Current date: 2026-06-04
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Number of records retrieved: 229
Keyword score statistics
score 10 -- 1 abstracts
score 6 -- 1 abstracts
score 5 -- 3 abstracts
score 4 -- 4 abstracts
score 3 -- 2 abstracts
score 2 -- 7 abstracts
in total -- 18 abstracts
Articles that appeared on 2026-06-04
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[abstract 1 / 18] Wow! (score: 10)
- Title: Simulating realistic radio morphologies of Fanaroff-Riley I JETs in a self-regulating cool-core clusterAuthors: Léna Jlassi, Rainer Weinberger, Christoph Pfrommer, Maria Werhahn, Joseph Whittingham, Philipp Girichidis,Comments:Subjects: astro-ph.GA astro-ph.HECreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
Active galactic nucleus (AGN) JETs radiate radio SYNCHROTRON emission displaying a wide range of morphologies. At the same time, they provide heat to prevent cooling flows in cool-core galaxy clusters. We produce mock radio observations of AGN JETs in a self-regulating cool-core galaxy cluster. To this end, we employ MAGNETo-hydrodynamical simulations of an idealised Perseus-like galaxy cluster, in which accretion-powered low-density JETs accelerate COSMIC RAY protons and electrons by means of a sub-grid model. Cosmic ray electron spectra are spatially and temporally evolved along Lagrangian tracer trajectories using the Fokker-Planck solver Crest to produce radio SYNCHROTRON emission. Self-regulated AGN JETs stabilize the cool-core cluster against cooling flows and produce realistic Fanaroff-Riley I (FRI) and disturbed lobe morphologies, in contrast to symmetrical lobe structures obtained with a single JET outburst of fixed power. Our mock radio observations are viewed in a BLAZAR configuration - along the JET axis - and exhibit complex radio-emitting lobe structures despite this. This highlights the strong deflection of light JETs by cold gas structures and suggests that small-scale BLACK HOLE and JET properties cannot be inferred from kpc-scale FRI radio lobe morphologies. Combining self-consistently evolved MAGNETic fields and electron spectra enables us to explain a known observational phenomenon, whereby radio observations of AGN lobes on galaxy cluster scales occasionally display similar spatial extents at different frequencies: in 1-50 $μ$G MAGNETic fields obtained in our cool-core environment, both freshly accelerated and hundreds-of-Myr-old electrons are able to contribute to the 150 MHz - 1.4 GHz frequency range.
[abstract 2 / 18] Yes (score: 6) - Title: Radiation-induced electron spin POLARIZATION in ultraRELATIVISTIC kinetic turbulenceAuthors: Peng Liu, Karen Z. Hatsagortsyan, Christoph H. Keitel, Zheng Gong,Comments: Comments are welcomeSubjects: physics.plasm-ph astro-ph.HECreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
Electron spin POLARIZATION in radiative plasmas with ultraRELATIVISTIC kinetic turbulence under highly MAGNETized conditions is investigated using particle-in-cell simulations. We observe that a significant spin POLARIZATION can be sustained when the leptons undergo energetic photon emission accompanied by spin flips during the nonequilibrium turbulent evolution.By analyzing the time evolution of spatially dependent spin POLARIZATION, we identify an electroMAGNETic (EM) regime of kinetic turbulence, distinct from the well-known density-dominated regime characterized by vortex currents and MAGNETic islands. While in the latter regime the spin POLARIZATION exists only transiently, in the EM regime significant anisotropic net POLARIZATION emerges and persists in non-dissipative scenarios. The correlation between spin signals and turbulence features is leveraged to introduce the characteristic parameter delimiting the EM regime via the ratio of electric and MAGNETic energy densities and to gain insight into complex plasma turbulence. This study demonstrates the versatility of a spin-resolved study of the plasma turbulence in extreme environments, such as BLACK HOLEs and MAGNETar MAGNETospheres.
[abstract 3 / 18] Yes (score: 5) - Title: Captured are circularized: A RELATIVISTIC treatment of extreme mass ratio inspirals crossing accretion disksAuthors: Yuhe Zeng, Zhen Pan,Comments: 15 pages, 14 figuresSubjects: astro-ph.HECreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
A small body orbiting around an accreting massive object and periodically crossing its accretion disk is a common configuration in astrophysics. In this work, we investigate the secular evolution of extreme mass-ratio inspirals (EMRIs), in which a stellar-mass object (SMO), e.g., a star or a stellar-mass BLACK HOLE (sBH), collides with the accretion disk of a central supermassive BLACK HOLE (SMBH), within a fully RELATIVISTIC framework. We find (1) the disk always tends to align the SMO no matter what the initial orbital inclination $ι$ relative to the disk is, (2) the final orbital eccentricity of the SMO captured by the disk is always low though the orbital eccentricity may temporarily grow when the orbital inclination $ι$ is large and the SMO is an sBH, and (3) via collisions with the accretion disk only, only a small fraction of sBHs that are initially close to the SMBH and close to the disk can be captured by the disk within typical disk lifetime of ACTIVE GALACTIC NUCLEi. Two-body scatterings between SMOs in the nuclear stellar cluster play an essential role in randomly kicking sBHs towards the disk and boosting the capture rate.
[abstract 4 / 18] Yes (score: 5) - Title: Blackholistic 2026 meeting reportAuthors: Rob Fender, Jane Dai, Erin Kara, Sera Markoff, Francesca Panessa, Jiri Svoboda, Heino Falcke,Comments: We encourage all who are interested in the subject matter of this meeting to visit our talks and poster archive at https://blackholesoxford2026.web.ox.ac.uk/programmeSubjects: astro-ph.HECreated: 2026-06-01; Updated: 2026-06-04; Datestamp: 2026-06-04
Accretion and RELATIVISTIC JET formation take place across the BLACK HOLE mass range, from BLACK HOLEs of just a few solar masses to those in excess of ten billion. Despite the enormous range in scales, qualitative similarities and quantitative scalings appear to connect the entire population. In March 2026, researchers from across the BLACK HOLE mass spectrum met in Oxford to educate, explore and forge new research directions. This is a brief report on the meeting and an opportunity to advertise the archive of talks, discussion sessions and posters.
[abstract 5 / 18] Yes (score: 5) - Title: Multifrequency Synthesis via CHIBI: Colorful Hierarchical Interferometric Bayesian ImagingAuthors: Erandi Chavez, Paul Tiede, Sara Issaoun, Michael D. Johnson, Dominic Pesce, Yuh Tsunetoe, Daniel C. M. Palumbo,Comments: 26 pages, 18 figures, to be published in ApJSubjects: astro-ph.IM astro-ph.HECreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
From MAGNETized plasma of RELATIVISTIC JETs to dust grains within protoplanetary disks, we study the emission mechanisms of radio sources via their rich spectral structure. Multifrequency Synthesis (MFS) is a technique in which interferometric data at multiple frequencies are imaged simultaneously, resulting in a denser sampling of spatial scales, higher imaging fidelity, and tighter constraints on the source's spectral structure and evolution. We describe a new method of MFS imaging reconstruction in a hierarchical interferometric Bayesian inference framework, CHIBI. The model parametrization is based on the spectral behavior of SYNCHROTRON radiation, the emission mechanism dominating the radio emission observed from galactic nuclei. We show results of this method on observations of JET sources from the MOJAVE catalog with the Very Long Baseline Array, and showcase the prospects for MFS imaging of M87* with simulated data from the Event Horizon Telescope (EHT) and future expansions such as the next generation EHT and the Black Hole Explorer. These demonstrations highlight the benefit of MFS to reconstruct higher-fidelity images and spectral index maps, producing scientifically richer results in a statistically grounded framework, implemented in Comrade.jl.
[abstract 6 / 18] Yes (score: 4) - Title: XRISM detection of the 6.4 keV Fe K$α$ line in the RADIO GALAXy Cygnus AAuthors: 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. Accepted for publication in ApJSubjects: astro-ph.HE astro-ph.COCreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
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 7 / 18] Yes (score: 4) - Title: The role of major mergers in triggering super-Eddington accretionAuthors: Riccardo Caleno, Tommaso Zana, Raffaella Schneider, Alessandro Lupi, Pedro R. Capelo, Lucio Mayer, Alessandro Trinca, Rosa Valiante, Marta Volonteri,Comments: 12+2 pages, 8 figures; submitted to A&ASubjects: astro-ph.GA astro-ph.CO astro-ph.HECreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
JWST observations have opened a new era in the exploration of the high-redshift Universe, revealing BLACK HOLEs (BHs) with masses of several million solar masses already at $z>8$, challenging our understanding of their growth mechanisms. In this context, super-Eddington (SE) accretion has emerged as a promising solution and has been widely adopted in both numerical simulations and semi-analytical models. In this work, we investigate whether a major merger between two relatively low-mass halos ($M_{\rm halo}\sim10^9\,\mathrm{M_\odot}$) at high redshift can trigger episodes of sustained SE accretion, with particular focus on the role of BH feedback. We employ state-of-the-art, high-resolution cosmological zoom-in simulations of a major merger at $z\sim11$. We explore different prescriptions for BH seeding and feedback, including physically motivated radiative and kinetic models (winds and JETs) across the three main accretion regimes: advection-dominated accretion flows (ADAF), radiatively efficient sub-Eddington accretion, and SE accretion. For the relatively low-mass halos studied here, our feedback prescription efficiently suppresses gas accretion, preventing substantial BH growth. We find that, although the merger drives gas inflows towards the central regions, this is not sufficient to trigger sustained SE accretion. Post-merger SE accretion episodes are observed only when BH feedback is entirely switched off. Amongst the feedback channels considered, kinetic feedback is the primary mechanism regulating BH growth. Moreover, the only significant SE accretion episodes occur immediately after BH seeding, while the merger itself does not produce a substantial enhancement of the accretion rate.
[abstract 8 / 18] Yes (score: 4) - Title: Temporal Invariance Is an Illusion: Time-Dependent Influences of the Galactic Magnetic Field on UHECR ObservationsAuthors: Veronika Vašíčková, Leonel Morejón, Karl-Heinz Kampert,Comments: 13 pages, 8 figures excl. appendix, or 18 pages, 12 figures incl. appendixSubjects: astro-ph.HECreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
Understanding the origin of the Ultra-High-Energy Cosmic Rays (UHECRs) requires explaining the features of their energy spectrum, mass composition, and arrival directions. Current modeling approaches neglect the time evolution of UHECR observables, a factor that is particularly important in the case of bursting UHECR sources. This study focuses on the influence of time delays caused by the galactic MAGNETic field (GMF) on the spectrum and arrival directions of UHECRs observed on Earth. Using CRPropa 3.2, we investigate the rigidity-dependence of the residence time of extragalactic COSMIC RAYs entering our Galaxy. We find that UHECRs entering the Milky Way can experience delays of hundreds of kiloyears relative to light, and we demonstrate that these delays significantly alter the UHECR observables. Notably, a cutoff emerges in the transient scenario within the rigidity range of $10^{18}-10^{19}$ V, which coincides with the spectral break observed in data. We find a progressive shift in composition favoring heavier nuclei, as well as a delay distribution that is correlated with GMF strength. This causes the particles to be less correlated with their initial direction the larger their delays. A dipole-like anisotropy develops over timescales of about $\sim$100 kyr in certain bursts scenarios. Our results provide an alternative explanation for the UHECR spectral cutoff that does not invoke limits on source acceleration. This could potentially revise existing constraints.
[abstract 9 / 18] Yes (score: 4) - Title: Shape of U: Measuring the Curvature of the Universe with Gravitational WavesAuthors: Arindam Sharma, Ish Gupta, Anuradha Gupta,Comments: 15 pages, 7 figuresSubjects: gr-qc astro-ph.CO astro-ph.HECreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
Gravitational waves (GWs) from compact binary mergers are standard sirens that can measure distances across the Universe without external calibrators. When an electroMAGNETic counterpart enables an independent redshift measurement, such "bright sirens" can be used to probe the expansion history of the Universe and constrain cosmological models. In this work, we investigate the ability of future GW observatories to measure the spatial curvature parameter, $Ω_{\rm k}$, in a non-flat $Λ$CDM cosmology. We focus on intermediate-mass binary BLACK HOLE mergers (with masses similar to GW231123) as bright siren sources, motivated by their detectability to high redshifts with next-generation ground-based detectors and by the possibility that mergers in ACTIVE GALACTIC NUCLEus disks may produce electroMAGNETic counterparts. Using Fisher matrix forecasts, we find that a network consisting of two Cosmic Explorer detectors and Einstein Telescope can constrain $Ω_{\rm k}$ to a $1σ$ uncertainty of $0.029$ with these bright sirens. We further show that multiband observations with LISA or the Lunar Gravitational Wave Antenna do not significantly improve these cosmological constraints, because the additional signal-to-noise ratios accumulated in their bands are modest. Further, a population of binary neutron stars as bright sirens provides substantially broader constraints on $Ω_{\rm k}$, with $1σ$ error of $0.055$. Our results show that bright intermediate-mass binary BLACK HOLE and binary neutron star mergers observed with next-generation GW detectors together can provide an independent and informative probe of spatial curvature, with systematics distinct from those of other cosmological observations.
[abstract 10 / 18] (score: 3) - Title: Learning collision operators from plasma phase space data using differentiable simulatorsAuthors: Diogo D. Carvalho, Pablo J. Bilbao, Warren B. Mori, Luis O. Silva, E. Paulo Alves,Comments: accepted for publication in Journal of Plasma Physics, code available at https://github.com/diogodcarvalho/ml-pic-collision-operatorsSubjects: physics.plasm-ph cs.LG physics.comp-phCreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
We propose a methodology to infer collision operators from phase space data of plasma dynamics. Our approach combines a differentiable kinetic simulator, whose core component in this work is a differentiable Fokker-Planck solver, with a gradient-based optimisation method to learn the collisional operators that best describe the phase space dynamics. We test our method using data from two-dimensional Particle-in-Cell simulations of spatially uniform thermal plasmas, and learn the collision operator that captures the self-consistent electroMAGNETic interaction between finite-size charged particles over a wide variety of simulation parameters. We demonstrate that the learned operators are more accurate than alternative estimates based on particle tracks, while making no prior assumptions about the relevant time scales of the processes and significantly reducing memory requirements. We find that the retrieved operators, obtained in the non-RELATIVISTIC regime, are in excellent agreement with theoretical predictions derived for electrostatic scenarios. Our results show that differentiable simulators offer a powerful and computational efficient approach to infer novel operators for a wide rage of problems, such as electroMAGNETically dominated collisional dynamics and stochastic wave-particle interactions.
[abstract 11 / 18] (score: 3) - Title: Dynamics and detectability of long-lived non-accretion phases for massive BLACK HOLE binaries in cold, thermally regulating disksAuthors: Christopher Tiede, David O'Neill, Daniel J. D'Orazio,Comments: 17 pages and 9 figuresSubjects: astro-ph.HE astro-ph.GACreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
We investigate whether the non-accreting phases found in thin, locally isothermal circumbinary disks survive when the disk thermodynamics are evolved self-consistently. We present grid-based hydrodynamics simulations of circumbinary accretion with an energy equation that includes viscous and hydrodynamic heating coupled to radiative blackbody cooling in the high-Mach number regime. We find that, although gas accumulates and heats at the far edge of the circumbinary cavity, the regions that launch accretion streams remain comparatively cold, leading to potentially long-lived suppression of the binary accretion rate as the large-scale feeding rate is reduced towards the Eddington limit. This runaway non-accretion problem, however, is weakened relative to locally isothermal solutions. Despite their low accretion rates, binaries interacting with disks in a non-accreting phase can remain sufficiently luminous and variable at optical and near-infrared frequencies to be detectable in upcoming wide-field surveys like LSST and the Roman Space Telescope. Because of the effective truncation of the surrounding disk, though, such systems are comparatively faint in high energy, photo-ionizing emission, and may therefore appear as intrinsically X-ray-weak AGN with weak or absent emission line features. We additionally suggest an update to grid-based sink prescriptions for approximating mass loss across an unresolved horizon when including an energy conservation equation.
[abstract 12 / 18] (score: 2) - Title: Modeling transport in weakly collisional plasmas using thermodynamic forcingAuthors: Prakriti Pal Choudhury, Archie F. A. Bott,Comments: 28 pages, 15 figures, 1 table, accepted in Physical Review ESubjects: physics.plasm-ph astro-ph.GA astro-ph.HECreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
How momentum, energy, and MAGNETic fields are transported in the presence of macroscopic gradients is a fundamental question in plasma physics. Answering this question is especially challenging for weakly collisional, MAGNETized plasmas, where macroscopic gradients influence the plasma's microphysical structure. In this paper, we introduce thermodynamic forcing, a new method for systematically modeling how macroscopic gradients in MAGNETized or unMAGNETized plasmas shape the distribution functions of constituent particles. In this method, we propose to apply an anomalous force to those particles inducing the anisotropy that would naturally emerge due to macroscopic gradients in weakly collisional plasmas in which thermal pressure is much larger than MAGNETic pressure. We implement thermodynamic forcing in particle-in-cell (TF-PIC) simulations using a modified Vay particle pusher and validate it against analytic solutions of the equations of motion. We then carry out a series of simulations of electron-proton plasmas with periodic boundary conditions using TF-PIC. First, we confirm that the properties of two electron-scale kinetic instabilities - one driven by a temperature gradient and the other by bulk-velocity gradient - are consistent with previous results. Then, we demonstrate that in the presence of both macroscopic gradients, heat-flux saturation is mediated by the bulk-velocity-gradient-driven electron firehose instability rather than the temperature-gradient-driven whistler instability. This suggests that saturation mechanisms may differ from our current understanding in the presence of multiple free energy sources. This work enables, for the first time, systematic and self-consistent transport modeling in weakly collisional plasmas, with broad applications in astrophysics, LASER-plasma physics, and inertial confinement fusion.
[abstract 13 / 18] (score: 2) - Title: TDE 2025abcr: A Tidal Disruption Event in the Outskirts of a Massive GalaxyAuthors: Robert Stein, Jonathan Carney, Charlotte Ward, Raffaella Margutti, Xander J. Hall, Itai Sfaradi, Igor Andreoni, Ryan Chornock, Suvi Gezari, Geoffrey Mo, Yuhan Yao, Eric C. Bellm, Joshua S. Bloom, Malte Busmann, Ilaria Caiazzo, S. Bradley Cenko, Matthew J. Graham, Steven L. Groom, Daniel Gruen, Erica Hammerstein, Mansi M. Kasliwal, Brendan O'Connor, Antonella Palmese, Josiah Purdum, Jillian C. Rastinejad, Reed Riddle, Ben Rusholme, Jesper Sollerman, Jean J. Somalwar, Sylvain Veilleux,Comments: accepted, 30 pages, 14 figuresSubjects: astro-ph.HE astro-ph.GACreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
Tidal disruption events (TDEs) have traditionally been discovered in optical sky surveys through targeted searches of nuclear transients. However, it is expected that some TDEs will occur outside the galaxy nucleus, arising from wandering BLACK HOLEs originating in galaxy mergers. Here we present observations of TDE 2025abcr, the first optical TDE discovered in the outskirts of a host galaxy. The TDE was identified by a custom 'off-nuclear' implementation of the ML classifier $\texttt{tdescore}$, which classifies new ZTF transients based on their lightcurves. Follow-up observations confirm that TDE 2025abcr is a TDE-H+He, occurring 9.5$"$ (9.3 kpc projected distance) from the nucleus of a massive galaxy ($\mathrm{M}_{\star}$ = $10^{11.18 \pm 0.03}\mathrm{M}_{\odot}$) with a central BLACK HOLE mass of $10^{8.82 \pm 0.65}\mathrm{M}_{\odot}$. TDE 2025abcr itself was likely disrupted by a much lighter BLACK HOLE ($10^{6.09\pm0.53}\mathrm{M}_{\odot}$, as estimated with peak luminosity scaling relations). The BLACK HOLE was either dynamically ejected from the nucleus or lies at the center of a very faint tidally-stripped dwarf galaxy undergoing a minor merger. Late-time observations of TDE 2025abcr could confirm the origin of this apparent 'wandering' BLACK HOLE. The rate of highly offset ($\gtrsim$3 kpc) TDEs can be constrained to $<$10% of the nuclear TDE rate, but our discovery implies that many dozens of similar sources will be detected by the Vera C. Rubin each year with resolvable offsets.
[abstract 14 / 18] (score: 2) - Title: Mapping the nuclear environments of extreme coronal line emitting galaxiesAuthors: Daniel Kynoch, Or Graur, Peter Clark, J. N. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, T. Claybaugh, A. de la Macorra, P. Doel, J. E. Forero-Romero, S. Gontcho A Gontcho, G. Gutierrez, R. Joyce, S. Juneau, M. Landriau, L. Le Guillou, A. Meisner, R. Miquel, J. Moustakas, S. Panda, W. J. Percival, F. Prada, I. Pérez-Ràfols, G. Rossi, E. Sanchez, D. Schlegel, J. Silber, D. Sprayberry, G. Tarlé, B. A. Weaver, R. Zhou, H. Zou,Comments: 31 pages, 6 figures. Submitted to MNRASSubjects: astro-ph.GACreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
Extreme coronal line emitters (ECLEs) are a rare class of galactic nuclei exhibiting unusually strong high-ionisation forbidden emission lines, and several ECLEs have been linked to tidal disruption events (TDEs). In this work, we compile and analyse optical spectra of 33 ECLEs, dividing them into variable, TDE-linked sources and non-variable, AGN-linked systems. Using multi-epoch spectroscopy from the Sloan Digital Sky Survey, Dark Energy Spectroscopic Instrument, and other facilities, we investigate the evolution of the emission line spectra and measure emission line profiles. Many variable ECLEs have changing spectra in which the highest-ionisation lines (e.g., [Fe X]-[Fe XIV]) appear and fade first, followed by [Fe VII], accompanied by brightening of [O III]. These changes may reflect a softening ionising continuum, the outward propagation of the ionisation front following the TDE flare, or both. Assuming virial motion, we translate line widths into characteristic radial distances, reconstructing the spatial distribution of line-emitting gas. Coronal lines are generally emitted at radii intermediate between the broad line region and the low-ionisation narrow line region. This ionisation stratification is seen in many sources, with similar incidence in variable and non-variable ECLEs, suggesting no apparent difference in circumnuclear gas distributions between active and quiescent nuclei. We find positive correlations between gas distance and BLACK HOLE mass for both [O III] and [Fe VII]: the log(Distance)-log(Mass) relations have slopes $0.63\pm0.08$ and $0.69\pm0.12$, respectively, broadly consistent with a Mass$^{0.5}$ dependence and with characteristic radii set primarily by photoionisation.
[abstract 15 / 18] (score: 2) - Title: Compact quasiaxisymmetric stellarators, a near axisymmetric theoryAuthors: Wrick Sengupta, Rogerio Jorge, Nikita Nikulsin, Stefan Buller, Richard Nies, Andrew Brown, Amitava Bhattacharjee,Comments:Subjects: physics.plasm-phCreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
We develop a theory of ridges in compact stellarators with quasiaxisymmetry (QA). The equilibrium with finite plasma currents and pressure is modeled by ideal MAGNETohydrostatics (MHS). Field lines are collimated near sharp ridges, much like X-points, making ridges attractive to divertor designs without the requirement of a rational rotational transform at the divertor. However, unlike X-points, which must cover the entire torus an integer number of times, sharp ridges are typically localized in certain parts of the flux surfaces. Motivated by recent work (Henneberg and Plunk, Phys. Rev. Research 6, L022052) on compact hybrid devices, we develop a perturbative treatment of nearly axisymmetric quasisymmetric devices by expanding in the deviation from perfect axisymmetry. As a result, we can analytically describe the key features of compact QA devices, such as the tendency for ridges to be localized on the inboard side, where the Gaussian curvature is typically negative, and the field strength is maximum. We provide comprehensive numerical evidence in support of our analytical theory.
[abstract 16 / 18] (score: 2) - Title: Predictions for the X-ray polarisation modulation in Cygnus X-1 from reflection off the stellar companion and its windAuthors: Bert Vander Meulen, Kun Hu, Victoria Grinberg, Henric Krawczynski,Comments: 10 pages, 10 figures, submitted to A&ASubjects: astro-ph.HECreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
Context. Cyg X-1 is one of the brightest X-ray binaries and has been observed multiple times with the Imaging X-ray Polarimetry Explorer (IXPE). Recent studies report tentative evidence for a polarisation modulation with the orbital period P, but a half-period (P/2) signal, expected from reflection off the companion star and its stellar wind, has not been reported. Aims. We aim to quantify the reflection-induced variations of the polarisation degree PD and polarisation angle PA in Cyg X-1 as a function of orbital phase and energy, and interpret these in terms of binary geometry and wind structure. Methods. We set up a radiative transfer model combining a general RELATIVISTIC description of the polarised source emission (kerrC) with a focussed stellar wind model for the binary medium. Using the 3D X-ray radiative transfer code SKIRT, we simulate broadband Stokes I, Q, and U fluxes, surface brightness maps, and linear polarisation maps over one binary orbit. Results. We find a prominent double-peaked (P/2) polarisation modulation, with a peak-to-peak PD amplitude of 0.25, 0.81, and 1.24 percentage points in the 2-4, 4-6, and 6-8 keV bands, respectively, with a strong energy dependence. The PA modulation is more modest, with |ΔPA| < 4.6°. Crucially, X-ray reprocessing reduces the overall PD relative to the source polarisation. Conclusions. The modulation is driven by reflection off the companion star and the focussed wind, which induces a polarisation signal that alternately reinforces and counteracts the source polarisation throughout the orbit. The diffuse scattering halo surrounding the source systematically reduces the PD, an effect that should be accounted for in all wind-fed XRBs. The PD amplitude increases with energy as absorption disproportionately attenuates the distant-reflection signal; as the extinction drops, the reflection signal becomes increasingly important.
[abstract 17 / 18] (score: 2) - Title: Periodic Radio and X-ray Emission from an Accreting White Dwarf BinaryAuthors: Kovi Rose, Joshua Pritchard, Tara Murphy, L. N. Driessen, D. L. Kaplan, M. Caleb, Ziteng Wang, A. Zic, I. Andreoni, J. Carney, B. N. Barlow, D. Dobie, M. Gu, G. Heald, D. Huber, E. Lenc, J. K. Leung, W. Lu, R. Momose, M. G. Pedersen, Y. Qu, N. Rea, I. de Ruiter, K. Shaji, G. R. Sivakoff, A. J. M. Thomson, Y. L. Wang, G. J. Yang, F. Zahedy,Comments: Published in Nature AstronomySubjects: astro-ph.HE astro-ph.SRCreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
Long period radio transients (LPTs) are coherent bursts of polarised radio emission that repeat periodically on timescales of minutes to hours. Little is known about the physical origins of these systems. Astronomers have proposed MAGNETars that rotate slowly and white dwarfs that rapidly orbit with a companion star as potential explanations. While several recent examples appear to support the latter hypothesis, the mechanism generating these bright radio pulses remains poorly understood. Here we report our discovery and classification of the LPT ASKAP J174508.9-505149 as an accreting white dwarf binary. This object has a ~1.3h spectroscopic orbital period and exhibits orbitally-modulated X-ray emission and radio bursts. These elliptically polarised radio bursts drift in emission frequency, potentially due to a longer beat period, and turn off for several hours at a time. Some long period radio transients have been associated with non-interacting white dwarf binaries. We have spectroscopically confirmed this system as an accreting cataclysmic variable, identified through characteristic optical emission lines and an ongoing X-ray outburst. Our results strengthen the link between at least some long period radio transients and white dwarf binaries.
[abstract 18 / 18] (score: 2) - Title: Fast-spinning massive BLACK HOLEs from slowly rotating low-metallicity stars: implications for GW231123Authors: N. H. Ismail, N. Yusof, R. Hirschi, A. Griffiths, M. Á. Aloy, S. Ekström, G. Meynet,Comments: 6 pages (including Appendix) and 2 figures. Submitted to Astronomy & Astrophysics Letter. Comments welcomeSubjects: astro-ph.SRCreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
The origin of massive BLACK HOLEs in the early universe remains uncertain and still unexplored. Pop III stars are among the first stellar sources capable of producing such remnants, but their evolution is very sensitive to rotation. We explore how slow initial rotation influences the evolution and BLACK HOLE formation of very massive Pop III stars, and assess their potential to become massive, fast-spinning BLACK HOLEs consistent with GW events such as GW231123. We compute a grid of non-rotating and slowly rotating Pop III stellar models with initial masses of 80, 85, and 90 $M_\odot$ using the GENEC code. Our models include rotationally induced mixing and angular-momentum transport by MAGNETic torques. We analyse the CO core masses and their volume-averaged adiabatic index to assess stability against electron-positron pair creation. From the angular-momentum profiles at the end of He burning, we estimate the resulting BLACK HOLE masses and dimensionless spins under the assumption of direct collapse. Our non-rotating and slowly rotating 80 and 85 $M_\odot$ models develop carbon-oxygen core masses between 31 and 36 $M_\odot$ and have an adiabatic index that remains above 4/3. Our models thus predict that Pop III stars can keep most of their mass and collapse directly to form BLACK HOLEs of 80 to 85 $M_\odot$ with dimensionless spins up to $a_{\rm BH} \lesssim 0.7$. Initially slowly rotating, massive Pop III stars can form very massive, rapidly spinning BLACK HOLEs just below the pair-instability regime. This supports interpreting the lower boundary of the PISN mass gap as a smooth, structure-dependent transition and identifies single-star Pop III evolution as a possible channel for massive fast-spinning BLACK HOLEs observed by gravitational-wave detectors, subject to the uncertain efficiency of internal angular-momentum transport and mass-loss prescriptions.
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