Current date: 2026-08-12
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Created/updated limit: 2026-08-05 (7 days ago)
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Scoring abstracts
Number of records retrieved: 735
Keyword score statistics
score 11 -- 3 abstracts
score 10 -- 1 abstracts
score 9 -- 1 abstracts
score 5 -- 1 abstracts
score 4 -- 4 abstracts
score 3 -- 7 abstracts
score 2 -- 17 abstracts
in total -- 34 abstracts
Articles that appeared on 2026-08-12
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[abstract 1 / 34] Wow! (score: 11)
- Title: PACHA: Probing AGN Coronae with High-redshift AGNAuthors: Xiurui Zhao, Elias Kammoun, Marco Ajello, Yanfei Jiang, Giorgio Lanzuisi, Anne Lohfink, Stefano Marchesi, Elena Bertola, Peter G. Boorman, Francesca Civano, Luca Comisso, Paolo Coppi, Isaiah S. Cox, Martin Elvis, Roberto Gilli, Fiona A. Harrison, Ross Silver, Daniel Stern, Nuria Torres-Alba, Qian Yang, Lizhong Zhang,Comments: 31 pages, Accepted to ApJ, 16 figures, 6 tablesSubjects: astro-ph.HE astro-ph.GACreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
The X-ray emission of ACTIVE GALACTIC NUCLEi (AGN) is generally attributed to inverse Compton scattering of accretion-disk photons by hot electrons in a compact corona. In local AGN, directly constraining coronal properties is challenging because the high-energy cutoff often lies beyond the NUSTAR bandpass. High-redshift, luminous QUASARs enable systematic constraints on the high-energy cutoff, as cosmological redshift shifts the spectal cutoff into the observable hard X-ray band. We present first results from the ``Probing the AGN Coronae with High-redshift AGN'' (PACHA) project, based on quasi-simultaneous NUSTAR and XMM-Newton observations of 13 radio-quiet AGN at $z>1$. We constrain the high-energy cutoff and coronal temperature at 90\% confidence level for 10 and 9 sources, respectively. The sample exhibits a mean cutoff energy of $E_{\rm cut}=80.8\pm8.1$ keV and a mean coronal temperature of $kT_{\rm e}=18.4\pm1.6$ keV, both significantly lower than those measured in local {\it SWIFT}-BAT AGN, while the mean optical depth ($τ=4.8\pm0.3$) is significantly higher. The uncertainties are at 1~$σ$. Combining our high-redshift sample with local AGN, we find a potential anti-correlation between cutoff energy and both X-ray luminosity and BLACK HOLE mass, with no significant dependence on Eddington ratio. Within a hybrid coronal framework, the inferred temperatures lie well below the pair-production limits for purely thermal coronae, indicating a substantial efficient Compton cooling and/or non-thermal electron component. The detection of low coronal temperatures in high-luminosity AGN is broadly consistent with predictions from recent radiation MHD simulations that consider purely thermal electron populations, implying that non-thermal electrons may not be the primary drivers of the observed coronal properties in these systems.
[abstract 2 / 34] Wow! (score: 11) - Title: Upstream neutrino production and delayed JET emission in the BLAZAR GB6 J1542+6129Authors: Emma Kun, Imre Bartos, Breshna Hadi, Anna Göblyös, Julia Becker Tjus, Peter L. Biermann, Anna Franckowiak, Francis Halzen, Santiago del Palacio, Claudio Ricci,Comments: 5 pages, 2 figures. Accepted to publish in A&ASubjects: astro-ph.HECreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
We present a multimessenger case study of the BLAZAR GB6 J1542+6129, examining whether its multiwavelength behavior is consistent with neutrino production in a compact region near the central BLACK HOLE, or with the parsec-scale radio JET. We perform a multimessenger analysis combining ~17 years of FERMI-LAT gamma-ray data with ~14 years of VLBI/MOJAVE. These are compared to the temporal properties of a suspected IceCube neutrino flare with a duration of $147^{+110}_{-25}$ days, enabling a direct test of spatial and causal connections between neutrino and electroMAGNETic emission regions. We find that the suspected neutrino flare appears to precede both a $γ$-ray flare and a pronounced increase in the VLBI core Doppler factor by up to ~1 year. The duration of the post-flare $γ$-ray activity is comparable to that of the neutrino flare, which, in our framework, is consistent with both signatures originating from a single propagating disturbance whose temporal structure is preserved during the propagation. The gamma-ray spectral energy distribution remains consistent in shape across the full, flare, and post-flare intervals, indicating stable particle acceleration conditions. The temporal ordering, taken at face value, places the neutrino production site upstream of the VLBI core. The observations of GB6 J1542+6129 are consistent with a disturbance-driven, multi-zone scenario in which neutrinos are produced in a compact, photon-rich inner region upstream of the parsec-scale VLBI core, plausibly at the coronal region, while the same disturbance later enhances Doppler-boosted leptonic emission once it reaches the radio core. While the data alone do not strictly establish this scenario on a population level, they show how time-domain multimessenger observations of a single AGN can localize neutrino emission relative to the parsec-scale radio JET in a particular source.
[abstract 3 / 34] Wow! (score: 11) - Title: Decoding the JET of BL Lacertae using RELATIVISTIC MAGNETo-hydrodynamicsAuthors: G. F. Paraschos, J. A. Kramer, I. Liodakis, S. G. Jorstad, A. P. Marscher, I. Myserlis, I. Agudo,Comments: 9 pages, 5 figures, accepted by A&ASubjects: astro-ph.HE astro-ph.GACreated: 2026-08-10; Updated: 2026-08-12; Datestamp: 2026-08-12
Blazars are a highly variable subclass of ACTIVE GALACTIC NUCLEi, whose RELATIVISTIC JET is pointed towards our line of sight at a small angle. Their variability is often characterised by multi-band flares. BL Lacertae (BL Lac), the namesake of a BLAZAR subclass recently exhibited the highest recorded linearly polarised optical flare. We investigate the origin of this flare via very-long-baseline interferometry observations. Our analysis shows that the sweeping, helical motion of the BL Lac JET, which is known to exhibit kink-like instabilities, can explain the observed flux density spike and polarisation angle rotation, as also confirmed by our state-of-the-art RELATIVISTIC MAGNETo-hydrodynamic simulations. As a by-product of these simulations we find that baryon loading of the JET is required to optimally replicate the observed JET morphology.
[abstract 4 / 34] Wow! (score: 10) - Title: Synchrotron-Regulated Relativistic Magnetohydrodynamic Turbulence: Emission, Polarization, and Faraday RotationAuthors: Xiaochen Sun, Luca Comisso Lorenzo Sironi, Anatoly Spitkovsky, Alexander Philippov,Comments: Submitted to AAS journalSubjects: astro-ph.HECreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
Relativistic MAGNETized plasmas in many high-energy astrophysical systems are both turbulent and strongly radiative, yet their nonlinear dynamics and radiative outcomes remain poorly understood. Here we present results from three-dimensional driven turbulence simulations in RELATIVISTIC MAGNETohydrodynamics with SYNCHROTRON cooling. We compute Faraday rotation measures, synthetic SYNCHROTRON spectra and linear POLARIZATION maps from the simulated turbulence. The balance between energy injection from turbulent driving and SYNCHROTRON cooling keeps the plasma, on average, RELATIVISTICally hot, thereby influencing the rotation measure. Synchrotron cooling triggers the thermal instability and drives the plasma into hot dilute and cold dense phases, which enhances the spatial and temporal variability of SYNCHROTRON emission, especially at high frequencies. These diagnostics show qualitative similarities to observations of fast radio bursts, pulsar wind nebulae, and BLAZARs, suggesting that turbulence may play an important role in shaping emission and propagation effects around high-energy sources.
[abstract 5 / 34] Wow! (score: 9) - Title: Explaining the X-ray Precursor, Ultra-long Prompt Emission, and Week-long Decay of GRB250702B with a Jetted Micro-TDEAuthors: Fulya Kıroğlu, Taeho Ryu, Alexander Tchekhovskoy, Kyle Kremer, Daichi Tsuna, Brian D. Metzger,Comments: 16 pages, 6 figures, submitted to ApJLSubjects: astro-ph.HECreated: 2026-08-10; Updated: 2026-08-12; Datestamp: 2026-08-12
The longest detected GAMMA-RAY BURST, GRB250702B, exhibited seven hours of prompt $γ$-ray emission, preceded by a soft X-ray precursor ($\sim1$ day earlier) and followed by a weeks-long fading X-ray tail. Lacking an established progenitor for all three phases, we propose that this ultra-long GRB (ULGRB) is powered by a JETted micro-tidal disruption event (micro-TDE), in which a spinning stellar-mass BLACK HOLE (BH) disrupts a Sun-like star and launches a RELATIVISTIC JET via the Blandford-Znajek mechanism. Micro-TDE debris disks have hours-to-days viscous timescales, naturally explaining ULGRB durations. Using 3D hydrodynamic AREPO simulations of a $1\,M_\odot$ star disrupted by a $10\,M_\odot$ BH, we show that within $\sim1$ day the debris forms a quasi-steady envelope with a low-density polar funnel ($ρ\propto r^{-2}$, half-opening angle $\approx15^\circ$). Applying an analytic JET-stability framework to these profiles, we find that the $r^{-2}$ funnel keeps the JET below the kink-instability threshold, enabling stable propagation and breakout for JET powers, $L_{\rm JET}\gtrsim10^{47}$ erg s$^{-1}$. We attribute the X-ray precursor to pre-disk stream-fed accretion; the prompt GRB to a tightly beamed JET ($θ_{\rm b}\lesssim1^\circ$, $L_{γ,\rm iso}\sim10^{51}$ erg s$^{-1}$) escaping the funnel, launched by a rapidly spinning BH ($a_\bullet\sim0.9$); and the weeks-long X-ray decline to disk-wind mass loss ($L_{\rm JET}\propto t^{-2}$) combined with JET widening ($θ_{\rm b}\propto t$, initially steepening the decay to $L_{\rm X,iso}\propto L_{\rm JET}/θ_{\rm b}^{2}\propto t^{-4}$). Our model reproduces the multi-phase evolution of GRB250702B and establishes JETted micro-TDEs as a physically motivated ULGRB engine.
[abstract 6 / 34] Yes (score: 5) - Title: An Optically Motivated Gamma-ray Study of FERMI-LAT NovaeAuthors: Owen K. Henry, Timothy A. D. Paglione, David Zurek, Joshua Tan,Comments: 12 pages, 3 figures, 1 tableSubjects: astro-ph.HECreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
High-energy (GeV) gamma-ray emission from nova eruptions was a surprise detection by the FERMI-LAT in 2010. Since then, it has been suggested that the gamma-rays from these systems are generated in collisionless non-RELATIVISTIC shocks. In this theory, the observed correlation between optical and gamma-ray nova lightcurves naturally arises if a portion of the optical luminosity is reprocessed shock power. In this work, we investigate this scenario by analyzing FERMI-LAT-detected novae in varied time bins and then correlating the bin size that maximizes the nova's significance (tgam) with the nova's optical eruption data. Furthermore, we investigate whether there is a common optical decay across the sources' measured tgam values in the population. We find that across our population, a nova's $t_3$ (the time it takes the nova V band brightness to decay 3 magnitudes) appears to be the favored analysis bin that optimizes the FERMI-LAT detection significance, although there is significant spread. Additionally, we report V679 Car, a source previously noted as a marginally detected gamma-ray nova, as a $>5 σ$ detection in this work. We perform cross-correlation analysis of gamma-ray and optical lightcurves.
[abstract 7 / 34] Yes (score: 4) - Title: How Flat is a Plateau? Evolution of Late-Time TDE DisksAuthors: Yael Alush, Nicholas C. Stone, Sjoert van Velzen,Comments: 13 pages, 9 figures, 9 tables. Comments are welcomeSubjects: astro-ph.HE gr-qcCreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
Late-time light curve plateaus in tidal disruption events (TDEs) are often approximated as flat and time-independent. This simplification is motivated by theoretical modeling of spreading late time TDE disks, which predicts slow light curve evolution. However, if time evolution can be detected, late-time light curves yield more information than previously accessible. In this work, we re-examine late-time TDE data to test how well the flat plateau assumption holds. We use Markov Chain Monte Carlo to estimate the maximum likelihood for a family of theory-agnostic models and apply the Akaike information criterion to find that roughly one third of our sample favors evolving plateaus, one third favors truly flat plateaus, and one third shows no statistically significant evidence for any plateau. Next, we refit the TDEs that exhibit statistically significant plateaus using a MAGNETically elevated $α$-disk model, motivated by the lack of clear thermal instability in late time TDE light curves. From these model-dependent fits, we obtain estimates for the supermassive BLACK HOLE (SMBH) mass, the mass of the disrupted star, and $α$. Fitted $α$ values have a mean $α=10^{-1.5}$, with scatter of 1 dex, broadly consistent with results from MAGNETohydrodynamic simulations, albeit with some outliers. Finally, we estimate the timescales of disk precession in MAGNETically elevated TDE models. Theoretically, we find that disk precession times may be orders of magnitude shorter than in unMAGNETized Shakura-Sunyaev disks, and grow in time as $T_{\rm prec}\propto t^{35/36}$; empirically, by using fitted $α$ parameters, we estimate that late time disks may experience $\sim$few-10 precession cycles.
[abstract 8 / 34] Yes (score: 4) - Title: The GMRT High-Resolution Southern Sky Survey for pulsars and transients -- VIII: Orbital Variability and the Evolution of a 1-Day He-WD Millisecond Pulsar J2101-4208Authors: Ankita Ghosh, Bhaswati Bhattacharyya, David L. Kaplan, David A. Smith, Andrew Lyne, Jayanta Roy, Laila Vleeschower, Gabriella Agazie, Lankeswar Dey, Sangita Kumari, Ujjwal Panda,Comments: Accepted for publication in the ApJSubjects: astro-ph.HECreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
We present timing and orbital phase-resolved polarimetry of the millisecond pulsar (MSP) J2101$-$4802, having a spin period of 9.48~ms and dispersion measure (DM) $25.05\ \mathrm{pc\ cm^{-3}}$ discovered with the Giant Meter Radio Telescope (GMRT). From the phase-connected timing of this MSP spanning 3.7 years, we identify that PSR J2101-4802 is in a $\sim$1-day binary orbit with a likely helium-white-dwarf (He-WD) companion having a median companion mass of $\simeq0.15\, M_\odot$, consistent with canonical recycling in the Galactic field. The timing solution further reveals an unusually large orbital period derivative, $\dot{P}_b$ ($\sim10^{-11}\,{\rm s\,s}^{-1}$), compared to typical Galactic-field MSP--HeWD binaries, which cannot be explained by the contributions from kinematic effects (Shklovskii and Galactic acceleration) or general-RELATIVISTIC damping. Using wideband, full-Stokes observations, we also trace the linear and circular POLARIZATION variation across the orbital phase and fit a rotating-vector model (RVM) to its position-angle swing across the pulse phase, yielding constraints on the emission geometry (MAGNETic inclination and impact angle) of this system. The combination of a $\sim$1-day orbit, $\sim0.15\,M_\odot$ companion, modest spin-down power, unusually large $\dot{P}_b$, and phase-locked MAGNETized intrabinary plasma signatures suggests that PSR~J2101$-$4802 represents a transitional system linking redback-like spiders to detached He--WD MSP binaries.
[abstract 9 / 34] Yes (score: 4) - Title: Discovery of four Narrow-line Type-1 Quasars at z = 2.54 -- 6.06 with Subaru 'Onohi'ula PFS-SSPAuthors: Ayumi Takahashi, Yoshiki Matsuoka, Yoshiki Toba, Tohru Nagao, Toshihiro Kawaguchi, Hiroaki Sameshima, Alberto Rodr\'ıguez-Ardila, Andy D. Goulding, Masayuki Akiyama, Denimara Dias dos Santos, Atsushi Hoshi, Kohei Ichikawa, Masatoshi Imanishi, Kazushi Iwasawa, Mitsuru Kokubo, Huynh Anh N. Le, Khee-Gan Lee, Masafusa Onoue, Masayuki Tanaka, Patrice Theulé, Hao Zhang, Jialai Wang, Xinfeng Xu, Yongquan Xue,Comments: 15 pages, 8 figures, submitted to PASJSubjects: astro-ph.GACreated: 2026-08-10; Updated: 2026-08-12; Datestamp: 2026-08-12
We report the discovery of four narrow-line type-1 QUASARs (NLQ1s) from the Subaru 'Onohi'ula Prime Focus Spectrograph Subaru Strategic Program (PFS-SSP). To extend a comprehensive understanding of this population to the distant universe, we searched for broad-line AGNs (QUASARs) whose rest-UV spectral shapes resemble those of local NLS1 galaxies, utilizing the Ly$α$ line profile. We identified four NLQ1s, including one candidate, at $z=2.54$ -- $6.06$. The obtained spectra show a prominent Ly$α$ emission line with a very low continuum level. The measured full width at half maximum (FWHM) of Ly$α$ ranges from $1410 \ \mathrm{km\,s^{-1}}$ to $1510 \ \mathrm{km\,s^{-1}}$ with a mean of $\sim 1430 \,\mathrm{km\,s^{-1}}$. Although we used only line width information for the NLQ1 selection, the resulting equivalent widths (EW) of Ly$α$ are higher (the mean $\sim 190$\,Å\ in the rest frame) than the typical values of QUASARs. Two QUASARs have exceptionally large Ly$α$ luminosity, accounting for $\sim 3$ -- $4$\% of the bolometric luminosity. We measured BLACK HOLE masses and Eddington ratios for three objects whose C\,\textsc{iv} line is available. The resulting BLACK HOLE masses are $\sim 10^{6.9}$ -- $10^{7.7}\, M_{\odot}$ with high Eddington ratios ($> 0.1$), consistent with those of NLS1 galaxies reported in the low-$z$ universe. N\,\textsc{v} and C\,\textsc{iv} broad absorption lines are detected in one object. This QUASAR can be classified as a mini-BAL QUASAR, which further supports the idea that this NLQ1 is indeed a luminous version of an NLS1 galaxy.
[abstract 10 / 34] Yes (score: 4) - Title: Wind-confined JET collimation revealed by the acceleration-phase photosphere of GRB 220426AAuthors: Felix Ryde, Asaf Pe'er,Comments: Submitted. 12 pages + appendicesSubjects: astro-ph.HECreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
We analyze the prompt emission of the exceptionally bright GRB 220426A observed by FERMI/GBM, whose time-resolved spectra are among the narrowest measured in any GRB. Here we show that observations during the first $\sim 5$s are consistent with the signal being emitted while the JET was still in the initial radiation-dominated acceleration phase. The time-resolved spectra allow the effective launch radius, $r_0$, to be inferred with unusual precision. We find $r_0 \sim \mathrm{few} \times 10^{10}\,\mathrm{cm}$, increasing linearly with time. These findings match the theoretical predictions of the recollimation shock, suggesting that this GRB shows the first clear evidence for the existence and evolution of a recollimation shock. Using this interpretation, the linear increase observed is sustained over a period longer than expected from a pure JET breakout. Therefore, the JET collimation must have persisted even after breakout. We suggest that the collimation was maintained by a finite, dense, wind-like circumburst medium, which would reproduce the observed behavior of the prompt emission. We conclude that late-stage progenitor mass-loss can shape the earliest prompt emission and that the photospheric emission provides a way to probe both the JET collimation and the innermost region of the circumburst medium (CBM) surrounding the progenitor, independently of the constraints from interacting SUPERNOVAe.
[abstract 11 / 34] (score: 3) - Title: Impact of Primordial Black Hole population on 21 cm observables at high redshiftAuthors: Atrideb Chatterjee, Barun Maity, Koushiki,Comments: Accepted in A&ASubjects: astro-ph.CO gr-qcCreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
The 21-centimetre (21-cm) signal is one of the most promising probes of the high-redshift Universe. It has typically been modelled without accounting for the effects of ACTIVE GALACTIC NUCLEi (AGNs) in the pre-JWST era, primarily due to the lack of observational evidence for AGNs at z > 6. However, following the discovery of several AGNs at redshifts as high as z~ 10 by JWST, it has become imperative to incorporate the impact of these early AGNs when predicting the 21-cm signal. Based on the assumption that these AGNs are seeded by primordial BLACK HOLEs (PBHs), we studied their impact with a semi-numerical model setup. Specifically, we extended the explicitly photon-conserving reionisation framework, SCRIPT, including essential cosmic dawn physics and PBH contributions. This enabled us to compute both the global signal and the power spectrum of the 21-cm line over the redshift range z ~ 30 - 5 within a self-consistent framework. Building on this set-up, we investigated the impact of different PBH mass functions (obeying current observational constraints) on the resulting signal. We find the X-ray heating from PBHs can substantially make the global 21-cm signal shallower and suppress the expected power spectrum amplitude during cosmic dawn. We also find that the choice of mass function plays a crucial role in shaping the 21-cm signal, and can, in fact, lead to significantly different predictions.
[abstract 12 / 34] (score: 3) - Title: A parametrized test of general relativity for inspiralling eccentric binaries in LISAAuthors: Pankaj Saini, Sylvain Marsat, Lorenz Zwick, János Takátsy, Johan Samsing,Comments: 27 pages, 14 figures, 1 tableSubjects: gr-qc astro-ph.HECreated: 2026-08-10; Updated: 2026-08-12; Datestamp: 2026-08-12
The space-based detector Laser Interferometer Space Antenna (LISA) will observe inspiralling BLACK HOLE binaries in the mHz band, many of which may retain orbital eccentricity. In contrast to quasicircular binaries, eccentric systems radiate through multiple orbital harmonics, while RELATIVISTIC periastron precession introduces a secular phase structure in the waveform. We exploit this structure to develop a parametrized test of general relativity (GR) for eccentric bound orbits. We construct a frequency-domain eccentric waveform model in which a phenomenological deviation parameter $δα$ modifies the GR prediction for the conservative azimuthal-to-radial frequency ratio, with $δα=0$ corresponding to GR. We consider two parametrizations of this deformation. In the first, $δα$ modifies only the explicit precession-dependent sideband structures of the waveform. In the second, the secular precession phase is assigned to the dominant lower-order angular carriers and retained in resummed form. The latter produces a substantially stronger response because the dominant waveform components coherently accumulate the modified phase. We implement both models within \textsc{lisabeta} and perform a Bayesian analysis including the time- and frequency-dependent LISA response and associated time-delay-interferometry observables. We find that LISA can place stringent constraints on the parametrized deviation. For a binary with chirp mass $3000 M_{\odot}$, initial eccentricity $e_0=0.5$ observed for four years at an SNR of $50$, the second model yields a $90\%$ credible bound of $|δα|\lesssim 10^{-4}$. Increasing eccentricity further sharpens the constraints by introducing additional harmonic structure and reducing degeneracies among the binary parameters. The framework developed here is general and can be extended to more complete eccentric waveform models.
[abstract 13 / 34] (score: 3) - Title: ElectroMAGNETic responses driven by gravitational-wave memory in MAGNETar-flare outflowsAuthors: Wen-Biao Han,Comments: 13 pages 6 figuresSubjects: astro-ph.HE gr-qcCreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
An asymmetric RELATIVISTIC outflow from a MAGNETar giant flare produces a step-like gravitational-wave (GW) memory. In the MAGNETized pair plasma surrounding the star, such GW memory drives transverse electroMAGNETic (EM) X-mode/fast-MAGNETosonic responses at the corresponding frequencies. We use this GW-memory spectrum to drive a global wave equation for a cold electron--positron pair plasma. With radiative boundary conditions excluding incoming waves, the driven response forms an outgoing EM mode that reaches the outer boundary of the source region. For central-engine energy-release timescales of $10$, $1$, and $0.15\,μ\mathrm{s}$, 90\% of the integrated response energy lies below 23.3 kHz, 233 kHz, and 1.51 MHz, respectively. The principal response occupies the 10 kHz--1 MHz frequency band; a substantial extension into the 1--3 MHz frequency band also appears when a submicrosecond asymmetric-energy component is present. The electroMAGNETic response can escape from the source region and potentially propagate in the interstellar medium.
[abstract 14 / 34] (score: 3) - Title: Development and Characterization of a Microwave Atmospheric Pressure Plasma JetAuthors: Suryasunil Rath, Satyananda Kar,Comments: 7 pages, 4 figuresSubjects: physics.plasm-phCreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
Over the past decade, atmospheric pressure discharges in the microwave frequency range have gained significant attention due to their promising applications in material processing, CO2 dissociation, waste management, hydrogen production, water treatment, and more. This study presents the development and characterization of a waveguide-based microwave atmospheric pressure plasma JET (MW-APPJs), focusing on its design, diagnostics, and operational parameters. The setup incorporates a microwave power source, microwave waveguide networks, including the applicator section, and diagnostic tools for measuring plasma properties. Optical emission spectroscopy (OES) is employed to analyze the reactive species and determine plasma parameters which include electron excitation temperature (Texc) and electron number density (ne). The characterization highlights the influence of spatial and temporal gradients, gas flow rates, and power input on plasma behaviour. From OES, the Texc and ne variations were against the power increment. The thermocouple variations are also plotted with power.
[abstract 15 / 34] (score: 3) - Title: Gas Flow Rate Influence on Gas Temperature Regulation in a Reinforced Radio-Frequency Cross-Field Atmospheric Plasma JetAuthors: Radhika T. P., Satyananda Kar,Comments: 10 pages, 12 figuresSubjects: physics.plasm-phCreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
This study investigates the effect of gas flow rate on the gas temperature and discharge characteristics of a reinforced radio frequency cross-field atmospheric pressure plasma JET (APPJ) with an additional floating electrode. The plasma JET length, electron excitation temperature, electron density, and reactivity were enhanced by introducing copper floating electrodes of varying widths. However, this enhancement was accompanied by an undesired rise in gas temperature, limiting the plasma's application for heat- sensitive materials. To control this temperature rise, the gas flow rate varied from 1.5 to 9 lpm, showing a significant reduction in gas temperature from 438 K to 402 K as the flow rate increased, particularly at higher input powers. The study reveals that while an increase in gas flow rate initially improves ionization and reactivity by increasing electron excitation temperature and density, the insufficient input power for ionization at higher flow rates causes a decline in these parameters due to reduced ionization efficiency. Further optimization was achieved by increasing input power, which allowed better utilization of neutral atoms and improved plasma reactivity even at higher flow rates. The findings highlight the importance of tuning both gas flow rate and input power to maintain optimal plasma performance for various applications, particularly where controlled gas temperature and high reactivity are essential.
[abstract 16 / 34] (score: 3) - Title: Real-time observations of the transition to the quiescent state in an accreting MAGNETised neutron star: No propeller required?Authors: Sergey S. Tsygankov, Galina Lipunova, Valery F. Suleimanov, Alexander Salganik, Alexander A. Mushtukov, Sofia V. Forsblom, Andrey S. Tavleev, Aleksei V. Kuzin, Juri Poutanen,Comments: 11 pages, 5 figures, A&A, in pressSubjects: astro-ph.HECreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
The final stages of outbursts in transient X-ray pulsars (XRPs), which are characterised by a significant decline in the mass accretion rate, provide valuable insight into the physics of the accretion disc and its interaction with the strong MAGNETic field of the neutron star (NS). In particular, the `propeller effect', or centrifugal inhibition of accretion, has been proposed as a key mechanism governing both the onset luminosity and the timescale of the rapid transition to the quiescent state. In addition, it offers an independent method for estimating the MAGNETic field strength of the NS. On the other hand, the decrease in the mass accretion rate itself is driven by processes occurring in the accretion flow at larger distances from the NS. Recovering the information encoded in the light curve therefore requires sensitive high-cadence X-ray monitoring capable of capturing the rapid and often unpredictable transition from the accreting regime to the quiescent regime. In this study, we present the results of the first comprehensive monitoring campaign that tracks the entire transition to quiescence in the transient XRP 4U 0115+63 utilising observations by the NICER X-ray telescope. We show that the observed behaviour can be explained by the thermal-viscous disc instability model (DIM), with the emission observed immediately after an outburst possibly arising from the ongoing accretion from the recombined (`cold') disc and the subsequent quiescent emission being produced by the cooling NS. We further applied this model to a larger sample of XRPs encompassing a broad range of physical parameters. Ultimately, our findings indicate that the temporal behaviour of XRPs, including the quiescent state, can be consistently explained within the DIM framework without requiring the propeller effect as the primary mechanism governing the observed transition.
[abstract 17 / 34] (score: 3) - Title: Fitting trends in QUASAR emission and absorption line redshiftsAuthors: Netra K Subramanian, Prasad Subramanian, Nimisha G Kantharia,Comments:Subjects: astro-ph.CO astro-ph.HECreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
The spectrum of a QUASAR consists of a few emission lines whose wavelengths are shifted by similar redshifts and numerous absorption lines whose wavelengths are shifted by different redshifts. Hence each QUASAR is characterised by an emission line redshift and the absorption lines redshifts are all less than the emission line redshift. The distribution of observed absorption line redshifts ($z_{abs}$) with respect to emission line redshift ($z_{em}$) for a large sample of QUASARs shows a systematic trend as pointed out by \citet{2016arXiv160901593K}. They noticed that increase in $z_{em}$ is accompanied by a monotonic increase in the lowest detected value of $z_{abs}$ and inferred that the emission and absorption lines were all formed in the QUASAR. This study focuses on modeling the systematic trend in the observed $z_{em} \rightarrow z_{abs}$ distribution. We considered the redshift data of absorption lines of singly ionized magnesium (denoted by MgII) and triply ionized carbon (denoted by CIV) for a large sample of QUASARs. We find that the envelope of data points defining the lowest value of the MgII absorption line redshift (which we denote by $z_{MgIImodel}$) for a given $z_{em}$ satisfies $z_{MgIImodel} = (0.418 \pm 0.008) z_{em} - (0.482 \pm 0.02)$ with an $R^2$ value of 0.99. The model can be used to predict the lowest expected MgII absorption line redshift for any $z_{em}$. We find a similar model for the lowest expected redshift of triply ionized carbon lines for any $z_{em}$ which is $z_{CIVmodel} = 0.845 (\pm 0.0002) z_{em} - 0.153 (\pm 0.0006)$.
[abstract 18 / 34] (score: 2) - Title: Comprehensive study of solar type II radio bursts and the properties of the associated shock wavesAuthors: K. Bhandari, D. E. Morosan, S. Normo,Comments: 13 pages (9 page main body, 4 page appendix), 13 figuresSubjects: astro-ph.SRCreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
Type II radio bursts are solar radio emissions generated by electrons accelerated by coronal shocks. These bursts are typically found close to expanding coronal mass ejections (CMEs), making them valuable for studying the properties and dynamics of CME-driven shocks in the solar corona. Here, we aim to determine the regions in the solar corona where shock waves accelerate electrons and determine their characteristic properties. To do this, we combine radio observations of type II solar radio bursts with MAGNETo-hydrodynamic (MHD) simulations of the solar corona. We analyse ten type II radio bursts from Solar Cycle 25 exhibiting emissions. The novelty of this study lies in using radio imaging data for all type II bursts to examine the positions of the radio sources. The radio source positions, combined with a geometrical fitting of the CME shock and the MHD simulations, are used to determine essential shock parameters at the acceleration region, such as the Alfvén Mach number $(M_{\rm A}$ and $θ_{\rm BN}$. The shock parameters are then combined with the properties of the radio emission and the associated eruption in a comprehensive study. We found that for all events, the type II bursts are located near or inside coronal streamers. The estimated shock speeds are high, resulting in the formation of super-critical shocks ($3.8~\leq~M_{\rm A}~\leq~7.7$) at the type II locations. In most events, type II bursts are located at oblique shocks rather than near-perpendicular geometries, suggesting that the shock structure is more complex at local scales than the simple spherical shock models usually applied to CME shocks. Our results suggest that CME-streamer interaction regions are necessary for the generation of type II bursts, as they provide ideal plasma conditions for the formation of super-critical shocks and the subsequent acceleration of electrons.
[abstract 19 / 34] (score: 2) - Title: Thermodynamic characteristics of a FERMI gas with an invariant energy scale and its astrophysical implicationsAuthors: Tiyasa Kar, Atul Kedia, Ramkumar Radhakrishnan,Comments: v2: Added appendices; minor revisions; 23 pages, 4 figures. v1: 16 pages, 4 figuresSubjects: astro-ph.HE gr-qc hep-phCreated: 2026-08-10; Updated: 2026-08-12; Datestamp: 2026-08-12
We investigate the thermodynamics of a RELATIVISTIC FERMI gas governed by a modified dispersion relation in the Magueijo Smolin (MS) formulation of Doubly Special Relativity (DSR), characterized by the presence of an invariant ultraviolet energy (deformation) scale. We study the system in two physically distinct regimes: the near degenerate low-temperature limit, and the high-temperature regime. In the low-temperature regime, we derive the thermodynamic quantities using the standard Sommerfeld expansion. In the high-temperature regime, we evaluate all thermodynamic quantities numerically from the exact grand canonical potential and demonstrate that the thermodynamics of the FERMI gas reduces to the standard RELATIVISTIC ideal gas behavior. We apply the resulting low-temperature equation of state to study compact astrophysical objects, namely, non-rotating white dwarfs and neutron stars. Helium white dwarfs exhibit a strong dependence on the deformation scale, while white dwarfs composed of heavier elements are less affected. For neutron stars, the modified equation of state leads to configurations that are smaller in radius and lower in mass than that is produced by nucleonic equations of state. Our results highlight how modified relativity theories can be probed by studying astrophysical objects.
[abstract 20 / 34] (score: 2) - Title: The CGM with local universe FRBs: evidence of strong AGN feedback in a massive elliptical galaxyAuthors: Samuel McCarty, Liam Connor, Ralf M. Konietzka,Comments: 20 pages, 9 figures, accepted to ApJSubjects: astro-ph.GACreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
Modern cosmology and galaxy formation rely on an understanding of how cosmic baryons are distributed, a significant portion of which exist in the diffuse gas confined to halos. Fast Radio Bursts (FRBs) are a promising probe of the Universe's ionized gas. At low redshift, the contribution to the dispersion measure (DM) from the intergalactic medium (IGM) and intervening halos is subdominant, allowing us to study the circumgalactic media (CGM) of the host galaxies, if the host interstellar medium (ISM) can be sufficiently suppressed. We select a sample of five local universe FRBs with host halos spanning a wide range in mass ($\sim10^{11-13}\,M_\odot$), and with indicators that host ISM DM is negligible. We use these FRBs to constrain the CGM in each halo by comparing to simulations and measuring the CGM mass assuming a range of spherical gas profiles. We find one of our sources, the only massive elliptical host galaxy, strongly disfavors low feedback scenarios in simulations, and has been evacuated of its baryons ($\sim\,10\%$ of the cosmological average $\frac{Ω_b}{Ω_m}$ within $R_\mathrm{vir}$). This galaxy shows evidence of a past episode of AGN activity, consistent with the picture of strong AGN feedback in galaxy group-scale halos. The gas mass measurements for the other sources tentatively support more baryon retention in $L_*$ galaxies compared to group-scale halos. Finally, we demonstrate that a large sample of local universe FRBs will enable precision measurements of halo gas.
[abstract 21 / 34] (score: 2) - Title: The Effect of Expansion and Instabilities in the Thermodynamic Regulation of the Young Solar Wind PlasmaAuthors: Matilde Coello-Guzmán, Víctor A. Pinto, Roberto E. Navarro, Pablo S. Moya,Comments:Subjects: astro-ph.SR physics.plasm-phCreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
Using Parker Solar Probe measurements of the solar wind, we demonstrate that $β_{\parallel}$ is the main driver that determines which instabilities limit proton temperature anisotropy. At radial distances from 10 to 30 solar radii, $β_{\parallel}<1$ drives electroMAGNETic ion-cyclotron and parallel firehose instabilities, in contrast to the situation at 1 astronomical unit, where, due to most $β_{\parallel}>1$, mirror and oblique firehose modes are dominant instead. Furthermore, we show that the temperature anisotropy radially evolves following the semi-empirical anti-correlation $T_\perp/T_\parallel\simβ_\parallel^{-0.55}$, consistent with observations at larger distances from the Sun.
[abstract 22 / 34] (score: 2) - Title: Computational and reduced-order modelling of elastic wave-driven impulse enhancement in pulsed JETs through passively flexible nozzlesAuthors: Daehyun Choi, Paras Singh, Saad Bhamla, Chandan Bose,Comments:Subjects: physics.flu-dynCreated: 2026-08-10; Updated: 2026-08-12; Datestamp: 2026-08-12
Elastic wave propagation and energy exchange in passively deforming cylindrical nozzles are investigated through three-dimensional, two-way fluid-structure interaction simulations. Flexible nozzles with varying stiffness (Eh = 75 to 500 N/m, E is Young's modulus, h is thickness) are subjected to pulsatile JET inflow at low Reynolds number (Re ~ 4400). Increased flexibility reduces deformation-wave speed following MoensKorteweg scaling, prolonging the expansion phase. This delayed expansion enhances JET entrainment and elastic energy storage while suppressing early shear-layer roll-up and vortex formation. During contraction, released elastic energy increases JET acceleration and vortex formation. For the most flexible nozzle, primary vortex-ring circulation increases by 52%, vortex convection distance by 9%, and peak outlet kinetic energy flux 4.6-fold versus a rigid nozzle, resulting in a 62% increase in total hydrodynamic impulse. A reduced-order model represents the coupled response as a lumped store-and-release oscillator, derived as a single-mode projection of the inviscid one-dimensional wave equation and closed at the exit by two terms: (i) an inertial end correction that adds the external fluid column of length Le = R accelerating with the JET, and (ii) a vortex-radiation damping term, active only during ejection, determined by the discharged-JET momentum theorem. This damping reproduces the post-overshoot velocity decay undamped closures fail to capture. The model predicts the simulated resonance frequency within 6% and momentum impulse within 4% across Eh = 75 to 500 N/m, and recovers energy histories. Outlet kinetic energy flux is predicted within 6% for the three stiffer nozzles and 14% for the most compliant.
[abstract 23 / 34] (score: 2) - Title: Horizon absorption in eccentric precessing binary BLACK HOLE inspirals and its importance for gravitational wave data analysisAuthors: Alberto Álvaro-Díaz, Gonzalo Morras,Comments: 15 pages, 9 figuresSubjects: gr-qc astro-ph.HECreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
During the evolution of a binary BLACK HOLE, energy and angular momentum are exchanged between the orbital motion and the individual BLACK HOLEs through horizon absorption, modifying both the binary dynamics and the BLACK HOLE masses and spins. This leaves an imprint on the emitted gravitational waves that may be relevant for the accurate modeling of signals observed by current and future detectors, while also offering a probe of the nature of compact objects. In this work, we derive, for the first time and at leading order in the post-Newtonian expansion, the effect of horizon absorption in binary BLACK HOLE inspirals with both orbital eccentricity and spin-induced precession, and we incorporate these corrections into the pyEFPEHM waveform model. We then quantify their impact through analytical estimates of the orbital dephasing, waveform mismatches, and Bayesian parameter-estimation studies. The effect is largest for systems with large spin components (anti-)aligned with the orbital angular momentum ($|\vecχ_i \cdot \hat{l}| \sim 1$), highly unequal mass ratios ($q=m_2/m_1 \ll 1$), and long inspirals spanning a wide frequency range ($\log(f_\mathrm{max}/f_\mathrm{min}) \gg 1$). For such systems, neglecting horizon absorption biases the recovered binary parameters at moderate signal-to-noise ratios. In quasi-circular binaries these biases largely absorb the effect, rendering it difficult to detect. In eccentric binaries, however, the richer signal morphology breaks this degeneracy, making horizon absorption potentially measurable in high signal-to-noise-ratio events.
[abstract 24 / 34] (score: 2) - Title: Beyond Feedback: Disentangling Baryonic Effects with tSZ$\times$FRB Cross-CorrelationsAuthors: Isabel Medlock, Daisuke Nagai,Comments: 17 pages, 6 figures, submitted to ApJSubjects: astro-ph.GA astro-ph.COCreated: 2026-08-06; Updated: 2026-08-12; Datestamp: 2026-08-12
Standard observational probes lack the sensitivity to characterize the interplay between feedback-driven gas ejection and non-thermal pressure support in groups and clusters, and current models lack the framework to disentangle it. Recent first detections of the tSZ$\times$FRB cross-power spectrum (Takahashi et al, 2025; Sharma et al 2026) have been interpreted as constraining AGN feedback and $σ_8$, but the baryon models used do not independently parameterize non-thermal pressure support, leaving feedback efficiency and gas thermodynamics degenerate. We demonstrate that this cross-correlation provides sensitivity to the thermal and non-thermal structure of cluster gas that neither observable alone can achieve, because the tSZ effect traces electron pressure while FRBs trace solely electron density. Using the Baryon Pasting (BP) framework, which separately parameterizes feedback efficiency $ε_f$ and non-thermal pressure amplitude $A_{\rm nt}$, we show that their joint constraint breaks this degeneracy. In the noise-free limit, adding the cross-power spectrum reduces $r_{\rm cond}$ from $0.96$ to $0.08$ (a 12-fold reduction) and improves the joint figure of merit by a factor of 19, with the constraining power concentrated at cluster interior scales ($\ell \gtrsim 3000$). Recent detections are consistent with our fiducial model and disfavor weak feedback ($ε_f^{95\%} \gtrsim 2.40\text{--}3.67 \times 10^{-6}$ across datasets). With $5\times10^4$ FRBs from DSA-2000 combined with SO, we forecast $3.8\%$ fractional precision on $A_{\rm nt}$, improving to $2.3\%$ with CMB-HD. These constraints directly inform the hydrostatic mass bias, with immediate implications for cluster-based cosmological inference from eROSITA, SO, and CMB-HD.
[abstract 25 / 34] (score: 2) - Title: A cosmic collision in the making: JWST/NIRISS reveals a merging and maturing protocluster core at z~3 around a red QUASARAuthors: C. Bertemes, D. Wylezalek, G. Noirot, R. Hviding, D. S. N. Rupke, N. L. Zakamska, S. Veilleux, L. Gatto, W. Liu, A. Vayner, Y. Ishikawa, Y. Chen, S. Sankar,Comments: Accepted for publication in A&A. 18 pages, 10 figures, including a 5-page appendix with 3 figuresSubjects: astro-ph.GACreated: 2026-08-10; Updated: 2026-08-12; Datestamp: 2026-08-12
We report the discovery of ``The Step'', a dense protocluster at z=3 revealed by JWST/NIRISS Wide-Field Slitless Spectroscopy (WFSS) of the field around the luminous QUASAR and starburst SDSSJ165202.64+172852.3. The protocluster contains at least 18 member galaxies and exhibits two substructures in the 3D position-velocity space - notably a distinctive step-like distribution, from which the nickname derives. We propose that the Step may be undergoing a merger of two haloes, which could also explain the large velocity span (700-850km/s) between galaxies along the densest line of sight. This sightline contains seven galaxies within 70 projected kpc from the QUASAR, consistent with a remarkably dense protocluster core. We derive a galaxy overdensity of a factor >100 in the core and >15 within 1 Mpc$^2$, making it one of the densest structures known at this redshift, and a very massive halo of $13.1 < log M_{\rm halo}/ M_\odot < 13.8$, which suggests the structure could potentially evolve into a massive, Coma-like cluster at z=0. Compared to the field, the star-forming galaxies in the Step show slightly elevated levels of STAR FORMATION. Yet, we find two quiescent galaxies with strong D4000 breaks and no evidence for ongoing STAR FORMATION. Compared to other z=3 protoclusters, the Step exhibits similar or slightly suppressed star-forming activity. We also identify two new AGN candidates and find tentative evidence for an enhanced AGN fraction (10-20%) compared to the field. The protocluster constitutes one of the emerging handful of maturing structures at 2 < z < 4 that host both star-forming and quenched galaxies. This redshift regime may thus be a key transitional epoch for cluster studies, where overdensities transition from being the most active sites of STAR FORMATION in the early Universe towards shaping the massive passive ellipticals seen in the cores of today's clusters.
[abstract 26 / 34] (score: 2) - Title: Lyman Break Galaxy selection and redshift measurement with supervised contrastive learningAuthors: J. Choppin de Janvry, C. Yèche, Arjun Dey, C. Magneville, C. Payerne, J. Aguilar, S. Ahlen, E. Armengaud, S. Bailey, F. Beutler, D. Bianchi, D. Brooks, A. Carnero Rosell, E. Chaussidon, T. Claybaugh, A. Cuceu, K. S. Dawson, A. de la Macorra, A. de Mattia, P. Doel, A. Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, Satya Gontcho A Gontcho, G. Gutierrez, H. K. Herrera-Alcantar, K. Honscheid, M. Ishak, S. Juneau, T. Karim, D. Kirkby, A. Kremin, A. Lambert, M. Landriau, L. Le Guillou, M. Manera, A. Meisner, R. Miquel, S. Nadathur, G. Niz, E. Paillas, N. Palanque-Delabrouille, W. J. Percival, F. Prada, I. Pérez-Ràfols, C. Ravoux, G. Rossi, R. Ruggeri, E. Sanchez, C. Saulder, D. Schlegel, M. Schubnell, H. Seo, J. Silber, M. Siudek, G. Tarlé, B. A. Weaver, H. Zou,Comments: 36 pages, 15 figures, submitted to JCAPSubjects: astro-ph.COCreated: 2026-08-10; Updated: 2026-08-12; Datestamp: 2026-08-12
Some of the next steps for high-precision cosmology lie within the high-redshift, high-density universe. Spectroscopic survey experiments such as the Dark Energy Spectroscopic Instrument (DESI)'s second phase DESI Run 2 will shift towards probing Lyman Break Galaxy (LBG) populations from z$\sim$2 to z$\sim$4.5. For this faint sample, spectroscopic redshift measurement and sample decontamination remains a challenge, even after target selection. We propose an approach based on supervised weighted contrastive learning, in order to both learn a redshift representation for spectra and decontaminate the sample from QUASARs and low redshift emission line galaxies. This strategy generalizes the contrastive learning loss approach with continuous relationship weights, such that the network simultaneously learns redshift and classification tasks. The model shows stronger outlier classification and comparable redshift identification performances when compared to the previous network used for DESI (a modified version of QuasarNET) on the same dataset. In particular, contrastive learning is well suited to the small, visually-inspected sample used for training and testing, especially given the multi-task nature of this work.
[abstract 27 / 34] (score: 2) - Title: An X-ray Absorption-Line Survey of the Circumgalactic Medium of M31 with XMM-NewtonAuthors: Kaile Wang, Zheng Zhou, Taotao Fang, Fabrizio Nicastro,Comments: Accepted for publication in ApJ. 13 pages, 5 figures, and 3 tablesSubjects: astro-ph.GACreated: 2026-08-10; Updated: 2026-08-12; Datestamp: 2026-08-12
X-ray absorption line spectroscopy provides a powerful method for probing the extended hot circumgalactic medium (CGM) of individual galaxies. In this study, we present the first survey of \osv and \oeit absorption lines toward the hot halo of M\,31, using $15$ and $18$ background ACTIVE GALACTIC NUCLEi, with impact parameters ranging from $R_{\rm imp}\sim300$--$730$~kpc and $\sim190$--$730$~kpc, respectively. We find a marginal excess absorption above the expected Milky Way (MW) foreground toward the innermost sightlines, consistent with an additional hot-CGM contribution associated with M\,31. Comparing sightlines inside and outside $R_{\rm imp}=300$--$350$~kpc, the excess corresponds to a mean equivalent width of $\sim4$--$9$~mÅ for the inner \osv sightlines at $R_{\rm imp}\sim310$~kpc and $\sim17$~mÅ for the inner \oeit sightlines at $R_{\rm imp}\sim200$~kpc, with a nominal combined significance level of $2.2$--$2.3\,σ$. The hot-CGM mass inferred from this excess is highly model dependent, especially on the assumed CGM boundary, and therefore does not yet provide a robust baryon census. Attributing the excess entirely to hot gas confined within approximately the virial radius of M\,31 would require a CGM mass exceeding the nominal ``missing'' baryon budget. The inferred mass decreases to a few $\times10^{11}~M_\odot$ when the assumed CGM boundary is extended to $400-500$~kpc. Deeper observations, both through longer exposures of existing sightlines and the inclusion of additional inner-halo targets, will be essential to robustly constrain the properties of the hot CGM of M\,31.
[abstract 28 / 34] (score: 2) - Title: 3D Binary Neutron Star Merger Ejecta Evolution up to Seconds Timescale: Dynamics, Element Distribution, and Light CurvesAuthors: Luis Felipe Longo Micchi, Fabio Magistrelli, Maximilian Jacobi, Sebastiano Bernuzzi,Comments: 25 pages, 19 figuresSubjects: astro-ph.HE gr-qcCreated: 2026-08-10; Updated: 2026-08-12; Datestamp: 2026-08-12
We present long-term, three-dimensional simulations of ejecta from four binary neutron star mergers to second-long time-scales. Numerical-relativity data serve as boundary conditions for a general-RELATIVISTIC hydrodynamics evolution incorporating an equation of state valid outside nuclear statistical equilibrium and an effective nuclear-heating prescription based on reaction-network calculations. We investigate the ejecta's dynamical and geometrical properties, the impact of nuclear heating, the formation and spatial distribution of elements, and compute multi-angle kilonova light curves. % Nuclear heating significantly affects ejecta dynamics, delaying homologous expansion beyond second time-scales and reshapes the spatial distribution of heavy nuclei. This effect is largest for asymmetric binaries with long-lived remnants; extending the evolution from ${\sim}150$~ms to ${\sim}1$~s widens the angular polar region containing 90\% of the heavy-element mass (\eg, $Z=56$, $Z=79$) from $|θ|\lesssim15^{o}$ to $|θ|\lesssim30^{o}$. Our nucleosynthesis results confirm that the $^{56}$Ni$\rightarrow^{56}$Co$\rightarrow^{56}$Fe decay chain dominates the heating at $\sim$100 days, with cobalt decay producing gamma-ray lines at 846.77 and 1238.288~keV. % Comparing kilonova ray-by-ray light curves obtained from multi-angle 3D profiles and averaged 2D profiles, we find the latter approach broadly robust, although 2D light curves should be treated as upper limits. Increasing dimensionality generally lowers the bolometric luminosity, with binary asymmetry strengthening the viewing-angle dependence. For observers aligned with a lanthanide curtain's densest region, 3D emission can match its 2D counterpart in brightness. We conclude that increased dimensionality alone is unlikely to reconcile current theoretical models with AT2017gfo observations.
[abstract 29 / 34] (score: 2) - Title: Does IRS13 require an intermediate-mass BLACK HOLE?Authors: Václav Pavlík, Vladimír Karas, Florian Peißker, Bhavana Bhat, Andreas Eckart,Comments: 4 pages, 3 figures, to appear in Proceedings of IAU Symposium No. 405 "Traversing the Galactic Center in Space and Time"Subjects: astro-ph.GACreated: 2026-08-10; Updated: 2026-08-12; Datestamp: 2026-08-12
We investigate whether the Galactic-centre association IRS13 requires an intermediate-mass BLACK HOLE (IMBH) to remain bound. Using high-precision $N$-body calculations of IRS13-like systems orbiting the Milky Way supermassive BLACK HOLE (SMBH), as well as simulations of more massive infalling clusters, we find that an IRS13-sized cluster dissolves on a very short timescale even when an IMBH of $4\times10^4\,M_\odot$ is present. The observed velocity dispersion can arise naturally from the tidal field of Sgr A* and the infall event itself; therefore, it need not imply a central IMBH. In the infalling-cluster runs, tidal stripping produces transient disks, spiral-like structures, and ring-like overdensities. These features suggest a broader interpretation: IRS13 is best viewed as a temporary phase-space overdensity, analogous in mechanism (though not in scale) to phase-wrapped shells and streams in disrupted galaxies.
[abstract 30 / 34] (score: 2) - Title: Two new highly scattered fast radio bursts: evidence for scatter broadening by the circumsource mediumAuthors: Joscha N. Jahns-Schindler, Keith W. Bannister, Adam T. Deller, Xinping Deng, Marcin Glowacki, Alexa C. Gordon, Vivek Gupta, Akhil Jaini, Clancy W. James, Ilya S. Khrykin, Yu Wing Joshua Lee, J. Xavier Prochaska, Hao Qiu, Hugh Roxburgh, Stuart D. Ryder, Ryan M. Shannon, Tim Sprenger, Nicolas Tejos, Yuanming Wang, Ziteng Wang,Comments: 19 pages, 11 figures, 2 tables; submitted to MNRAS, comments welcomeSubjects: astro-ph.HECreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
We found two highly scattered Fast Radio Bursts (FRBs) during commissioning of the Commensal Realtime ASKAP Fast Transient COherent (CRACO) backend. FRB 240210D and FRB 240312D have scattering times of $34\pm6$ and $300\pm48$ ms, respectively, when scaled to 1 GHz. FRB 240312D originates near a spiral arm of a face-on galaxy at a redshift of only 0.05. Scintillation from a Milky Way screen constrains the distance of the scattering screen to $\sim 10$ pc from the source. FRB 240312D is therefore the first highly scattered FRB where scattering screens in the host galaxy centre, a background galaxy, or intervening structures can all be excluded, leaving only the circumsource medium. Integral field spectroscopy of the host reveals a Milky Way-like galaxy with a star-formation region at the FRB position. We find refractive scattering in a pulsar wind nebula as the most likely scattering origin. However, the explanation is not completely satisfactory as it requires a fine-tuned orientation. Hence, additional theoretical studies under different FRB progenitor models are needed. From the two FRBs, we calculate a total rate of $R_\mathrm{tot}=210^{+460}_{-180}\,\mathrm{events}\,\mathrm{sky}^{-1}\mathrm{day}^{-1}$ with durations between 55.2 ms and 1 s and above a fluence of 9 Jy ms consistent with the rate of shorter FRBs. This elevated rate suggests that the strong scattering seen in other FRBs likewise does not arise from chance-aligned sightlines, but is instead causally linked to the FRB sources.
[abstract 31 / 34] (score: 2) - Title: Constraining ModMax Black Holes with EHT and GRAVITY Observations: Optical Signatures and Accretion Disk PropertiesAuthors: Tursunali Xamidov, Mirjavoxir Mirkhaydarov, Sanjar Shaymatov, Pankaj Sheoran, Chengxun Yuan,Comments: 12 pages, 6 captioned figures, 2 tablesSubjects: gr-qcCreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
In this work, we study photon propagation and the radiative properties of a thin accretion disk around a ModMax BLACK HOLE and examine the effects of the charge $Q$ (i.e. $Q^2 = Q^2_e +Q^2_m$ is the total dyonic charge, with $Q_e$ and $Q_m$ denoting the electric and MAGNETic charges, respectively) and the nonlinearity parameter $v$. We determine the event-horizon, photon-sphere, and shadow radii and find that increasing $Q$ decreases these radii, whereas increasing $v$ shifts them toward their Schwarzschild values. Using the EHT shadow measurements of M87$^\star$ and Sgr~A$^\star$, together with the available mass and distance measurements, we perform an MCMC analysis to constrain the ModMax parameters. The strongest upper limits are found to be $Q<0.391$ and $v<4.153$ at the 95\% credible level. We also investigate a Novikov-Thorne thin accretion disk and generate simulated disk images using backward ray tracing. The observed flux increases with $Q$, while increasing $v$ produces a slight decrease in the disk brightness. These results show how the ModMax parameters affect the black-hole shadow and thin-disk emission and provide observational constraints on $Q$ and $v$.
[abstract 32 / 34] (score: 2) - Title: High-energy electron-positron beam collisions with large-angle disruptionsAuthors: W. Zhang, T. Grismayer, L. O. Silva,Comments: 20 pages, 15 figures, with appendices. Submitted to Physical Review Accelerators and BeamsSubjects: physics.acc-ph hep-ex physics.plasm-phCreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
We show that the beam and field dynamics in high-energy electron-positron ($e^-e^+$) collisions are characterized by a new dimensionless parameter introduced as $\varepsilon$ in this study. The disruption effect deflects the particles transversely at angles equal to $\varepsilon$. The particles simultaneously undergo deceleration of longitudinal velocities (a ``braking effect"). The deceleration scales as $\propto \varepsilon^2$. A longitudinal electric field is further provoked, whose amplitude scales as $\propto \varepsilon$. We identify $\varepsilon \gtrsim 1$ (with large-angle disruptions) as a novel extreme regime, where the transverse motion becomes strongly RELATIVISTIC. The braking effect completely stops and further reverses the beam propagation. Our theoretical model is in excellent agreement with electroMAGNETic particle-in-cell simulations. The previous beam-beam studies, including legacy numerical codes, apply only to the $\varepsilon \ll 1$ regime. They fail to capture the correct beam features and collision luminosities, and overestimate beam-beam effects (including beamstrahlung and pair production) for considerable $\varepsilon$, thus demonstrating the need for fully electroMAGNETic particle-in-cell codes to study these regimes.
[abstract 33 / 34] (score: 2) - Title: Periodic orbits and gravitational wave signatures from MAGNETic dipoles around MAGNETized Kerr BLACK HOLEsAuthors: Shokhzod Jumaniyozov, Javlon Rayimbaev, Chengxun Yuan, Satimbay Palvanov, Khurshida Khaknazarova, Faisal Javed,Comments: 19 pages, 12 figuresSubjects: gr-qcCreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
We study periodic orbits and the associated gravitational radiation of a MAGNETized (uncharged) test particle carrying a MAGNETic dipole moment with coupling constant beta, moving in the equatorial plane of a rotating, MAGNETized Kerr BLACK HOLE immersed in an external asymptotically uniform MAGNETic field, starting from the effective potential derived for such particles. We compute the marginally bound orbit (MBO) and the innermost stable circular orbit (ISCO) as functions of the BLACK HOLE spin a and the MAGNETic coupling beta, and map out the allowed region of the orbital energy-angular momentum (L, E) plane for bound motion. We then classify periodic orbits using the topological zoom-whirl scheme of Levin and Perez-Giz, characterized by three integers (z,w,v) through the rational rotation number q=w+v/z, and construct a family of closed rosette orbits at fixed angular momentum. Using the numerical-kludge, restricted-quadrupole approximation for an extreme-mass-ratio inspiral consisting of a stellar-mass MAGNETized secondary orbiting a supermassive MAGNETized Kerr BLACK HOLE, we compute the time-domain gravitational waveforms h_+(t), h_\times(t) produced by these periodic orbits and their frequency-domain characteristic strain, and compare the latter with the anticipated instrumental sensitivity curves of LISA, Taiji and TianQin. We find that the MAGNETic coupling βsystematically shifts the MBO and ISCO outward and lowers their orbital energy and angular momentum, that the zoom-whirl structure of the periodic orbits is imprinted directly on the burst-like morphology of the emitted waveform, and that the resulting gravitational-wave signals fall within the sensitivity band of upcoming space-based detectors for suitably close and massive sources.
[abstract 34 / 34] (score: 2) - Title: All You Need is not $Ω_\mathrm{gw}$: Beyond the Mean of the Cross-Correlation Estimator when Searching for an Astrophysical Gravitational-Wave BackgroundAuthors: Haowen Zhong, Francesco Iacovelli, Vuk Mandic, Emanuele Berti,Comments: 14 pages, 9 figuresSubjects: gr-qc astro-ph.HE astro-ph.IMCreated: 2026-08-11; Updated: 2026-08-12; Datestamp: 2026-08-12
Searches for the stochastic gravitational-wave background (SGWB) using ground-based detectors rely heavily on the cross-correlation estimator $\bar C_f$, whose statistical properties determine the theoretical foundation for inference frameworks built on it. Past analyses usually assume Gaussianity of $\bar C_f$, but this assumption has not been systematically tested for a background of astrophysical origin like the one produced by compact binary coalescences. In this work, we decompose $\bar C_f$ into three physically motivated components: (1) the mean intensity, (2) the geometrical shot noise, and (3) the POLARIZATION leakage, and we compute 90\% credible intervals for its cumulants up to fourth order for the binary BLACK HOLE, binary neutron star, and neutron star-BLACK HOLE populations by propagating local merger rate uncertainties. We find that for the upcoming LIGO O5 sensitivity, $\bar C_f$ remains effectively Gaussian for all three populations, validating current Gaussian likelihood frameworks. For Cosmic Explorer (CE), however, the $\bar C_f$ produced by binary BLACK HOLEs becomes non-Gaussian, with skewness and excess kurtosis of $0.31^{+0.04}_{-0.03}$ and $1.3^{+0.4}_{-0.3}$, respectively, in the most sensitive band over a one-year observation period. For binary neutron star and neutron star - BLACK HOLE mergers, $\bar C_f$ remains largely Gaussian even at CE. These results indicate that the Edgeworth expansion provides an adequate leading-order description of the non-Gaussianity expected in the next-generation era, while also motivating the development of more sophisticated statistical methods for a more accurate treatment.
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