Current date: 2026-07-01
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Created/updated limit: 2026-06-24 (7 days ago)
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Scoring abstracts
Number of records retrieved: 873
Keyword score statistics
score 9 -- 1 abstracts
score 8 -- 1 abstracts
score 6 -- 2 abstracts
score 5 -- 9 abstracts
score 4 -- 10 abstracts
score 3 -- 11 abstracts
score 2 -- 22 abstracts
in total -- 56 abstracts
Articles that appeared on 2026-07-01
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[abstract 1 / 56] Wow! (score: 9)
- Title: Magnetic field and plasma number density from radio and millimeter core measurements in AGN JETsAuthors: E. E. Nokhrina, A. P. Lobanov, A. Yu. Istomin, V. A. Frolova,Comments: 7 pages, 5 figures, accepted for publication by MNRASSubjects: astro-ph.HECreated: 2026-06-30; Updated: 2026-07-01; Datestamp: 2026-07-01
Understanding the mechanism for launching RELATIVISTIC JETs in ACTIVE GALACTIC NUCLEi relies upon measuring the MAGNETic field strength and emitting plasma number density, tracing their evolution along the JET, and determining the relation between their rest frame energy densities. This can be achieved using measurements of the size and brightness temperature of the compact region at the JET base (the ``core'') obtained with very long baseline interferometry (VLBI) across frequencies from 2 to 230~GHz. We develop a framework for independently estimating the MAGNETic field B* and the emitting plasma number density N* as functions of the JET width $d$, using multifrequency VLBI observations of the core size and brightness temperature. We apply the standard model of self-absorbed SYNCHROTRON emission, assuming power-law dependencies of the JET Doppler factor, Lorentz factor, MAGNETic field strength, and plasma density on the JET width. For an arbitrary JET boundary shape, we derive the dependencies B*(d) and N*(d), and explore a possible relation between the rest frame energy densities of the MAGNETic field and the emitting plasma. Analysis of core widths and brightness temperatures measured at multiple frequencies points to the possible presence of a MAGNETic flux decay and effective plasma acceleration within the observed cores at least in some sources of the sample.
[abstract 2 / 56] Wow! (score: 8) - Title: The impact of plasma instability cooling on intergalactic MAGNETic field constraints in GeV cascades for optimized instability cooling parametersAuthors: Suman Dey, Simone Rossoni, Günter Sigl,Comments: 18 pages, 25 figures, and 6 tablesSubjects: astro-ph.HECreated: 2026-06-30; Updated: 2026-07-01; Datestamp: 2026-07-01
ElectroMAGNETic cascades are initiated by TeV gamma rays propagating through the intergalactic medium (IGM), and they can be used to constrain the weak intergalactic MAGNETic field (IGMF) in cosmic voids. Primary TeV photons produce electrons and positrons through electroMAGNETic pair production, which can be deflected out of the line-of-sight to the observer by IGMF. In addition, electron-positron pairs can perturb the IGM, triggering plasma instabilities that can cool down the pairs before they upscatter cosmic background photons to GeV energies via inverse Compton (IC) scattering. In this work, we investigate the influence of plasma instabilities on the cascade spectrum by introducing a parameterized instability model within the publicly available Monte Carlo framework CRPropa 3.2 in the presence of IGMF. We first determine the instability parameters that best reproduce the FERMI-LAT observations in the absence of any IGMF. We then use extended-emission observations within the observer's field of view, including the effects of the IGMF, to constrain the IGMF strength in the presence of the corresponding best-fit instability-cooling parameters, based on the FERMI-LAT spectral observations of the BLAZAR 1ES 0229+200. We find that plasma instabilities with a characteristic length scale of $120$ kpc and a spectral index of $α=-0.5$ are consistent with the observed photon spectra. We also find that the fit of the observed data is improved by the presence of an IGMF: we obtain an IGMF lower limit of $B \gtrsim 2.7 \times 10^{-17}$ G for an observer field of view $1.0^\circ$.
[abstract 3 / 56] Yes (score: 6) - Title: The Lifetimes of High-redshift Quasars Suggest Magnetic Disk SupportAuthors: Jarrett Johnson, Phoebe Upton Sanderbeck, Nicole Lloyd-Ronning, Madeline Marshall, Kelcey Davis,Comments: 6 pages, 2 figures, accepted for publication in ApJSubjects: astro-ph.GA astro-ph.COCreated: 2026-06-29; Updated: 2026-07-01; Datestamp: 2026-07-01
It has recently been suggested that a variety of data on ACTIVE GALACTIC NUCLEi (AGN) can be explained if AGN disks are supported against gravitational fragmentation by MAGNETic fields that are advected into the disk from the surrounding galaxy. Here we derive the maximum timescales over which accretion onto a BLACK HOLE (BH) powering an AGN can be maintained at a given rate, both with and without MAGNETic disk support. We then compare these timescales to the lifetimes of episodes of sustained luminous accretion that are inferred from measurements of the photoionized proximity zones around high-redshift QUASARs. While some of the shortest inferred QUASAR lifetimes are consistent with pure gas pressure support, we find that some additional MAGNETic support is likely required to explain the longest inferred QUASAR lifetimes of > 10$^4$ yr. For these longest-lived AGN, we find that MAGNETic pressure in their disks can be up to a hundred times higher than the gas pressure. In addition, the lack of inferred QUASAR lifetimes that are definitively > 10$^6$ yr is consistent with gas pressure and advected MAGNETic fields being the principal sources of disk support. This adds to the body of evidence that MAGNETic fields play an important role in sustaining the rapid growth of supermassive BHs in the early universe.
[abstract 4 / 56] Yes (score: 6) - Title: AGN Feeding & Feedback Over the Galactic ScalesAuthors: Filippo M. Maccagni, Vincenzo Mainieri, Isabella Prandoni, Massimo Gaspari, W. J. G. de Blok, Ilaria Ruffa, Stanislav S. Shabala, Dipanjan Mukherjee, Mayur B. Shende, Antonino Marasco, Paolo Serra,Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no: AASKAII/Maccagni01Subjects: astro-ph.GACreated: 2026-06-30; Updated: 2026-07-01; Datestamp: 2026-07-01
Active Galactic Nuclei (AGN) are key drivers of galaxy evolution, triggered by cold gas accreting onto a super-massive BLACK HOLE. However, the processes regulating this gas accretion (feeding) and how AGN alter the interstellar medium to affect STAR FORMATION (feedback) remain poorly understood. A major observational challenge is the vast range of spatial scales involved: AGN fuelling and JET-ejection occur over the sub-pc scales, while AGN feedback shocks and heats the ISM preventing STAR FORMATION over the galactic and circum-galactic scales. Moreover, it is unclear how short stochastic AGN episodes are connected with the long timescales of gas accretion and STAR FORMATION. In this manuscript, we illustrate how SKAO will provide the unprecedented opportunity to solve the observational limitations of AGN feeding and feedback studies by observing hundreds of nearby AGN down to low radio powers ($10^{21}$ W Hz$^{-1}$). Simultaneous SKA-Low and Mid observations of nearby galaxies will trace the thermal emission associated with STAR FORMATION and AGN feedback and the SYNCHROTRON emission of their JETs of RELATIVISTIC plasma. These broad-band radio observations enable the detailed characterisation of the AGN duty-cycle, unravelling the time-scales of the nuclear activities. Reaching in 10 hours neutral atomic hydrogen (HI) column density sensitivities $\sim 10^{19}$ cm$^{-2}$ at arcsecond resolution, SKA AA4 observations will trace the typical low column density of HI gas in AGN inflows and outflows, to understand the impact AGN feedback over the full galaxy and trace fuelling processes from the environment onto the SMBH. Combining SKA with mm, sub-mm and optical Integral Field Spectrographic observations at comparable arcsecond resolution will provide an exhaustive understanding of the link between multi-phase AGN feeding and feedback processes and STAR FORMATION.
[abstract 5 / 56] Yes (score: 5) - Title: Comments on the paper "Eliminating beam-induced depolarizing effects in the hydrogen JET target for high-precision proton beam polarimetry at the Electron-Ion Collider"Authors: Andrei Poblaguev,Comments: 5 pages. Comment on arXiv:2508.01366Subjects: physics.acc-phCreated: 2026-06-24; Updated: 2026-07-01; Datestamp: 2026-07-01
A critical review of the methodology used in F. Rathmann et al., Phys. Rev. Accel. Beams 29, 021001 (2026), to evaluate beam-induced dePOLARIZATION of the Atomic Polarized Hydrogen Gas Jet (HJET) target at the Electron--Ion Collider (EIC) is presented. It is shown that several key assumptions underlying that analysis -- including the introduction of a photon emission threshold, the application of FERMI's Golden Rule to coherent hyperfine transitions, the interpretation of power broadening as a physical linewidth increase, and the treatment of spatial MAGNETic fields -- are either incorrect or internally inconsistent. As a consequence, the predicted large dePOLARIZATION effects are demonstrated to be artifacts of the adopted methodology rather than genuine physical phenomena. A consistent quantum-mechanical treatment based on the time-dependent Schrödinger equation shows that beam-induced dePOLARIZATION probabilities at the EIC are negligibly small.
[abstract 6 / 56] Yes (score: 5) - Title: The MAGNETic mayhem in Abell 2199: discovery of SYNCHROTRON threads and homogeneous diffuse radio lobesAuthors: R. Timmerman, L. Rudnick, A. Botteon, G. Brunetti, R. Kale,Comments: Accepted for publication in MNRAS, 12 pages, 11 figuresSubjects: astro-ph.CO astro-ph.GACreated: 2026-06-29; Updated: 2026-07-01; Datestamp: 2026-07-01
Sensitive low-frequency radio observations have started uncovering examples of SYNCHROTRON-emitting threads, isolated from the rest of radio emission in galaxy clusters. As the bridge of radio emission previously detected between the radio lobes of 3C 338 in Abell 2199 is a candidate of such a structure, we observed this galaxy cluster using the International LOFAR Telescope. These observations revealed the presence of multiple narrow isolated SYNCHROTRON threads in 3C 338: east, west and north of the AGN and its radio lobes. Chandra X-ray observations show that these structures most likely do not reside within cavities in the intracluster medium (ICM), and are therefore considered to be distinct structures from the radio lobes. Non-detections in 1.5 GHz Very Large Array observations imply that the spectral index of these newly-discovered isolated threads is likely $α_{1500}^{144} < -3.0$ or steeper. We consider these isolated SYNCHROTRON threads to most likely display examples of MAGNETic threads within the ICM that have captured SYNCHROTRON-emitting plasma, as has recently been proposed. Furthermore, our observations reveal the radio lobes to show an almost perfectly uniform spectral index, unlike what would be expected if substantial age differences are present in the radio lobes according to standard spectral ageing models. We find that the RELATIVISTIC plasma in 3C 338 is consistent with a homogeneous COSMIC RAY electron population, with the spectral variations dependent on the local MAGNETic field strength. Finally, we explore the various models that could explain this trend in the radio lobes.
[abstract 7 / 56] Yes (score: 5) - Title: Prospects for Improving the Theoretical Uncertainty for Tests of General Relativity with the EHTAuthors: Lia Medeiros, George N. Wong, Feryal Ozel,Comments: Submitted to ApJSubjects: astro-ph.HE gr-qcCreated: 2026-06-29; Updated: 2026-07-01; Datestamp: 2026-07-01
We characterize the relationship between the size of the bright ring observed in simulated BLACK HOLE images and the size of the analytic BLACK HOLE shadow. Calibrating this relationship is crucial for mass measurements and, when independent mass measurements are available, for tests of general relativity using Event Horizon Telescope (EHT) images. We perform this calibration using a large set of high-resolution simulated images generated with different accretion-flow modeling approaches and spanning a wide range of system parameters and initial conditions. We show that the theoretical uncertainty in this relationship can be reduced significantly through future observations, improved imaging techniques, and the application of astrophysical or model-based constraints. In particular, the uncertainty decreases compared to existing measurements when (i) observing at 345 GHz, (ii) applying geometric image constraints, such as the ring width inference from the PRIMO image reconstruction algorithm, (iii) incorporating astrophysical constraints such as the BLACK HOLE spin axis in M87 being aligned (or anti-aligned) with the large-scale JET observed at longer radio wavelengths, and (iv) assuming that the accretion flow can be described by a MAGNETically arrested field configuration. Finally, we quantify how the uncertainty is expected to decrease as additional observations are obtained in subsequent years and identify dwell-time filtering, i.e., evaluating the persistence of a geometric measurement over time, as a promising avenue for improving the precision of the calibration.
[abstract 8 / 56] Yes (score: 5) - Title: Active Galactic Nuclei as high-energy neutrino sourcesAuthors: Filippo D'Ammando,Comments: Invited review article for The Astronomy and Astrophysics Review. Accepted for publication. 59 pages, 25 figuresSubjects: astro-ph.HE astro-ph.GACreated: 2026-06-29; Updated: 2026-07-01; Datestamp: 2026-07-01
Identifying the sources of the high-energy astrophysical neutrinos has been one of the main topics in astrophysics since the first observation of high-energy neutrinos by the IceCube Neutrino Observatory. Active Galactic Nuclei (AGN) are sources of high-energy gamma-rays and are considered to be promising candidates to be sources of high-energy neutrinos and ultra-high energy COSMIC RAYs as well. However, several studies suggest that the neutrino emission from the $γ$-ray BLAZAR population only accounts for a small fraction of the total astrophysical neutrino flux. We present and discuss recent results on the search for correlations between astrophysical neutrinos and both gamma-ray and radio bright AGN. The IceCube Collaboration has reported high-energy neutrino events that may come from both the radio-loud AGN TXS 0506+056 and the radio-quiet AGN NGC 1068. Other cases of possible associations between high-energy neutrino events and individual BLAZARs were claimed with controversial results. We discuss the properties of these sources together with the different neutrino production mechanisms proposed for those sources. Finally, we outline future prospects in the field, focusing on remaining open questions, the development of upcoming neutrino facilities, and the evolving multi-frequency landscape within the multi-messenger era.
[abstract 9 / 56] Yes (score: 5) - Title: Coherent and Incoherent Emission from the Ordered Magnetospheres of Low-Mass Stars, UCDs, and Massive StarsAuthors: Francesco Cavallaro, Paolo Leto, Barnali Das, Corrado Trigilio, Grazia Umana, Cristobal Bordiu, Filomena Bufano, Carla S. Buemi, Joseph R. Callingham, Laura Driessen, Adriano Ingallinera, Sara Loru, Stanley Owocki, Simone Riggi, Alan C. Ruggeri, Giovanni Sabatini, Matt E. Shultz, Alessio Traficante,Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/Cavallaro01. Advancing Astrophysics with the SKA II (AASKAII) outlines the transformative scientific advances that will be enabled by the SKA telescopesSubjects: astro-ph.SRCreated: 2026-06-29; Updated: 2026-07-01; Datestamp: 2026-07-01
Massive early-type (B/A) stars and ultracool dwarfs (UCDs) represent two distinct regimes in which ordered, large-scale MAGNETospheres are observed. In rapidly rotating massive stars, incoherent radio emission is explained by the centrifugal breakout (CBO) mechanism: plasma confined within the rigidly rotating MAGNETosphere accumulates beyond the co-rotation radius, where centrifugal forces trigger breakout events and MAGNETic RECONNECTion, generating non-thermal electrons that produce incoherent gyro-SYNCHROTRON emission. Empirically, the radio luminosity correlates with the power released by CBO events, establishing a clear link between stellar rotation, MAGNETic confinement, and radio output. In UCDs, persistent non-thermal radio emission exhibits similar luminosity trends to those of massive MAGNETic stars, despite the absence of strong stellar winds. This similarity suggests that a CBO-like process may also operate in these fully convective, low-mass objects, though the plasma source and acceleration mechanisms remain uncertain. In both classes, coherent electron cyclotron maser emission (ECME), characterized by strong POLARIZATION and rotational modulation, is observed, indicating common MAGNETospheric processes analogous to planetary auroral emission. The Square Kilometre Array (SKA) will be able to deeply observe about 70\% of the sky. We expect to observe $\sim 1000$ UCDs, enabling better statistical analysis of their emission and a test of the CBO hypothesis.
[abstract 10 / 56] Yes (score: 5) - Title: Boosting Water Maser Studies in AGN with the SKAAuthors: Andrea Tarchi, Paola Castangia, Elisabetta Ladu,Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/Tarchi01. Advancing Astrophysics with the SKA II (AASKAII) outlines the transformative scientific advances that will be enabled by the SKA telescopesSubjects: astro-ph.GACreated: 2026-06-30; Updated: 2026-07-01; Datestamp: 2026-07-01
Extragalactic water maser sources are unique tools to derive fundamental physical quantities of the host galaxies. In nearby and distant ACTIVE GALACTIC NUCLEi (AGN), water masers are used to determine the geometry of accretion disks around super-massive BLACK HOLEs, precise BLACK HOLE masses, and standard-candles-independent distances to the host galaxy. In addition, they allow detailed studies of the interaction between nuclear JETs/outflows and the interstellar medium, providing clues on AGN feedback mechanisms. So far, however, extragalactic maser searches have yielded detection rates of few percent, and only relatively few maser sources have been found, mostly in the nearby Universe. Because of its unprecedented sensitivity, the SKA will allow to significantly increase the number of known water maser sources especially in the more distant Universe. This will lead to the chance of performing statistically-relevant studies of the maser phenomenon (and its occurrence), derive extragalactic maser luminosity functions and, ultimately, to perform the aforementioned studies for larger samples and up to cosmological distances. In this Chapter, we will provide a quantitative analysis of the expected number of new extragalactic water maser sources already at the reach of the SKA-Mid telescope (in AA4 configuration) through targeted and blinds surveys. In addition, we will discuss the main requirements for the upcoming SKA design, in terms of baselines and frequency coverage, that may maximize the exploitation of such wealth of new targets, allowing a true step forward in AGN-related maser science.
[abstract 11 / 56] Yes (score: 5) - Title: Scattering of Strong Radio Waves by Particles in Strongly Magnetized Plasmas and Implications for Fast Radio BurstsAuthors: Yuanhong Qu, Pawan Kumar,Comments: 14 pages, 8 figuresSubjects: astro-ph.HECreated: 2026-06-30; Updated: 2026-07-01; Datestamp: 2026-07-01
Fast Radio Bursts (FRBs) are millisecond-duration radio transients that are widely believed to originate within MAGNETar MAGNETospheres. Large-amplitude radio waves associated with FRBs propagate through strongly MAGNETized plasmas, where nonlinear scattering can affect their propagation. By solving the RELATIVISTIC motion of a single particle interacting with electroMAGNETic waves of arbitrary POLARIZATION and propagation angle $θ_B$, we compute the scattering cross section and the corresponding optical depth. The scattering cross section of the O-mode can exceed that of the X-mode when $a\sinθ_B < ω_B/ω$, and becomes comparable to that of the X-mode when $a\sinθ_B > ω_B/ω$, where $θ_B$ is the angle between the wave vector and the background field. In the strongly MAGNETized and quasi-parallel limits, the cross sections asymptotically recover the linear regime scalings and are strongly suppressed by RELATIVISTIC particle motion, leading to optical depths well below unity. We also show that curvature radiation losses of O-mode waves are strongly suppressed for quasi-parallel propagation, allowing them to escape from the MAGNETosphere at moderate multiplicities. We propose that Alfvén waves excited by MAGNETar crust quakes can reach amplitudes comparable to the background MAGNETic field, thus straightening field lines and reducing $θ_B$. This geometrical alignment enhances the ability of FRBs to freely propagate through the open field line region. These results suggest that large-amplitude waves propagating quasi-parallel to open MAGNETic field lines can avoid significant single-particle scattering losses, providing a possible condition for their escape.
[abstract 12 / 56] Yes (score: 5) - Title: A simulation-based analytic model of RADIO GALAXies II: self-consistent radiative lossesAuthors: M. J. Hardcastle,Comments: 7 pages, 2 figures, accepted by MNRASSubjects: astro-ph.GACreated: 2026-06-30; Updated: 2026-07-01; Datestamp: 2026-07-01
The evolution of the radio properties of high-redshift radio-luminous ACTIVE GALACTIC NUCLEi is well known to be strongly affected by inverse-Compton losses which increase rapidly at higher redshifts due to the higher energy density in the cosmic microwave background radiation. Dynamical models of these sources, however, generally neglect the effects of radiative losses on the dynamics and energetics of the sources themselves. In the framework of an analytical model I developed in a previous paper, I show that the assumption that these losses can be neglected becomes unsafe at high redshifts. The effects on the source dynamics and energetics can result in significantly lower predicted luminosities for high-redshift sources in both radio (SYNCHROTRON) and X-ray (inverse-Compton) bands. Modelling of the population of these powerful sources needs to take account of these results in order to infer JET powers at high redshift, and also to make a correct prediction of the number of sources that may be available to provide a background for studies of the 21-cm forest.
[abstract 13 / 56] Yes (score: 5) - Title: Unveiling Radio Transients with SKAO TelescopesAuthors: James C. A. Miller-Jones, Kaustubh M. Rajwade, Patrick A. Woudt, Jason W. T. Hessels,Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/Miller-Jones01. Advancing Astrophysics with the SKA II (AASKAII) outlines the transformative scientific advances that will be enabled by the SKA telescopesSubjects: astro-ph.HECreated: 2026-06-30; Updated: 2026-07-01; Datestamp: 2026-07-01
Transient astrophysics provides a set of unique laboratories for studying fundamental physics. From the launching of powerful RELATIVISTIC JETs to merging neutron stars, highly-MAGNETised compact objects, or stellar explosions, transients probe the Universe at its most extreme. The SKAO will provide an unrivalled set of capabilities for transient observations on timescales from nanoseconds to decades, opening new discovery space. With its sensitivity, broad spectral coverage, wide field of view, and high survey speed, SKAO will allow us to discover and understand rare events that provide powerful new insights into regimes of high energy density, strong gravity, and intense MAGNETic fields. Complemented by a suite of multi-wavelength and multi-messenger facilities, and supported by a network of smaller existing radio telescopes and new computational capabilities, SKAO will unveil the most powerful and exotic events in our Universe, addressing some of the key questions in modern astrophysics and cosmology.
[abstract 14 / 56] Yes (score: 4) - Title: Unified kinetic theory of induced scattering: Compton, Brillouin, and Raman processes in MAGNETized electron and positron pair plasmaAuthors: Rei Nishiura, Shoma F. Kamijima, Kunihito Ioka,Comments: 35 pages, 7 figures. Published in Physical Review DSubjects: astro-ph.HE physics.plasm-phCreated: 2026-06-30; Updated: 2026-07-01; Datestamp: 2026-07-01
We extend a unified theoretical framework for induced (stimulated) scattering-parametric instabilities of electroMAGNETic waves, including induced Compton, stimulated Brillouin, and stimulated Raman scattering (SRS) in strongly MAGNETized electron-positron pair plasma. By solving the dispersion relations derived from kinetic theory, taking into account the ponderomotive force due to the beat of incident and scattered waves, we obtain analytical expressions for the linear growth rates of the ordinary, neutral, and charged modes of density fluctuations. Our results clarify which type of scattering dominates under different thermal coupling, resonance, and density conditions. In strong MAGNETic fields, scattering of perpendicularly polarized waves is generally suppressed, but by different powers of the cyclotron frequency. Moreover, SRS, which is forbidden in unMAGNETized electron and positron pair plasma, becomes possible in the charged mode. This framework enables a comprehensive evaluation of induced scattering in extreme astrophysical and laboratory plasma, such as fast radio burst (FRB) emission and propagation in MAGNETar MAGNETospheres.
[abstract 15 / 56] Yes (score: 4) - Title: Line-Tied Flux Rope Relaxation and Reconnection: A 3D Kinetic Case StudyAuthors: Joshua Pawlak, James Juno, Jason M. TenBarge,Comments: 17 pages, 10 figures, accepted for publication to Physics of PlasmasSubjects: physics.plasm-phCreated: 2026-06-29; Updated: 2026-07-01; Datestamp: 2026-07-01
Magnetic flux ropes are ubiquitous MAGNETic structures found in plasmas ranging from astrophysical to laboratory. We employ a newly-developed parallel-kinetic-perpendicular-moment (PKPM) model to simulate the 3D interaction and evolution of two line-tied flux ropes at realistic laboratory plasma parameters, while retaining essential parallel kinetic physics in the system. We find that ropes undergo a current-dependent transition from a diaMAGNETic to paraMAGNETic regime, which we quantify with a simple analytic model. Although the macroscopic structural evolution qualitatively differs significantly between these regimes, analyzing the RECONNECTion in proper field-aligned coordinates reveals that the underlying kinetic dynamics remain similar. Using the squashing factor and quasi-potential as diagnostics of 3D MAGNETic RECONNECTion, we identify the formation of a quasi-separatrix layer and show that these quantities provide consistent metrics for RECONNECTion rate and structure.
[abstract 16 / 56] Yes (score: 4) - Title: Spatiotemporal Properties of Compressible Magnetohydrodynamic Turbulence from Space PlasmaAuthors: Siqi Zhao, Huirong Yan, Terry Z. Liu, Chuanpeng Hou, Ka Ho Yuen,Comments: 13 pages, 9 figuresSubjects: physics.plasm-ph astro-ph.GA astro-ph.SR physics.space-phCreated: 2026-06-30; Updated: 2026-07-01; Datestamp: 2026-07-01
Previous studies have established that a weak-to-strong transition occurs in Alfvenic MAGNETohydrodynamic (MHD) turbulence as energy cascades from large to small scales. However, the spatiotemporal (frequency-wavenumber) properties of compressible MHD turbulence involving all eigenmodes, which encode the strength of nonlinear interactions, remain difficult to characterize observationally. Consequently, whether a similar weak-to-strong transition occurs in compressible turbulence remains elusive. Using a novel multi-spacecraft, POLARIZATION-based mode-decomposition technique with measurements from the Cluster spacecraft in Earth's MAGNETosheath, we obtain spatiotemporal power spectra of all MHD eigenmodes and present the first quantitative assessment of nonlinear frequency broadening. Our results show that slow modes exhibit a weak-to-strong transition, evolving from wave-like peaks to frequency-broadened spectra as nonlinearity increases, whereas fast modes remain weakly turbulent with narrow peaks near their eigenfrequencies. Both Alfvenic and compressible fluctuations contribute significantly to low-frequency, large-scale quasi-two-dimensional structures. These findings provide a comprehensive observational characterization of compressible turbulence across mode composition, spatiotemporal scales, and weak-strong turbulence regimes, with implications for energetic particle transport, turbulent dynamos, plasma heating, and solar wind-MAGNETosphere coupling.
[abstract 17 / 56] Yes (score: 4) - Title: Hunting Wandering 3[abstract 18 / 56] Yes (score: 4)Authors: Urvi Thakurdesai, Anthony J. Taylor, Steven L. Finkelstein, Gene C. K. Leung, Oscar A. Chavez Ortiz, Jonathan R. Trump, Bren E. Backhaus, Nikko J. Cleri, Francesco D'Eugenio, Fabio Pacucci, Anton M. Koekemoer, Pablo Arrabal Haro, Micaela Bagley, Mark Dickinson, Jeyhan Kartaltepe, Casey Papovich, Nor Pirzkal,Comments: 15 pages, 8 figures, 1 table. Accepted for publication in ApJSubjects: astro-ph.GACreated: 2026-06-29; Updated: 2026-07-01; Datestamp: 2026-07-01
The early growth and assembly of supermassive BLACK HOLEs (SMBHs) remain key topics of interest in galaxy evolution. One of the scenarios predicted by theoretical models is that frequent minor mergers and asymmetric gas inflows may cause SMBHs to temporarily reside off-center within their host galaxies in the early universe. To observationally test this scenario, we investigate whether spatially offset ionization signatures-which may be indicative of ACTIVE GALACTIC NUCLEi (AGN)-can be identified. Using JWST NIRSpec PRISM spectroscopy from the Cosmic Evolution Early Release Science (CEERS) survey, we analyze the 2D spectra of 90 high-redshift galaxies (3 < z < 8), including two known broad-line AGN. By measuring key emission lines such as Hα, H\b{eta}, [OIII]λ5007, [NeIII]λ3868, and [OII]λλ3727, 3729 we derive spatial flux ratio profiles, and focus on [OIII]/Hβ as a tracer of high-ionization mechanisms that may indicate AGN activity. We identify 26 galaxies (~30% of the sample) with significant localized peaks in [OIII]/Hβ. Out of these 26 galaxies, 12 sources (~46%) exhibit significant spatial offsets between the peak [OIII]/Hβ ratio and the stellar continuum center. Six of these sources show the highest amount (> 1.5) pixel spatial offsets. This spatial offset between ionization structure and stellar centers offers a promising avenue to probe early SMBH evolution and its connection to galaxy formation.
arXiv:2606.30742 [pdf, ps, other]Extended Ly$α$ emission is ubiquitous around QUASARs and traces cool circumgalactic gas, providing insight into halo gas dynamics and ACTIVE GALACTIC NUCLEi (AGN) feedback. However, its connection to the cold molecular gas of the host galaxies remains largely unexplored. We aim to characterize the molecular gas reservoirs in QUASARs at cosmic noon and investigate how they are linked to extended Ly$α$ emission. To this end, we present ALMA CO(4-3) observations of 37 QUASARs at $z\sim3$ from the QSO MUSEUM survey, previously mapped in Ly$α$ with VLT/MUSE. We derive molecular gas masses and gas fractions, explore correlations with Ly$α$ nebula and QUASAR properties, and search for CO-emitting companions. Of 37 QUASARs, 21 are detected in CO(4-3), with gas masses $M_\mathrm{gas}\approx(3-40) \times10^9\,\mathrm{M_\odot}$. Quasars with the most massive molecular gas reservoirs are associated with the centrally dimmest Ly$α$ nebulae, while those hosting the centrally brightest Ly$α$ nebulae are generally not detected in CO. This suggests that gas and dust in the hosts regulate Ly$α$ escape and consequently affect the emission from halo gas. We find evidence that QUASARs with lower Eddington ratios harbor more massive gas reservoirs, whereas strongly accreting QUASARs ($λ_\mathrm{Edd} \gtrapprox 0.9$) likely deplete their gas through QUASAR-driven outflows. Despite their higher molecular gas masses within the sample, CO-detected low-Eddington QUASARs exhibit low gas fractions, with a median $M_\mathrm{gas}/M_* \sim 0.10$, below those typical of inactive star-forming galaxies. Six QUASARs are marginally resolved in CO, with effective radii up to $\sim 8\,\mathrm{kpc}$. In addition, we detect 14 high-fidelity companion galaxies, indicating overdense QUASAR fields with a QUASAR-galaxy cross-correlation length of $9.81^{+2.22}_{-2.05}\,h^{-1}\mathrm{cMpc}$.
arXiv:2606.30839 [pdf, ps, other]We aim to characterize the post-collapse evolution of accretion-induced collapse (AIC) remnants of rapidly rotating, MAGNETized white dwarfs, focusing on their rotational, MAGNETic, and thermal structure, as well as the development of instabilities and their energy content. We perform nine axis-symmetric general-RELATIVISTIC neutrino MAGNETohydrodynamic (MHD) simulations of collapsing, rapidly rotating, MAGNETized white dwarfs. The simulations follow the system from collapse through bounce and up to $\sim$1 s post-bounce. The simulations are performed by the conformally flat general RELATIVISTIC neutrino MHD code \texttt{Gmunu}. The collapse produces a rapidly rotating proto-MAGNETar surrounded by a persistent accretion disk lasting at least $\sim 1$ s after bounce. The remnant mass and spin span 1.15--1.45 $M_{\odot}$ and 2.9--4.9 kHz, respectively, with stronger initial MAGNETic fields generally leading to lower rotation rates. During the first $\sim 10$ ms, the proto-MAGNETar exhibits global oscillations that drive both gravitational-wave emission and coherent modulation of the poloidal MAGNETic field energy. The MAGNETic energy evolution, normalized to its bounce value, follows an approximately universal behavior across all models. The remnant interior remains strongly MAGNETized ($\gtrsim 10^{13}$ G) and hot ($\gtrsim 20$ MeV) up to 1 s after bounce, with maxima of both quantities co-located in the inner $\sim 10$ km. The MAGNETic field topology shows surface poloidal fields of ${\sim}10^{12}$ G and toroidal fields of ${\sim}10^{14}$ G, with strong toroidal components extending into the equatorial region. When the MAGNETic energy exceeds the rotational energy ($\sim 10^{52}$ erg), the remnant core becomes unstable, leading to episodic MAGNETic flux expulsion, mass ejection, and flare-like activity in which MAGNETic energy is released and thermalized in the surrounding material.
arXiv:2606.30990 [pdf, ps, other]We develop a new analytical model describing the radiative and dynamical structure of an accretion-powered X-ray pulsar, including RELATIVISTIC effects and a detailed representation of the rotational and MAGNETic geometry of the neutron star and the two accretion columns. The model provides for the first time a simultaneous calculation of both the phase-averaged spectrum and the pulse profile for an accretion-powered X-ray pulsar. The X-ray continuum spectrum is calculated using the analytical model of Becker & Wolff (2022), which assumes a conical accretion column geometry. The trajectory of the radiation escaping from the two columns is tracked through the curved spacetime using the Schwarzschild metric. The angular distribution of the radiation escaping from the surfaces of the columns (the beaming pattern) is represented using a set of "LASER-like" emission directions, with associated amplitudes, called weight coefficients, that each contribute "sub-profiles" to the observed pulse profile. The sub-profiles provide basis functions that are used to fit the observed pulse profile. This yields a set of weight coefficients that determine the beaming pattern of the emission from the accretion column. We use the new model to analyze NUSTAR data for Her X-1, allowing the determination of the temperature, accretion rate, and MAGNETic field strength, as well as the rotational inclination angle and the latitudes of the two MAGNETic poles. The method also yields the beaming pattern of the emission, hence providing for the first time a self-consistent phenomenological description of the physical and radiative structures of the two accretion columns.
arXiv:2606.31436 [pdf, ps, other]We estimated the spins of a sample of 58 low-mass AGNs. Analysis of the obtained spins showed that they decrease with increasing SMBH mass, leading us to hypothesize that mergers and/or chaotic accretion are the primary mechanisms for mass growth. In this regard, we proposed a more general hypothesis about the evolution of AGNs. We assume that early low-mass SMBHs have high spins, then, during their evolution, the spins initially decrease and then begin to increase, with the rate of increase gradually slowing.
arXiv:2606.31673 [pdf, ps, other]A highly star-forming galaxy at z ~ 2 hosting an obscured, luminous ACTIVE GALACTIC NUCLEus (AGN) and a RELATIVISTIC radio JET sets the stage for a cosmic crime scene. The victim is STAR FORMATION, the suspect is AGN feedback. These systems offer a rare opportunity to catch this process in the act. We propose SHARP@ELT integral-field spectroscopic observations of heavily obscured, luminous AGN with resolved radio emission to witness the onset of feedback and its impact on the host interstellar medium (ISM). Such objects trace a short-lived (< 10^5 yr) evolutionary phase in which a recent starburst, newly triggered radio JETs, and a deeply embedded AGN coexist. In this phase, feedback is expected to suppress STAR FORMATION while clearing the dusty nuclear regions. Using SHARP/VESPER, we will derive spatially resolved maps of stellar ages, STAR FORMATION rate density, gas density, and ionization state, alongside the kinematics of stars and ionized gas. By directly comparing these properties with the radio structures, we will quantify the effects of both JET-driven and radiative feedback on the ISM. Our sample consists of eleven luminous, obscured AGN at 1.5 < z < 2.5 with resolved radio emission on scales of ~1-15 kpc. Exploiting the VESPER multi-Integral Field Selector capability, we will obtain resolved continuum and emission-line maps for at least 110 galaxies at cosmic noon, enabling a comprehensive characterization of their environment, multiphase ISM, and nuclear activity within 55 h of integration time. SHARP will thus reveal AGN feedback at the epoch when it is most effective, providing a decisive step toward understanding its role in galaxy evolution.
arXiv:2606.31773 [pdf, ps, other]AGN feedback driven by radio JETs plays a key role in regulating the cold ISM of galaxies. Neutral hydrogen traced through the H1 21-cm line provides a powerful probe of the kinematics, distribution, and physical conditions of cold gas in the central regions of AGN. Previous observations have detected H1 column densities down to $\sim10^{20}$ cm$^{-2}$, but typically at arcsecond-scale resolution, inhibiting the characterization of small-scale H1 gas clouds and their connection to molecular gas reservoirs and sites of JET-ISM interaction. High-resolution H1 imaging is therefore required to determine whether the atomic gas is associated with circumnuclear structures, JET-driven outflows, compressed gas layers, or fragmented cold clouds embedded within a disturbed multiphase ISM. In this chapter, we focus on molecular gas-rich radio AGN hosting large-scale JETs and exhibiting strong interactions between the radio plasma and the surrounding ISM, where atomic, molecular, and ionized gas coexist. These systems provide ideal laboratories for investigating the spatial distribution and kinematics of H1, constraining the impact of radio JETs on the cold gas, and determining whether the gas is associated with inflowing, outflowing, or otherwise disturbed components. SKA-VLBI will deliver milliarcsecond-scale imaging and $μ$Jy-level sensitivity, resolving H1 gas clouds on parsec scales across extended radio structures. This capability will enable detailed constraints on the location, morphology, and kinematics of atomic gas from the nuclear regions to kiloparsec-scale JET-ISM interaction sites. Combined with molecular gas observations at other wavelengths, these measurements will provide a comprehensive view of the JET-ISM interactions, the impact of AGN-driven feedback, and the role of cold gas in galaxy evolution.
arXiv:2504.01830 [pdf, ps, other]A photon at ${\cal E} \simeq 251 \, \rm TeV$ from GRB 221009A was detected by the Carpet collaboration in 2022 using a partial data set. Very recently, Carpet has completed its full data analysis reporting further support for its previous photon now at ${\cal E} = 300^{+ 43}_{- 38} \, {\rm TeV}$. Within standard propagation models, this observation is in strong tension with conventional expectations since such a photon is absorbed by the CMB. Further, we show that this detection is strongly disfavored within the explored scenarios involving axion-like particles (ALPs) alone. Instead, we find that the considered photon is compatible with specific Lorentz invariant violation (LIV) frameworks with the LIV scale obeying in the linear case ${\cal E}_{{\rm LIV}, 1} < 1.22_{-0.22}^{+0.19} \times 10^{21} \, {\rm GeV}$ at $95 \%$ CL and in the quadratic case ${\cal E}_{{\rm LIV}, 2} < 2.03_{-0.22}^{+0.17} \times 10^{13} \, {\rm GeV}$ at $95 \%$ CL. Finally, we outline scenarios where standard photon-ALP oscillations are combined with LIV-induced modifications of photon propagation, which provide a consistent interpretation of the observations of GRB 221009A including the highest energy photons detected by the LHAASO and Carpet collaborations.
arXiv:2507.01169 [pdf, ps, other]Solar flare ribbons are extensive brightenings in the chromosphere during flares, often showing fine scale structuring that reflects the underlying energy release. Using high cadence imaging from the Swedish 1-m Solar Telescope/CRISP during an X1.5-class limb flare on 10 June 2014, we identify and track 232 coherent, thread-like substructures, which we term for the first time ``riblets''. From a statistical analysis, riblets have well defined lifetimes and plane-of-sky speeds (typically 5-15 s and 50-150 km/s respectively), establishing them as distinct ribbon substructures. From analysis of their temporal distributions, their distance-time (X-T) evolution uniquely reveal approximately linear and non-linear (accelerating/decelerating) classes, a discrepancy that may be influenced by projection geometry. From analysis of their spatial distributions, we find no clear correspondence between the properties of adjacent riblets, suggesting that local atmospheric conditions (fine-scale thermodynamic and/or MAGNETic structuring) govern their kinematics more than spatial variations in electron-beam energy flux. From analysis of their spectral distributions, clusters of riblets do show temporal and spatial coincidence with hard X-ray emission signatures, consistent with episodic electron-beam injection into the chromosphere. Using FERMI/GBM spectroscopy, we derive thick-target parameters suitable for flare simulations, with representative values $δ_{\rm low}\approx 5.93$, $E_{\rm c}\approx 24.7$ keV, and an implied beam energy flux $\mathcal{F}_{\rm beam}\approx 1.5\times 10^{10}$ erg cm$^{-2}$ s$^{-1}$ (based on RHESSI footpoint area). Together, these results identify riblets as the fundamental building block of flare ribbons and provide quantitative constraints for forward tests of riblet formation mechanisms.
arXiv:2510.19729 [pdf, ps, other]We present an analysis of neutrino-driven MAGNETohydrodynamic (MHD) waves and instabilities in a rotating MAGNEToplasma with weak neutrino interactions. We show that neutrino-driven shear Alfv{é}n and oblique MAGNETosonic waves can be coupled by the Coriolis force, forming new wave modes affected by this force, as well as neutrino beam and two neutrino flavor oscillations. Our work extends previous theories by demonstrating that shear Alfv{é}n waves are influenced by neutrino effects and by identifying instabilities resulting from resonant interactions with both a streaming neutrino beam and flavor oscillations. We find that the Coriolis force, plasma density, and MAGNETic field strength significantly affect the profiles of instability growth rates. Such a growth rate for MAGNETosonic waves appears much higher than the Alfv{é}n wave, implying that MAGNETosonic waves provide a superior mechanism for energy extraction from the neutrino beam. For typical parameters relevant to the protoneutron star surface, the instability time for MAGNETosonic waves may vary in the range 0.09-0.14 s, which is within the predicted time of the neutrino-driven explosion (0.3 s after bounce) reported in the recent three-dimensional MHD simulations of core-collapse SUPERNOVAe. Our findings may shed new light on the physical mechanisms underlying core-collapse SUPERNOVAe.
arXiv:2604.21759 [pdf, ps, other]We model the multi-band lightcurves of 80 SNe Ic-BL, including 11 associated with lGRBs, using a MAGNETar engine model with $^{56}$Ni decay. We find that the data are all consistent with a MAGNETar central engine, and such a model yields high-quality fits across the sample. The medians with $1σ$ regions of the key parameters are $P_{\rm{i}}\sim2.04^{+1.84}_{-0.96}\,{\rm{ms}}$, $B_{\rm{p}}\sim3.96^{+3.28}_{-1.40}\times10^{15}\,{\rm{G}}$, $M_{\rm{ej}}\sim2.30^{+1.48}_{-1.02}\,M_\odot$, and $M_{\rm{Ni}}\sim0.18^{+0.14}_{-0.09}\,M_\odot$, with strong and statistically significant correlations observed for both $M_{\rm{ej}}-P_{\rm{i}}$ (anti-correlation) and $M_{\rm{Ni}}-M_{\rm{ej}}$ (correlation). Comparing the SN Ic-BL samples with and without lGRB association using fitting parameters, we find no significant difference between them, although the GRB-associated sample is slightly brighter, possibly due to an observational bias. Relative to ordinary SNe Ic, SNe Ic-BL have similar $^{56}$Ni and ejecta masses, suggesting comparable pre-SN progenitor properties, with differences possibly arising from the presence of a MAGNETar engine. In comparison with other possible MAGNETar-powered SESNe, including SLSNe Ic and FBOTs, we confirm a strong universal $M_{\rm{ej}}-P_{\rm{i}}$ correlation, indicating a common origin. SNe Ic-BL and SLSNe Ic have similar ejecta mass distributions, typically $M_{\rm ej}\gtrsim0.5\,M_\odot$, while FBOTs mostly lie below this value. Differences between SNe Ic-BL and SLSNe Ic may arise from MAGNETar properties, with SN Ic-BL MAGNETars rotating faster and having stronger fields. Moreover, the $P_{\rm{i}}-B_{\rm{p}}$ distribution of lGRB MAGNETars largely overlaps with that of SN Ic-BL MAGNETars. In connection with binary simulation results, we propose a unified physical classification and progenitor framework for MAGNETar-powered and ordinary SESNe.
arXiv:2606.30727 [pdf, ps, other]The search for and the characterization of ultra-compact dual ACTIVE GALACTIC NUCLEi (AGN) are among the hottest topics of current extragalactic astrophysics. These systems involve two accreting massive BLACK HOLEs (MBHs) embedded within the same host galaxy, with relative projected separations from a few hundred pc down to a few pc. They are central to understanding hierarchical galaxy formation, BLACK HOLE growth and demographics, and accretion-feedback coupling in the most extreme interaction phases. Even more compellingly, such tight pairs are the most direct precursors of gravitationally bound binary MBHs (sub-pc scale separation), which are among the loudest emitters of gravitational waves (GWs) in the low-frequency ranges. SHARP will deliver the first statistical census and physical characterization of ultra-compact dual AGN up to cosmic distances, finally bridging the observational gap between kpc-scale pairs and sub-pc GW-emitting binaries, and enabling a breakthrough understanding of MBH growth, feedback and co-evolution across cosmic time.
arXiv:2606.30757 [pdf, ps, other]The advent of JWST has revealed a large population of AGN at $z>4$, which are $\sim1$ dex more abundant than previously expected, including also the enigmatic population of Little Red Dots (LRDs). Remarkably, the vast majority of JWST-discovered AGN and LRDs are not detected in X-rays, and most of them also show faint rest-frame UV continua and faint high-ionization emission lines, as well as unusually faint emission in the Mid and Far infrared. Recent studies investigating their radio properties have reported no significant detections, even in deep stacking analyses, reaching sensitivities of 0.5-0.1 $μ$Jy at $z\sim 5-6$, corresponding to $L_{R}\lesssim 10^{39}\rm \ erg\ s^{-1}$. While these non-detections may be consistent with a standard radio-quiet nature, some results suggest that the radio emission might instead be significantly suppressed by other physical phenomena. Three main scenarios have been proposed in the literature to explain the physical properties of these objects across the electroMAGNETic spectrum: Compton-thick absorption by a broad-line region with high covering-factor, intrinsically weak emission driven by high accretion rates, or the presence of a cocoon of dense ionized gas that produces strong scattering effects. The unprecedented sensitivity of SKAO will enable the detection of the radio emission of these AGN in all three cases. Because each scenario is expected to produce distinct radio signatures, future SKAO continuum surveys will be able to distinguish between them, uncovering the physical processes responsible for their peculiar properties. Observations spanning a wide range of integration times (1-1000 hours) and frequencies with SKA-Mid and SKA-Low (0.2-11 GHz) will allow us to characterize these objects from the local Universe to high redshift, investigate possible radio variability, and test alternative scenarios to BLACK HOLE accretion.
arXiv:2606.30894 [pdf, ps, other]Reflection off the companion star and its focused stellar wind is predicted to modulate the X-ray POLARIZATION of BLACK HOLE X-ray binaries at half the orbital period ($P_{\rm orb}/2$), with an energy-dependent amplitude. We test this prediction against all publicly available IXPE observations of Cygnus X-1, comprising 26 one-day bins from 12 observation IDs spanning 2022-2024. Since the normalized Stokes parameters correlate linearly with the spectral hardness ratio in all three energy bands (2-4, 4-6, and 6-8 keV), we employ a simultaneous harmonic regression that decouples spectral variability from orbital modulation at both $P_{\rm orb}/2$ and $P_{\rm orb}$, complemented by direct fitting of 3D Monte Carlo radiative transfer stellar companion and wind-scattering templates. After removing the spectral hardness trend, neither approach reveals statistically significant orbital modulation: permutation tests yield $p > 0.01$ in all bands, with 99% confidence upper limits of 0.47%, 0.67%, and 1.81% on the $P_{\rm orb}$ amplitude and 0.54%, 0.77%, and 2.13% on the $P_{\rm orb}/2$ amplitude in the 2-4 keV, 4-6 keV, and 6-8 keV bands, respectively. The best-fit stellar companion and wind-scattering amplitude scaling factors in the three bands of $A = $ 0.78$\pm$0.89, 0.96$\pm$0.62, and $-$1.02$\pm$1.11 are consistent with a null result. These non-detections are sensitivity-limited, as the predicted stellar companion and wind-scattering RMS amplitudes in the three bands of $\approx$0.10%, $\approx$0.33%, and $\approx$0.49% are at or below the statistical noise floor of $\sim$0.15%, $\sim$0.31%, and $\sim$0.84%. We quantify the additional exposure required to detect the predicted signal and constrain the wind physics.
arXiv:2606.31138 [pdf, ps, other]Two-fluid nonlinear MHD simulations using the TM1 code demonstrate that the formation of MAGNETic islands at the top and bottom of the H-mode pedestal, together with the strong screening of resonant fields in the gradient region of the pedestal, can account for ELM suppression and density pump-out by n = 2 Resonant Magnetic Perturbations (RMPs) in low-collisionality DIII-D ITER Similar Shape (ISS) plasmas. Using experimentally relevant transport coefficients, neoclassical resistivity, electron collisionality, and RMP amplitudes, nonlinear MHD simulations reproduce the observed level of density reduction (density pump-out) in DIII-D due the formation of narrow MAGNETic islands and resulting enhanced collisional transport in the resistive foot of pedestal. For large amplitude RMPs (Br/Bt>1*10-4) simulations predict field penetration and pressure reduction at the top of the pedestal consistent with experimental observations at the onset of ELM suppression. The predicted reduction in the height and width of the pedestal by MAGNETic island enhanced transport provides a quantitative mechanism for the stabilization of the Peeling-Ballooning Mode (PBM). Importantly, these simulations predict strong screening of resonant fields in the steep gradient region of the pedestal due to strong ExB and diaMAGNETic flows. However, if the plasma resistivity is made artificially larger (~10X) than neoclassical, the simulations predict MAGNETic stochasticity throughout the plasma edge and the collapse of the pedestal due to the reduction in the penetration threshold with increasing resistivity. A scaling relation for resonant field penetration at the pedestal top, using several hundred nonlinear simulations, reproduces the density and ExB dependence of the ELM suppression threshold observed in DIII-D.
arXiv:2606.31235 [pdf, ps, other]Static resonant MAGNETic perturbations (RMPs) generated by saddle coil current have been applied in J-TEXT tokamak experiments in order to study their effects on tearing mode instabilities. With increasing the RMP amplitude in time during the discharge, the mode stabilization is first observed, but a large locked mode follows if the RMP amplitude is increased to a too large value, indicating that the RMP amplitude is important in determining the plasma response and the tearing mode behavior. By careful adjustment of the RMP amplitude, the (partial) stabilization of the m/n =2/1 tearing mode by RMPs of moderate amplitude has been achieved without causing mode locking (m and n are the poloidal and toroidal mode numbers). To compare with experimental results, nonlinear numerical modeling based on reduced MHD equations has been carried out. With experimental parameters as input, both the mode locking and mode stabilization by RMPs are also obtained from numerical modeling. Further calculations have been carried out to study the plasma parameters affecting the mode stabilization by RMPs, including the plasma rotation frequency, viscosity, Alfvén velocity, and the RMPs amplitude. It is found that the suppression of the tearing mode by RMPs of moderate amplitude is possible for a sufficiently high ratio of plasma rotation velocity to the Alfvén speed. A larger plasma viscosity enhances the mode stabilization.
arXiv:2606.31289 [pdf, ps, other]Power color-color diagrams (PCCDs) provide a useful diagnostic tool for studying the evolution of outbursts in BLACK HOLE X-ray binaries. In this paper, we present power color-color diagrams of three sources (MAXI J1348-630, MAXI J1820+070 and SWIFT J1727.8-1613) observed with Insight-HXMT in a wide energy range of 2-80 keV. We compared the hue regions defined by RXTE, which are associated with different spectral states, with the Insight-HXMT results. We find that, for hard and hard-intermediate states, the trajectories of Insight-HXMT in the power color-color diagrams are generally consistent with those of RXTE. In the soft and soft-intermediate states, weak variability generally prevents robust hue constraints. Nevertheless, a few points in MAXI J1348-630 deviate from the RXTE-defined regions, possibly because of averaged variable power spectra and the presence of a type-A QPO. The trajectories of MAXI J1348-630 and MAXI J1820+070 exhibited roughly consistent patterns over different energy bands, whereas SWIFT J1727.8-1613 was an exception during its very high state, caused by an additional low-frequency component in the low-energy band. We found that the very high state can be identified through the power color-color diagram, exhibiting a hue similar to that of the hard-intermediate state but not forming a loop pattern. We also investigated the relationship between hue and hardness and found that, although they are generally anti-correlated, they provide consistent timing for the spectral state transitions.
arXiv:2606.31477 [pdf, ps, other]Isolated stellar-mass BLACK HOLEs (IBHs) are expected to be abundant in the Milky Way, yet their electroMAGNETic signatures remain largely undetected. We investigate the detectability of IBHs in molecular clouds using a 1D, multi-wavelength emission model that incorporates MAGNETic flux transport controlled by the MAGNETic Prandtl number $P_m$. We find that MAGNETically arrested disks (MADs) form for $P_m\gtrsim 1$, where the MAGNETic flux threading the BLACK HOLE is in a saturation value. On the other hand, MAD formation is restricted to a limited parameter range for $P_m<1$, In our model, outer parts of accretion disks, around 100 gravitational radii, efficiently emit infrared photons detectable by WISE. This feature is not captured by the conventional one-zone model. X-ray emission depends strongly on $P_m$; For $P_m=1$ where MAD is formed, X-ray emission is dominated by nonthermal radiation, whereas inverse Compton emission becomes dominant for $P_m=0.5$ where the MAGNETic field is weaker than the saturation value. X-ray detection is plausible if they are in dense molecular-cloud filaments for $P_m\ge1$, although it is challenging for $P_m< 1$. These results demonstrate that MAGNETic flux transport plays a key role in shaping the multiwavelength observational signatures of IBHs.
arXiv:2602.04979 [pdf, ps, other]We present a systematic study of the environments of 25 luminous QUASARs at $z > 6.5$ from the ASPIRE program. Using JWST/NIRCam WFSS data, we identified 487 galaxies at $5.3 \lesssim z \lesssim 7.0$ exhibiting [OIII] emission. Among these, 122 [OIII] emitters lie within $|Δv_{\rm los}| < 1000~{\rm km~s^{-1}}$ of the QUASARs, corresponding to a $\sim9.4$-fold enhancement relative to the average galaxy density at other redshifts. Furthermore, we identified 16 [CII]-emitting galaxies at the QUASAR redshifts from ALMA mosaic observations. A cross-correlation function (CCF) analysis between QUASARs and [OIII]+[CII] emitters yields a cross-correlation length of $r_0^{\rm QG} = 8.68^{+0.51}_{-0.55}~h^{-1}~\mathrm{cMpc}$ and a auto-correlation of $r_0^{\rm{QQ}}=15.76^{+2.48}_{-2.70}~h^{-1}~{\rm cMpc}$, indicating that $z \sim 7$ QUASARs reside in DARK MATTER halos with $M_{\rm halo} = 10^{12.27^{+0.21}_{-0.26}}~M_\odot$. Notably, the number of [OIII]-emitting galaxies at QUASAR redshifts varies significantly from field to field, ranging from zero to twenty, highlighting a diverse QUASAR environment. Remarkably, seven QUASARs trace significant galaxy overdensities (i.e., protoclusters), with $δ_{\rm gal} > 5$ within a volume of $V \sim 500~{\rm cMpc^3}$. We also find that $|Δv_{\rm los}|$ increases rapidly toward smaller galaxy-QUASAR separations in protocluster fields, consistent with galaxy kinematics around extremely massive halos in cosmological simulations. By combining JWST and ALMA data, we reveal the complex and diverse environments of these early QUASARs, providing robust evidence that the earliest luminous QUASARs are effective tracers of galaxy overdensities, albeit with substantial field-to-field variation.
arXiv:2602.22370 [pdf, ps, other]Ultracold neutral plasmas provide a useful system for studying extreme parameter regimes plasma physics in an accessible laboratory setting. The parameter space of plasma physics can be characterized in part by coupling strength and degree of MAGNETization. The range of achievable strong coupling is determined in part by the lowest possible temperatures that can be achieved. This work examines the early-lifetime electron heating of moderately coupled, strongly MAGNETized plasmas. This heating is dominated by disorder-induced heating and heating due to Rydberg atom formation. By using experimentally informed simulations, it is found that disorder-induced heating has a large influence in electron temperature well into the plasma lifetime. Additionally, the dependence of the minimum achievable electron temperature on MAGNETization and initial electron energy is examined. In this work, we find electron temperatures as low as $0.52^{+.10}_{-.05}\ \mathrm{K}$ (for electron density, $n_{e}$, of $6.1 \times 10^{12}\ \mathrm{m^{-3}}$), which determines the maximum coupling strength for the measured experimental conditions.
arXiv:2604.17441 [pdf, ps, other]These notes give a concise introduction to General Relativity at the advanced undergraduate level, starting from the weak field limit and gravitational waves, then introducing curved manifolds and Riemannian geometry. The nonlinear gravitational action is used to derive the nonlinear field equations, with applications to BLACK HOLEs and cosmology. It is assumed that special relativity and electroMAGNETic waves have been previously studied. Some advanced topics such as Rindler and Hawking radiation are derived, and recent developments in gravitational wave detection are briefly covered. Problems are included, both those suitable for homework, and simpler ones that could be worked out by students during class sessions.
arXiv:2605.14065 [pdf, ps, other]The interaction of electrically charged particles with MAGNETic fields is a fundamental problem in several areas of physics. An example is the motion of energetic particles through a MAGNETized plasma. The most accurate and reliable way to explore theoretically the interactions between particles and fields is via test-particle simulations. In such simulations one creates the turbulent MAGNETic field and solves the Newton-Lorentz equation numerically by employing an integration scheme. In the current article we discuss exponential integrators and derive systematically from this the Rodrigues scheme as well as the famous Boris integrator. For an approach where one creates the MAGNETic field anew at each time step, both integrators are overall comparable. In theory the Rodrigues approach should be more accurate due to the fact that the occurring matrix exponential is evaluated without further approximations. Practically, both methods provide very similar results. It is argued in the current article that a Rodrigues based integrator is a very strong alternative because for the specific problem discussed here, it does not require longer computing times.
arXiv:2605.18973 [pdf, ps, other]The association of broad-lined Type Ic SUPERNOVAe with long-duration GAMMA-RAY BURSTs (GRBs) has been known for 28 years. However, only about seventy GAMMA-RAY BURST SUPERNOVAe (GRB-SNe) have been identified, of which only half have spectroscopic classifications. At $z=0.153$, GRB 260310A is the 12th spectroscopically confirmed GRB-SN discovered within 1 Gpc, offering a critical opportunity to follow one of these rare SUPERNOVAe in detail. We present optical to near-infrared imaging and spectroscopy of GRB 260310A and SN 2026fgk out to 65 d after discovery. The optical afterglow is among the brightest ever observed from a GRB. Spectra obtained more than two weeks after the explosion reveal broad absorption features that securely identify SN 2026fgk as a Type Ic-BL SUPERNOVA. Modeling of the multi-wavelength ($grizJK_s$) lightcurve shows that the SUPERNOVA is approximately half the luminosity ($k_\textrm{98bw}=0.4-0.6$) of the canonical GRB-SN 1998bw. We derive a nickel mass of $M_\textrm{Ni}=0.4-0.5$ $M_\odot$ with a total ejected mass of $M_\textrm{ej}\approx4-6 $ $M_\odot$ and kinetic energy $E_\textrm{K}=(3-8)\times10^{51}$ erg. The GRB exploded at an extremely large offset of 15 kpc from its host galaxy. Long-slit spectra reveal a ``bridge'' of nebular emission extending along the galaxy's disk to the GRB location, which has a sub-solar metallicity ($\sim$\,$0.4Z_\odot$), compared to a near solar metallicity for the host galaxy. This indicates that the large offset arises from the galaxy's extended light profile rather than an isolated environment.
arXiv:2606.30711 [pdf, ps, other]JWST's Little Red Dots (LRDs) display a unique constellation of features that do not occur simultaneously in any other class of galaxies or AGN. Here we observe that many of these features find parallels in the 19th century Great Eruption (GE) of $η$ Carinae and a sub-class of SUPERNOVAe (Type IIn). Drawing on these stellar phenomena -- outflows trapped by dense circumstellar gas envelopes -- we sketch a possible scenario for LRDs. Outflows from the central engine produce an enshrouding envelope of gas that may be thought of as a slow wind. This dense wind and its enormous extent produce an opacity so high that a pseudo-photosphere forms within the wind, obscuring the central engine and manifesting as a blackbody-like continuum. Radiation from the buried engine powers the system. The engine may also launch fast winds that crash into the existing envelope to generate shocks. Lines form within the wind above the photosphere -- electron scattering and absorption in the clumpy (ionized + neutral) medium account for broad wings and P-Cygni cores. A key implication is that inferences of ``overmassive BLACK HOLEs" may be interpreting this wind-like physics as a virial broad-line region. We propose an escape velocity argument to constrain the mass of the engine, which yields $M<10^{5} M_\odot$ for the typical LRD. The lack of variability and low surface gravity of the photosphere provide further support for intermediate mass ($M\approx10^{3-6} M_\odot$), but very luminous super-Eddington ($L_{\rm{bol}}/L_{\rm{edd}}\gtrsim5$) systems harboring a supermassive star or intermediate mass BLACK HOLE. Paralleling the evolution of IIn SNe, dust production in the envelope may mark the beginnings of classical AGN. This paper explores a possible self-consistent explanation for the entire life-cycle of LRDs, from their enshrouding in dense gas to their fates as seeds of massive BLACK HOLEs.
arXiv:2606.30726 [pdf, ps, other]While AGN feedback is a key driver of massive galaxy evolution, its physical properties and observational signatures in the dwarf regime remain poorly understood. We investigate the impact of AGN-driven outflows on the ISM of dwarf galaxies and assess whether these events can be robustly identified through emission-line diagnostics. We analysed a high-resolution cosmological MAGNETo-hydrodynamical zoom-in simulation from the AURIGA project. We focused on a dwarf galaxy with 1e9.7 M*/Msun hosting a BH of 1e7 Msun. We identified individual outflow episodes via pressure peaks in the gas surrounding the central BH, tracked the thermodynamic and kinematic history of such gas, and computed synthetic, spatially resolved nebular emission using photoionisation models to construct BPT diagnostic diagrams. We show that AGN activity in this regime produces compact, over-pressurised central bubbles reaching >1e6 K temperatures. These structures accelerate the ISM up to 600km/s, exceeding those driven by stellar feedback: the outflowing material does not escape the halo, but instead decelerates and redistributes within 10kpc from the galaxy center. Synthetic emission-line modelling reveals clear, time-dependent signatures of such AGN-driven feedback. Over its life cycle, the simulated AGN-hosting galaxy traces the locus of observed dwarf AGNs and migrates from the SF sequence in the BPT diagrams through the composite region into the AGN regime, highlighting a self-regulation mechanism in which the BH accretes its fuel supply, progressively moving towards the low-ionisation nuclear region. Our results suggest that AGN-driven outflows in dwarfs primarily regulate the central ISM through episodic heating and rapid gas recycling, rather than large-scale gas ejection. These processes generate observable spectroscopic signatures, offering a promising avenue for identifying AGN feedback in low-mass galaxies.
arXiv:2606.30886 [pdf, ps, other]We investigate the multipolar surface MAGNETic-field structure of the high-mass millisecond pulsar PSR J0740+6620 using the 32-bin bolometric NICER pulse profile of Dittmann et al. (2024). Building on the neural-network surrogate framework of Olmschenk et al. (2025), we model the emitting regions as open-field-line footpoints of an offset dipole plus axisymmetric quadrupole static vacuum field, rather than as prescribed geometric hotspots. We fix the stellar mass, radius, observer inclination, and hotspot temperature ratio to the Dittmann et al. (2024) maximum-likelihood values and explore the resulting 11-dimensional MAGNETic-field space. To make this feasible, we train convolutional neural-network surrogates on $5.12\times10^7$ synthetic bolometric light curves and use them in a parallel ensemble Markov Chain Monte Carlo calculation on 4000 CPU cores, accelerating likelihood evaluations by a factor of $\gtrsim 400$. We perform independent inferences for two calibrated temperature-weight prescriptions, Tw=1.31 and Tw=1.41, encoding the relative bolometric weight associated with the hotspot temperature difference. The posteriors, posterior-predictive light curves, and maximum-likelihood values are very similar, indicating weak sensitivity to this choice. The offset model reproduces the observed double-peaked profile and yields broad, multimodal posteriors, reflecting both the background-dominated data and degeneracies of the multipolar parameterization. The hotspot-density map shows that pulse phases constrain the approximate azimuthal placement of the emission, while latitude, surface extent, and morphology remain weakly constrained. A restricted zero offset run is disfavored within the adopted field basis. This work extends neural-network-accelerated MAGNETic-field inference to PSR J0740+6620 and motivates future energy-dependent, force-free, and joint X-ray/$γ$-ray extensions.
arXiv:2606.30969 [pdf, ps, other]We investigate the repetitive Penrose process for charged particles in an initially extremal Kerr--Newman BLACK HOLE and develop a nonlinear iterative framework in which the black-hole mass, angular momentum, electric charge, and irreducible mass are updated after every extraction event. By imposing the triple turning-point condition, we obtain an analytic solution of the conservation equations, allowing the entire extraction sequence to be followed self-consistently. The dynamics are governed by two electroMAGNETic couplings. The coupling $\hat Q\hat q_0$ determines whether the incident particle can continue to access the ergoregion and therefore controls the termination of the repetitive process, whereas $\hat Q\hat q_1$ governs the depth of the negative-energy states and the extraction efficiency. An attractive interaction ($\hat Q\hat q_1<0$) significantly enhances both the energy return on investment and the energy utilization efficiency and, above a critical charge, produces a transient increase of the dimensionless spin despite the continuous loss of angular momentum. We identify a four-region structure in the captured-particle charge parameter space. Near the critical charge $\hat q_1\simeq-54.85405$, the evolution approaches the reversible Christodoulou--Ruffini limit with the energy utilization efficiency approaching unity while the BLACK HOLE remains sub-extremal. Beyond this point the irreducible mass decreases, indicating the breakdown of the test-particle approximation. Unlike the repetitive Penrose process in the extremal Reissner--Nordström spacetime, the Kerr--Newman BLACK HOLE can evolve through the neutral state and reverse the sign of its electric charge without violating the area theorem or cosmic censorship, demonstrating that the discharge barrier found in the Reissner--Nordström case is not a generic property of charged BLACK HOLEs.
arXiv:2606.31035 [pdf, ps, other]Far-from-equilibrium plasmas require nonlinear Coulomb collisions, but direct three-dimensional Hermite discretization of the Landau operator needs an impractical dense tensor. By porting quantum chemistry Coulomb-integral methods, we reduce the six-dimensional integrals to one-center Coulomb moments and separable exponential-sum contractions. This gives a four-order-of-magnitude working-memory reduction and enables nonlinear relaxation tests. Numerical simulations preserve invariants and show that finite-basis linearization changes relaxation and produces a fourfold angular error.
arXiv:2606.31124 [pdf, ps, other]We present an estimate of the Sivers asymmetry in back-to-back $J/ψ$-photon and $J/ψ$-JET production in electron-proton collisions in the kinematics of the upcoming Electron-Ion Collider (EIC) in a transverse momentum dependent (TMD) factorization framework, and also incorporating the TMD evolution. We use the non-RELATIVISTIC Quantum Chromodynamics (NRQCD) model to study the production mechanism of $J/ψ$. The gluon induced channel dominates, and these are promising probes of the less known gluon Sivers function. We incorporate the TMD evolution in the cross section and Sivers asymmetry in the Collins-Soper-Sterman (CSS) approach and show that the asymmetry is sizable even after the evolution. Although the cross section for $J/ψ$-JET production depends on the long-distance matrix element (LDME) set chosen, the asymmetry remains largely unaffected. The asymmetry is independent of the LDME at leading order for $J/ψ$-photon production. Thus, the Sivers asymmetry in both processes is a robust probe of the gluon Sivers function.
arXiv:2606.31203 [pdf, ps, other]The scaling law for the n=2 error field (EF) penetration threshold is predicted numerically based on nonlinear single-fluid and two-fluid modeling using the TM1 code. The simulated penetration threshold of radial MAGNETic field br at the plasma edge is scaled to the electron density ne, temperature Te, viscous time, toroidal field Bt and the natural frequency by scanning these parameters separately. Single fluid modeling shows that the EF threshold scaling is similar with the analytical scaling law in both the Rutherford and visco-resistive regimes. However, two-fluid modeling shows that the scaling law differs significantly in particular regarding the dependence on plasma rotation. In detail, the scaling coefficient on density decreases from 0.67 to 0.56 and on temperature decreases from 0.67 to 0.32, while on viscous time is around -0.45 and on toroidal field decreases slightly from -1.15 to -1, when the ratio ExB over electron diaMAGNETic drift frequency varies from 0 to 10. Scans of the plasma rotation reveals that the penetration threshold linearly depends on the perpendicular rotation frequency (or natural frequency), and there is a minimum in the required field amplitude when electron fluid frequency near 0. In addition, the enduring mystery of non-zero penetration threshold at zero plasma natural frequency in EF experiments is resolved by two-fluid simulations. We find that the very small island and smooth bifurcation in EF penetration near zero frequency is hard to detect in the experiment, leading to a finite penetration threshold within the capability of the experimental measurements.
arXiv:2606.31364 [pdf, ps, other]Classically, BLACK HOLEs (BHs) are the most compact objects predicted in nature with C=0.5 in the Schwarzschild limit; C is defined as the mass-to-radius ratio in geometric units. In this work we perform a novel measurement on the nature of putative BH mergers in the gravitational wave (GW) data by directly probing the binary's closest approach through an effective compactness parameter. We confidently show all such high-significance signals in GWTC-3 are consistent with the BH hypothesis for the first time. Our hierarchical analysis yields $C_{\rm eff} = 0.5^{+0.3}_{-0.1}$, and we further limit the merger rate of low-compactness exotic binaries to $< 0.7\,{\rm Gpc}^{-3}\,{\rm yr}^{-1}$. This work establishes compactness as a key observable in GW astronomy.
arXiv:2606.31433 [pdf, ps, other]The modulation of galactic COSMIC RAYs, driven by the evolution of the heliospheric MAGNETic field, strongly influences the intensity of COSMIC RAYs reaching near-Earth space. Characterizing this process is crucial both for advancing our understanding of cosmic-ray transport and for assessing radiation exposure and related hazards in space environments. Here we present a newly developed forecasting framework built on a numerical description of charged particle transport in the heliosphere and its dependence on solar activity, designed for the long-term forecasting of galactic cosmic-ray fluxes. It solves a one-dimensional, spherically symmetric form of the Parker transport equation, including diffusion, solar-wind advection, and adiabatic energy losses. The model has been validated using multi-species flux measurements from space-based experiments: PAMELA, AMS-02, and ACE. Its strategy is based on Hilbert-Huang transform filtering and cross-correlation between delayed solar proxies and effective model parameters. Our charge-sign- and rigidity-dependent parametric description of the diffusion-advection processes yields good overall agreement with the data, as shown by the reconstruction uncertainty. The robustness of this approach is validated across a broad set of multichannel datasets covering different particle species, energy ranges, and phases of solar activity, supporting its applicability to space radiation monitoring and forecasting. Furthermore, when coupled with solar-proxy forecasting models, it enables decadal-scale predictions of galactic cosmic-ray fluxes, thereby supporting long-term planning and radiation-risk assessment for future space missions.
arXiv:2606.31476 [pdf, ps, other]We investigate the Landau-Zener description of resonant axion-photon conversion in neutron star MAGNETospheres. We find that this picture often fails for axion conversions to millimeter-to-optical band photons due to the characteristic resonance width exceeding the size of the conversion region. This comparison of scales yields a simple criterion for evaluating the validity of the Landau-Zener formula. We verify this criterion numerically, and show that when invalid, the Landau-Zener conversion probability may significantly deviate from the numerical result. In light of these findings, we revise constraints on axions from neutron star optical-band POLARIZATION searches.
arXiv:2606.31515 [pdf, ps, other]Little Red Dots (LRDs) are a population of high-z sources discovered by JWST whose compactness, broad permitted lines, strong absorption features, continuum shapes and luminosities point to accreting supermassive BLACK HOLEs (SMBHs) embedded in dense gas. To date, the metallicity of the hosts of these systems has not been systematically measured. We determine the gas-phase metallicities of LRD host galaxies and test whether their narrow-line emission is consistent with metal poor STAR FORMATION or AGN activity. We assemble a sample of 24 LRDs at z ~ 2.3-7 with medium and high-resolution JWST/NIRSpec data. We derive oxygen abundances and electron temperatures using the direct Te method applied exclusively to the narrow components of emission lines, and cross-check against widely used strong line calibrations. We derive a sample-averaged abundance of $Z_{T_\mathrm{e}} = 0.08_{-0.03}^{+0.11}\,\mathrm{Z_{\odot}}$ ($T_\mathrm{e} = 23000_{-7000}^{+17000}$\,K), placing LRDs firmly in the metal-poor regime of high redshift star forming galaxies. The R-hat calibration yields a consistent average of $Z_{\hat{\mathrm{R}}} = 0.07_{-0.04}^{+0.07}\,\mathrm{Z_{\odot}}$, with only 4% scatter relative to the direct Te method, providing a robust proxy for systems where the [O III]4363Å line is not detected. We also identify two extremely metal-poor LRDs with metallicities <1.3%. The general population of LRDs are among the lower metallicity galaxies found by JWST at this epoch; they exhibit a narrow range of metallicities with a range of about 0.6 dex, which remains remarkably stable over cosmic time. Such low metallicity may then be a defining property of the class. The fact that LRDs have substantial metallicity across most of the class poses a challenge to models that require formation via pristine gas collapse, while their generally low metallicity indicates that they are not standard AGN.
arXiv:2606.31531 [pdf, ps, other]Globular clusters (GCs) can act as gravitational lenses for gravitational waves(GWs) in the wave-optics regime, imprinting frequency-dependent signatures on the observed signal. We investigate whether such lensing effects can be used to probe intrinsic properties of GCs, in particular their central velocity dispersion. Modeling GCs as singular isothermal spheres, we simulate lensed GW150914-like signals and perform Bayesian parameter estimation using waveform templates that include both source and lens parameters. We show that the effective lensing mass can be recovered and, when combined with GW sky localization information and GC catalogs, allows for an estimate of the cluster velocity dispersion. For favorable source-lens alignments, the injected values are well recovered within credible intervals. Our results demonstrate that lensed GWs can provide a complementary probe of GC dynamics and motivate searches for such signatures in current and future observations.
arXiv:2606.31897 [pdf, ps, other]We present a high-frequency, wideband observing campaign of the hyperactive repeating fast radio burst FRB 20240114A with the Allen Telescope Array. Between 27 January and 29 October 2024, we obtained 1167 hr of on-source observations across 1344 MHz of simultaneous bandwidth covering frequencies from approximately 900 MHz to 7620 MHz. We detected 97 bursts between ~900 MHz and ~5 GHz, including a strong S-band activity episode, while no bursts were detected in the highest-frequency tunings above ~5 GHz despite substantial exposure. This campaign provides one of the very few extended samples of repeating-FRB activity above 3 GHz, a regime that remains sparsely sampled. We find that the burst rate varies strongly with both observing frequency and epoch, confirming that the emission from FRB 20240114A is highly chromatic and band-limited. We measure the spectro-temporal properties of the bursts and their sub-components, confirming that fractional bandwidth remains approximately scale-invariant. Sub-burst durations decrease toward higher frequencies, and the magnitude of the downward drift rate increases with frequency. The cumulative spectral-energy-density distribution above our completeness threshold is well described by a shallow power law, indicating that high-energy bursts contribute substantially to the observed energy output. We also compare our detections with recently proposed long-timescale frequency-modulation models and find that the ATA high-frequency burst storm is not consistent with a strictly phase-coherent modulation inferred from other datasets. Our results demonstrate that incomplete time-frequency coverage can bias interpretations of burst activity and highlight the need for sustained, simultaneous wideband monitoring of hyperactive repeaters.
arXiv:2606.31926 [pdf, ps, other]Tidal Disruption Events (TDEs) serve as direct probes of the population of supermassive BLACK HOLEs in the center of galaxies and are nowadays regularly detected in optical wide-field time-domain sky surveys. Recent studies have demonstrated that a large fraction of TDEs can be uniquely identified in the infrared (IR) waveband, but these studies have to date been limited to relatively nearby events. In this work, we searched for highly luminous IR-bright TDEs that are rare and thus missed by searches in the local universe. We performed a systematic search of the NEOWISE archive and developed a new selection criterion based on the evolution of the W1-W2 color to select TDE candidates. We identified 10 IR bright TDEs with peak luminosities above $L_{\rm peak\, W2} \simeq 3 \times 10^{43}$ erg s$^{-1}$ and estimated an event rate of $1.2^{+0.5}_{-0.4}\times10^{-10}$ Mpc$^{-3}$year$^{-1}$ for the luminosity range of our sample. Compared to the existing local luminosity function of lower luminosity events, we detect a suppressed rate for these highly luminous events. This turn-over in the luminosity function can be naturally explained by the suppressed amount of TDEs taking place in systems with larger BLACK HOLE masses, thereby confirming the TDE nature of our sources.
arXiv:2606.31992 [pdf, ps, other]High-order accurate simulations of special RELATIVISTIC hydrodynamics (RHD) are prone to numerical breakdown if intrinsic physical constraints (positive rest-mass density/pressure and subluminal velocity) are violated near strong discontinuities. In this work, we develop a robust and efficient physical-constraint-preserving (PCP) flux-limiting framework for high-order schemes, using finite-difference WENO as a representative example. By leveraging the geometric quasilinearization (GQL) representation, which equivalently reformulates the nonlinear RHD constraints into a family of linear inequalities, we integrate a Zalesak-type Flux-Corrected Transport (FCT) update into a scalar-style limiter that acts directly on conservative variables. A critical innovation is the explicit, non-iterative determination of limiting parameters via a rational stereographic parameterization of the GQL normal vector. This technique transforms the required worst-case minimization over auxiliary variables into a generalized Rayleigh-quotient formulation, allowing the optimal parameters to be obtained by solving small symmetric eigenvalue problems ($2\times2$ in 1D; $(d+1)\times(d+1)$ in $d$ dimensions). Relaxed variants are further introduced to reduce computational costs in multidimensions while retaining the PCP guarantee. Extensive numerical benchmarks ranging from 1D to 3D, including ultra-RELATIVISTIC Riemann problems and astrophysical JETs, demonstrate that the proposed method robustly enforces physical admissibility, sharply resolves discontinuities, and maintains design-order accuracy for smooth solutions.
arXiv:2606.31998 [pdf, ps, other]The standard $α$-disk formalism parametrizes turbulent angular momentum transport through a dimensionless coefficient $α$, assumed to be spatially and thermodynamically invariant. While analytically convenient, this assumption leads to the well-known thermal and viscous instabilities in radiation-pressure dominated (RPD) regions. We show that this instability is not the consequence of radiation pressure, but is due to enforcing a constant $α$ across distinct thermodynamic regimes. Requiring the steady thin-disk (TD) to remain thermally stable and single-valued in the $\dot{M}$--$Σ$ plane yields a necessary condition on the stress response, expressed as $η_{\rm x} \equiv d\lnα_{\rm x}\,/\,d\ln X > 4/7$, where $X \equiv P_{\rm gas}/P_{\rm rad}$. The resulting viscosity law $α_{\rm x} \equiv α(X)$ emerges directly from the internal consistency of TD equations, without modifying the stress law or invoking any additional physics. $α_{\rm x}$ removes the RPD unstable branch. The disk structure becomes smooth and globally single-valued, with higher $Σ$ and $τ$ in the inner RPD disk, while preserving the standard effective-temperature profile. This increases thermal and inflow timescales, offering a natural route to accretion-state dependent variability without large-amplitude radiation-pressure limit cycles. It also motivates revisiting AGN disk tensions, including microlensing sizes and continuum reverberation lags with improved radiative-transfer modeling. The results show that the RPD instability, and possibly some associated AGN disk tensions, reflect an inconsistent viscosity closure.
arXiv:2606.32021 [pdf, ps, other]Title: Flexibility as a Universal Nature-Inspired Mechanism for Thrust EnhancementAuthors: Roberta Santoriello, Francesco Viola, Vincenzo Citro,Comments: Manuscript: 21 pages, 4 figures. Supplementary materials: 9 pages, 2 figures, 1 tableSubjects: physics.flu-dynCreated: 2026-06-30; Updated: 2026-07-01; Datestamp: 2026-07-01Nature has equipped JET-propelled swimmers with flexible nozzles that outperform rigid ones, yet the origin of this advantage has remained unexplained. By tracking where and when energy is exchanged between fluid and structure, three-dimensional numerical simulations resolve the underlying mechanism: a standing-wave response of the nozzle, in which the structure dilates and then recoils synchronously, charging and releasing energy to enhance thrust. Outside of this regime, the structure exhibits a traveling wave response, with expansion and contraction coexisting along the nozzle, reducing the thrust gain. We propose a physics-based model that captures the boundary between standing and traveling responses in a closed form, showing that the optimum occurs when the natural period of the structure matches the pulse duration. Beyond this optimum the strain imposed by the nozzle curvature required for steering selects the geometry observed across marine species. The propulsion and maneuverability are reconciled within a single framework that yields design principles for soft robotic propulsors.
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