribution at birth, a quantity that remains poorly constrained in newborn neutron stars, yet is crucial for determining their MAGNETic evolution and the emergence of MAGNETars.

[abstract 25 / 42] (score: 2)
arXiv:2605.19476 [pdf, ps, other]

Title: Prospect of Measuring the Cosmic Dipole by Associating Strongly Lensed Gravitational Waves with Galaxy Surveys

Authors: Anson Chen, Jun Zhang,

Comments: 31 pages, 10 figures

Subjects: astro-ph.CO gr-qc

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

The cosmic dipole observed in the cosmic microwave background (CMB) is traditionally interpreted as being caused by the observer's motion relative to the background. However, tensions with dipole measurements from RADIO GALAXy counts motivate the need for independent probes. This work investigates the feasibility of using strongly lensed gravitational wave (GW) events to measure the cosmic dipole. Strongly lensed GWs produce multiple time-delayed images, which can be used to infer the distances to both the lens and the source. These distances, associated with the observed redshifts of the lens and the source from galaxy catalogues, encode information about the background cosmology and cosmic dipole effects. By reconstructing a statistical sample of doubly lensed GW events based on the singular isothermal sphere lens model, the cosmic dipole can be estimated jointly with background cosmological parameters. Using realistic simulations for Einstein Telescope and Cosmic Explorer, we forecast that a dipole magnitude $g$ consistent with both the CMB and number count measurement could be detected with 10 years of observation. Furthermore, constraints on $g$ are greatly improved by combining constraints from doubly lensed events with those from triply or quadruply lensed events. In the most optimistic scenario, where we measure the number count dipole magnitude with 10 years of observation, we obtain $g = (2.45^{+1.53}_{-1.28}) \times 10^{-3}$ from the combined constraint, provided that systematic uncertainties are mitigated. Although challenging, strongly lensed GWs offer a novel approach to measuring the cosmic dipole, providing an independent consistency test with different systematics from electroMAGNETic probes.

[abstract 26 / 42] (score: 2)
arXiv:2606.00498 [pdf, ps, other]

Title: Suppression of boosted relic neutrinos by photon backgrounds during ultra-high-energy COSMIC RAY propagation

Authors: Gabriel Azeredo, Vitor de Souza,

Comments: 18 pages, 5 figures

Subjects: astro-ph.HE hep-ph

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

Constraining the cosmic neutrino background (C$ν$B) represents a major experimental challenge in cosmology. Recent studies have suggested that relic neutrinos boosted by ultra-high-energy COSMIC RAYs (UHECRs) may generate observable diffuse neutrino fluxes. Previous estimates have not effectively propagated the primary COSMIC RAYs, often neglecting crucial energy losses and the unavoidable, competing interactions with diffuse photon backgrounds. Here we revisit these expectations using a realistic Monte Carlo propagation framework. This approach allows us to consistently incorporate COSMIC RAY energy losses, nuclear photodisintegration, and production of secondary neutrinos. We show that interactions with diffuse photon backgrounds strongly suppress the boosted relic neutrino flux predicted in simplified propagation scenarios. Furthermore, we demonstrate that to produce any observable suppression on the UHECR energy spectrum at Earth, or for the boosted C$ν$B component to become comparable to the cosmogenic neutrino flux, the C$ν$B density must be enhanced by a factor, the so-called overdensity, of extreme magnitude ($η\gtrsim 10^{8}$).

[abstract 27 / 42] (score: 2)
arXiv:2607.08972 [pdf, ps, other]

Title: Self-similar Worthington JETs

Authors: José M. Gordillo, Javier Rodríguez-Rodríguez, Vatsal Sanjay,

Comments:

Subjects: physics.flu-dyn

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

When a micron-sized bubble bursts, capillary waves deform the cavity into a cone that ejects a Worthington JET. The JET is born by inertial focusing, and the local collapse follows self-similar Euler solutions set by the semiangle $β$. Writing $r_j$ and $v_j$ for the dimensionless JET-base radius and velocity, the local Weber number $We_j=r_j v^2_j$ measures inertia relative to capillarity. The theory, supported by accurate numerical simulations gives $r_j\proptoτ^{α(β)}$ with $α\simeq0.63$ and, hence $We_j\gg1$, with $We_j\to\infty$ as $r_j\to0$, so inertia increasingly overwhelms capillarity. In simulations, the interface collapses onto a universal shape for more than two decades in dimensionless time when lengths are scaled using our prediction for $r_j$. For water, this gives incipient radii of $\mathcal{O}(1)$ nm, predicting nanometric sea-spray aerosols.

[abstract 28 / 42] (score: 2)
arXiv:2607.09850 [pdf, ps, other]

Title: Low-hard to high-soft spectral state transitions in the faintest early-X-ray-detected optical tidal disruption event TDE 2025aarm

Authors: Pietro Baldini, Arne Rau, Andrea Merloni, Jean Somalwar, Seán J. Brennan, Elias Kyritsis, Hannah C. I. Wichern, Peter Boorman, Panos Charalampopoulos, Lixin Dai, Gaurava K. Jaisawal, Chichuan Jin, Tianying Lian, Kirpal Nandra,

Comments: 12 pages, 6 figures (+ appendices). Submitted to A&A

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

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

We report the X-ray and optical spectroscopic properties of TDE 2025aarm, the second closest tidal disruption event (TDE) discovered to date. The proximity of this source, combined with a deep and intense X-ray monitoring campaign spanning six months, allowed us to probe the source down to an unprecedented 0.2-10 keV luminosity of $\sim7\times10^{39}$ erg s$^{-1}$ close to the optical peak. This renders TDE 2025aarm the faintest early-X-ray-detected TDE to date. After the first X-ray detection, the source brightened by nearly two orders of magnitude, reaching a peak luminosity of $\sim5\times10^{41}$ erg s$^{-1}$ about four months after the optical peak. Through time-resolved X-ray spectral analysis, we find that TDE 2025aarm evolved from an initially hard, power-law-dominated X-ray state into a softer, disk-dominated state as the luminosity increased, before hardening again at later times. Such low-hard-to-high-soft state transitions are commonly observed in BLACK HOLE X-ray binaries (XRBs) but have not previously been reported in thermal TDEs. We show that the spectral evolution can be described by variations in the relative contributions of an accretion disk and a Comptonizing component, qualitatively resembling the disk--corona evolution observed in XRBs. We also present the results of our optical spectroscopic follow-up campaign with HET/LRS2, confirming the TDE classification and revealing NIII Bowen fluorescence features. The extremely faint early-time X-ray emission of TDE 2025aarm further supports the idea that the historical dichotomy between X-ray-bright and X-ray-undetected TDEs is largely driven by selection effects related to the depth, cadence, and duration of X-ray follow-up observations. TDE 2025aarm therefore provides new insight into both the accretion physics of TDEs and the possible universality of accretion across several orders of magnitude in BLACK HOLE mass.

[abstract 29 / 42] (score: 2)
arXiv:2607.11979 [pdf, ps, other]

Title: Optical and thermodynamic properties of Kerr-Bertotti-Robinson BLACK HOLEs

Authors: Hassan Hassanabadi, Michael R. R. Good, Soroush Zare, Orlando Luongo, Fariba Kafikang,

Comments:

Subjects: gr-qc

Created: 2026-07-13; Updated: 2026-07-15; Datestamp: 2026-07-15

We investigate the thermodynamic and optical properties of Kerr--Bertotti--Robinson BLACK HOLEs, namely rotating BLACK HOLEs immersed in an external Bertotti--Robinson electroMAGNETic background. In the fixed-$a$ ensemble, we derive the horizon mass relation, the Hawking temperature, the entropy, the Helmholtz-type free energy, the heat capacity, and the extremal remnant configuration. These quantities reduce smoothly to their Kerr counterparts as $B\to0$. In the weak-field regime, the leading thermodynamic corrections arise at order $B^2$; the extremal radius is shifted at this order, whereas the remnant mass receives its first correction only at order $B^4$. We also introduce a formal AdS-like thermodynamic interpretation of the Bertotti--Robinson scale, treating the associated pressure as an effective response variable rather than a genuine cosmological pressure. Because the spacetime is not asymptotically flat, we further compute the finite-radius Komar mass and the Komar charge associated with the horizon generator. Using the Hamilton--Jacobi formalism, we derive the separated null-geodesic potentials, the impact parameters of spherical photon orbits, and the celestial coordinates of the shadow boundary for a finite-distance observer. We then characterize the photon-region boundaries, ergosphere thickness, photon--ergosphere gap, shadow area, and MAGNETic shadow susceptibility. Within the perturbative regime considered, the Bertotti--Robinson background decreases the averaged ergosphere thickness and shadow area, increases the photon--ergosphere gap, and produces a negative shadow susceptibility whose magnitude is enhanced by rotation.

[abstract 30 / 42] (score: 2)
arXiv:2607.11993 [pdf, ps, other]

Title: Spinning particle dynamics, epicyclic frequencies, and transient QPO signatures in Schwarzschild spacetime

Authors: Uktamjon Uktamov, Ali Övgün, Reggie C. Pantig, Bobomurat Ahmedov,

Comments: 18 pages, 11 figures

Subjects: gr-qc

Created: 2026-07-13; Updated: 2026-07-15; Datestamp: 2026-07-15

We study the motion of spinning test particles in Schwarzschild spacetime within the Mathisson--Papapetrou--Dixon pole--dipole approximation, imposing the Tulczyjew--Dixon spin supplementary condition. Restricting to equatorial orbits with the particle spin aligned with the orbital angular momentum, and retaining terms through linear order in the specific spin $s$, we derive the spin-corrected radial potential, circular-orbit conditions, bound periodic trajectories, epicyclic frequencies, and Lyapunov exponents of unstable circular orbits. The spin--curvature coupling shifts the circular-orbit energy and angular momentum and moves the innermost stable circular orbit to $r_{\rm ISCO}=6M-2\sqrt{2/3}\,s+\mathcal{O}(s^2)$ in the sign convention adopted here. We construct bound periodic orbits using the Levin--Perez-Giz zoom--whirl taxonomy and show how the particle spin deforms the corresponding energy--angular-momentum map. We then obtain the coordinate-time azimuthal and radial epicyclic frequencies and use them as kinematical inputs for RELATIVISTIC-precession and resonance prescriptions for quasi-periodic oscillations. Finally, we relate the Lyapunov exponent of unstable circular orbits to the local separatrix structure governing near-homoclinic zoom--whirl motion. The resulting formulation provides a compact analytic connection between linear-in-spin MPD dynamics, periodic-orbit taxonomy, epicyclic-frequency shifts, and transient strong-field phenomenology in a nonrotating black-hole background. Also, we study the gravitational waveforms from the periodic orbits of a massive spinning particle around a BLACK HOLE, presenting those associated with extreme mass-ratio inspirals involving a stellar-mass compact spinning object orbiting a supermassive BLACK HOLE.

[abstract 31 / 42] (score: 2)
arXiv:2607.12272 [pdf, ps, other]

Title: A Collocated Boris Integrator in Flux Coordinates: Balancing Accuracy, Conservation, Cost and Robustness

Authors: Mingyuan Li, Chang Liu,

Comments: 10 pages, 8 figures

Subjects: physics.plasm-ph physics.comp-ph

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

When the guiding-center description fails and the full gyromotion must be resolved for energetic particles in complex configurations like stellarators, charged-particle integrators must be formulated directly in the curvilinear flux coordinates. The Boris algorithm, which adopts a staggered scheme in Cartesian coordinates, is phase-space-volume-preserving and second-order accurate; but a direct port to flux coordinates degrades the position update to first order, because the evolving basis vectors of the curvilinear frame make the starting-point metric deviate from the ideal midpoint metric. We construct a collocated, midpoint-predicted Boris algorithm in flux coordinates, restoring second-order accuracy at the cost of one additional field evaluation per step. In reactor-scale stellarator MAGNETic fields, the scheme recovers second-order convergence in every coordinate component, retains near-machine-precision energy conservation and a bounded MAGNETic moment, and demonstrates greater orbit robustness than Staggered Boris and RK4 at coarse time steps.

[abstract 32 / 42] (score: 2)
arXiv:2607.12285 [pdf, ps, other]

Title: Pulsar anti-glitches: starquakes driven by MAGNETism?

Authors: Hanyuan Long, Ruipeng Lu, Weiyang Wang, Shunshun Cao, Hao Tong, Han Yue, Renxin Xu,

Comments: RAA sumbitted

Subjects: astro-ph.HE

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

In the conventional starquake model of pulsar glitches, it is usually assumed that such events arise from fault slip induced by the self-gravity of compact objects. This inevitably decreases the moment of inertia, producing a glitch with an amplitude of only $Δν/ν> 0$. However, an increasing number of anti-glitches ($Δν/ν< 0$) have been observed in extremely MAGNETized pulsars, the MAGNETars, and this cannot be explained by that framework. In the present study, we hypothesis that MAGNETic stresses within a compact object can make for elastic deformations that trigger fault slipping, resulting in a ``MAGNETism-driven starquake'' when the local breaking threshold is exceeded. This process can then either decrease or increase the moment of inertia, naturally generating a glitch or an anti-glitch, respectively. With an order-of-magnitude calculation in this brief report, we present a simple relationship between the MAGNETic field $B$ and the amplitude $Δν/ν$, which is consistent with the observational distribution of existing glitch and anti-glitch data. Further discoveries of glitch/anti-glitch events, alongside more quantitative models of elastic-MAGNETic stress coupling, would be welcome and could eventually provide clear tests for the hypothesis.

[abstract 33 / 42] (score: 2)
arXiv:2607.12465 [pdf, ps, other]

Title: Accretion-disk formation around orbiting stellar BLACK HOLEs in gaseous star clusters

Authors: Zacharias Roupas,

Comments:

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

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

We consider low-mass BLACK HOLEs (BHs) moving in regular orbits in the cores of non-rotating gaseous star clusters, representative of proto-stellar clusters or the centers of protogalaxies. We argue that as the BH's sphere of influence -- the Bondi sphere -- is advected along the BH trajectory, the transverse velocity shear between the inner and outer hemispheres injects angular momentum, driving the formation of an accretion disk. Coriolis forces oppose angular momentum injection, delaying disk formation but not preventing it. The disk lies in the BH orbital plane and is counter-rotating with respect to the orbital BH motion. We verify this picture with 2D and 3D hydrodynamic simulations in the non-inertial frame of the orbiting BH. We find that the disk-formation timescale following a disruption event is of order the Bondi crossing timescale, $τ_{\rm d} \sim R_{\rm B}/V_{\bullet}$, and that the disk radius is of order $R_{\rm d} \sim ω_{\bullet}^2 R_{\rm B}^4/ G m_{\bullet} $, set by the circularization radius of gas captured in the Bondi sphere. For the case of a BH with $m_{\bullet} = 50\,{\rm M}_\odot$, inside the core of a typical compact proto-stellar cluster, these values read $τ_{\rm d} \sim 0.1 P_{\rm orbit}$ and $R_{\rm d} \sim 10^{-3} R_{\rm B}$.

[abstract 34 / 42] (score: 2)
arXiv:2607.12486 [pdf, ps, other]

Title: Role of spin-curvature and MAGNETic interactions on circular orbits of particles with MAGNETic monopole around Bardeen BLACK HOLEs

Authors: Shokhzod Jumaniyozov, Javlon Rayimbaev, Yuan Chengxun, Ahmadjon Abdujabbarov, Faisal Javed, Satimbay Palvanov,

Comments: 15 pages, 8 figures, submitted to Journal of Cosmology and Astroparticle Physics

Subjects: gr-qc

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

We investigate the dynamics of MAGNETically charged spinning test particles in the spacetime of the Bardeen regular BLACK HOLE, sourced by nonlinear electrodynamics and featuring a MAGNETic monopole charge parameter g. Employing the Mathisson-Papapetrou-Dixon equations supplemented by the Tulczyjew spin condition and extended to include MAGNETic interactions via the generalized Lorentz force, we derive the effective potential governing the radial motion in the equatorial plane. We analyze the properties of circular orbits, including the location and parameters of the innermost stable circular orbit, and examine how they are modified by the particle's spin s, specific MAGNETic charge lambda, and the BLACK HOLE's MAGNETic charge g. Prograde spin and attractive MAGNETic interactions reduce the ISCO radius, whereas repulsive interactions and retrograde spin shift it outward. We further impose timelike constraints to exclude unphysical superluminal trajectories, delineating the admissible parameter space. Finally, we explore high-energy particle collisions near the horizon, computing the critical angular momentum and the center-of-mass collision energy. Due to the regular core of the Bardeen spacetime, the Bañados-Silk-West effect is significantly suppressed or capped at finite values, in contrast to singular BLACK HOLE solutions. These results highlight distinctive phenomenological signatures of regular BLACK HOLEs and offer potential observational probes of nonlinearity in electrodynamics and of MAGNETic monopoles through accretion processes, extreme-mass-ratio inspirals, and ultra-high-energy particle interactions.

[abstract 35 / 42] (score: 2)
arXiv:2607.12512 [pdf, ps, other]

Title: First reduced model for integrated computations of helicon wave heating and current drive in MAGNETic fusion plasmas

Authors: Zi-Chen Kan, Lei Chang, Zhen-Yu Wang, Hua-Sheng Xie, Ping-Wei Zheng, Lai Wei, Qi-Bin Luan, Xue-Mei Zhai, Zhao-Qing Hu, Zheng-Xiong Wang, Matthew Hole, Zhi-Song Qu,

Comments:

Subjects: physics.plasm-ph

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

Fast predictive modelling of radio-frequency heating and current drive is important for integrated tokamak scenario design, yet kinetic calculations of helicon-wave absorption remain too computationally expensive for large-scale parameter scans. We present a reduced model for helicon-wave heating and current drive that retains the dominant parallel electron Landau-damping channel. The wave response is evaluated on the cold-plasma dispersion root, and a single-Landau-pole correction is introduced to obtain compact expressions for the local damping rate and current-drive efficiency. The model is benchmarked against the Chiu-Chan heating model using approximately 1.6 million samples covering representative conditions of EAST, HL-3, DIII-D and KSTAR. The reduction error is found to be governed primarily by the electron Landau parameter and electron beta. Within an identified sub-lower-hybrid-frequency validity window, results from different devices collapse onto a common error curve, which enables an empirical correction that is further tested using ITER-like and BEST-like extrapolation cases. Near and above the lower-hybrid frequency, the agreement deteriorates rapidly owing to changes in the cold-dispersion root structure and the breakdown of the single-branch WKB description. When coupled to a reduced current-drive source, the corrected heating model gives a median deviation of 10.8 percent from the Landau-channel Ehst-Karney reference and reproduces published CFETR current-density profiles. The resulting model provides a computationally efficient reduced closure for helicon-wave heating and current-drive calculations, together with physically interpretable limits on its range of validity.

[abstract 36 / 42] (score: 2)
arXiv:2607.12601 [pdf, ps, other]

Title: Unraveling the Generation Mechanism of a Mid-Latitude Plasma Blob and the Evidence of Its Rare Interaction with a MSTID Phase Front

Authors: D. Patgiri, R. Rathi, V. Yadav, D. Chakrabarty, M. V. Sunil Krishna, S. Kannaujiya, S. Sunda, Y. Otsuka, A. Shinbori, M. Nishioka, S. Perwitasari, P. Pavan Chaitanya, S. Sarkhel,

Comments:

Subjects: physics.space-ph

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

We report observations of two distinct nighttime F-region irregularities, plasma blob (localized density enhancement) and medium-scale traveling ionospheric disturbance (MSTID), in O(1D) 630.0 nm all-sky airglow images from Hanle (32.7°N, 78.9°E; Mlat~24.1°N), Ladakh, India, during the geoMAGNETically quiet (Ap=6) night of 06 July 2021. Global vertical total electron content (VTEC) maps revealed that the plasma blob developed beyond the southern edge of imager's field-of-view before appearing in airglow images and propagated predominantly westward, as confirmed from both the airglow and VTEC datasets. The existence of the plasma blob and MSTID outside the imager field-of-view was further confirmed by temporal VTEC fluctuations recorded by multiple GNSS receivers. Additionally, FORMOSAT-7/COSMIC-2 signal-to-noise ratio and ICON/MIGHTI wind profiles indicated the presence of sporadic-E (ES) layers at E-region near both the plasma blob and the MSTID. We propose that POLARIZATION electric field associated with either MSTID or ES-layers mapped along MAGNETic field lines to lower latitudes, driving upward plasma transport from F-peak region through vertical uplift of the F-layer. This F-layer uplift was confirmed by simultaneous in-situ O+/H+ density enhancements/reductions at LEO altitudes measured by FORMOSAT-7/COSMIC-2. Upward-transported plasma experienced reduced chemical loss at higher altitudes, producing localized VTEC enhancements (plasma blob). The plasma subsequently diffused along MAGNETic field lines to higher/lower latitudes/altitudes (~250 km), entering imager's field-of-view, where enhanced dissociative recombination of O2+ produced high intensity airglow region. Interestingly, interaction between the plasma blob and MSTID's plasma-depleted front caused gradual decay and bifurcation of the front due to plasma influx from the high-density blob region.

[abstract 37 / 42] (score: 2)
arXiv:2607.12708 [pdf, ps, other]

Title: Perturber-Driven Dynamics of Supermassive Black Hole Binaries in Galaxy Merger

Authors: Julian Chan, Alessia Gualandris, Walter Dehnen, Justin I. Read,

Comments: Accepted for publication in Monthly Notices of the Royal Astronomical Society (MNRAS) on 13 July 2026

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

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

The orbital eccentricity of massive BLACK HOLE binaries (MBHBs) at binary formation shapes the stochastic gravitational-wave background (GWB) detectable by pulsar timing arrays (PTAs). Previous $N$-body simulations show large run-to-run scatter in this quantity, dominated by Poisson noise, raising the question of whether physical substructure adds genuine astrophysical stochasticity. We test this with high-resolution re-simulations of a major merger from IllustrisTNG100-1, evolved with the Griffin $N$-body code. A no-perturber control is compared with two matched suites in which $f_{\mathrm{target}}=0.1$ of the primary bulge mass is redistributed into equal-mass perturbers of $10^7,M_\odot$ ($μ_{\mathrm{p}}\approx3.2\times10^{-3}$) and $10^8,M_\odot$ ($μ_{\mathrm{p}}\approx3.2\times10^{-2}$), with four realisations per scenario. The control gives $σ_e\approx0.11$, consistent with the Poisson noise floor at this resolution. The $10^7,M_\odot$ case gives $σ_e\approx0.115$, indistinguishable from the control, whereas the $10^8,M_\odot$ case gives $σ_e\approx0.26$, a factor of $2.4$ above the floor, although statistically marginal given only four realisations. This excess scatter coincides with larger event-aligned residuals in orbital energy and angular momentum and stronger torque spikes, consistent with near-impulsive perturber--MBHB encounters. In binary--single scattering theory, the transition is set by the perturber--MBHB mass ratio $μ_{\mathrm{p}}$: the $10^7,M_\odot$ case remains diffusive, whereas the $10^8,M_\odot$ case approaches the near-impulsive regime. Because the expected perturber population in massive ellipticals lies mostly below this regime, perturber-driven eccentricity randomisation is unlikely to affect GWB-relevant MBHB mergers.

[abstract 38 / 42] (score: 2)
arXiv:2607.12846 [pdf, ps, other]

Title: Inferring 3D Coronal Magnetic Fields Through Seismology Assisted Inversions of $IQU$-only Spectropolarimetric Observations

Authors: Alin Răzvan Paraschiv,

Comments: 16 pages. Accepted for publication in The Astrophysical Journal

Subjects: astro-ph.SR

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

The routine measurements of the Stokes $IQUV$ signals of emission lines in the solar corona is still a challenging endeavor, particularly for observations using small-aperture instruments. Therefore, recent studies have explored the use of coronal seismology and propagating Alfvénic waves as alternative diagnostics of the coronal MAGNETic field. In particular, Yang et al. (2024) showed that plane-of-sky (POS) phase-speed measurements provide a direct and consistent diagnostic of the POS MAGNETic-field component (B$_{\text{POS}}$). Building on recent theoretical advances in solar coronal POLARIZATION, we devise a novel inversion scheme and extended the CLEDB software package (Paraschiv & Judge 2022) to exploit Stokes $IQU$ observations of two coronal emission lines combined with coronal-seismology derived B$_{\text{POS}}$ estimations. Using this framework, we perform a comprehensive statistical analysis demonstrating that this combination of diagnostics allows us to infer both MAGNETic field orientation and strength with an accuracy comparable to that of Stokes $IQUV$ spectropolarimetry. This type of diagnostics is particularly suited for the Fe XIII 1074.7 nm and 1079.8 nm line pair routinely observed by new-generation instruments such as DKIST Cryo-NIRSP, DL-NIRSP, MLSO CoMP/UCoMP, and targeted by the future COSMO and CORSAIR efforts.

[abstract 39 / 42] (score: 2)
arXiv:2607.12905 [pdf, ps, other]

Title: A new model for runaway electron transport based on chaotic Hamiltonian systems

Authors: Dániel Jánosi, Anikó Horváth, Hannes Bergström, Matthias Hölzl, Gergely Papp, Gábor Veres, Gergo I. Pokol, György Károlyi,

Comments:

Subjects: physics.plasm-ph

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

The transport of runaway electrons (RE) in ergodic MAGNETic geometries is an area of active study. Computing the transport from the direct simulation of particle trajectories is computationally expensive. Instead, diffusion models, such as the one by Rechester and Rosenbluth, are often employed to incorporate transport effects into reduced simulations. However, the comparison of diffusion-based to direct simulations reveals that the transport is typically not purely diffusive. In this paper, we introduce a simple transport model, based on chaos theory, which goes beyond the Rechester-Rosenbluth approximation. Besides chaotic diffusion, our model takes into account the effect of so-called sticky regions, a trapping layer around MAGNETic islands, where particle escape slows down to a power-law decay rather than an exponential decay. We demonstrate the applicability of the model both in the Ullmann-Caldas map with parameters corresponding to the TBR-1 tokamak, and in a JOREK simulation of a JET disruption scenario, with remarkably good fits achieved in both cases.

[abstract 40 / 42] (score: 2)
arXiv:2607.12927 [pdf, ps, other]

Title: Mixing and sharpening at the interface of a two-layer fluid forced by random JETs

Authors: Noé Clavier, Hugo Pradel, Romain Volk, Mickaël Bourgoin, Yvan Dossmann,

Comments: 23 pages, 12 figures

Subjects: physics.flu-dyn physics.geo-ph

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

Understanding mixing at density interfaces is essential for predicting transport in stratified environmental flows. Laboratory studies have mostly relied on steady, spatially uniform forcing, whereas turbulence in nature is intermittent and heterogeneous. Here, we present experiments on a two-layer salt-stratified fluid forced by random turbulent bursts generated with a randomly actuated synthetic JET array (RASJA). Density fields are recorded with the light attenuation technique, allowing us to resolve the interface evolution. We measure that the upward velocity of the interface decreases with the density jump, in agreement with the power-law found in previous oscillating-grid studies. At large density differences, the interface sharpens during mixing, contrary to the smaller density jump case. Background potential energy analysis demonstrates irreversible mixing in both cases, with comparable energy changes. These results extend classical laboratory observations to a more isotropic forcing, offering new insights into the dynamics of mixing in geophysical settings.

[abstract 41 / 42] (score: 2)
arXiv:2607.12971 [pdf, ps, other]

Title: A new model for the continuum spectra of AM CVn binaries and multi-messenger inference with normalizing flows

Authors: Nathan Steinle, Samar Safi-Harb, Austin MacMaster, Liliana Rivera Sandoval, Katelyn Breivik, Tyrone E. Woods, Tom Maccarone, Tom Wagg,

Comments:

Subjects: astro-ph.HE gr-qc

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

Future electroMAGNETic telescopes, such as $\textit{NewAthena}$, $\textit{CASTOR}$, and an $\textit{AXIS}$-like mission, along with milli-Hz gravitational-wave (GW) detectors such as $\textit{LISA}$, are expected to unearth the population of Galactic ultra-compact binaries (UCBs). Joint multi-messenger detections will probe the uncertain formation, evolution, and observables of mass-transferring UCBs such as AM CVns, but theoretical tools need to be advanced to anticipate future data challenges. Motivated by this, we present a new forward model for the continuum emission of AM CVn binaries that connects source binary parameters to X-ray, optical, and ultraviolet observables. The model assumes GW-driven mass transfer with physically motivated prescriptions for accretion energetics, emission geometry, absorption, and instrumental response. Combining this with $\textit{LISA}$ observations and the output of binary population synthesis enables exploration of the multi-messenger properties of AM CVns. Although uncertain, our model predicts that approximately one per $7000$ AM CVn binaries will permit a joint multi-messenger detection with $\textit{LISA}$, $\textit{CASTOR}$, and $\textit{AXIS}$. We also develop a framework for inferring binary parameters from the inverse model with a convolutional neural net and normalizing flows. Testing the trained flow with our synthetic AM CVn population, we find mean absolute fractional error on the inferred accretor mass of $0.05$ M$_{\odot}$, donor mass of $0.26$ M$_{\odot}$, orbital period of $0.1$ s, and distance of $0.2$ pc, while Spearman's rank shows strongly correlated true and predicted distributions except for the donor mass. These efforts lay a foundation for follow-up studies that will explore detailed binary astrophysics and observational requirements for effective multi-messenger scientific discovery in the coming decade.

[abstract 42 / 42] (score: 2)
arXiv:2607.13018 [pdf, ps, other]

Title: Antikick Relation in High-Energy Head-On Collisions of Spinning Black Holes

Authors: Carlos O. Lousto, James Healy, Alessandro Ciarfella, Hiroyuki Nakano,

Comments: 9 pages, 5 figures, 3 tables

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

Created: 2026-07-14; Updated: 2026-07-15; Datestamp: 2026-07-15

The collision of BLACK HOLEs at RELATIVISTIC speeds probes gravity in its most extreme dynamical regime. While the maximum gravitational recoil from \emph{grazing} high-energy collisions ($\approx28\,562$~km/s, i.e., $\sim0.1c$) and the maximum radiated energy $E_{\rm rad}$ and remnant spin $α_f^{\max}$ from such encounters ($E_{\rm rad}/M_{\rm ADM}\approx32\%$ where $M_{\rm ADM}$ is the ADM mass, and $α_f^{\max}\approx0.987$) have been established previously~\cite{Healy:2022jbh,Healy:2024lhl}, here we focus on the \emph{head-on} high-energy collision of equal-mass spinning BLACK HOLEs and on the detailed structure of the resulting recoil. Performing a sequence of full numerical simulations for spin magnitudes $s=0.5,0.65$, and $0.8$ over a range of initial momenta $γv$, we characterize the peak recoil $V_p$, the final recoil $V_f$, and the antikick $ΔV\equiv V_f-V_p$, and we provide phenomenological fits of their dependence on $γv$ and $s$. We complement these results with a zero-frequency-limit (ZFL) analysis of the radiated energy and momentum, a quasinormal-mode model of the antikick, and a superposed boosted double-Kerr close-limit estimate. We find that in the RELATIVISTIC regime ($γv>1$) the peak and final recoil are directly proportional, $V_p\approx7.4\,V_f$ (equivalently $ΔV \approx-6.4\,V_f$), largely independent of both the initial momentum and the spin magnitude, pointing to a common post-merger relaxation. While the ZFL predicts a leading linear-in-spin dependence, the close-limit analysis predicts a leading $s^3$ dependence of the recoil amplitude; with the three spin magnitudes studied here the empirical exponent is $s^{1.27\pm0.08}$, motivating an even higher energy collision spin sequence study.