Current date: 2026-07-21
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Number of records retrieved: 1129
Keyword score statistics
score 8 -- 1 abstracts
score 7 -- 1 abstracts
score 6 -- 1 abstracts
score 5 -- 3 abstracts
score 4 -- 7 abstracts
score 3 -- 10 abstracts
score 2 -- 32 abstracts
in total -- 55 abstracts
Articles that appeared on 2026-07-21
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[abstract 1 / 55] Wow! (score: 8)
- Title: Hadronic Scenario for Galactic PeVatron LHAASO J1912+1014u Supported by FERMI-LAT $γ$-ray Data and FUGIN CO DataAuthors: Tsunefumi Mizuno, Hidetoshi Sano, Takeru Murase, Tomohiko Oka, Hiromasa Suzuki, Naohito Nakahara,Comments: This is a pre-copyedited, author-produced version of an article accepted for publication in ApJ following peer reviewSubjects: astro-ph.HECreated: 2026-07-19; Updated: 2026-07-21; Datestamp: 2026-07-21
LHAASO has reported 43 sub-PeV $γ$-ray sources, which are promising candidates for cosmic-ray (CR) accelerators above the PeV energy, commonly called as PeVatrons. Multi-wavelength observations are crucial for identifying the underlying particle species and estimating the CR energy content of these sources. In this work we investigate the region around LHAASO J1912+1014u (and HESS J1912+101) using FERMI-LAT $γ$-ray data and FUGIN CO data. We analyzed 15 years of FERMI-LAT data in the 0.4--409.6 GeV energy range. By improving the standard FERMI-LAT diffuse emission model, we significantly reduced the large residuals around the source in the 1.6-12.8 GeV band. We detected a statistically significant excess above the diffuse background, which likely represents $\ge$10 GeV emission associated with the LHAASO/H.E.S.S. source. The GeV excess exhibits a hard spectrum (photon index of about 2.1) and is well reproduced by interstellar gas templates with systemic velocities of about 25 $\mathrm{km~s^{-1}}$ or 60 $\mathrm{km~s^{-1}}$. We performed a comprehensive fit to the GeV--TeV spectral energy distribution. Although a leptonic scenario can reproduce the observed spectrum, a hadronic scenario is favored once electron cooling is considered. The inferred CR proton spectrum has an index of $\sim$2.2, and the total CR proton energy above 1 GeV is (1--5) $\times 10^{49}~\mathrm{erg}$, depending on the assumed velocity range of the associated interstellar gas. A stringent upper limit on diffuse X-ray emission further supports the proton PeVatron scenario.
[abstract 2 / 55] Wow! (score: 7) - Title: Simultaneous radio, optical and X-ray monitoring of hard X-ray selected AGN: a variability studyAuthors: L. Hernández-García, F. Panessa, D. Williams-Baldwin, P. Arévalo, A. M. Muñoz Arancibia,Comments: 13 pages plus Appendix, 5 figures, 3 tables. Accepted in A&ASubjects: astro-ph.HE astro-ph.GACreated: 2026-07-17; Updated: 2026-07-21; Datestamp: 2026-07-21
AGN emission is intrinsically variable across the electroMAGNETic spectrum. Mapping the coupling between the accretion disk, the X-ray corona, and ejection flows is key to understanding the energy flow within the central engine. We characterize the multi-wavelength variability of 14 hard X-ray selected AGN from the INTEGRAL/IBIS catalog in the radio, optical, and X-ray bands, to determine the coupling between these frequencies and how variability relates to the physical properties of the central engine, with emphasis on the radio band. We analyzed multi-epoch observations from AMI-LA at 15 GHz, ZTF in the g and r bands, and SWIFT/XRT over 2018--2020. Variability was quantified using the normalized excess variance, the fractional variability amplitude, and the Mexican Hat filter at 70- and 200-day timescales. We also characterized the radio-loudness of the sample and evaluated the impact of variability on the Fundamental Plane of BLACK HOLE activity by comparing time-averaged with strictly simultaneous data. Significant variability is detected in 86% of the sample, with a clear amplitude stratification: the fractional rms amplitude is highest in X-rays, with a median of 30% (11-67%), followed by the optical g and r bands at 19% (2-33%) and 8.5% (0.2-24%), and the radio band at 10% (4-23%). The Mexican Hat analysis reveals a red-noise power spectrum dominated by long-term fluctuations. The sample follows the expected Fundamental Plane scaling; although individual sources shift within the relation due to stochastic fluctuations, this dispersion accounts for only ~3% of the total scatter. Our findings support a core-dominated origin for the 15 GHz emission, likely a compact JET base or a MAGNETized corona, while differences in variability patterns, radio-loudness, and Fundamental Plane location point toward distinct accretion/ejection processes and degrees of corona-JET coupling.
[abstract 3 / 55] Yes (score: 6) - Title: Probing the emission geometry of the X-ray pulsar 2S 1417$-$624 during a weak outburst with NICER, IXPE, and NUSTARAuthors: Menglei Zhou, Pengju Wang, Honghui Liu, Lorenzo Ducci, Sergey S. Tsygankov, Qingchang Zhao, Juri Poutanen, Long Ji, Valery F. Suleimanov, Alexander A. Mushtukov, Qi Liu, Camille M. Diez, Luis Abalo, Victoria Grinberg, Andrea Santangelo,Comments: 14 pages, 13 figures, 8 tables. Accepted for publication in Astronomy & AstrophysicsSubjects: astro-ph.HECreated: 2026-07-20; Updated: 2026-07-21; Datestamp: 2026-07-21
We report results from a multi-mission observational campaign of the transient X-ray pulsar 2S~1417$-$624 during its 2025 outburst, using data from NICER, IXPE, and NUSTAR. Phase-averaged and phase-resolved spectroscopy with NICER and NUSTAR reveal that a typical broken power-law model with a high-energy cut-off well describes the broadband spectra. Several spectral parameters, however, show clear and systematic modulations with pulse phase, indicating variations in the physical conditions of the emitting plasma over the neutron star's rotation. IXPE provides the first polarimetric measurements of this source, yielding a phase-averaged POLARIZATION degree (PD) of $4.8 \pm 1.2$% and a POLARIZATION angle (PA) of ${17}^{\circ} \pm {7}^{\circ}$, both quoted at the $1σ$ confidence level. Fitting the phase-resolved PA with the rotating vector model (RVM) gives a MAGNETic obliquity of $θ= 69_{-29}^{+13}$ deg, indicating a significantly inclined MAGNETic geometry that may approach a quasi-orthogonal configuration. In addition, using the unbinned photon-by-photon method, we obtain a PD of $5.9 \pm 1.2$% across the pulse phase, together with a pulsar geometry consistent with that inferred from the binned analysis, assuming the variable PA predicted by the RVM. A simultaneous RVM fit across the three energy bands, 2--5 keV, 5--6 keV, and 6--8 keV, provides the strongest constraints on the geometrical parameters, yielding $θ= {84}_{-6}^{+4}$ deg. Together, these findings demonstrate pronounced phase-dependent spectral and POLARIZATION variability, offering valuable constraints on the geometry and emission processes within the accretion region of this transient X-ray pulsar.
[abstract 4 / 55] Yes (score: 5) - Title: Revisiting early afterglows of GAMMA-RAY BURSTs with finite-thickness ejecta: Implications from XRF 080330 and GRB 080710Authors: Kaori Obayashi, Ryo Yamazaki, Yo Kusafuka, Katsuaki Asano,Comments: 25 pages, 8 figures, 4 tables, JHEAp, in pressSubjects: astro-ph.HECreated: 2026-07-18; Updated: 2026-07-21; Datestamp: 2026-07-21
We revisit the physical origin of the achromatic peaks and breaks observed several thousand seconds after the burst in the multi-wavelength afterglows of XRF 080330 and GRB 080710. Using a numerical afterglow model that consistently incorporates finite ejecta thickness and a generalized external density profile, we perform Bayesian inference to estimate model parameters describing these events. Our analysis shows that the gradual rise and achromatic temporal features in both events are more naturally explained by JET dynamical evolution with finite shell thickness rather than by off-axis viewing effects. The inferred initial radial width of the ejecta is of order $10^{13}$ cm for both bursts, implying a central engine activity timescale significantly longer than that suggested by the prompt gamma-ray duration alone. Taken together, these results demonstrate that early afterglow light curves are strongly influenced by transition dynamics when finite ejecta thickness is properly taken into account, thereby providing a physical link between the prompt and afterglow phases and highlighting limitations of simply applying the thin-shell approximation when interpreting early-time afterglows. Furthermore, Bayesian model comparison favors a generalized circumburst density profile over the canonical uniform or steady-wind models, suggesting that fixing the external density structure to idealized profiles a priori may obscure crucial information about the progenitor's pre-burst activity.
[abstract 5 / 55] Yes (score: 5) - Title: Circular POLARIZATION of gravitational waves from MAGNETorotational SUPERNOVAeAuthors: Shota Shibagaki, Tomoya Takiwaki, Kei Kotake, Takami Kuroda, Tobias Fischer,Comments: 5 pages, 5 figures. Updated to match published versionSubjects: astro-ph.HECreated: 2026-07-17; Updated: 2026-07-21; Datestamp: 2026-07-21
Context. Gravitational waves (GWs) provide a unique probe of the explosion mechanism of massive stars and the evolution of nascent proto-neutron stars (PNSs). Magnetorotational explosions are one of the promising noncanonical core-collapse SUPERNOVA scenarios, possibly linked to MAGNETar formation and energetic SUPERNOVA explosions. However, the GW signatures of such events remain incompletely understood. Aims. We investigate the origin and nature of GW POLARIZATION arising from a MAGNETorotational core-collapse model and examine its potential detectability by current GW observatories. Methods. We performed a 3D GRMHD simulation of a rapidly rotating, strongly MAGNETized 20 $M_{\odot}$ progenitor, including multi-energy neutrino transport. The GW signals were extracted using the standard quadrupole formalism, and their POLARIZATION states were analyzed with Stokes parameters. Results. Strong circular POLARIZATION emerges along the rotation axis during the early post-bounce phase ($\lesssim$ 230 ms). The characteristic GW spectrum peaks at ~90 Hz, consistent with the emission at twice the local angular velocity (~45 Hz) around the PNS surface at cylindrical radii of ~50 km. These features are attributed to the low-$T/\vert{}W\vert{}$ instabilities and nonaxisymmetric motions near the PNS and not to the MHD JETs themselves. The POLARIZATION signals lie within the sensitivity bands of current detectors such as Advanced LIGO, Advanced Virgo, and KAGRA. Conclusions. Models launching MAGNETorotationally driven JETs can produce circularly polarized GW signals originating from the inner PNS region. This provides an observational signature that complements previous findings from nonMAGNETized rotating models. Thus, GW POLARIZATION is a promising diagnostic of noncanonical core-collapse SUPERNOVAe. Future third-generation detectors will be crucial to fully exploit this potential.
[abstract 6 / 55] Yes (score: 5) - Title: The Complete Catalog of Gamma-Ray Transients Observed by GRBAlpha & VZLUSAT-2 CubeSat MissionsAuthors: Marianna Dafcikova, Jakub Ripa, Andras Pal, Norbert Werner, Michaela Duriskova, Yasushi Fukazawa, Martin Kolar, Laszlo Meszaros, Filip Munz, Masanori Ohno, Lea Szakszonova, Hiromitsu Takahashi, Masato Yokota, Jean-Paul Breuer, Hsiang-Kuang Chang, Balazs Csak, Vladimir Daniel, Juraj Dudas, Marcel Frajt, Gabor Galgoczi, Peter Hanak, Filip Hroch, Chin-Ping Hu, Jan Hudec, Nikola Husarikova, Yuto Ichinohe, Jakub Kapus, Miroslav Kasal, Martin Koleda, Robert Laszlo, Chih-Hsun Lin, Tsung-Che Liu, Tsunefumi Mizuno, Kazuhiro Nakazawa, Hirokazu Odaka, Michal Pazderka, Ales Povalac, Maksim Rezenov, Martin Sabol, Kaustubha Sen, Miroslav Smelko, Petr Svoboda, Martin Topinka, Che-Chih Tsao, Tomas Urbanec, Ivo Vertat, Tomas Vitek, Chih-En Wu,Comments: submitted to The Astrophysical Journal Supplement Series, after revisionSubjects: astro-ph.HECreated: 2026-07-20; Updated: 2026-07-21; Datestamp: 2026-07-21
We present the largest sample of gamma-ray transients observed by any CubeSat mission so far. Observations were acquired by a 1U CubeSat GRBAlpha, the smallest astrophysical space observatory, and a 3U CubeSat VZLUSAT-2. Both missions were technological pathfinders and carried a novel CsI scintillator-based detector read-out by silicon photomultipliers. They operated on Sun-synchronous low Earth orbits below 550 km for about four years; GRBAlpha between March 2021 and June 2025 while VZLUSAT-2 between January 2022 and November 2025. Despite being technological experiments, they observed over 300 gamma-ray transients including GAMMA-RAY BURSTs (GRBs), solar flares, soft gamma repeaters and one outburst from an X-ray binary. Among these are the two brightest GRBs ever observed, GRB 221009A and GRB 230307A, without saturation and GRBs at redshifts up to z=4.2. GRBAlpha also contributed to the InterPlanetary Network. Regular monitoring of transients was demonstrated by a detection rate of two transients or one GRB a week and the shortest time between two subsequent detections of only 42 minutes. We show that a constellation of nanosatellites around the Earth would observe at least 60% of FERMI/GBM GRBs with 5$σ$ significance and over 90% at 3$σ$ level. GRBAlpha and VZLUSAT-2 prove that routine monitoring of the gamma-ray sky can also be done by low-cost and quickly developed nanosatellite missions.
[abstract 7 / 55] Yes (score: 4) - Title: Simulating the LOcal Web (SLOW) -- VI: Gamma-ray Emission in the Local UniverseAuthors: Ludwig M. Böss, Ildar Khabibullin, Daniel Karner, Klaus Dolag, Ulrich P. Steinwandel, Elena Hernandez-Martinez, Jenny G. Sorce,Comments: 13 pages, 9 figures, accepted in A&A. Comments welcomeSubjects: astro-ph.HE astro-ph.COCreated: 2026-07-17; Updated: 2026-07-21; Datestamp: 2026-07-21
Context: Diffuse $γ$-ray emission from cosmic-ray (CR) protons scattering off the gas in the intracluster and intergalactic medium remains out of reach for current observations. Detecting this emission would provide constraints on the nonthermal pressure support by CR protons in these environments. Aims: We provide estimates for diffuse $γ$-ray emission in the \textit{FERMI}-LAT band from galaxy clusters and the cosmic web in the local Universe. Methods: In this work, we show results from the first cosmological MAGNETohydrodynamic simulation with an on-the-fly spectral CR model. We modeled CR injection at shocks, accounted for adiabatic energy changes and advection of CR protons, and obtained their $γ$-ray emissivity directly from the simulated CR energy density and spectra. To do this, we used constrained initial conditions that evolved in a field closely resembling that of the local Universe, allowing a direct comparison to \textit{FERMI}-LAT data on massive clusters. Results: We find CR proton acceleration at all structure formation and accretion shocks in galaxy clusters and cosmic web filaments. These protons provide the basis for diffuse $γ$-ray emission in these regimes. The absolute value of the diffuse $γ$-ray emission in our simulation lies a few orders of magnitude below the current upper limits found by \textit{FERMI}-LAT. Under the assumption of our model, a sensitivity of $F_γ< 10^{-11} \: γ~ \text{s}^{-1}~\text{cm}^{-2}$ would be required for a detection of diffuse emission in Coma. This provides a lower limit for diffuse emission from CR protons accelerated at structure formation shocks.
[abstract 8 / 55] Yes (score: 4) - Title: A variable ADAF disk model for X-ray binary systemsAuthors: Chun Xu,Comments: preprint. 6 pages, 2 figuresSubjects: astro-ph.HECreated: 2026-07-18; Updated: 2026-07-21; Datestamp: 2026-07-21
We propose a variable ADAF disk model for X-ray binary systems. In this model, the accretion flow consists of an outer thin disk and an inner thick ADAF torus. The ADAF is turbulent, optically thick, and variable in size. A complete cycle of ADAF contraction, transition to a thin disk, and subsequent re-expansion corresponds to the rapid rise, peak, and decay phases observed in the X-ray outbursts of BLACK HOLE binaries. This cycle also tracks the canonical evolution through the low-hard, high-soft, and back to the low-hard state in the hardness-intensity diagram. Turbulence in the ADAF, along with second-order FERMI acceleration, naturally generates a power-law particle spectrum that directly corresponds to the power-law X-ray spectra observed in most X-ray binary systems. This model unifies the presence of near-ISCO Fe emission lines with the truncated disk paradigm, as observed in the BLACK HOLE system GX 339-4. It explains the 35-day period in the neutron star system Her X-1 more effectively through variable ADAF sizes than through a precessing disk. This variable ADAF framework may be extended to explain similar phenomena in ACTIVE GALACTIC NUCLEi.
[abstract 9 / 55] Yes (score: 4) - Title: Constraints on Line-of-Sight Acceleration from O1-O4Authors: Labani Roy, Alexander H. Nitz,Comments: 14 pages including references, 15 figures, data release at URL - https://github.com/labani-01/LOS-acceleration_LIGO-peSubjects: astro-ph.HE gr-qcCreated: 2026-07-20; Updated: 2026-07-21; Datestamp: 2026-07-21
A compact binary will experience a center-of-mass (CoM) acceleration in the vicinity of a massive third object. The line-of-sight (LOS) component of this acceleration is imprinted on gravitational waves (GWs) produced by the compact binary as a time-varying Doppler shift. The observation of a non-zero LOS acceleration may indicate the binary is in a dense environment, such as an ACTIVE GALACTIC NUCLEus (AGN) disk or nuclear star cluster, etc. We measure the LOS acceleration of all compact binaries observed through the first part of the fourth observing run (O1-O4a) of Advanced LIGO and Virgo in addition to select binaries from later observing runs. We introduce a new method to model the LOS acceleration by directly applying the time-varying Doppler shift in the time domain to the signal produced in the binary's frame; this method can be applied to any waveform model including those with higher order modes, eccentricity, and precession. We find the LOS acceleration for all known binaries to date is consistent with zero. We find that the effects of eccentricity and LOS acceleration are partially degenerate as observed in binaries such as GW200105. Current ground-based observatories are sensitive enough to only constrain scenarios that produce high accelerations, e.g $\sim 10^{-2~}(10^{-6})~\textrm{c}/s$ for binary BLACK HOLE (BBH) (binary neutron star (BNS)) sources; however, next-generation observatories may be able to constrain the accelerations expected in some dense environments.
[abstract 10 / 55] Yes (score: 4) - Title: Hunting Wandering 3[abstract 11 / 55] 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 ApJ. V2: updated to match journal proofsSubjects: astro-ph.GACreated: 2026-07-20; Updated: 2026-07-21; Datestamp: 2026-07-21
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, Hβ, [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:2607.16748 [pdf, ps, other]We report a $γ$-ray excess toward the radio-quiet narrow-line Seyfert 1 galaxy 1H 1934-063 using data collected by the Large Area Telescope (LAT) on board the FERMI Gamma-ray Space Telescope and taking into account the LAT 16-year Source List (FL16Y). During the flare interval, the excess is detected in the 1--500 GeV band at a significance of $\sim 5.2σ$ (TS = 27.12), with a photon flux of $(4.94\pm2.33)\times10^{-10}$ ph cm$^{-2}$ s$^{-1}$ and a hard photon index of $Γ=1.50\pm0.25$. The best-fit $γ$-ray position is consistent with the radio position of 1H 1934-063, while the nearby source FL16Y J1936.9-0552 is not significantly detected during the same interval. In the absence of contemporaneous multiwavelength data, the broadband interpretation cannot be tightly constrained. A compact nonthermal component can produce the hard GeV emission, but the present data do not allow a unique physical interpretation. The excess therefore provides an interesting case for probing high-energy activity in radio-quiet NLS1 galaxies, although the underlying physical mechanism remains uncertain.
arXiv:2607.16880 [pdf, ps, other]We describe a classical (non-quantum) radiation process: additional (to Hawking) emission by a BLACK HOLE evaporating in an external MAGNETic field in vacuum. The electroMAGNETic radiation process is completely electric charge-free and bears some resemblance to the Gertsenshtein-Zel'dovich effect. The time evolution of the spacetime metric perturbs a static background MAGNETic field, inducing a radiative field that acts as an effective electroMAGNETic source even in the absence of physical charges or currents. To isolate the dynamic effects of the time-dependent spacetime on the external MAGNETic field, we approximate Hawking radiation as a spherically symmetric outflow of null fluid governed by the prescribed time-dependence of the central mass $M(t)$. We employ Laplace transform, which selects the retarded outgoing branch of the electroMAGNETic response, producing fields proportional to $Θ(t-r)$ and thereby fixing a causal radiative arrow of emission. The emitted spectral energy is red-dominated, scaling as $d\mathcal{E}_B/dω\propto B_0^2 m_0^2 τ_H^{-2/3} ω^{-8/3}$, where $τ_H$ is the Hawking evaporation timescale, and corresponds to a pure Transverse Electric (TE) mode. There is no final bright burst at the end of the evaporation. We offer classical analogues for this mechanism as transmission-line emission and, separately, as the displacement current emission from a medium with time-varying dielectric permittivity.
arXiv:2607.17729 [pdf, ps, other]The growth of galaxies in the early Universe is thought to be dominated by compact, intensely star-forming systems, yet the corresponding growth of supermassive BLACK HOLEs (SMBHs) within such environments remains poorly constrained. Green Pea galaxies are nearby analogs of rapidly assembling galaxies in the early Universe owing to their compact morphologies, intense STAR FORMATION, low metallicities, and extreme ionization conditions. Although galaxy interactions are thought to trigger episodes of rapid SMBH growth, direct observations of simultaneous accretion onto multiple SMBHs in compact, intensely star-forming galaxies are lacking. Here we report the discovery of the first confirmed dual ACTIVE GALACTIC NUCLEus (AGN) in a Green Pea system, SDSS J162209.41+352107.5. Chandra imaging resolves two luminous hard X-ray sources separated by 8.4 kpc in projection, demonstrating simultaneous accretion onto two SMBHs. Follow-up Keck spectroscopy confirms that the two optical nuclei share a common redshift and independently exhibit broad Balmer emission and high-ionization AGN emission lines. Unlike most known dual AGN, which are typically found in massive mergers, J162209.41+352107.5 is a compact low-mass system analogous to galaxies thought to dominate early phases of galaxy assembly. These findings demonstrate that efficient growth of multiple SMBHs can occur in such environments and establish Green Pea galaxies as nearby laboratories for investigating the interplay between galaxy interactions, STAR FORMATION, and black-hole growth under conditions analogous to those prevalent in the young Universe.
arXiv:2503.00163 [pdf, ps, other]The study of collisionless shocks and their role in COSMIC RAY acceleration has gained importance through observations and simulations, driving interest in reproducing these conditions in laboratory experiments using high-power LASERs. In this work, we examine the role of three-dimensional (3D) effects in ion acceleration in quasi-perpendicular shocks under laboratory-relevant conditions. Using hybrid particle-in-cell simulations (kinetic ions and fluid electrons), we explore how the Alfvénic and sonic Mach numbers, along with plasma beta, influence ion energization, unlocked only in 3D, and establish scaling criteria for when conducting 3D simulations is necessary. Our results show that efficient ion acceleration requires Alfvénic Mach numbers $\geq 25$ and sonic Mach numbers $\geq 13$, with plasma-$β\leq 5$. We theoretically found that, while 2D simulations suffice for current laboratory-accessible shock conditions, 3D effects become crucial for shock velocities exceeding 1000 km/s and experiments sustaining the shock for at least 10 ns. We surveyed previous laboratory experiments on collisionless shocks and found that 3D effects are unimportant under those conditions, implying that 1D and 2D simulations should be enough to model the accelerated ion spectra. However, we do find that the same experiments are realistically close to accessing the regime relevant to 3D effects, an exciting prospect for future laboratory efforts. We propose modifications to past experimental configurations to optimize and control 3D effects on ion acceleration. These proposed experiments could be used to benchmark plasma astrophysics kinetic codes and/or employed as controllable sources of energetic particles.
arXiv:2510.24897 [pdf, ps, other]We study hierarchical triple systems formed by a compact binary orbiting a supermassive BLACK HOLE (SMBH), focusing on the role of RELATIVISTIC MAGNETic tidal interactions. Extending previous analyses of precession resonances to 0.5 post-Newtonian order, we incorporate quadrupolar MAGNETic tidal moments, which have no Newtonian counterpart. We find that MAGNETic tides introduce new resonances absent at lower order, leading to additional eccentricity excitations and significantly modifying the binary's long-term evolution. Numerical solutions of the Lagrange Planetary Equations confirm these analytical predictions and reveal how resonance strength depends on orbital eccentricity and inclination. The resulting dynamics accelerates the binary merger and imprints distinctive signatures on gravitational waves, potentially observable by LISA. Our findings identify MAGNETic tidal coupling as a novel strong-gravity effect and establish its importance for the resonant dynamics of compact-object binaries near SMBHs.
arXiv:2601.01949 [pdf, ps, other]The nature of the central engine powering short GAMMA-RAY BURSTs (sGRBs) in binary neutron star (BNS) mergers remains a key open question in the era of multi-messenger astronomy. The ergostar hypothesis, that a rapidly rotating star with an ergoregion can act as a powerful energy source, offers an alternative explanation to the BLACK HOLE-accretion disk paradigm. In this work, however, we examine this hypothesis using a phenomenological EOS of strangeon matter, i.e., condensed matter with nucleon-like units for three flavors of QUARKs. By constructing a large suite of uniformly rotating equilibrium models, we systematically investigate the parameter space of the stable ergostars and calculate their maximum extractable energy. We demonstrate that strangeon matter supports a vast and robust parameter space for dynamically stable ergostars, even without requiring differential rotation. We find that the extractable rotational energy from these configurations can be on the order of $0.01 M_\odot$, representing a massive energy reservoir, even when accounting for baryonic mass variations (e.g., mass ejection and particle capture during the Penrose process). Our results suggest that BNS merger remnants composed of exotic matter could play a crucial, previously underestimated role in high-energy astrophysics.
arXiv:2606.11133 [pdf, ps, other]Persistent, low-luminosity low-mass X-ray binaries (LMXBs) offer a unique opportunity to study accretion in this poorly understood regime, as well as to unveil new members of the ultracompact X-ray binary (UCXB) family, characterised by orbital periods ($P_{\rm orb}$) shorter than $\sim 80$ min. We report on a NUSTAR archival observation that, for the first time above 10 keV, spatially resolves the Galactic Centre pair SLX 1744$-$299 and SLX 1744$-$300. We find SLX 1744$-$300 to be slightly brighter, with a flux ratio of $\sim 1.15$, increasing to $\sim 1.3$ when extrapolated to 0.5$-$10 keV. Both the timing (root-mean-square variability) and spectral properties (well described in both cases by a thermal Comptonisation model) indicate that the systems were in the hard state. The two sources, however, display markedly different behaviour throughout the observation. SLX 1744$-$299 shows a gradual flux decline consistent with a decrease in the mass-accretion rate, whereas SLX 1744$-$300 remains steady but exhibits two short-recurrence Type-I X-ray bursts indicative of mixed H/He burning. Combining our results with previously reported upper limits on the distance, we derive low persistent X-ray luminosities of $L_{\rm X}\lesssim 1.1\times10^{36}$ erg s$^{-1}$ and $L_{\rm X}\lesssim 2.6\times10^{36}$ erg s$^{-1}$ (3$-$78 keV) for SLX 1744$-$299 and SLX 1744$-$300, respectively. The corresponding mass-accretion rates, when compared with the critical values from the disc instability model, favour $P_{\rm orb}\lesssim 90$ min and $P_{\rm orb}\lesssim 105-155$ min. Although both limits are formally compatible with the UCXB regime, the case of SLX 1744$-$299 appears significantly more compelling, also considering the previously reported intermediate-duration burst.
arXiv:2607.16576 [pdf, ps, other]Semi-analytic models of black-hole movies require both an emitting flow prescription and a time-dependent source variability. Existing prescriptions are often limited to either equatorial emission or time-independent sources. In this work we present a unified model for these two ingredients. First, we prescribe an off-equatorial, nongeodesic Kerr fluid rotation law by lifting an equatorial specific-angular-momentum profile to cylindrical surfaces, setting the polar component of the four-velocity to zero, normalizing the flow with the full Kerr metric at the spacetime point, and retaining the option to recover a geodesic-like plunging prescription when needed. Second, we use this velocity as the disk advection field in a four-dimensional inhomogeneous, anisotropic Matérn-like Gaussian random field. We provide a parametrized model for a torus-like disk and a central JET through a single composite correlation tensor. The resulting effective model is an implementation-ready prescription for time-dependent thick-disk and disk-JET emission for RELATIVISTIC studies.
arXiv:2607.16590 [pdf, ps, other]During the gravitational collapse of a massive star into a regular BLACK HOLE, a new form of matter must be produced in order to prevent the formation of a central singularity. Since such matter is not present in the initial stellar configuration, it must emerge dynamically during the collapse. This formation process is expected to be accompanied by a strong release of energy in the form of electroMAGNETic radiation, which may be observable. Here we investigate the gravitational collapse of baryonic matter into Dymnikova-Hayward-Bardeen regular BLACK HOLEs. We estimate the radiation density and the corresponding bolometric luminosity generated by the formation of the matter sector responsible for singularity avoidance. We show that such processes provide a possible mechanism for GAMMA-RAY BURSTs. Moreover, compatibility with GAMMA-RAY BURST requires small regularization effects. As a result, the corresponding regular BLACK HOLEs differ weakly from the Schwarzschild BLACK HOLE.
arXiv:2607.17682 [pdf, ps, other]We report dual-perspective microwave and HXR observations of an X-class flare on 2024 May 15, taking advantage of the unique geometry of a front-side view from the Earth and a back-side perspective from the Solar Orbiter (SolO). Using spatially resolved imaging spectroscopy from Siberian Radioheliograph (SRH) together with Chashan Broadband Solar millimeter spectrometer (CBSmm) and STIX data, we identify a set of nonthermal flaring loops in an asymmetric MAGNETic field, with microwave sources located near the loop top and HXR sources associated with the southern footpoint. Compared with HXR, the microwave emission shows an opposite ascending trend, an increasing time lag in time profile, and a distinctive ``SHH'' spectral pattern, which we attribute to energy-dependent trapping and precipitation of energetic electrons in an asymmetric MAGNETic configuration. Flux pulsations and their spectral and POLARIZATION signatures are consistent with intermittent particle acceleration rather than MHD wave modulation. Microwave MAGNETic diagnostics, corroborated by non-linear force free field (NLFFF) extrapolation, provide key constraints on the three-dimensional MAGNETic configuration. The dual-perspective flux profile comparison and consistent QPP signatures across wavelengths together support a self-consistent picture of energy-dependent electron trapping, precipitation, and transport in these asymmetric loops.
arXiv:2607.17752 [pdf, ps, other]Reliable STAR FORMATION rates (SFRs) are essential for studying the connection between BLACK HOLE growth and QUASAR host galaxies. We study the far-infrared (FIR) SFRs and the host galaxy properties of 202 SDSS and PG QUASARs at $0.02
arXiv:2607.17821 [pdf, ps, other]Recent high-resolution observations from the Solar Orbiter mission can help detect the indirect signatures of heating at the smallest scales. In this work we measure the properties and investigate the physical origin of propagating disturbances (PDs) in the intensity at the smallest resolvable scales with Solar Orbiter/EUI along coronal loops. We used two sequences of EUI/HRIEUV at high spatial (down to 125 km per pixel) and temporal resolutions (5 s of cadence). We placed slits along 13 active region (AR) coronal loops. We measured the plane-of-sky (PoS) velocities and the intensity perturbation damping along the slits of PDs. We also measured the periodicity of PDs in one slit by using a Fourier analysis. We report the detection of PDs that have high PoS velocities ranging between 500 and 2000 km/s (which we call "fast" PDs). They are only visible in the upper part of the coronal loops. The intensity increase associated with these fast PDs is on the order of 4\% to 8\% of the HRIEUV intensity, and we measured little to no damping of their intensity with distance. We also measured a peak in the Fourier power spectra at 2 min above the 95\% confidence limit that is associated with fast PDs. The fast PDs are detected in the same coronal loops as PDs with a lower PoS velocity (70 to 90 kms/s), which we refer to as "slow" PDs. Unlike the fast PDs, these slow PDs are only visible in the lower part of the coronal loop, and they show clear intensity damping. Slow PDs show properties consistent with slow MAGNETo-acoustic modes or upflows. On the other hand, fast PDs cannot be explained by slow MAGNETo-acoustic modes. Instead, they show properties consistent with fast flows induced by MAGNETic RECONNECTion, current sheet generated by propagating transverse oscillations, and fast MAGNETohydrodynamics modes or Alfvén waves.
arXiv:2607.17887 [pdf, ps, other]We compute the instantaneous angular momentum flux from nonspinning BLACK HOLE binaries in Einstein-Maxwell-dilaton theory for generic noncircular orbits up to relative first post-Newtonian order. Working in the Einstein frame and using the direct integration of the relaxed field equations approach, we construct the scalar, electroMAGNETic, and tensor gravitational fields in the wave zone and express the required source multipole moments in the center-of-mass frame. In addition to the leading $1/R$ radiative fields, we retain the next-to-leading $1/R^2$ terms in the wave-zone fields, which describe finite-distance corrections and do not contribute to the flux at null infinity. We obtain separately the scalar, electroMAGNETic, and tensor contributions to the angular momentum flux. The scalar and electroMAGNETic channels begin with dipole radiation, while the tensor channel begins at quadrupole order. Our results recover the quasicircular balance relation, the known general-RELATIVISTIC limit, and the expected scalar- and electroMAGNETic-dipole suppression limits. Together with the previously known energy flux, these results provide the dissipative information required for future studies of orbit-averaged eccentric evolution and waveform phasing in Einstein-Maxwell-dilaton theory.
arXiv:2509.08765 [pdf, ps, other]Data-driven acceleration of scientific computing workflows has been a high-profile aim of machine learning (ML) for science, with numerical simulation of transient partial differential equations (PDEs) being one of the main applications. The focus thus far has been on methods that require classical simulations to train, which when combined with the data-hungriness and optimization challenges of neural networks has caused difficulties in demonstrating a convincing advantage against strong classical baselines. We consider an alternative paradigm in which the learner uses a classical solver's own data to accelerate it, enabling a one-shot speedup of the simulation. Concretely, since transient PDEs often require solving a sequence of related linear systems, the feedback from repeated calls to a linear solver such as preconditioned conjugate gradient (PCG) can be used by a bandit algorithm to online-learn an adaptive sequence of solver configurations (e.g. preconditioners). The method we develop, PCGBandit, is implemented directly on top of the popular open-source software OpenFOAM, which we use to show its effectiveness on a set of fluid and MAGNETohydrodynamics (MHD) problems.
arXiv:2512.00165 [pdf, ps, other]Neutrino self-interaction beyond the Standard Model is well motivated by the nonzero masses of neutrinos, which are the only known particles guaranteed to have new physics. Cosmic messengers, especially neutrinos, play a central role in probing new physics, as they provide experimental conditions far beyond the reach of laboratories and serve as the link between laboratory fundamental-physics discoveries and their roles in the Universe, where many new physics motivations originate. In this work, we propose a novel probe of neutrino self-interactions through ultra-high-energy neutrinos scattering off the cosmic neutrino background when the lightest neutrino species remains RELATIVISTIC today. This allows us to ``Widen the Resonance'' of such scattering. Meanwhile, we also provide a semi-analytic framework for cosmogenic UHE neutrino production, avoiding computationally intensive simulations and yielding results precise enough for BSM studies. The widened resonance enables future ultrahigh-energy neutrino telescopes, in particular GRAND, to probe mediator masses from MeV to GeV, reaching couplings down to $g \sim 10^{-3}$ -- up to two orders of magnitude beyond current bounds. Our results enhance the discovery potential of $ν$SI in the high-mass regime, potentially offering crucial insights into the connections between the neutrino sector and dark sector.
arXiv:2512.20054 [pdf, ps, other]The vast majority of massive binary systems in the universe is evidently unsuited to produce merging binary BLACK HOLEs. However, several narrow evolutionary paths of isolated massive binaries towards this goal have recently been identified. Due to the high degree of simplification and assumptions applied in previous modelling of these paths, conclusions remained vague so far. For one of these paths, the stable mass transfer channel, we now construct detailed binary evolution models which include internal differential rotation as well as mass and angular momentum transfer between the stars, all the way from the zero-age main sequence to the formation of the BLACK HOLEs, only skipping the rapid late burning stages. This allows us to follow the mass and chemical structure evolution of the mass accreting component, which turns out to have a key influence on the phase of reverse mass transfer, that allows the obtained BLACK HOLE spins and mass ratios to naturally fall into the regime observed for the gravitational-wave source in the 10--25$M_\odot$ primary BLACK HOLE mass range. As for this channel, also a large number of progenitor binaries are known, we conclude that it likely contributes to the observed population of gravitational wave sources.
arXiv:2601.06416 [pdf, ps, other]We investigate the integrability of spinning compact body dynamics at quadratic order in spin in four-dimensional Einstein spacetimes admitting a non-degenerate Killing--Yano tensor. Working within the Mathisson--Papapetrou--Tulczyjew--Dixon framework under the Tulczyjew--Dixon spin supplementary condition, we model the spin-induced quadrupole with a deformability parameter $κ$, where $κ=1$ corresponds to BLACK HOLEs. The dynamics is formulated as a Hamiltonian system on a 10-dimensional physical phase space obtained by Dirac--Bergmann reduction. For $κ=1$, we establish Liouville--Arnold integrability at quadratic order in spin by constructing five independent, Poisson-commuting first integrals, including a generalization of the Carter constant and the Rüdiger constant to quadratic-in-spin order in Einstein spacetimes beyond Kerr. For $κ\neq 1$, the Rüdiger and Carter constants are no longer conserved; integrability does not persist at this order. All our results are carried out in a covariant manner and numerically verified, and Kerr is recovered as a special case. These results show that integrability can extend beyond Kerr and beyond the linear-in-spin regime, while its breakdown for $κ\neq 1$ points to the spin-induced quadrupole as a decisive probe of compact body structure.
arXiv:2601.12422 [pdf, ps, other]We present a method to test the impact of ad-hoc modifications of some of the generic parameters of hadronic interactions -- cross section, elasticity, and multiplicity -- on any observable quantity using full 3-dimensional simulations of extensive air showers induced by ultra-high-energy COSMIC RAYs. Our approach not only extends the existing 1-dimensional tools to three dimensions, but also introduces more flexible features to better respond to the needs of both theory and experiment. We first thoroughly validate the \conexD framework for the simulation of both longitudinal and lateral features of air showers, in particular for a non-standard configuration of the framework in which different energy thresholds for modifications are applied. Moreover, we show that the implementations of the ad-hoc modifications in this configuration are consistent with the previous one-dimensional simulations. Lastly, we discuss the importance of studying the interaction modifications in three dimensions and the effects of parallel modifications of multiple parameters.
arXiv:2604.05085 [pdf, ps, other]The Penrose process and the collisional Penrose process involve particles decaying or interacting very close to a spinning BLACK HOLE, respectively, during which some particles are pushed into negative energy trajectories and fall into the BLACK HOLE while others gain that energy and escape the system. These two processes are difficult to observe as they occur very rarely by chance. Here we report a new observational signature of similar, but less extreme processes occurring in and near the ergospheres of rapidly spinning BLACK HOLEs. We find that the reflection of the thermal emission from a geometrically thin, optically thick accretion disk can lead to the formation of a power-law component, even in the absence of a corona. Unlike the well-known Penrose processes, the scattering particles lose a good fraction of their energy, but are not pushed into negative energy trajectories. We emphasize that this new component has distinct spectral and polarimetric properties that can be used for its identification as long as it out-competes other power-law emission components. We emphasize that the new component needs to be taken into account when interpreting spectral and spectropolarimetric observations of BLACK HOLEs. The detection and unambiguous identification of the new component with current or future broadband X-ray spectral and spectropolarimetric missions can open a new window into testing Einstein's theory of gravity close to the edges of BLACK HOLEs, and opens up new opportunities to constrain BLACK HOLE spins and inclinations.
arXiv:2604.05617 [pdf, ps, other]We develop a unified bifurcation-theoretic description of Friedmann--Robertson--Walker cosmologies with a scalar field, a barotropic fluid of index $γ$, and spatial curvature. For the exponential potential $V(ϕ)=V_0e^{λϕ}$, the slope $a=\sqrt{3/2}\,λ$ is a distinguished parameter, and the local phase portrait is organised by the loci $|a|=3$, $a^2=3$, $a^2=\tfrac92γ$, $γ=\tfrac23$, and $γ=2$, corresponding to kinetic, curvature, scalar--fluid exchange, and degeneracy thresholds. For the quadratic potential $V(ϕ)=\tfrac12m^2ϕ^2$, the effective slope is dynamical. We introduce the bounded variable $ζ=\arctanλ$, obtaining a closed autonomous four-dimensional system in $(X,Y,Ω_k,ζ)$ without time-rescaling. This exposes invariant gates, robust equilibrium continua, and $γ$-thresholds controlling loss and recovery of normal hyperbolicity. Near the organising loci we compute translated JETs, perform centre(-like) reductions, and derive canonical normal forms governing persistence and transitions. These are assembled into an explicit stratification of the exponential parameter plane and a pull-back stratification for the massive extensions, with physical path maps into the corresponding unfolding charts. The framework shows how fluid and curvature modes provide deformation directions within the FRW class and yields a regime-level interpretation: slow roll and ultra slow roll arise as persistent attracting balances and nonhyperbolic bottleneck passages, while quadratic invariant slices recover the oscillatory periodic-orbit/invariant-torus sector. It also organises critical slowing, curvature leakage, tracker exchange, and admissible sequences of such episodes along massive trajectories.
arXiv:2604.08202 [pdf, ps, other]In this work, I investigate the quantum dynamics of a spin-1/2 particle propagating in the spacetime of a static, spherically symmetric Einstein-Gauss-Bonnet (EGB) BLACK HOLE within the framework of RELATIVISTIC quantum mechanics. Starting from the Dirac equation in curved spacetime-formulated using the tetrad formalism and the associated spin connection we construct the corresponding Dirac Hamiltonian in EGB geometry. Next, I employ Heisenberg's equations of motion to derive explicit operator expressions for the particle's velocity and force, providing a fully quantum description of fermionic motion in a higher-curvature gravitational background. It is observed that the spacetime geometry modifies the Dirac dynamics through the EGB metric function, leading to corrections in the velocity and force operators that depend explicitly on the Gauss-Bonnet coupling parameter, $ξ$. In the weak-field limit, the expectation values of these operators satisfy Ehrenfest's theorem, demonstrating that the corresponding classical Einstein-Gauss-Bonnet dynamics emerges naturally as the semiclassical limit of the underlying quantum theory. In particular, the effective radial force includes higher-curvature contributions that become increasingly significant in the strong-gravity regime, while continuously reducing to the Schwarzschild result as the Gauss-Bonnet parameter approaches zero. These results establish a direct connection between RELATIVISTIC quantum dynamics and modified gravity, providing an operator-based framework for investigating fermionic motion in Einstein-Gauss-Bonnet spacetimes.
arXiv:2605.01146 [pdf, ps, other]The study of X-ray pulsar accretion columns helps us characterize accretion physics in this extreme regime of strong gravity and strong MAGNETic fields. Previous observations of the X-ray pulsar Hercules X-1 revealed a highly broadened Fe K emission line, associated with Doppler motions exceeding 0.1c, suggesting its origin in the accretion column. We obtained a high-spectral resolution view of the Fe K energy band of Hercules X-1 thanks to a 200 ks observation with the XRISM observatory. The XRISM/Resolve microcalorimeter spectra allow us to separate the different spectral components and accurately model them with phenomenological models. We confirm the presence of a broad line near 6.5 keV with a typical $1σ$ width of 1 keV. Performing a pulse-phase-resolved analysis, we find that the feature is strongly variable with Her X-1 pulse phase. This is consistent with the proposed origin due to collisional recombination or by reprocessing of the primary X-ray emission in the accretion column, where strong variability with pulse phase is expected due to the rotation of the columns alongside with the neutron star. Additionally, the Fe K line pulsation pattern evolves with the 35-day cycle of Hercules X-1, supporting the scenario that the neutron star and its accretion columns undergo precession, in agreement with recent polarimetric results from the IXPE observatory. We discuss the future applications of modeling of this broad line in X-ray pulsars with physical spectral models. This could be used to detect and track neutron star precession, advancing our understanding of neutron star interiors.
arXiv:2605.16506 [pdf, ps, other]We present a full 3D numerical evolution code to study neutron stars in massive-scalar-tensor theories. The code is embedded in the Einstein Toolkit framework and its implementation constitutes a modified version of the Baumgarte-Shapiro-Shibata-Nakamura formalism with an additional nonminimally coupled scalar field. The approach we follow preserves the standard hydrodynamic evolution for matter fields, allowing eventually for a straightforward inclusion of more microphysical effects and better flexibility. Using this code, we examine the gravitational collapse of rapidly rotating, scalarized neutron stars to a BLACK HOLE by exploring the influence of the scalar field on the dynamical features of the process and on the gravitational-wave emission. We find that for the configurations studied in this work, there is an observational degeneracy in the tensorial gravitational-wave emission between collapsing scalarized stars and their counterparts in general relativity. However, this degeneracy can be broken through the emission of scalar radiation, which carries an energy of ~10^-3 M_sun c^2. This is orders of magnitude higher than the quadrupolar emission (~10^-7 M_sun c^2) and might be used as an observational probe of modified gravity. We also find that rapid rotation can enhance this signal, since fast rotating stars can sustain larger scalar field amplitudes.
arXiv:2606.21029 [pdf, ps, other]Timelike orbits constitute a crucial probe for exploring the intrinsic properties of curved spacetimes, and the carried gravitational radiation signals provide a direct window into strong field gravity. In this paper, we develop a versatile computational framework based on Mathematica and the OpenMP parallel architecture to simulate the rational orbits of timelike particles and their gravitational radiation in static spherically symmetric spacetimes. Specifically, requiring only the user defined covariant metric, this numerical tool can efficiently calculate rational orbits across various configurations, as well as the corresponding gravitational wave POLARIZATION states and characteristic strains. The package presented here offers a highly efficient and comprehensive one-stop solution for investigating the properties of curved spacetimes and their potential observational signatures. To demonstrate the reliability and capability of our code, we apply it to the Schwarzschild spacetime as a test case, illustrating the functionality of the code across several key aspects, including the effective potential, stable orbital regions, rational and irrational orbits, and gravitational wave signals. Furthermore, we show that the gravitational waves emitted by an extreme-mass-ratio inspiral system composed of an intermediate mass BLACK HOLE and the Galactic Center supermassive BLACK HOLE have the potential to be identified by future space detectors.
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:2607.16420 [pdf, ps, other]Fast X-ray transients (FXTs) detected by the Einstein Probe mission have emerged as a rapidly growing class of extragalactic transients, whose physical origin remains uncertain. Compact binary coalescence (CBC) systems have been proposed as one possible progenitor for at least a subset of these events, making FXTs promising targets for multi-messenger studies with gravitational-wave (GW) observations. This work presents the first systematic investigation of GW counterparts to FXTs observed by Einstein Probe and assesses the detectability of associated CBC. We focus on FXTs detected during the second half of the fourth observing run (O4b) of the Advanced LIGO-Virgo-KAGRA detector network by searching for temporal coincidences with GW candidates from the fifth Gravitational-Wave Transient Catalog (GWTC-5). We analyze a sample of 47 FXTs, including 11 with measured redshifts, and assess the significance of the association between FXTs and GW candidates using a ranking statistic. We find no significant GW counterpart associated with any FXT in our sample. In the absence of a detection, we place 90% exclusion-distance constraints under the assumptions of binary neutron star and neutron star-BLACK HOLE progenitor scenarios. For observations with the full LIGO and Virgo detector network, the typical median exclusion distances are $\sim$178 Mpc and $\sim$349 Mpc, respectively. These constraints disfavor a nearby compact-binary merger origin. Longer periods of joint observations by the LVK and Einstein Probe, combined with improved GW detector sensitivity, will enhance the prospects for identifying genuine GW-FXT associations and place tighter constraints on the progenitor scenarios of these events.
arXiv:2607.16434 [pdf, ps, other]Photometric redshift estimation for ACTIVE GALACTIC NUCLEi (AGNs) remains a fundamental challenge for current and upcoming large-scale photometric surveys. Traditional spectral energy distribution (SED) fitting suffers from color-redshift degeneracies, particularly for AGNs whose power-law continua hide the strong spectral features required to anchor redshift estimates. While AGN variability provides additional constraining power, existing frameworks require multi-band light curves that are not always available. This work presents VAR-PZnn, a fully connected mixture density network that integrates 26 variability features extracted from ZTF g-band light curves with optical photometry from Pan-STARRS1, mid-infrared (MIR) photometry from CatWISE, and, for a subsample, NIR photometry from UKIDSS. The model is trained and tested on 72,728 spectroscopically confirmed AGNs/QSOs spanning 0.01 < z < 4.5 and g-band magnitudes from 17 to 21.5. For the main sample, we achieve σ_{NMAD} = 0.058 and an outlier fraction of η= 8.2%, which reduces to 5.4% when the 10% of sources with the highest predicted uncertainty are excluded. An ablation study demonstrates that MIR photometry provides the dominant constraint for photo-z accuracy, while variability features serve as a secondary refiner. Using UKIDSS NIR data as a proxy for future synergies between LSST and space-based missions like Euclid and Roman, we obtain η= 13.3% without MIR data and η= 4.6% when MIR is available. We benchmark against Low-Resolution Templates (LRT) SED fitting (η= 28.7%) and the VAR-PZ framework; applying single-band VAR-PZ priors worsens LRT performance to η= 39.4% due to single-band light-curve degeneracies, confirmed via simulations (η= 27.6% to 28.1%). This framework provides a scalable approach for the Legacy Survey of Space and Time (LSST).
arXiv:2607.16509 [pdf, ps, other]A database of 192 L-H transitions in DIII-D is used to assess the effects of applied three-dimensional (3D) MAGNETic fields on the H-mode power threshold and the stability of zero-dimensional (0-D) empirical regressions. The dataset includes nominally axisymmetric discharges and discharges with resonant or non-resonant MAGNETic perturbations. Filtering criteria reduce uncertainties associated with absorbed power, neutral-beam modulation, and fast-ion losses, while applied-field components are quantified using equilibrium reconstruction and spectral analysis. Measured threshold powers show substantial scatter and systematic deviations from the 2008 ITPA multi-machine scaling, including for discharges without applied perturbations. TRANSP modeling indicates that empirical estimates can substantially underpredict fast-ion losses, particularly at low plasma current and with non-axisymmetric fields. Adding global 3D-field metrics does not robustly isolate the effects of applied perturbations. A fully unconstrained regression retains a 70% residual root-mean-square error and produces nonphysical parameter dependencies, including a plasma surface-area exponent of 2.79. Extrapolations to ITER-relevant conditions consequently have broad confidence intervals. These results show that hidden-variable dependencies can strongly affect empirical threshold parameterizations even in a restricted single-machine dataset. Machine-specific conditions, local edge physics, and power-accounting uncertainties limit the predictive capability of purely 0-D scalings. Improved predictions for ITER and future devices will require better fast-ion-loss treatment and physics-based, edge-localized quantities.
arXiv:2607.16779 [pdf, ps, other]Formation dynamics and stability starting from various phase space vortex (PSV) or Bernstein-Greene-Kruskal (BGK) structures i.e electron acoustic wave (EAW), Langmuir (LAN) waves is investigated in the presence of a quasi-stationary ion scale (QSIS) inhomogeneity using high resolution Vlasov-Poisson simulations with VPPM-OMP 1.0 solver. In a one dimensional, collisionless, periodic, unMAGNETized plasma with kinetic ions and kinetic electrons, we first create a QSIS inhomogeneity using low amplitude electric field drive at ion acoustic (IA) frequency with k eq = mk min [where m = 2 is the mode number, k min corresponds to the longest scale in the system]. While creating QSIS inhomogeneity, we have demonstrated the existence of ion trapped particle instability (ITPI) which saturates as the amplitude of sideband modes become comparable to that of the primary nonlinear mode (quite analogous to the trapped particle instability in large amplitude electron plasma waves). Also, mode transition from m = 2 to m = 1 is observed during relaxation period due to the energy cascading process. Finally, an electron acoustic (EA) perturbation of scale k p = k min [m = 1] is applied on top of the QSIS inhomogeneity to determine its response in the presence of background ion scale inhomogeneity. Some key observations such as formation of transient PSV, wave-wave mode coupling interaction and various frequency generation alongwith comparative investigation with EA perturbation launched in the absence of ion scale inhomogeneity is also reported.
arXiv:2607.17144 [pdf, ps, other]Microlensing, the influence of stars within a galactic gravitational lens, has emerged as a powerful probe of compact mass and, through differential magnification, sub-parsec scale sources at cosmological distances. The recent discovery of a double-source-plane gravitational lens system in which the most distant source is a QUASAR offers the prospect of compound microlensing, in which QUASAR light rays are influenced by compact masses within the two foreground lensing galaxies. Here, we present the first numerical simulations of this "microlensing of microlensing". We consider the recently discovered "Einstein zig-zag" lens, J1721+8842, as a fiducial case, and construct microlensing magnification maps for each of the six QUASAR images in this system. Due to the secondary microlensing effects of the myriad of initial microimages, the resulting maps contain more complex caustic features than seen in the case of single plane microlensing. This is reflected in the expected lightcurves seen for each of the images.
arXiv:2607.17160 [pdf, ps, other]Context. Accretion streamers connected to protostellar disks and/or envelopes are thought to transport material across several thousand of au. Whether the motions of the gas comprising these streamers are dominated by gravity, large scale external turbulence or the action of MAGNETic fields is still under scrutiny. Aims. The aim of this work is to understand the role of the MAGNETic fields in the star-formation processes, in particular the role that MAGNETic forces have in potentially leading flows of gas and the accretion onto the envelopes and disks orbiting protostars. Methods. First, we try to identify the large-scale accretion streamers toward the high-mass Young Stellar Object GGD 27-MM1 and fit their trajectories using the so-called Mendoza's model, a modification of the classical model of pure gravitational infalling motion of fluid particles in a potential well. Second, we estimate the strength of the MAGNETic field associated with the streamers. Then, we determine if the streamers are dominated by MAGNETic or centrifugal forces. Results. Inspecting the Atacama Large Millimeter/submillimeter Array (ALMA) H$_2$CO cube we were able to identify four accretion streamers spreading up to $\sim$7,000 au and fit their trajectories in the position-position-velocity space. The polarized continuum emission reveals a good alignment of the MAGNETic field and the trajectory of the streamers. Using the Davis-Chandrasekhar-FERMI method, we derive estimates for the MAGNETic field strength, find that the streamers are sub-alfvénic, and discuss (after estimating energy terms for turbulence, ordered motions, MAGNETic forces and gravity) a possible qualitative scenario in which, the gravitational well of the GGD 27-MM1 protostar dominates streamer gas motions over turbulence and MAGNETic forces at distances of $\sim 3,000$ au.
arXiv:2607.17198 [pdf, ps, other]In contrast to conventional linear coupling frameworks, the proposed work investigated the nonlinear effects that become more significant in the strong field regime of a BLACK HOLE. We have investigated a new class of Kalb Ramond BLACK HOLEs generated by a nonlinear logarithmic coupling of the field, referred to as a Logarithmic Kalb Ramond BLACK HOLE. The logarithmic coupling introduces strong-field modifications to the spacetime geometry, leading to significant departures from the Schwarzschild and Reissner Nordstrom BHs. We analyze the motion of test particles using the effective potential formalism and derive the conserved energy and angular momentum for circular equatorial geodesics. The stability of circular orbits and the location of the innermost stable circular orbit are examined, revealing a strong dependence on the model parameters Q, l, and $β$. The epicyclic frequencies (radial, vertical, and azimuthal) together with the associated periastron precession demonstrate that nonlinear logarithmic corrections can substantially modify quasi periodic oscillation observables. We further investigate the Hawking temperature and energy emission rate, which show that the nonlinear coupling also impacts distinct imprints on the thermodynamic behavior and evaporation characteristics of the BLACK HOLE. Our results also identify the BH parameters as key regulators of the orbital dynamics, oscillatory properties, and thermal evolution, providing a unified framework for probing nonlinear KR gravity through strong-field astrophysical phenomena.
arXiv:2607.17199 [pdf, ps, other]The modification and enhancement of antiferroMAGNETic two-dimensional semiconductor is considered crucial for realizing novel electronic properties and facilitating promising applications. For this purpose, we investigate six antiferroMAGNETic 2D bilayer Janus YIBr structures with different stacking variations by means of first-principles calculation and an effective low-energy model. The calculation of MAGNETic anisotropy energy shows that the direction of easy axis varies with different stacking. First-principles-calculated energy bands reveal that there is a Dirac RELATIVISTIC dispersion relation in the valence band in a wide energy window of 0.3 eV at least. The calculations for spin, atom properties and Berry curvature description show that there is spin, valley and layer coupling with spin splitting, valley POLARIZATION and quantum valley Hall insulators can be achieved in the bilayer Janus structures. Further analyses of the effect of external electric field can be used to control spin, valley and layer of the hole near the FERMI level. These can be useful in future exploration for novel properties, control methods and more functionalities in bilayer Janus structures.
arXiv:2607.17338 [pdf, ps, other]Primordial BLACK HOLEs (PBHs) are not only considered as a candidate for DARK MATTER, but also as potential sources of gravitational waves from binary BLACK HOLE mergers by the LIGO-Virgo-KAGRA and as seeds for the supermassive BLACK HOLEs observed by the James-Webb Space Telescope, thereby remaining intense interest in cosmology and astrophysics. Fast radio bursts (FRBs) are bright millisecond-duration radio transients whose physical origin remains elusive, which have rapidly developed into one of the most active and rapidly evolving fields in astronomy. The microlensing effect of FRBs offers a clean and powerful probe of PBHs, especially in the mass range above stellar-mass window. In this work, we derive a complete transformation that converts any upper limit on the abundance of PBHs originally derived for `bare' PBHs with monochromatic mass distribution, into the corresponding constraint on `dressed' PBHs with arbitrary extended mass distributions. Based on this framework, we estimate the future constraints on the dressed PBH abundance \(f_{\mathrm{PBH}}\) from FRB observations assuming an expected sample of \(10^5\) FRBs accumulated over the next decade well within the projected detection capabilities of SKA. Our results indicate that including halo enhancement tightens the upper limits on \(f_{\mathrm{PBH}}\) by approximately one order of magnitude, with the most stringent constraint reaching \(\sim10^{-4}\) for the typical mass range from stellar-mass to intermediate-mass BLACK HOLEs.
arXiv:2607.17363 [pdf, ps, other]ORB5X is a C++17/Kokkos AI-assisted translation of ORB5, a global electroMAGNETic gyrokinetic particle-in-cell code for toroidal confined plasmas. The translation preserves the mathematical model and the main numerical algorithms of the Fortran implementation, i.e. a Lagrangian gyrokinetic formulation, marker-particle representation of the distribution functions, finite-element B-spline representation of the fields, Fourier filtering in the angular directions, MPI domain decomposition and cloning, and HDF5 diagnostic output. The main software change is the replacement of Fortran modules and allocatable arrays by typed C++ classes, structs, namespaces, and Kokkos Views and kernels for performance portability across multicore CPU and GPU backends. This paper summarizes the physical models, the numerical scheme, the distributed and shared-memory parallel design, the AI-assisted code translation workflow, and the validation path used to compare ORB5X against the original Fortran reference codebase. The initial tests for ITG, ITPA, and chirping show an agreement of almost machine accuracy between ORB5X and ORB5 for the electrostatic and electroMAGNETic field components. Furthermore, we demonstrate that with the modern CMake and Kokkos, ORB5X can be easily compiled and run on personal Linux and Mac laptops, as well as on high-performance computing clusters such as LUMI, ALPS, CINECA, and Discoverer.
arXiv:2607.17376 [pdf, ps, other]Large-eddy simulation (LES) turbulence models often fail to capture the effects of chemical heat release and the resulting modulation of turbulence in premixed flames, underscoring the need for a framework that remains accurate across a broad range of physical regimes. We develop an augmented eddy-viscosity closure, based on deep neural networks calibrated jointly with the LES solution using adjoint-based optimization and differentiable programming, ensuring consistency with the governing partial differential equations (PDEs). Several objective functions and training methods are examined, and each model is assessed for its capability to interpolate and extrapolate across a wide range of Damköhler numbers. Relative to the Smagorinsky-model baseline, the best neural network model improves a posteriori errors in the LES primitive variables by 25-50% and in the resolved Reynolds stress and scalar flux by more than 60%. Crucially, the model generalizes across Damköhler number regimes, maintaining stability and accuracy even for out-of-sample conditions. These results demonstrate that PDE-consistent deep learning closures can recover both mean fields and resolved turbulence statistics in LES of turbulent premixed flames and can therefore provide a broadly applicable framework for turbulent combustion modeling.
arXiv:2607.17448 [pdf, ps, other]Recent JWST observations have revealed a population of compact, optically red sources known as Little Red Dots (LRDs). A popular interpretation is that LRDs host massive BLACK HOLEs embedded in dense gaseous envelopes, yet the physical origin of such envelopes remains unclear. We propose that the optically thick outflow driven by supercritical accretion onto BLACK HOLEs may explain the envelope. Based on an analytic radiative hydrodynamic outflow model, we relate the outflow properties to the BLACK HOLE mass $M$ and dimensionless accretion rate $\dot{m}$. With $M\sim10^5-10^7\,M_\odot$ and $\dot m \sim 1500-5000$, the outflow photosphere reaches luminosities of $10^{43}-10^{45}\,\rm erg\,s^{-1}$ and temperatures of $\sim 3000-6000$ K, effectively matching the red optical continua observed in LRDs. The presence of a thick scattering region beyond the photosphere is central to deciphering the distinctive properties of LRDs. For each object, if one derives $M$ and $\dot{m}$ from the observed luminosity and temperature, while accounting for both kinematic broadening and scattering effects, the model predicts an emission line FWHM consistent with observations within a factor of 1.5 for more than 80\% objects. Furthermore, with Cloudy simulations, we find that the partially ionized gas beyond the photosphere produces Balmer breaks broadly consistent with measurements.
arXiv:2607.17609 [pdf, ps, other]The existence of an upper mass limit for compact stars is one of the fundamental predictions of general relativity (GR), with important implications for the outcome of compact binary mergers and the nature of the proposed neutron star BLACK HOLE mass gap. The LIGO Virgo collaboration announced the discovery of a compact binary merger, GW190814, containing a compact star with mass 2.5 to 2.67 $M_\odot$ [R. Abbott et al.(2020) ApJ Lett., 896, L44], which provided an exciting new stimulus to the ongoing debate on whether a gap exists between the maximum mass of NS and the minimum mass of BLACK HOLE. Such GW detection has also challenged conventional stellar models and renewed interest in exploring whether modified theories of gravity can accommodate such ultra-massive compact objects without invoking BLACK HOLE formation. The present work investigated the structure and physical properties of compact stars within the framework of Finslerian gravity, employing the Heintzmann IIa gravitational potentials and showed that the our model can substantially enhance the maximum mass of compact stars upto $2.67 M_{\odot}$, thereby offering a plausible explanation for massive compact objects such as the secondary component of GW190814. In addition, the moment of inertia is found to increase, indicating stronger rotational support and a redistribution of the internal mass profile. The analysis focuses on key astrophysical observables, including the mass radius and moment of inertia mass relations, and a detailed comparison with the GR counterpart is performed. Assuming a linear equation of state, we construct a class of physically viable anisotropic stellar models and analyze their behavior under the influence of Finslerian corrections. The physical viability of the model is rigorously tested through stability criteria.
arXiv:2607.17728 [pdf, ps, other]Active galactic nuclei (AGN) are among the most complex classes of astrophysical objects, displaying a wide range of variability and observational properties. Identifying unusual AGN is crucial for understanding the physical mechanisms behind their emission better and for discovering potentially new subclasses or rare behaviors. With the increasing volume of data from next-generation surveys, machine-learning-based anomaly detection offers a promising approach to flagging and investigating such outliers systematically. We explore the use of unsupervised algorithms with a feature-driven approach to flag anomalous AGN, further explored by a human expert. The main focus is on obscured AGN, which tend to be harder to characterize. The algorithm we used was an AutoEncoder, which we trained on features extracted from the light curves rather than working with the light curves directly. The unsupervised nature of the method allows the detection of anomalies without relying on labeled data. To properly characterize the feature space and the detection process, we used the SHAP method. Our method flagged $11.18\%$ of the AGN we studied as anomalous. We focused in particular on anomalous obscured AGN and identified a refined subset of features that yields a comparable performance to the full set. Together with an in-depth analysis of the anomalies, this provides insight into how the AutoEncoder assigns anomalous status and which features are most indicative of astrophysically interesting behaviors or phenomena.
arXiv:2607.17787 [pdf, ps, other]Gravitational waves (GWs) have proven to be a powerful probe of compact binary populations. In the millihertz frequency range accessible to Laser Interferometer Space Antenna LISA, binary white dwarfs (BWDs) are expected to constitute a dominant source, forming both individually resolvable signals and an unresolved Galactic background. In this work, we construct a Milky Way like population model and calculate the GW background from unresolved Galactic BWD in the LISA sensitivity range, with particular emphasis on exploring and constraining uncertainties in binary stellar evolution. We employ COMPAS binary population synthesis framework to generate synthetic populations of BWD in the Milky Way. Various physically motivated evolution prescriptions and initial model parameters are used to study diverse population of BWDs. From these populations, we construct the GW background and investigate the dependence of the background spectrum on the assumptions on binary analysis. We discuss the possibility of constraints on binary evolution that LISA GW observations may yield. We find that the shape and amplitude of the background are sensitive to key binary evolution parameters like common envelope evolution and mass-transfer efficiencies. Variations in these assumptions lead to measurable differences in the predicted background spectrum. Our results demonstrate that LISA observations of the unresolved BWD background have the potential to constrain binary evolution models. This highlights the importance of GW background modelling as a complementary tool for studying the formation and evolution of compact binaries in the Milky Way.
arXiv:2607.17788 [pdf, ps, other]The [O II] $\lambda3727$ emission line is a widely used STAR FORMATION rate (SFR) tracer. However, its application to type I QUASARs is not straightforward, because the line can be affected by dust extinction, metallicity and contamination from the AGN narrow-line region (NLR). We test the reliability of [O II] SFRs using a sample of 202 SDSS and PG QUASARs, by comparing [O II] SFRs and reference far-infrared (FIR) SFRs derived from multiwavelength SED decomposition. We measure [O II], [O III], and narrow Balmer emission lines by spectral fitting. Then, we calculate [O II] SFRs after correcting dust extinction and metallicity. We then compare these SFRs with the FIR SFRs, both with and without subtracting the AGN contribution estimated from [O III]. After this correction, the median offset between [O II] and FIR SFRs is $-0.20\pm0.72$ dex for the full analysis sample and $-0.17\pm0.69$ dex for sources with S/N $>5$ in both [O II] and [O III]. Without subtracting the AGN contribution, the corresponding offsets are $0.00\pm0.69$ and $0.12\pm0.66$ dex. We conclude that [O II] is useful as a statistical SFR tracer for QUASAR host galaxies, but individual objects still require careful treatment of AGN contamination, extinction, metallicity, aperture effects, and redshift-dependent systematics.
arXiv:2607.17869 [pdf, ps, other]During the formation of a star cluster a spin-mass correlation of stellar BLACK HOLEs is generated as they grow via accretion of the residual gas. Moreover, the BLACK HOLE spin tends to be anti-aligned with its orbital angular momentum in the cluster. We show that GW231123, reported by the LIGO-Virgo-KAGRA (LVK) collaboration, lies on our predicted high-mass, high-spin plateau of the spin-mass correlation with positive Bayesian evidence over the LVK prior. Furthermore, vector resonant relaxation (VRR) equilibrium is favored over the isotropic LVK prior in reproducing the distribution of the relative spin tilt. The joint Bayes factor suggests strong evidence for the favored cluster models. GW231123 is thus consistent with our proposed channel that generates correlated BLACK HOLE masses and spins, and drives the spins' orientations.
arXiv:2607.17888 [pdf, ps, other]In this work, we investigate the nonlinear dynamics of isolated current-carrying edge-localized mode (ELM) filaments using a reduced electroMAGNETic fluid model in slab geometry. Numerical simulations show that unidirectional parallel current significantly suppresses radial filament velocity and reduces the outward propagation velocity by weakening the curvature-driven interchange force. The reduction in radial velocity is found to follow a modified scaling relation, demonstrating that increasing current progressively weakens outward filament propagation. Analysis of the vorticity equation shows that the electroMAGNETic current source changes from a dipolar structure to a remarkable spiral pattern, and overcomes the conventional curvature drive in the nonlinear phase. This current-driven source directly imprints its topology on the vorticity field, resulting in spiral vorticity, enhanced angular momentum, increased rotational energy, and localized shear layers. The filament therefore undergoes a transition from a conventional propagating state to a rotationally self-organized electroMAGNETic structure. These findings demonstrate that parallel current acts as an effective electroMAGNETic vorticity source and provides new insight into the nonlinear dynamics of ELM filaments in tokamak edge plasmas.
arXiv:2607.17918 [pdf, ps, other]The impact of an externally imposed MAGNETic field on numerical simulations of two-dimensional Rayleigh-Bénard convection (RBC) is investigated. Initially, the RBC model is examined in the absence of a MAGNETic field to establish a baseline. Then, a background MAGNETic field is introduced, and its influence on the transition to chaos is explored. For the purely hydrodynamic case and a range of the reduced Rayleigh number, the system exhibits traveling rolls which, after an attractor-merging crisis, give way to chaotic traveling rolls. Upon imposing a background MAGNETic field, there is a notable increase in the occurrence of traveling roll dynamics. Furthermore, the presence of the MAGNETic field favors the splitting/breaking of convective rolls, indicating a possible mechanism for transition to two-dimensional turbulence, with the structure of the convection cell being disrupted. A detailed analysis of the velocity field reveals that the collision between a saddle point and the center of a convective roll restores the system's original topology, with two symmetric kinetic vortices. During this collision, a MAGNETic vortex splits in two as a result of a MAGNETic RECONNECTion. This behavior occurs intermittently in time.
arXiv:2607.18203 [pdf, ps, other]Title: Equilibrium of a Rapidly Rotating Axisymmetric Magnetic Mirror MachineAuthors: Richard Fitzpatrick,Comments:Subjects: physics.plasm-phCreated: 2026-07-20; Updated: 2026-07-21; Datestamp: 2026-07-21A recent paper [Hazeltine, et al., Phys. Plasmas 33, 072501 (2026)] has questioned whether the standard result, (ultimately) due to Ferraro, that the plasma angular velocity is approximately constant along individual equilibrium MAGNETic field-lines in a rotating axisymmetric MAGNETic mirror machine, continues to hold when the rotation becomes sonic or supersonic. In order to resolve this issue, the equilibrium of a rapidly rotating mirror is investigated, starting from first principles, using an ideal two-fluid model with anisotropic pressure. It is found that, as long as the ion gyro-radius is much less than the machine size, and the angular velocity of the plasma is much less than the ion gyro-frequency, the Ferraro result holds good.
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