Current date: 2026-09-17

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Datestamp limit: 2026-09-17 (0 days ago)

Created/updated limit: 2026-09-10 (7 days ago)

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OAI-PMH request: http://export.arxiv.org/oai2?verb=ListRecords&from=2026-09-17&until=2026-09-17&set=physics&metadataPrefix=arXiv

Scoring abstracts

Number of records retrieved: 822

Keyword score statistics

score 11 -- 1 abstracts

score 9 -- 1 abstracts

score 7 -- 4 abstracts

score 6 -- 3 abstracts

score 5 -- 5 abstracts

score 4 -- 5 abstracts

score 3 -- 5 abstracts

score 2 -- 15 abstracts

in total -- 39 abstracts

Articles that appeared on 2026-09-17

[abstract 1 / 39] Wow! (score: 11)
arXiv:2609.18353 [pdf, ps, other]

Title: The unidentified PeV source LHAASO J2108+5157: A microQUASAR remnant?

Authors: Josep Mart\'ı, Pedro L. Luque-Escamilla, Leandro Abaroa, Gustavo E. Romero, Valent\'ı Bosch-Ramon, Josep M. Paredes, Cintia S. Peri,

Comments: 4 pages, 2 main figures and 2 appendices. Accepted as a Letter in Astronomy & Astrophysics

Subjects: astro-ph.HE

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

Context. LHAASO~J2108+5157 is one of the most intriguing Galactic ultra-high-energy $γ$-ray sources. It is detected up to hundreds of TeV but lacks a clear counterpart at lower frequencies. FERMI-LAT observations have revealed a compact GeV source spatially coincident with the PeV emission, while VERITAS and LST-1 impose stringent upper limits in the intermediate TeV band, producing a pronounced spectral suppression between the GeV and TeV domains. Aims. We investigate a time-dependent hadronic scenario in which a past episode of microQUASAR JET activity injected RELATIVISTIC protons that are now observed in a relic phase. Methods. Energy-dependent diffusion naturally segregates the particle population: Lower-energy protons remain confined near dense molecular gas and account for the GeV emission, whereas higher-energy particles reach more distant material, producing the hard TeV--PeV component. Results. For representative interstellar conditions, the model is simultaneously consistent with the broadband spectral energy distribution, the spatial compact--extended dichotomy, and the lack of detectable radio or X-ray counterparts. Conclusions. The observed bimodal $γ$-ray phenomenology thus emerges as a transport effect of a single injected proton population, supporting the interpretation of LHAASO~J2108+5157 as a fossil microQUASAR remnant observed at an intermediate evolutionary stage and highlighting relic JET systems as a viable class of Galactic PeVatrons.

[abstract 2 / 39] Wow! (score: 9)
arXiv:2606.08862 [pdf, ps, other]

Title: Disk reflection as the origin of the X-ray POLARIZATION of NGC 4151 with IXPE

Authors: E. Kammoun, M. Dovčiak, J. Podgorný, I. E. Papadakis, V. Binas-Valavanis, S. Bianchi, V. E. Gianolli, F. Ursini, J. A. García,

Comments:

Subjects: astro-ph.HE

Created: 2026-09-15; Updated: 2026-09-17; Datestamp: 2026-09-17

We present an X-ray spectro-polarimetric study of the nearby type-1 ACTIVE GALACTIC NUCLEus NGC 4151 using two long IXPE observations obtained in 2022 and 2024, supported by simultaneous XMM-Newton and NUSTAR spectroscopy. IXPE measures a POLARIZATION degree of $\sim 6-7\%$ above 4 keV, with a POLARIZATION angle parallel to the radio JET, and a distinct low-energy component with a different angle, indicating at least two polarized components in the $2-8$ keV band. Previous work interpreted the hard X-ray POLARIZATION as evidence for a radially extended slab-like corona. Here we test an alternative scenario in which the observed POLARIZATION is produced predominantly by RELATIVISTIC reflection from an accretion disk illuminated by a compact, lamp-post-like corona. Using recently developed models, we fit the IXPE Stokes spectra with a lamp-post plus distant-torus geometry, including partial-covering absorption and an additional soft polarized power-law component. We find that the data require a low coronal height ($h<9\,R_{\rm g}$ at $3σ$) and a relatively large torus opening angle ($>45^\circ$ at 3$σ$), while the disk reflection contributes $\sim 20\%$ of the 2-8 keV flux. The soft polarized component carries only $\sim 1-5\%$ of the flux but has a high POLARIZATION degree ($>10\%$) and a POLARIZATION angle around $20^\circ$. The same configuration provides acceptable fits to the $0.4-79$ keV XMM-Newton and NUSTAR spectra, demonstrating that disk reprocessing by a compact corona can simultaneously account for both the POLARIZATION and broadband spectral properties of NGC 4151.

[abstract 3 / 39] Wow! (score: 7)
arXiv:2602.08319 [pdf, ps, other]

Title: Neutrino Emission from Gamma-ray Burst Jet inside the Cavity within Active Galactic Nucleus Accretion Disks

Authors: Hao-Yu Yuan, Wen-Long Xu, Kai Wang, Wei-Hua Lei,

Comments: 15 pages, 8 figures. Accepted for publication in ApJ

Subjects: astro-ph.HE

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

Active galactic nucleus (AGN) accretion disks are promising sites for compact binary mergers. Short GAMMA-RAY BURST (SGRB) JETs from binary neutron star coalescence can propagate within low-density cavities carved by circumbinary outflows. We investigate the high-energy neutrino emission and detectability of such SGRB JETs, adopting three seed photon components: prompt GRB emission, AGN disk thermal radiation, and external inverse Compton (EIC) scattered photons. Our results show that neutrino emission is dominated by proton-photon ($pγ$) interactions, with prompt GRB photons and AGN disk photons serving as the dominant target components. The inclusion of AGN disk photons significantly reshapes the neutrino spectrum, shifting the emission peak to lower energies. This effect becomes more pronounced as the mass of the central supermassive BLACK HOLE decreases and the burst location approaches the BLACK HOLE. For a fiducial model with a $10^6~ M_\odot$ central BLACK HOLE and the burst at 10 Schwarzschild radii, IceCube and IceCube-Gen2 achieve maximum luminosity distances of $\sim$180 Mpc and $\sim$400 Mpc, respectively. Next-generation high-sensitivity neutrino observatories, combined with multi-messenger observations, hold promise for identifying such GRBs in AGN environments.

[abstract 4 / 39] Wow! (score: 7)
arXiv:2607.20209 [pdf, ps, other]

Title: Shock acceleration in vortex driven MAGNETic fields of BLACK HOLEs

Authors: Zaza N. Osmanov,

Comments: 7 pages, 2 figures

Subjects: astro-ph.HE

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

The aim of this work is to investigate particle acceleration by shock waves in the MAGNETospheres of supermassive BLACK HOLEs, where the MAGNETic field is vortex-driven. For this purpose, we investigated the first-order FERMI acceleration process at RELATIVISTIC shocks in the MAGNETospheres of supermassive BLACK HOLEs. In our analysis, we considered SYNCHROTRON radiation and inverse Compton scattering as the principal energy-loss mechanisms limiting the maximum attainable particle energy. We investigated the acceleration of both protons and electrons and demonstrated that, for a typical supermassive BLACK HOLE with a mass of $10^8$ solar masses, protons can be accelerated to energies of several hundred PeV, whereas electrons can attain energies of up to approximately 120 GeV.

[abstract 5 / 39] Wow! (score: 7)
arXiv:2609.17813 [pdf, ps, other]

Title: Radiation Magneto-hydrodynamic Simulations of MRI with Zero-Net-Vertical-Flux: Necessity of Resolving the Thermal Scale For Strongly Magnetized Initial Conditions

Authors: Yi-Xian Chen, Yan-Fei Jiang, Jeremy Goodman,

Comments: 18 pages, 9 figures. submitted to AAS Journals, comments welcome

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

Created: 2026-09-15; Updated: 2026-09-17; Datestamp: 2026-09-17

We perform 3D radiation MAGNETo-hydrodynamic (RMHD) shearing-box simulations of local patches of optically thick accretion disks, applicable to sub-Eddington ACTIVE GALACTIC NUCLEi (AGN) at $\sim 1000$ gravitational radii around a supermassive BLACK HOLE (SMBH) of $10^7-10^8M_\odot$. In particular, we set up zero-net-vertical-flux (ZNVF) simulations with strong net azimuthal fields ($B_y$) characterized by initial gas-to-MAGNETic pressure ratio $β_0$. We find that $β_0 \sim 1$ simulations relax to the classical MRI state with steady-state $β\sim 10-20$ and slow periodic reversals of the mean azimuthal field (dynamo cycles), losing memory of their initial $B_y$ configuration. The outcome of simulations starting from $β_0=0.1$ (superthermal MAGNETic pressures) depends upon the numerical resolution as quantified by the number of grid cells per thermal scale height $H_\mathrm{th}$. Resolved simulations ($Δz\le H_\mathrm{th}/5$) settle into final states similar to the larger-$β_0$ runs, exhibiting thermally dominated midplanes heated by MRI turbulence and undergoing dynamo cycles. In contrast, lower resolution $β_0 = 0.1$ runs evolve towards states dominated by a coherent mean field, similar to what is observed in recent isothermal MHD simulations. However, those disks fail to sustain sufficient turbulent heating near the midplane and undergo runaway cooling and contraction. While such states might be sustained in global models with even lower initial $β_0$ and/or continuous $B_y$ injection, our results indicate that they could arise purely from under-resolving the midplane MRI dynamo that would otherwise be able to generate and emanate randomized fields. We highlight the need to resolve a fraction of the thermal scale height (the classical MRI wavelengths) for strongly MAGNETized initial conditions to obtain converged outcomes in RMHD simulations.

[abstract 6 / 39] Wow! (score: 7)
arXiv:2609.19108 [pdf, ps, other]

Title: Radiation-Driven Magnetic Fields in Sub-Keplerian Accretion Flows: An Alternative to MRI

Authors: Mukesh Kumar Vyas, Asaf Pe'er,

Comments: Submitted to Physical Review Letters

Subjects: astro-ph.HE

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

Large scale MAGNETic fields play a crucial role in shaping the dynamics and structure of the inner parts of accretion disks and the resulting JETs from the vicinity of BLACK HOLEs and neutron stars. Currently, the primary mechanism considered for generating and amplifying large scale MAGNETic fields in accretion disks is the MAGNETo-rotational instability (MRI). Here we show that non-conservative radiation fields provide a rapid and independent mechanism for generating and amplifying MAGNETic fields in accretion flows. A luminous, compact corona generates a radiation-driven poloidal field that is subsequently amplified by differential rotation, yielding quadratic MAGNETic-field growth and, over a broad range of coronal luminosities and sizes and MRI amplification locations, MAGNETization on timescales comparable to or shorter than those of the MRI. The mechanism therefore provides not merely an alternative to MRI, but an additional and, over a substantial region of parameter space, dominant channel for MAGNETic-field generation from initial conditions with zero MAGNETic field. Since the radiation-driven source arises directly from the non-conservative nature of the radiation field, such MAGNETic-field generation is an inevitable consequence of sufficiently strong and anisotropic radiation sources in black-hole accretion flows. More generally, the mechanism requires only a non-conservative radiation field and differential plasma motion, and is therefore expected to operate in a broad range of luminous astrophysical systems, including ACTIVE GALACTIC NUCLEi, GAMMA-RAY BURSTs, and tidal disruption events.

[abstract 7 / 39] Yes (score: 6)
arXiv:2605.15145 [pdf, ps, other]

Title: Eclipses of Nearby Millimeter-bright Galactic Nuclei by Stars in Nuclear Star Clusters

Authors: Michal Zajaček,

Comments: 24 pages, 15 figures, 5 tables; accepted for publication by the AAS journals

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

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

It is of a general interest to look for signatures of stellar bodies orbiting supermassive BLACK HOLEs (SMBHs) in galactic nuclei other than the Galactic center. Previously stellar transits were analyzed in UV, optical, and X-ray domains as well as potential microlensing signatures due to more compact bodies orbiting SMBH accretion disks. Here we complement previous studies by considering nearby ($z=0.001$) millimeter-bright ACTIVE GALACTIC NUCLEi targeted by different facilities in the millimeter domain. At these wavelengths the JET base and the nuclear ring are sufficiently compact so that they can be occulted by large evolved stars in dense nuclear star clusters. We find that in the millimeter domain evolved stars with stellar radii of $\gtrsim 500\,R_{\odot}$ can cause eclipses with the relative depth of $\sim 10-40\%$. Typical recurrence timescales are at least 10 years and the eclipse durations are $\sim 10$ days. Towards lower frequencies the eclipse temporal profiles become shallower and broader while towards higher frequencies they are deeper and narrower. Although expected to be rare due to selection effects and evolved stars being prone to tidal disruption, eclipses of millimeter radio cores can be applied to estimate the distance of the extragalactic star from the SMBH and its stellar radius. In case the eclipse is recurring, we provide a relation for estimating the SMBH mass.

[abstract 8 / 39] Yes (score: 6)
arXiv:2609.03140 [pdf, ps, other]

Title: Thermal and non-thermal emission from supermassive BLACK HOLE circumbinary disks: Disks, Coronae, Streams, and Cavities

Authors: Chris Nagele, Julian H. Krolik, Brooks E. Kinch, Jeremy D. Schnittman, Scott D. Noble,

Comments: Submitted to ApJ Comments welcome!

Subjects: astro-ph.HE

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

The search for electroMAGNETic signals from supermassive BLACK HOLE (SMBH) binary systems is one of the cornerstones of multi-messenger astrophysics, complementing gravitational wave observations of such systems by pulsar timing arrays and LISA. Although extensive simulations have been run to understand the time variability of the bolometric luminosity from accreting binary SMBH systems, comparatively few spectral predictions have been made, and none that go beyond simple emission models. In this paper, we post-process a \texttt{HARM3D} simulation snapshot of a binary at $20 M$ separation accreting at 0.01 Eddington. For BLACK HOLE masses $10^6$, $10^7$, and $10^8\, M_\odot$, we self-consistently solve for the radiated spectrum on the basis of time-steady radiation transfer, thermal balance, and ionization equilibrium, including all relevant RELATIVISTIC effects as well as emission and absorption processes. Although most of the bolometric luminosity is radiated thermally by the disk, the low density regions evacuated by the binary's quadrupole moment produce copious X-rays, with $\sim40\%$ of the observed luminosity in a soft X-ray power law ($Γ= 2.3$). We identify two modes of observed azimuthal variation. The X-ray continuum varies by $\sim10\%$ due to an underlying asymmetry in the gas temperature of spiral shocks in the disk. The Fe~K$α$ equivalent width dips by $\sim25\%$ when the line of sight to the inner disk is partially obscured by the lump. These two effects share the same period and are $\sim π/2$ out of phase; the period is order days to weeks for typical AGN masses and a 20$M$ separation.

[abstract 9 / 39] Yes (score: 6)
arXiv:2609.17776 [pdf, ps, other]

Title: The Hidden Evolution of Gamma-Ray Burst Jets Revealed by Gravitational Waves

Authors: Gerardo Urrutia, Fabio De Colle, Agnieszka Janiuk, Claudia Moreno, Enrico Ramirez-Ruiz,

Comments: 15 pages, 8 figures, submitted to ApJ

Subjects: astro-ph.HE

Created: 2026-09-15; Updated: 2026-09-17; Datestamp: 2026-09-17

Gamma-ray burst (GRB) JETs can propagate through massive stars, where the high opacity of the stellar envelope traps electroMAGNETic radiation and limits observations of the JET at early times. Gravitational waves (GWs), in contrast, can escape these dense environments and provide direct information of the JET dynamics. Previous studies have shown that GRB JETs can emit GWs at low frequencies, while high-frequency emission may arise from JET-driven cocoons. However, the cocoon contribution typically requires energies much larger than those inferred from observations and produces stochastic fluctuations that can resemble noise. In this work, we show that high-frequency GW signals, can instead be generated by variability in the central engine. We consider JET models with different luminosity histories. We find that the GW emission depends on both the central engine history and the interaction of the JET with the stellar envelope. Rapid luminosity fluctuations are progressively suppressed as the JET propagates through the star, while the GW signal preserves information about the early JET evolution. Jets powered by strongly variable engines produce a GW signal peaking at tens of Hz, whereas smoothly varying engines are dominated by low-frequency emission. For a source at 36 Mpc, comparable to the distance of the closest GRB observed to date, the high-frequency signal from our most energetic variable models can reach amplitudes detectable by current ground-based interferometers. Our results suggest that the detection or non-detection of GWs from nearby GRBs and Type Ic broad-lined SNe could help constrain the mechanisms operating in the central engine.

[abstract 10 / 39] Yes (score: 5)
arXiv:2605.07479 [pdf, ps, other]

Title: Diffuse gamma-ray emissions around the stellar cluster Berkeley 59

Authors: Ziwei Ou, Xiaolong Yang, Songpeng Pei,

Comments:

Subjects: astro-ph.HE

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

We report a detailed analysis on the young stellar cluster Berkeley 59 using FERMI-LAT. Using up-to-date source catalog and background models, we found significant extended GeV emission around Berkeley 59, which can be modeled by a radial disk of 1.02 degree radius with a significance of the extension of 10.6 sigma. We investigated the molecular, neutral and ionized gas content and the hadronic origin. The gamma-ray spectrum of Berkeley 59 has a photon index of 2.88. The derived gas mass from H2 and HII around Berkeley 59 is about 289 solar mass. We derived the relationship between COSMIC RAY acceleration efficiency and diffusion coefficient. Our results suggest that the extended gamma-ray emission originates from COSMIC RAYs accelerated by cluster winds interacting with surrounding gas.

[abstract 11 / 39] Yes (score: 5)
arXiv:2606.06802 [pdf, ps, other]

Title: Radiation Pressure Instability in the "turn-on" Changing-Look AGN SDSS J1430+2303

Authors: Han He, Bei You, Marzena Śniegowska, Bożena Czerny, Claudio Ricci, Xinwu Cao,

Comments: submitted to A&A. 15 pages, 13 figures, 3 tables

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

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

We aim to investigate the multi-wavelength variability, spectral, and timing properties of the changing-look ACTIVE GALACTIC NUCLEus (CL AGN) SDSS J1430+2303, and to explore the physical origin of its peculiar variability pattern that has not been observed before in other CL AGN. We perform a multi-wavelength analysis using optical, ultraviolet, and X-ray observations. We investigate the long-term optical color variation, characterize the evolution of the X-ray spectrum and timing properties, and construct broad-band spectral energy distributions to constrain the BLACK HOLE mass, spin, and Eddington ratio. The optical flux increased by an order of magnitude over four years, accompanied by a spectral transition from Seyfert 1.9 to 1.2. The long-term color variation follows the ``bluer-when-brighter'' trend, with a color-magnitude slope consistent with previous statistical results for CL and Type 1 AGNs. During the brightened high state, the optical, ultraviolet, and X-ray light curves exhibited rapid decaying periods with progressively decreasing amplitudes, a behavior not previously reported in other CL AGNs. X-ray spectral analysis reveals a remarkably weak soft excess that declines more steeply than the hard X-rays as the total luminosity decreases. X-ray timing analysis shows a nearly constant break frequency and a hard lag at $\sim10^{-4}$ Hz during the luminosity decline, suggesting a stable disk--corona geometry. Broad-band spectral energy distribution fitting constrains the BLACK HOLE mass to $M_{\rm BH}=3.8-19.5\times10^7\,M_\odot$ and favors a high spin ($a\gtrsim0.77$), while the correspondingly low Eddington ratio can account for the observed weak soft excess. We propose that the observed multi-wavelength decaying periods and their progressively decreasing amplitudes are associated with a shrinking unstable zone driven by radiation-pressure instability in the accretion disk.

[abstract 12 / 39] Yes (score: 5)
arXiv:2609.17661 [pdf, ps, other]

Title: 1D PIC Simulations of Resonant Scattering-Driven Pair Cascades in Magnetar Magnetospheres

Authors: Jens F. Mahlmann, Alexander A. Philippov, Adrien Soudais, Andrei M. Beloborodov, Lorenzo Sironi,

Comments: 15 pages, 8 figures, submitted to ApJL

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

Created: 2026-09-15; Updated: 2026-09-17; Datestamp: 2026-09-17

Hard X-rays in persistent MAGNETar emission originate from radiative processes in pair-loaded MAGNETospheric plasma, yet self-consistent kinetic simulations of such radiation-rich systems remain limited. We perform 1D particle-in-cell simulations of pair creation mediated by resonant inverse Compton scattering (RICS) along isolated field lines in twisted MAGNETospheres, capturing particle acceleration and radiative drag from first principles. The drag force, which strongly depends on the particle Lorentz factor and location, plays a key role in the MAGNETospheric circuit. Strong RICS drag impedes the flow of electrons and positrons, particularly along extended field lines. Nevertheless, the plasma sustains the circuit by self-organizing into a single accelerating gap near the star in one hemisphere. The accelerated plasma flow from the gap becomes loaded with copious electron-positron pairs in extended RICS zones, and also carries ions extracted from the star and accelerated in the gap. When radiative drag stops the pair-loaded flow at the MAGNETic equator, the ion component transfers momentum through streaming instabilities, delivering a small lepton population into the opposite hemisphere and sustaining the circuit. The gap confined to a single (anode) hemisphere implies asymmetric hard X-ray production, possibly detectable in phase-resolved MAGNETar spectra.

[abstract 13 / 39] Yes (score: 5)
arXiv:2609.17665 [pdf, ps, other]

Title: Unifying spatial correlation with hierarchical population inference to constrain the AGN channel for binary BLACK HOLE mergers

Authors: Lucas Pouw, Lorenzo Speri, Niccolò Veronesi, Elena Maria Rossi,

Comments: 20 pages, 15 figures, 4 tables

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

Created: 2026-09-15; Updated: 2026-09-17; Datestamp: 2026-09-17

The origin of the stellar-mass binary BLACK HOLEs (BBHs) observed in gravitational wave (GW) events by the LIGO-Virgo-KAGRA (LVK) detectors remains uncertain. One promising formation pathway is the ACTIVE GALACTIC NUCLEus (AGN) channel, in which BBHs embedded in AGN accretion discs experience enhanced merger rates and may produce rapidly spinning BLACK HOLEs in the upper mass gap. Previous constraints on the AGN contribution to the LVK merger population have relied either on spatial correlations between GW localisations and AGN catalogues or on modelling the intrinsic properties of GW sources. We develop a hierarchical Bayesian framework that unifies these approaches within a single likelihood for the fraction of AGN-hosted GW events, $f_{\rm agn}$. This framework, combined with the latest gravitational wave transient catalogue GWTC-5.0 and the electroMAGNETic Quaia AGN catalogue, cannot exclude an AGN contribution to the observed merger rate. For unobscured AGN in the optical and infrared bands with bolometric luminosities $L_{\rm bol}\geq\{10^{44.5},10^{45.5},10^{46.5}\}\,\mathrm{erg\,s^{-1}}$, we exclude $f_{\rm agn} \geq \{0.52,0.41, 0.61\}$ at the 95 percent credible level under our fiducial model. The methodology and results presented in this work lay down the pathway for combining the full GW posterior with electroMAGNETic observations to infer the properties of GW populations and AGN discs.

[abstract 14 / 39] Yes (score: 5)
arXiv:2609.18693 [pdf, ps, other]

Title: Baryon-to-meson ratios in the Lund JET plane: resolving string-junction and thermal-fragmentation effects

Authors: Robert Vertesi,

Comments: Submitted to JPhysG

Subjects: hep-ph

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

Baryon-to-meson ratios inside charged JETs are studied in the Lund JET plane using PYTHIA simulations of pp collisions at $\sqrt{s} = 14$ TeV, with 15 < $p_{\rm T}^{\rm ch,JET}$ < 30 GeV/$c$ in an acceptance compatible with the future ALICE 3 detector. Jets are reclustered with the Cambridge--Aachen algorithm and identified hadrons are tagged at the splitting where they first separate from the leading branch. Three model configurations are compared: Monash, color RECONNECTion beyond leading color (CR-BLC), and CR-BLC combined with thermodynamical string fragmentation (Thermal+CR-BLC). The $Λ_c^+/{\rm D}^0$ ratio rises with $\log(1/z)$ in the two configurations that include color-string junctions and is approximately flat under Monash. The same trend is present at the first Cambridge--Aachen branching, indicating that the effect is set at the level of the color topology rather than through the cumulative action of many soft splittings. Light- and strange-sector ratios show no $z$-dependent signature of either mechanism, but the angular projection reveals non-trivial structure at the first branching that is washed out when emissions are summed. The Cambridge--Aachen declustering and the Lund plane together separate the kinematic signatures of the two baryon-enhancement mechanisms in PYTHIA and provide observables accessible to future ALICE 3 measurements.

[abstract 15 / 39] Yes (score: 4)
arXiv:2609.17723 [pdf, ps, other]

Title: Uncovering New Ionized Winds and Relativistic Hot Outflows in MCG-6-30-15 with \emph{Chandra} HETG and a Bayesian Framework

Authors: Erika B. Hoffman, Anna Ogorzałek, Christopher S. Reynolds, Lia Corrales,

Comments: 28 pages, 13 figures, Submitted to The Astrophysical Journal

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

Created: 2026-09-15; Updated: 2026-09-17; Datestamp: 2026-09-17

Active Galactic Nuclei (AGN) feedback plays a key role in galaxy evolution. Highly ionized outflows, detected in X-ray absorption, are a promising candidate for QUASAR-mode feedback. We present a new Bayesian analysis of 0.65 Ms of \emph{Chandra} High Energy Transmission Gratings (HETG) observations of MCG-6-30-15 from 2000 and 2004. Our approach detects new wind components, improving estimates of outflow demographics and impact. These include a hot ultra-fast outflow (UFO; 0.08c), recently confirmed by XRISM but seen in HETG for the first time, which has the power to potentially influence its host galaxy. We also detect the first potentially collisionally ionized absorbers in this source, a physical process typically not considered in previous analyses, but potentially important for wind impact and demographics. The warm absorber complex is resolved in unprecedented detail, uncovering evidence of a correlation between outflow velocity and ionization, constraining its geometry. We also confirm the presence of dust in the wind, clearly distinguishing it from the cold ISM components, which may impact wind acceleration. Our work highlights the power of applying new methods to deep, legacy HETG datasets, and the limitations of current atomic databases when considering OIV, V, and VI K-shell transitions. Furthermore, our work establishes a baseline for decade-scale outflow variability for new observations with XRISM and NewAthena in the future.

[abstract 16 / 39] Yes (score: 4)
arXiv:2609.18192 [pdf, ps, other]

Title: RadioAstron space-VLBI imaging of the JET in M87: II. The parsec-scale structure at 4.8 GHz

Authors: Evgeniya V. Kravchenko, Tuomas Savolainen, Alexey S. Nikonov, Ilya N. Pashchenko, Elena E. Nokhrina, Petr A. Voitsik, Leonid I. Gurvits, Yuri Y. Kovalev, Jae-Young Kim, Mikhail M. Lisakov, Andrei P. Lobanov, Kirill V. Sokolovsky,

Comments: 15 pages, 15 figures, 3 tables. Accepted by MNRAS

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

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

We present RadioAstron observations of the M87 JET obtained on 2014 February 4-5 at 4.8 GHz ($λ=6.2$ cm). The correlated signals between the 10-m space antenna and ground-based radio telescopes were detected up to projected baselines of $\thicksim3$\,Earth diameters (0.65~G$λ$). The orientation of the JET downstream of the core shifts northward, consistent with the long-term oscillating trend reported in other studies. An elliptical body mode of the Kelvin-Helmholtz instability can create the observed helical shape of the JET. The estimated wavelength of this instability mode suggests that its origin may be related to some processes in the accretion disc. We present 1.7 - 4.8 GHz and 4.8 - 15.4 GHz spectral index maps showing flattening of the spectrum along the outer streamlines and along the JET spine. Simulations and analysis show that this spectral flattening is partially artificial and is a common systematic effect of the CLEAN procedure of VLBI imaging. The spectral index of the M87 JET is consistent with the optically thin emission, while its steepening can be produced by the propagation of the instability modes causing higher pressure regions near the JET boundary and in its interior.

[abstract 17 / 39] Yes (score: 4)
arXiv:2609.18226 [pdf, ps, other]

Title: Detectability of 100 TeV Gamma Rays from PeV Cosmic Rays Accelerated in the Early Phase of a Supernova Shock Wave

Authors: Tomotaka Nishikawa, Tsuyoshi Inoue, Alexandre Marcowith,

Comments: 17 pages, 17 figures

Subjects: astro-ph.HE

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

Galactic COSMIC RAYs (CRs) are thought to be accelerated by diffusive shock acceleration in SUPERNOVA remnants (SNRs), but observations of SNRs aged ~100-1000 yr suggest maximum CR energies below the PeV level. Recently, Inoue et al. (2021) showed with kinetic-MHD simulations that CRs can be accelerated to ~3 PeV when a blast wave shock propagates through dense circumstellar material (CSM) within tens of days after explosion. Such CSM can be produced by a red-supergiant (RSG) wind with an observationally motivated mass-loss rate of ~10^-3 Ms/yr. 100 TeV gamma-rays from neutral pion decay can test PeV CR acceleration. However, hadronic gamma-rays from very young SNRs can be significantly attenuated by SUPERNOVA photospheric photons and the cosmic background radiation. Using the CR distribution functions and CSM density profiles from Inoue et al. (2021), we calculate time-dependent gamma-ray fluxes from Type II-P SNe, including both attenuation processes. We find that photospheric photons attenuate the intrinsic 1-100 TeV gamma-ray flux by about one order of magnitude. For the dense CSM case with dot{M}_RSG ~ 10^-3 Ms/yr and an outer CSM radius of ~ 3x10^15 cm, CTA can detect 100 TeV gamma-rays with a 50 h observation out to ~ 4 Mpc (this is reduced to 3 Mpc if the spatial extent of the CSM is shrunk to 2x10^15 cm). These results suggest that early 100 TeV observations of nearby Type II-P SNe can probe PeV CR acceleration in sufficiently dense and extended CSM.

[abstract 18 / 39] Yes (score: 4)
arXiv:2609.18606 [pdf, ps, other]

Title: Shadow and Polarized Images of Schwarzschild-MOG Black Hole Illuminated by Thick Accretion Disk

Authors: Cheng Hu, Huan Ye, Hong Lei, Zi-Chao Lin,

Comments: 32 pages, 9 figures

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

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

Recent EHT polarimetric observations provide a powerful probe of near-horizon physics and modified gravity. We investigate the shadow and POLARIZATION images of a static Schwarzschild-MOG BLACK HOLE illuminated by geometrically thick, optically thin accretion flows. Adopting a phenomenological model and the Hou disk model, and solving null geodesics and RELATIVISTIC radiative transfer, we study how the MOG parameter, inclination angle, anisotropic SYNCHROTRON emission, and flow geometry affect the total intensity and linear POLARIZATION. It is found that the MOG parameter mainly enlarges and brightens higher-order photon rings and broadens the shadow, while the inclination angle breaks axial symmetry and enhances polarized emission inside the shadow. The Hou disk model suppresses off-equatorial radiative interference and localizes POLARIZATION signals within higher-order rings. Electric vector position angle (EVPA) patterns are mostly azimuthal but vary rapidly near lensed images. These results provide theoretical diagnostics for constraining MOG with EHT/ngEHT polarimetric observations.

[abstract 19 / 39] Yes (score: 4)
arXiv:2609.18699 [pdf, ps, other]

Title: Studying the Intermittency of Magnetized Interstellar Medium by Synchrotron Polarization Intensity and its Gradient

Authors: Ru-Yue Wang, Jian-Fu Zhang,

Comments:

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

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

Based on synthetic POLARIZATION observations, we qualitatively investigate the intermittency of the MAGNETized interstellar medium (ISM) through SYNCHROTRON POLARIZATION intensity (SPI) and SYNCHROTRON POLARIZATION gradient (SPG). Three principal findings emerge from our analysis: (1) The intermittency of the MAGNETized ISM is strongly modulated by MAGNETization and compressibility, with pronounced modulation effects predominantly observed in regimes characterized by strong MAGNETization and high compressibility. (2) The characterized intermittency of the MAGNETized ISM demonstrates a dependence on the electron spectral index under conditions where the random MAGNETic field dominates. (3) SPG enables the identification of finer three-dimensional fractal structures in the case of strong Faraday dePOLARIZATION. The synergistic application of SPI and SPG substantially enhances the reliability of probing MAGNETized ISM intermittency from real observations.

[abstract 20 / 39] (score: 3)
arXiv:2510.14059 [pdf, ps, other]

Title: Probing Helium Reionization Through the $^{3}\mathrm{He}^{+}$ Hyperfine Transition Line

Authors: Arghyadeep Basu, Benedetta Ciardi, Enrico Garaldi,

Comments: 8 pages, 7 figures, Version accepted for publication in MNRAS Main Journal

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

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

We investigate the hyperfine transition of $^{3}\mathrm{He}^{+}$ as a promising probe of the IGM during the final stages of helium reionization. Utilising the most recent helium reionization simulation, we generate three-dimensional maps of the 3.5cm ($8.67$,GHz) differential brightness temperature and analyze its evolution. Our `fiducial' results show that the volume-averaged brightness temperature declines rapidly from $\sim 10^{-2}\,μ\mathrm{K}$ (in the `optimistic' approach, i.e. $T_{\rm s} = T_{\rm gas}$, $\sim 1,μ\mathrm{K}$) at $z = 3$ to $\sim 8 \times 10^{-5},μ\mathrm{K}$ ($\sim 2.5 \times 10^{-3},μ\mathrm{K}$) by $z = 2.3$, tracing the He,\textsc{ii} to He,\textsc{iii} transition driven by QUASARs. The power spectrum of the 3.5cm signal exhibits a scale-dependent evolution, peaking on small scales and declining as reionization progresses. We explore the cross-correlation of the 3.5cm transition line with the distribution of AGNs, which shows a transition from positive to negative correlation as ionized regions grow. Although current observational upper limits lie several orders of magnitude above theoretical predictions, future radio arrays such as \texttt{SKA-mid} offer promising prospects. Overall, this study highlights the $^{3}\mathrm{He}^{+}$ hyperfine transition as a sensitive tracer of the thermal and ionization history of the IGM during helium reionization. The predicted signal is also subject to additional uncertainty from spin temperature modelling, and the true amplitude is expected to lie between the limiting cases explored in this work.

[abstract 21 / 39] (score: 3)
arXiv:2602.23521 [pdf, ps, other]

Title: ALMA High-J CO Spectroscopy of High-Redshift Galaxies. I. An Archive-based Catalog of CO Spectral Line Energy Distributions

Authors: Ken-ichi Tadaki,

Comments: Published in ApJS. Figure 4 provides a class-averaged comparison of CO SLEDs for Hot DOGs, SMGs, and quasars

Subjects: astro-ph.GA

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

High-J CO emission in high-redshift galaxies has been studied primarily on an individual-source basis, limiting our ability to draw population-level conclusions about molecular-gas excitation. To address this limitation, we present a catalog of CO spectroscopy based on archival data from the Atacama Large Millimeter/submillimeter Array (ALMA) for a sample of galaxies at z > 3, focusing on high-J transitions (Jup = 9-17). Combining ALMA archival data with published measurements, we compile CO spectral line energy distributions (SLEDs) for 38 well-studied systems spanning z = 3.1-6.9, including 5 hot dust-obscured galaxies (Hot DOGs), 17 submillimeter-bright galaxies (SMGs), and 16 optically selected QUASARs. The class-median SLEDs rise steeply to Jup = 9 and remain approximately flat through Jup ~ 11-12. SMGs show relatively stronger low- to mid-J emission relative to CO J=9-8, while Hot DOGs exhibit tentative evidence for higher excitation. Comparison with simple excitation models suggests that X-ray dominated region (XDR) heating or dense, shock-heated gas can account for the extended high-J CO SLEDs. A tentative anti-correlation between the CO(9-8)-to-infrared luminosity ratio and excitation among the dusty galaxy populations suggests that the enhanced excitation in Hot DOGs may be driven by XDR heating from obscured AGN activity rather than by shocks. Because the sample is restricted to sources with detected high-J CO lines, it is biased toward highly excited systems. It nonetheless provides a reference for designing future systematic surveys of high-J CO emission with a statistically complete or flux-limited sample.

[abstract 22 / 39] (score: 3)
arXiv:2605.03089 [pdf, ps, other]

Title: Evidence for anisotropic non-Maxwellian velocity distributions in the solar transition region

Authors: Paola Testa, Bart De Pontieu, Kyuhyoun Cho, Thomas Ayres, Alexander Russell,

Comments: 9 pages, 5 figures, accepted for publication in ApJ Letters

Subjects: astro-ph.SR

Created: 2026-09-15; Updated: 2026-09-17; Datestamp: 2026-09-17

Spectroscopic observations of the solar transition region have long shown excess line broadening and non-Gaussian profiles, but their spatial distribution and prevalence are not well established, and their physical origin remains the subject of debate. Here we analyze SiIV line profiles in full-disk mosaics of observations with Interface Region Imaging Spectrograph (IRIS; De Pontieu et al. 2014), and find that non-Gaussian k-like profiles, indicative of suprathermal velocity distributions, are pervasive (comprising ~60% of the observed profiles). In addition, we find that their occurrence depends strongly on the angle between the line of sight and the MAGNETic field as inferred from NLFFF extrapolations. k-like profiles become increasingly prevalent when the MAGNETic field is oriented transverse to the observer, whereas Gaussian profiles become more prevalent when the field is aligned with the line of sight. This geometric dependence provides evidence that the observed velocity distributions in the transition region are non-Maxwellian and anisotropic. Our findings provide evidence for the importance, in the solar transition region, of kinetic processes, and the key role the MAGNETic field plays in the superposition of signals, and/or the generation or relaxation of non-Maxwellian particle distributions, likely caused by MAGNETic energy release through RECONNECTion. These effects are not captured by the MAGNETohydrodynamic approaches that are typically invoked to study the solar atmosphere. Our results highlight the need and provide constraints for more advanced multi-fluid and/or kinetic modeling of the solar transition region.

[abstract 23 / 39] (score: 3)
arXiv:2607.27333 [pdf, ps, other]

Title: Relativistic effects of PSR~J1856--0039 double neutron star system in a 2.36-hour compact orbit

Authors: Z. L. Yang, J. L. Han, W. Q. Su, P. F. Wang, C. Wang, T. Wang, D. J. Zhou, Yi Yan, J. Xu, W. C. Jing, N. N. Cai, R. X. Xu, H. G. Wang, X. P. You,

Comments: 9 pages, 4 figures, Published by Phys. Rev. Lett

Subjects: astro-ph.HE

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

Compact double neutron star (DNS) systems are unique laboratories for testing gravitational theories and studying DNS mergers. Here we report the properties of a new DNS system, PSR J1856--0039, discovered in the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The pulsar is mildly recycled with a period of 23.4~ms in a compact eccentric orbit ($e=0.106$) with an orbital period of 2.36 hours. By following up FAST observations, we measured the RELATIVISTIC effects, including the orbital period derivative $\dot{P}_{\rm orb}=-1.284\pm0.019\times10^{-12}$ s s$^{-1}$, periastron advance $\dotω=17.5859\pm0.0007$ deg yr$^{-1}$, and Einstein delay $γ=0.445\pm0.011$ ms. This DNS system has a low orbital inclination of $i=133^\circ.2\pm1^\circ.1$ and the lowest total mass of any known DNS, $M_{\rm tot}=2.48841\pm0.00015 M\odot$, with a determined pulsar mass of $1.304\pm0.022 M_\odot$ and a companion mass of $1.185\pm0.022 M_\odot$, one of the lowest neutron-star masses. The observed orbital decay due to gravitational-wave emission $\dot{P}^{\rm GW}_{\rm orb,obs}$ and the orbital decay predicted by general relativity $\dot{P}^{\rm GW}_{\rm orb,pred}$ are consistent at a level of $\dot{P}^{\rm GW}_{\rm orb,obs}/\dot{P}^{\rm GW}_{\rm orb,pred}=$1.009(14) (68% confidence). This DNS will merge after 82 Myr and may form a stable neutron star or collapse into a BLACK HOLE after spin-down. Long-term monitoring could potentially probe the Lense-Thirring precession.

[abstract 24 / 39] (score: 3)
arXiv:2609.18086 [pdf, ps, other]

Title: FRB 20250607A: Weirder Than Fiction

Authors: J. C. F. Balzan, A. Bera, C. W. James, B. W. Meyers, A. T. Deller, R. M. Shannon, Z. Wang,

Comments: 18 pages, 15 figures, 1 table

Subjects: astro-ph.HE

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

We present a detailed analysis of FRB 20250607A, a two-component FRB detected by the CRAFT survey which exhibits several unusual component-dependent properties, including apparent differential DM, circular polarisation, and time-resolved RM, together with a polarisation-angle (PA) swing that persists through the scattering tail. The scattering timescale and scintillation bandwidth are inconsistent with a single thin-screen origin, placing the dominant scattering screen within $\lesssim61$ kpc of the FRB source. The lack of PA flattening in the scattering tail is a behaviour not previously reported in an FRB or pulsar and difficult to reconcile with a simple propagation origin. We find no statistically significant differential DM between the two components despite an apparent, and visually obvious, difference in their dispersion, indicating that current uncertainties may be overly conservative. If this apparent differential DM is true, it implies a substantial difference in electron column density between the component sightlines. Two further CRAFT FRBs, FRB 20190611B and FRB 20210407E, show similarly large component-dependent electron-column differences, corresponding to electron-density contrasts consistent with plasma local to a neutron-star MAGNETosphere. We find no evidence for generalised Faraday rotation, and FRB 20210407E shows component-dependent PA structure. Taken together, these results suggest that the observed DM, circular polarisation, and PA behaviour may arise from differing sightlines through an inhomogeneous or evolving MAGNETosphere rather than from independent phenomena. Multi-component FRBs therefore provide a sensitive probe of plasma structure local to their progenitors.

[abstract 25 / 39] (score: 2)
arXiv:2601.05734 [pdf, ps, other]

Title: A nonlinear voice from GW250114 ringdown

Authors: Yi-Fan Wang, Sizheng Ma, Neev Khera, Junquan Su, Huan Yang,

Comments: 16 pages, 11 figures, substantially revised in v2. Data release at https://github.com/yi-fan-wang/nonlinear-ringdown-GW250114. Comments welcome!

Subjects: gr-qc astro-ph.HE

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

Gravitational-wave astronomy, by detecting ripples in spacetime, has opened a new window to observe compact objects and probe theories of gravity in the nonlinear strong-field regime. The ringdown signal of a binary BLACK HOLE merger contains a superposition of damped sinusoids known as quasi-normal modes (Ref.[1]), whose frequencies are completely determined by the mass and spin of the remnant BLACK HOLE and form the basis of BLACK HOLE spectroscopy (Refs.[2-4]). A crucial prediction yet to be observationally confirmed is the existence of quadratic quasi-normal modes, which represent fundamental properties associated with wave-wave coupling in general relativity, and the leading mode is predicted to be detectable with next-generation ground-based detectors (Refs.[5-7]) using traditional methods. Here we show the first observational evidence for a set of quadratic quasi-normal modes in the ringdown of the binary BLACK HOLE merger GW250114, the loudest gravitational-wave event detected to date, enabled by a novel analysis. These nonlinear modes result from the quadratic coupling of the linear $(2,2,n)$ modes with $n\leq3$. Starting the analysis at a time corresponding to four times the remnant mass ($M_\mathrm{f}$) after the merger, the evidence for their presence reaches a Bayes factor of 62. A phenomenological test allowing these modes to deviate from the theoretical prediction rejects the zero-amplitude hypothesis at a significance of 3.4 $σ$, while the inferred amplitude and complex frequency are consistent with the prediction of general relativity. This finding provides the first observational evidence of gravitational wave-wave interaction and extends BLACK HOLE spectroscopy from the linear to the nonlinear regime. It also establishes a new direction for testing the fundamental nonlinear structure of general relativity with the most extreme gravity.

[abstract 26 / 39] (score: 2)
arXiv:2602.21004 [pdf, ps, other]

Title: Molecular bipolar outflow in SN 1987A supports the jittering-JETs explosion mechanism

Authors: Noam Soker,

Comments: International Journal of Astronomy and Astrophysics (IJAA)

Subjects: astro-ph.HE

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

I examine high-quality CO and SiO molecular maps of the core-collapse SUPERNOVA (CCSN) remnant SN 1987A from the literature and find that the molecular gas exhibits a bipolar structure, correlated with the visible bipolar morphology (termed the keyhole) and the bipolar morphology of the iron emission map. I apply a method commonly used in the study of JET-shaped planetary nebulae. The keyhole has a morphology similar to that of many JET-shaped pairs of bubbles in cooling-flow clusters of galaxies and planetary nebulae. Therefore, the findings of this study, which make the bipolar structure of SN 1987A robust, strengthen the claim that a pair of energetic JETs shaped the keyhole and its surroundings. According to the jittering-JETs explosion mechanism (JJEM), this pair of JETs was the most energetic of several pairs that exploded SN 1987A. This study adds to the accumulating evidence that the JJEM is the primary explosion mechanism for CCSNe, responsible for the majority, if not all, CCSNe.

[abstract 27 / 39] (score: 2)
arXiv:2606.01853 [pdf, ps, other]

Title: Possible High-Energy Neutrino Emission from Dark Matter Annihilation in the Disrupting Dwarf Galaxy Boötes~III

Authors: Shunhao Ji, Zhongxiang Wang,

Comments: 7 pages, 6 figures, accepted for publication in Physical Review D

Subjects: astro-ph.HE

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

We report the first search for high-energy neutrino emissions from DARK MATTER (DM) annihilation in stellar-stream cores. Motivated by a recent gamma-ray study that proposed these cores as a new class of indirect DM targets, we analyze three stream cores in the Northern Hemisphere using the public ten-year track-like neutrino data released by IceCube. Under the $χχ\toν\barν$ annihilation hypothesis, the most significant excess among the three targets is found at the position of the nearby dwarf galaxy Boötes~III, the core of the Styx stream, with the DM mass of $m_χ\simeq10$--$31~{\rm TeV}$. The excess has a post-trial significance of $3.1σ$. Considering the existing IceCube dwarf-galaxy limit for the same channel, we obtain a limit on the J-factor $J_{\rm ann}$, $\log_{10}(J_{\rm ann}/{\rm GeV^2\,cm^{-5}})\gtrsim 19.1^{+0.3}_{-0.5}$. This limit is broadly consistent with empirical estimates of $J_{\rm ann}$ for Boötes~III. The results provide the first candidate target with a possible HE neutrino signal associated with DM annihilation. This neutrino excess and the general existence of DM-induced neutrino signals from other similar sources will be confirmed with the near-future large high-energy neutrino detectors, thus enabling us to probe the nature of DM particles.

[abstract 28 / 39] (score: 2)
arXiv:2606.04887 [pdf, ps, other]

Title: A Reduced-Order Particle-in-Cell Method with Azimuthal Fourier-Decomposed Fields for Nominally Axisymmetric Plasmas

Authors: Shaun Andrews,

Comments: 26 pages, 11 figures; Accepted for Publication in Physics of Plasmas

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

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

A reduced-order Particle-in-Cell method is introduced for kinetic simulation of otherwise axisymmetric cylindrical plasmas that exhibit azimuthal instabilities. The method spatially decomposes all field quantities into a small number of azimuthal Fourier modes $m=0,...,N_m,\quad N_m \ll N_θ$, reducing the costly three-dimensional field solve $\mathcal{O}(N_zN_rN_θ)$ to a family of decoupled independent two-dimensional problems $\mathcal{O}((N_m+1)N_zN_r)$ on the meridional plane - one per mode - while particles continue to move in full three-dimensional space. Fields are reconstructed at particle positions by coherent superposition of these modal contributions, preserving complete azimuthal variation at a fraction of the cost of a conventional three-dimensional simulation. For initial validation, the method is tested against two benchmark problems with restricted axial dimension: The diocotron instability of a hollow electron annulus across three geometrically distinct configurations, recovering linear growth rates and eigenpotential structures within 7% of closed-form analytic predictions, and reproducing the non-linear vortex dynamics characteristic of the instability saturation; and a further benchmark against the community-standard Landmark Penning discharge problem recovers the rotating-spoke frequency, radial plasma profiles, and modal energy hierarchy in quantitative agreement with long-time reference simulations, at approximately 640 CPU-hours - a factor of 46 speed-up compared to the median benchmark cost. The approach represents a step toward addressing the important gap between computationally prohibitive full three-dimensional kinetic simulation and the physically limited reduced-dimensionality models on which predictive modelling of anomalous transport in MAGNETised plasma devices currently relies.

[abstract 29 / 39] (score: 2)
arXiv:2607.14982 [pdf, ps, other]

Title: Testing the Isotropy of the Universe with the CHIME/FRB Catalog I

Authors: Jun-Yi Shen, Yuan-Chuan Zou,

Comments: 14 pages, 3 figures, submitted to PRD

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

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

We test the isotropy of the Universe using 536 Fast Radio Bursts (FRBs) from the first CHIME/FRB catalog, employing two complementary statistical methods: the two-point angular correlation function (2PACF) and the sigma-map method, with observational biases corrected using CHIME injection data. Both analyses are consistent with the isotropic expectation, but are limited by the small sample size. The 2PACF suffers from an ill-conditioned covariance matrix, preventing robust parameter inference. The sigma-map angular power spectrum shows no statistically significant directional anisotropy, though the uncertainties at low multipoles remain large. Future FRB surveys are expected to improve these limitations.

[abstract 30 / 39] (score: 2)
arXiv:2608.27560 [pdf, ps, other]

Title: Resolved Dust in $z\approx1$ Galaxies with JWST/MIRI MRS: Survey Description and First View on PAHs, Mid-IR Atomic Emission, and Warm H$_2$

Authors: Wuji Wang, Andreas L. Faisst, Thomas S. -Y. Lai, Kyle Finner, Jed McKinney, Andrew J. Battisti, Irene Shivaei, Leindert A. Boogaard, Daizhong Liu, Yu-Heng Lin, Lun-Jun Liu, Georgios Magdis, Vincenzo Mainieri, Alexander Rodriguez, John D. Silverman, Zhaoxuan Liu, Minju M. Lee, Ghassem Gozaliasl, Maximilien Franco,

Comments: Accepted for publication in ApJ; main text 20 pages, 12 figures, 3 Tables

Subjects: astro-ph.GA

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

Dust is a key component of galaxies that regulates their thermal balance and, consequently, STAR FORMATION and the build-up of stellar mass. Polycyclic aromatic hydrocarbons (PAHs) are responsible for reprocessing radiative energy of the galaxies thus tracing dust evolution. Using JWST/MIRI MRS, we present the first resolved view of the PAHs and mid-infrared emission lines in a sample of eight $z\approx1$ galaxies. A key novelty is our ability to directly map PAH emission near the end of cosmic noon at JWST's limits. The sample is selected to be on the star-forming main-sequence with stellar masses $M_{\star}=10^{10.6-11.2}\,M_{\odot}$ and infrared luminosities $L_{\rm IR}=10^{11.5-11.9}\,L_{\odot}$. Two of them contain ACTIVE GALACTIC NUCLEi (AGN), and two are interacting systems. We detect and quantify primary PAH emissions from 3.3$\,\rm μm$ to 11.3$\,\rmμm$ throughout the galaxies, alongside atomic fine structure lines (Ar, Ne, and Fe), Br$α$, and H$_{2}$ rotational transitions. Through PAH ratio diagnostics and comparison to theoretical models, we qualitatively probe the physical properties of PAH molecules, i.e., size and charge. The AGN and mergers in our sample exhibit a higher fraction of neutral PAHs, possibly related to high radiation intensity and/or shocks, as suggested by increased atomic and H$_{2}$ line ratios. Leveraging the IFU data, we find that the grain sizes of the centrally located PAHs tend to be larger and less ionized than those in the outskirts of the galaxies. Finally, we compare our results to observations of PAHs in local and similar-redshift galaxies, revealing a potential evolutionary trend when controlling $L_{\rm IR}$.

[abstract 31 / 39] (score: 2)
arXiv:2609.10688 [pdf, ps, other]

Title: Energy deposition in planetary and exoplanetary atmospheres induced by COSMIC RAYs

Authors: Jesse Polman, Ingo Leya,

Comments: Accepted to A&A. 13 pages, 9 figures

Subjects: astro-ph.EP astro-ph.HE

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

Cosmic rays can significantly alter the abundances of certain species in the upper layers of planetary atmospheres, especially in terms of their biosignatures. To fully understand the extent of this effect, it is essential to accurately model the interactions of COSMIC RAYs with planetary MAGNETic fields. We used the CosmicTransmutation code to study the effect of a planetary MAGNETic field on the flux of galactic COSMIC RAYs and stellar energetic particles. We found that both particle sources are significantly affected by MAGNETic fields, even though the effects are different due to the varying energy ranges that characterize each source. The stellar energetic particle energy flux is significantly higher for an Earth-like planet with no MAGNETic field, but with a MAGNETic field of 30\,$μ$T or higher, the energy flux of the two sources becomes comparable. We find that the atmospheric pressures the COSMIC RAYs reach are significantly lower than those found in previous studies using simpler models and that the effect of the atmospheric composition on this outcome is small. We found similar results using the model for the exoplanet K2-18b, even though the radius is significantly larger than Earth's. Because the two COSMIC RAY sources cover different energy ranges and are affected by the MAGNETic field in different ways as a result, both sources should be considered. Future studies should focus on combining an accurate modelling procedure of the interaction between COSMIC RAYs and planetary MAGNETic fields with atmospheric chemistry models. This will require general circulation models to capture the latitudinal and longitudinal dependencies in full.

[abstract 32 / 39] (score: 2)
arXiv:2609.17680 [pdf, ps, other]

Title: A dense, metal-rich absorber driven by a heavily dust-obscured galaxy: The direct evidence of CGM enrichment at $z\sim7$

Authors: Qinyue Fei, Seiji Fujimoto, Gabriel Brammer, Lise Christensen, Marianne Vestergaard, Rohan P. Naidu, Robert A. Simcoe, Norman Murray, Luis C. Ho, Ruancun Li, Volker Bromm, Javier Álvarez-Márquez, Hollis B. Akins, Yoshihisa Asada, Simona Di Stefano, Kohei Inayoshi, Vasily Kokorev, Jorryt Matthee, Romain A. Meyer, Ava Polzin, Francesco Valentino, Fabian Walter, Marcel Neeleman, Fengwu Sun, Yunjing Wu, Mengyuan Xiao,

Comments:

Subjects: astro-ph.GA

Created: 2026-09-15; Updated: 2026-09-17; Datestamp: 2026-09-17

We report the serendipitous discovery of a dense, metal-enriched circumgalactic medium (CGM) absorber at z=7.03, together with its host galaxy, identified along the sightline toward a red QUASAR. The absorber exhibits the largest rest-frame equivalent widths and column densities observed to date at z>5, tracing a metal-enriched gaseous halo. Using deep JWST/NIRSpec and NOEMA observations, we characterize the absorber's physical properties and identify its host, ND1, as a vigorously star-forming galaxy at an exceptionally close impact parameter of ~16kpc, so heavily dust-obscured that it is detected only in the longest-wavelength NIRCam bands. Detections of [OIII]$λ$5007, H$α$, and [CII]$λ158\,μ$m emission anchor the systemic redshift to z~7.0321, revealing a coherent ~50km/s blueshift of the absorbing gas relative to the host, suggesting outflow-driven metal transport into the halo. The outflow velocity, combined with the measured column density, implies an outflow rate of $\dot{M}_{\rm out}=64 M_\odot\,yr^{-1}$ and a mass loading factor $η=3$, indicating an energetic, chemically-enriched wind launched from a dust-obscured starburst. While the overall ionization state and [Mg/Fe] ratio align with empirical cosmic evolutionary trends, the absorber displays an enhanced carbon-to-oxygen ([C/O]) ratio. This abundance pattern suggests the nucleosynthetic yields of Population~III stellar explosions, and aligns with the host's star-formation history extending to $z \gtrsim 8$, potentially offering a rare fossil record of primordial metal enrichment. Our findings demonstrate that intense star-formation feedback can rapidly and efficiently pollute the CGM/IGM well into the Epoch of Reionization. The NIR-dark nature of the host further implies that rest-UV surveys may systematically miss the dusty sources that drive CGM- and IGM-scale metal enrichment in the early Universe.

[abstract 33 / 39] (score: 2)
arXiv:2609.18006 [pdf, ps, other]

Title: A Possible Hidden Hot Halo Component Revealed by Joint X-ray and Sunyaev--Zel'dovich Observations

Authors: Jiang-Tao Li, Rui Huang, Joel N. Bregman, Q. Daniel Wang, Cameron Pratt,

Comments: 11 pages, 6 figures, 1 table, published by ApJ on September 18. Related press release: http://english.pmo.cas.cn/research/rp/202609/t20260915_1200453.html

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

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

Massive galaxies are expected to host extended halos of hot gas that contain a substantial fraction of their baryons and feedback energy. X-ray observations probe the dense, X-ray-bright component of this circumgalactic medium (CGM), while the thermal Sunyaev-Zel'dovich (SZ) effect is also sensitive to lower-density gas through its integrated thermal pressure. We present the first spatially resolved joint X-ray and SZ analysis of a massive isolated disk galaxy, using deep XMM-Newton observations of NGC 4594 from the X-raying the Accretion Reservoir Transferred to the ATmosphere Orbiting a Massive Spiral (XART-ATOMS) program, together with multiple independent Planck-based SZ reconstructions. The measured SZ signal in the inner halo appears to exceed the value predicted from the X-ray-derived gas properties, even after accounting for major systematic uncertainties. Our preferred interpretation is that an additional lower-density CGM component contributes little to the observed soft X-ray emission but carries substantial thermal pressure. Under a simple two-phase model in approximate pressure equilibrium, the most probable X-ray-to-SZ ratio implies that the detected X-ray-emitting gas occupies only a small fraction of the halo volume, with a characteristic filling factor of f_X ~ (4-6)x10^-3 near r~50 kpc. Such a small filling factor implies that single-phase X-ray analyses can underestimate the baryon mass contained in the hot CGM by a factor of ~2.5, while the thermal energy content of the CGM is underestimated by about one order of magnitude. The non-detection of the additional component in the X-ray spectra requires it to be very hot and/or spatially extended, so weak in the soft X-ray emissions. These results favor the presence of a "hidden" X-ray-faint hotter halo component, while alternative interpretations, including a nonthermal contribution, are not excluded.

[abstract 34 / 39] (score: 2)
arXiv:2609.18026 [pdf, ps, other]

Title: MLegS: A modern mapped Legendre spectral method solver for unbounded domains with parallelization

Authors: Sangjoon Lee, Jinge Wang,

Comments: 34 pages, 12 figures, and 2 tables

Subjects: physics.comp-ph cs.NA math.NA

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

MLegS is an open-source Modern Fortran code package for solving linear and nonlinear time-dependent partial differential equations on radially unbounded domains. It builds on an earlier in-house prototype, recasting it as a modular solver with a unified interface for fields, transforms, and spectral operators. Within this framework, the numerical formulation maps $0\leq r<\infty$ onto a finite interval, where associated Legendre functions provide the radial basis, while Fourier series represent the periodic azimuthal and axial directions. The mapped radial basis represents radial infinity without imposing an artificial boundary condition at finite radius while incorporating the regularity required at $r=0$ according to azimuthal order. The implementation distributes the corresponding field layouts using the Message-Passing Interface (MPI), with strong- and weak-scaling measurements extending to 512 cores across four compute nodes. Beyond parallel performance, three examples assess the solver across diffusion, reaction-diffusion, and vortex dynamics: closed-form diffusion solutions establish spectral spatial convergence and the design orders of both semi-implicit integrators; a Fisher-Kolmogorov-Petrovsky-Piskunov front matches the linearized solution and propagates at the classical speed within its logarithmic correction; and vortex-pair simulations based on toroidal-poloidal decomposition yield a measured Crow growth rate $2.7\%$ above the theoretical prediction and demonstrate the RECONNECTion of the vortex pair.

[abstract 35 / 39] (score: 2)
arXiv:2609.18097 [pdf, ps, other]

Title: Improved lattice Boltzmann method for conjugate MAGNETohydrodynamic simulations

Authors: Jun Li, Wai Hong Ronald Chan, Kun Ting Eddie Chua,

Comments: The first conjugate MHD simulations by an improved LBM

Subjects: physics.comp-ph

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

In the simulation of conjugate MAGNETohydrodynamic (MHD) flows, where a moving conducting fluid dynamically interacts with bounding conducting walls under the influence of an externally imposed MAGNETic field, resolving the electrical conductivity transition across the fluid-solid interface introduces significant numerical challenges. In problems with high MAGNETic Reynolds numbers, it is required to solve the full MAGNETic induction formulation that has a curl-of-curl term for the MAGNETic diffusion, which is simplified to a divergence term in the original vector-valued lattice Boltzmann method (LBM). The resulting LBM scheme is valid for simulating fluid domains with a constant conductivity where its bounding solid walls are modelled using appropriate boundary conditions. The current study shows that this scheme is also valid for two-dimensional conjugate MHD simulations where the MAGNETic field component with non-zero gradients is perpendicular to the conductivity gradient. For general conjugate MHD simulations, we improve the LBM scheme by considering the difference between the curl-of-curl term and the simplified divergence form, which is treated as a source term in the LBM evolution algorithm and computed using an efficient LBM discretisation scheme. The improved LBM scheme automatically satisfies the required conjugate constraints at the fluid-solid interface as a volume integral inside two adjacent boundary layers. The accuracy of the improved LBM scheme is verified by piecewise analytical solutions in benchmark problems with an abrupt conductivity jump across the fluid-solid interface.

[abstract 36 / 39] (score: 2)
arXiv:2609.18102 [pdf, ps, other]

Title: Cat's cradle diagrams for substructure studies

Authors: Peter Skands,

Comments:

Subjects: hep-ph

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

We propose Cat's Cradle diagrams as a framework to analyse the perturbative accuracy of gauge quantum field theories across different kinematic regions, interpolating between the power countings of fixed-order perturbation theory and soft-collinear resummation. We propose a simple intermediate counting aimed at quantifying parametric accuracy for resolved JET substructure, nested so that $N^nLO \subset N^nLJ \subset N^{n+1}LL$. We show that the resolved JET-substructure power counting, $N^nLJ$, emphasises contributions that are important for resolved substructure but which are lumped together with less dominant terms in both of the two other countings. It may therefore furnish a complementary quantification of relative parametric accuracy in a kinematic region "midway" between the hard (fixed-order) and soft-collinear (resummation) regimes. We discuss practical applications to parton showers, in the context of a hard process with a characteristic hard scale of order 200 GeV.

[abstract 37 / 39] (score: 2)
arXiv:2609.18233 [pdf, ps, other]

Title: Toward Autonomous Radio Follow-up of Multi-messenger Transients with RADAR: From Alert Parsing to Inference and Observation Scheduling

Authors: Mihael Hategan-Marandiuc, Tanner O'Dwyer, Alessandra Corsi, Eliu Huerta, Zilinghan Li, Ian T. Foster, Kyle Chard, Ryan Chard, Amal Gueroudji,

Comments: 22 pages, 3 figures, 5 tables

Subjects: astro-ph.HE astro-ph.IM

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

Multi-messenger astronomy (MMA), the joint study of cosmic sources through gravitational waves (GWs), electroMAGNETic (EM) radiation, neutrinos, and COSMIC RAYs, is rapidly reshaping time-domain astrophysics. Realizing the promise of MMA will require coordinating heterogeneous observing resources and automating the chain from alert to analysis to follow-up. RADAR (Radio Afterglow Detection and AI-driven Response) is a federated, privacy-enhancing framework for the radio follow-up of GW events, previously validated on GW170817. Here, we extend it along three axes. First, we benchmark three large language models (LLMs; GPT-5.5, Claude-Opus-4.7, and Gemini-3.5-Flash) against the GW170817 radio light curve dataset. GPT-5.5 attains the highest event-level $F_1$ score, the harmonic mean of precision and recall, at $0.893 \pm 0.010$, and the highest GCN-level recall, $0.794 \pm 0.013$, improving on previous GPT-4.1 results by 16\% and 10\%, respectively, while Claude-Opus-4.7 achieves the highest precision, $0.978 \pm 0.014$. Second, we introduce concurrent likelihood evaluation, which speeds up the MCMC computation by a factor of $40\times$ over our previous results. Third, we present an LLM-driven scheme that converts natural-language observing requests into submission-ready scheduling blocks for the Karl G. Jansky Very Large Array. Together, these developments advance RADAR toward a scalable, largely autonomous system for GW radio follow up.

[abstract 38 / 39] (score: 2)
arXiv:2609.18523 [pdf, ps, other]

Title: WFST Follow-up of S251112cm: Searching for an Optical Counterpart to a Subsolar-mass Compact-binary Merger Candidate

Authors: Zhengyan Liu, Zelin Xu, Ji-an Jiang, Wen Zhao, Zhiping Jin, Zigao Dai, Dezheng Meng, Yefei Yuan, Xuefeng Wu, Lulu Fan, Xu Kong, Xander J. Hall, Brendan O'Connor, Feng Li, Ming Liang, Binyang Liu, Zhen Wan, Hairen Wang, Jian Wang, Tinggui Wang, Hongfei Zhang, Xianzhong Zheng, Qingfeng Zhu,

Comments: 15 pages, 8 figures, 2 tables. Submitted

Subjects: astro-ph.HE

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

ElectroMAGNETic counterparts to gravitational-wave (GW) sources probe the properties, environments, and evolution of compact-object mergers. S251112cm belongs to an emerging class of GW candidates with possible subsolar-mass components. We present an optical counterpart search for S251112cm with the Wide Field Survey Telescope (WFST). The observations began 20.2 hr after the GW trigger and continued for three nights, covering approximately $780~\mathrm{deg}^{2}$ and $51\%$ of the localization probability in the updated skymap. We searched for newly emerging, rapidly evolving, off-nuclear optical transients and identified four candidates whose host-galaxy distances are broadly consistent with the GW distance estimate. However, all four evolve substantially more slowly than AT 2017gfo, ruling out an AT 2017gfo-like origin and disfavoring their association with S251112cm as rapidly evolving kilonova counterparts. Combining WFST and DECam observations increases the covered localization probability to approximately 67%. Conditional on the counterpart lying within this footprint, we constrain a grid of binary-neutron-star kilonova models. For viewing angles $θ_{\rm obs}<60^{\circ}$, with the other parameters fixed to the best-fitting values for AT 2017gfo, models with dynamical ejecta mass $M_{\rm dyn}\gtrsim0.01\,M_{\odot}$ or wind ejecta mass $M_{\rm wind}\gtrsim0.05\,M_{\odot}$ are disfavored over most of the covered GW probability. Beyond kilonova models, our phenomenological analysis constrains rapidly evolving optical transients with $T_{\rm rise,1/2}\leq2$ days to peak absolute magnitudes fainter than approximately -13 mag. To our knowledge, the coordinated WFST and DECam observations provide the strongest optical constraints to date on possible rapidly evolving counterparts to this new class of GW candidates involving subsolar-mass compact objects.

[abstract 39 / 39] (score: 2)
arXiv:2609.18883 [pdf, ps, other]

Title: Helicon wave propagation, plasma generation and interaction with low-frequency waves in toroidal MAGNETic configurations

Authors: Simon P. H. Vincent, Mounir Alfazzaa, Patrick Quigley, Cyrille Sepulchre, Philippe Guittienne, Rémy Jacquier, Marcelo Baquero-Ruiz, Ivo Furno,

Comments:

Subjects: physics.plasm-ph

Created: 2026-09-16; Updated: 2026-09-17; Datestamp: 2026-09-17

Helicon waves are widely used for efficient plasma production in low-temperature devices and have recently attracted attention as a candidate for current drive in fusion plasmas. Yet experimental investigations of helicon waves in toroidal geometries, and of their interaction with plasma dynamics, remain extremely limited. In this work, we present, to our knowledge, the first detailed experimental characterization of helicon waves in a toroidal configuration. A birdcage resonant antenna operating at 13.56 MHz is used to launch helicon waves in the toroidal basic plasma physics device TORPEX, either into a pre-existing MAGNETron-generated plasma, or as the plasma source. Measurements are performed in pure toroidal and simple MAGNETized torus MAGNETic configurations, for both argon and hydrogen plasmas. Three-axis MAGNETic probe measurements enable clear identification of a dominant m=+1 helicon mode over our parameter space. The helicon amplitude is found to scale linearly with the antenna power, and decreases with the confining MAGNETic field amplitude. As the antenna power is increased the helicon amplitude exhibits a saturation, correlated with enhanced low-frequency fluctuations and turbulent transport. In addition, a strong interaction between helicon waves and low-frequency density fluctuations is observed, revealing a non-linear coupling between RF waves and plasma turbulence. These results provide the first detailed experimental characterization of helicon waves in a toroidal low-temperature plasma device and establish TORPEX as a unique testbed for studying toroidal helicon wave physics under controlled and well-diagnosed conditions.