Current date: 2026-06-23
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Datestamp limit: 2026-06-23 (0 days ago)
Created/updated limit: 2026-06-16 (7 days ago)
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Suggested sets: physics, physics:astro-ph, physics:gr-qc, physics:physics
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Scoring abstracts
Number of records retrieved: 1300
Keyword score statistics
score 15 -- 1 abstracts
score 9 -- 3 abstracts
score 7 -- 3 abstracts
score 6 -- 4 abstracts
score 5 -- 3 abstracts
score 4 -- 8 abstracts
score 3 -- 14 abstracts
score 2 -- 39 abstracts
in total -- 75 abstracts
Articles that appeared on 2026-06-23
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[abstract 1 / 75] Wow! (score: 15)
- Title: Fast Optical Variability of the TeV Blazar PKS 1725+123 Observed by SVOM-VT and Insights from Multi-wavelength Follow-up ObservationsAuthors: Shuo-Yu Liu, Yu-Wei Yu, Ji-Shun Lian, Xin-Ke Hu, Alexis Coleiro, Zhu-Heng Yao, Li-Ping Xin, Jing Wang, Hua-Li Li, Zi-Qi Wang, Jin Zhang, Floriane Cangemi, Bertrand Cordier, Antoine Foisseau, Olivier Godet, Andrea Goldwurm, Diego Gotz, Sebastien Guillot, Xu-Hui Han, Ning Jiang, Cyril Lachaud, Sebastien Le Stum, En-Wei Liang, Pierre Maggi, Yu-Lei Qiu, Jerome Rodriguez, Lian Tao, Jian-Yan Wei, Chao Wu, Liang Zhang, Shuang-Nan Zhang, Shi-Jie Zheng,Comments: 23 pages, 8 figures, accepted for publication in ApJLSubjects: astro-ph.HECreated: 2026-06-20; Updated: 2026-06-23; Datestamp: 2026-06-23
PKS 1725+123 is a flat-spectrum radio QUASAR (FSRQ) with a redshift of $z=0.586$. The detection of this object in the TeV band was reported by the MAGIC telescopes and H.E.S.S. in August 2025. Subsequently, we promptly initiated Target-of-Opportunity observations using the Space-based multi-band astronomical Variable Objects Monitor (SVOM) satellite. By analyzing the observational optical data from SVOM-VT and comprehensively examining the FERMI-LAT and SWIFT-XRT observational data, it was found that the source is in a high-flux state across the optical, X-ray, and GeV $γ$-ray bands around the time of the TeV detections. Its optical flux reaches a historically unprecedented high level and shows significant variability on timescale as short as minutes. The variability is accompanied by changes in the color index, exhibiting a \textit{bluer when brighter} behavior during the high-flux state. Based on the simultaneous multi-wavelength data, we construct the broadband spectral energy distribution (SED) of the source in the high-flux state. PKS 1725+123 demonstrates a remarkably high SYNCHROTRON peak frequency, which is distinctly different from that of other FSRQs. We propose a two-zone spine-sheath JET model to reproduce this SED. The optical--X-ray emission is generated by the SYNCHROTRON process of the RELATIVISTIC electrons within a compact zone. The inverse Compton (IC) scattering processes of the same electron population contribute to the low-energy end of the FERMI-LAT spectrum, while the high-energy end of the FERMI-LAT spectrum is ascribed to the IC scattering of the SYNCHROTRON photons within the compact zone by the higher-energy electrons in an extended region.
[abstract 2 / 75] Wow! (score: 9) - Title: Radio Follow Up of a Sub-threshold GRB in the Sky Localization Area of GW241125Authors: Natalie Gottschlich, Alessandra Corsi, S. Bradley Cenko, Divyajyoti, James DeLaunay, Derek B. Fox, Tanner O'Dwyer, Samuele Ronchini,Comments: 16 pages, 10 figuresSubjects: astro-ph.HE gr-qcCreated: 2026-06-18; Updated: 2026-06-23; Datestamp: 2026-06-23
Since the FERMI satellite's identification of a candidate $γ$-ray burst (GRB) temporally coincident with GW150914, several tentative, and often debated, associations between electroMAGNETic (EM) transients and gravitational-wave (GW) signals from binary BLACK HOLE (BBH) mergers have been reported. One such event, S241125n (later confirmed as GW241125_010116), was identified during the fourth observing run (O4) of Advanced LIGO and found to be spatially (within large GW localization uncertainty) and temporally coincident with a subthreshold GRB detected by the SWIFT Burst Alert Telescope Gamma-ray Urgent Archiver for Novel Opportunities (BAT-GUANO). Here, we present results from a radio follow-up campaign targeting the BAT-GUANO localization region, carried out with the Karl G. Jansky Very Large Array (VLA). We also re-analyze SWIFT/XRT observations of the field, and combine these results with optical upper limits. Our analysis constrains the isotropic kinetic energy of a putative RELATIVISTIC JET launched in the BBH merger to $\lesssim 3 \times 10^{50}$ erg for $n_{ISM} = 1.0 cm^{-3}$. We also discuss both the challenges and the diagnostic power of radio follow up in assessing candidate BBH-GRB associations, and present projections for analogous radio studies in the LIGO-Virgo-KAGRA observing run 5 (O5), and in the era of next-generation ground-based instrumentation. The enhanced sensitivity and localization capabilities of detector networks such as Cosmic Explorer and the Einstein Telescope, paired with the enhanced sensitivity of next-generation radio interferometers such as the next-generation VLA and the Square Kilometre Array, will significantly strengthen coordinated multi-messenger follow-up of BBHs. These next-generation facilities are likely to provide an answer to whether BBHs host RELATIVISTIC ejecta powered by mini-disk accretion.
[abstract 3 / 75] Wow! (score: 9) - Title: The Fundamental Planes of Black Hole Activity for High-Synchrotron-Peaked BL Lacertae ObjectsAuthors: Qing-Chen. Long, Ai-Jun. Dong, Qi-Jun. Zhi,Comments: 12 pages, 6 figures, 2 table, accepted for publication in MNRASSubjects: astro-ph.HECreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
The radio--X-ray correlation and Fundamental Plane (FP) of BLACK HOLE activity can serve as a diagnostic tool for the origin of X-ray emissions. There was a scaling relation between radio and X-ray emissions for High-SYNCHROTRON-peaked BL Lacertae objects (HBLs), i.e., $L_{\rm{R}}\propto L_{\rm{X}}^{0.64}$, which can be explained by ADAF-dominated mode or SYNCHROTRON cooling (Syn-c). However, many results of studying BLAZAR physics show that the X-ray emissions of HBLs are mainly produced by the SYNCHROTRON process of JETs. Therefore, Syn-c appears to provide a plausible explanation for this relation. To further clarify the origin of X-ray emissions of HBLs, we constructed a sample containing 69 HBLs in this paper to re-investigate their radio--X-ray correlation and FP. Considering the Doppler beaming effect, we find that the intrinsic radio--X-ray correlation and FP of HBLs are $L_{\rm R,int}\propto L_{\rm X,int}^{0.68}$ and $\log L_{\rm R,int}=(0.57\pm0.06)\log L_{\rm X,int}+(0.33\pm0.11)\log M_{\rm BH}+(12.65\pm2.00)$, respectively. Our results agree with the scaling relation mention above, which suggests these scaling relations are not artificial. By employing the theoretical model of Syn-c, we find that these shallow radio--X-ray correlations and FP are caused by Syn-c, which implies that the X-ray emissions of HBLs may be produced by rapidly cooling, high-energy electrons accelerated at a shock. This is consistent with results of the recent X-ray POLARIZATION observations of HBLs. Our results provide the observational evidence of $L_{\rm R}\propto L_{\rm X_{\text{Syn-c}}}^{0.6\sim0.7}$.
[abstract 4 / 75] Wow! (score: 9) - Title: Intraday Optical Variability of BL Lacertae during its Highly Active 2020-2024 PhaseAuthors: A. Takey, Ergün Ege, B. M. Mihov, E. G. Elhosseiny, Aykut Ozdonmez, Murat Tekkesinoglu, Hüseyin Er, Aditi Agarwal, L. S. Slavcheva-Mihova, M. Emir Kenger, M. S. Rizk, I. Zead, F. I. Elnagahy, W. A. Badawy, S. K. J. Pacif,Comments: Accepted for publication in MNRASSubjects: astro-ph.HE astro-ph.GACreated: 2026-06-20; Updated: 2026-06-23; Datestamp: 2026-06-23
We present an analysis of the intraday flux and spectral variability of BL Lacertae from 2020 September 30 to 2024 December 7, covering its highest recorded brightness and low, intermediate, and high flux states. Our study involved 62 nights of multi-band (BVRI) optical monitoring using four ground-based telescopes located in Egypt, Türkiye, and Bulgaria. We assessed intraday flux variability using the power-enhanced F-test and the nested ANOVA test. Significant variability was detected in 88 out of 117 light curves, consistent with previous studies of this object during active epochs. The maximum variability amplitude is 44.5 per cent in the B band. Spectral analysis reveals a bluer-when-brighter trend during intraday flares, supporting a SYNCHROTRON origin for the variable emission. For a subset of well-sampled flares, we model their profiles with a double exponential function, deriving rise and decay time-scales, thereby constraining the characteristic times of particle acceleration and cooling processes within the RELATIVISTIC JET. Assuming a turbulent JET model, we determined limits on the radii and MAGNETic field strengths of the emitting regions. We detected soft time lags for a multi-band flare and from their analysis, derived the Doppler factor and MAGNETic field strength of the corresponding emitting region. Our long-term, high-cadence study confirms that BL Lacertae was in an exceptionally active phase during the 2020-2024 period, with intraday variability being a common phenomenon. The results underscore the dynamic nature of the JET emission region and provide valuable observational constraints for models of BLAZAR variability and JET physics.
[abstract 5 / 75] Wow! (score: 7) - Title: Do Prompt Gamma-ray Burst Fireball Composition Impact on Afterglow Emission? Cases Study for Long GRBs 080916C/090902B and Short GRBs 090510/130603BAuthors: Yu Gan, Ren-Jie Xiong, Zi-Qi Wang, Qi-Yu Yan, Liang-Jun Chen, Xiao-Li Huang,Comments: 13 pages, 4 figures, 1 table, Accepted for publication in ApJSubjects: astro-ph.HECreated: 2026-06-20; Updated: 2026-06-23; Datestamp: 2026-06-23
Broadband observations with the {\em FERMI} mission reveal that a large fraction of GAMMA-RAY BURST (GRB) spectra are dominated by non-thermal emission, while a small fraction are dominated by thermal/quasi-thermal emission, likely indicating the difference in JET composition among GRB. By selecting two typical long GRBs (080916C and 090902B) and two short GRBs (130603B and 090510), we present a comparative analysis to investigate whether the composition of prompt GRB JETs influences the afterglow emission for bursts originating from both massive star collapse and compact binary mergers. Incorporating emission from both primary and cascade electron populations, we fit the multi-wavelength afterglow lightcurves of these GRBs with the standard forward shock model and analyze the particle acceleration and radiation physics of the JETs. Our results show that the afterglow lightcurve evolution with the characteristic parameters is not related to the composition of the GRB fireball but rather depends on the ambient medium density. The early UV-optical afterglows of the two long GRBs are dominated by SYNCHROTRON emission from cascaded $e^{\pm}$ pairs produced via the $γγ$ annihilation process, whereas this is not the case for the two short GRBs. These results suggest that the internal energy of the fireball is converted into JET kinetic energy during the prompt phase, and that the fireball composition leaves no detectable footprint on the afterglow JET. Instead, the density of the ambient medium plays an essential role in shaping the afterglow emission.
[abstract 6 / 75] Wow! (score: 7) - Title: Multiwavelength variability of the high-energy neutrino candidate PKS 0735+178 over three decadesAuthors: T. Mufakharov, Yu. Sotnikova, V. Vlasyuk, D. Kudryavtsev, A. Pushkarev, A. Mikhailov, M. Khabibullina, Yu. Kovalev, Y. Kovalev, A. Popkov, A. Erkenov, O. Spiridonova, T. Semenova, P. Tsybulev, D. Nezamov,Comments: Accepted for publication in MNRASSubjects: astro-ph.HE astro-ph.GACreated: 2026-06-20; Updated: 2026-06-23; Datestamp: 2026-06-23
We present the multiwavelength variability of the BL Lac object PKS 0735+178, associated with the high-energy neutrino event IC211208A. The light curves cover the radio (1-230 GHz), optical, and FERMI-LAT $γ$-ray bands over a $\sim$30 years time-scale. The light curves are correlated, with delays from 0 to 1200 days increasing towards lower frequencies, consistent with emission from an opacity-stratified JET. The bright flare after the IC211208A event indicates emission from a compact, optically thick region with enhanced activity and more efficient particle acceleration. Short optical and $γ$-ray bursts have been detected very close to the neutrino event, within a few days. The $\sim$12-day lag between the $γ$-ray and optical emissions is detected for the first time, suggesting that the emission regions are not co-spatial. A characteristic variability time-scale of $\sim$10-11 yr is robustly detected in the radio-mm bands ($\geq3σ$), while the optical and $γ$-ray data show weaker, shorter-period signals. The independent constraints from the VLBI core-shift measurements and radio time delays yield consistent estimates of the JET geometry and disturbance propagation, supporting variability governed by JET propagation effects. The long-term modulation is consistent with a slow variation in energy release at the JET base, while individual flares arise from shocks propagating downstream. Jet precession may contribute to the long-term modulation; however, the required viewing angles are inconsistent with the VLBI constraints, indicating that precession alone cannot explain the observed variability.
[abstract 7 / 75] Wow! (score: 7) - Title: Migration Traps as Variability Attractors: Optical/UV Signatures of Embedded Stellar-Mass Black Holes in Active Galactic Nucleus DisksAuthors: Jing-Tong Xing, Tong Liu, Mouyuan Sun, Ya-Ping Li, Shuying Zhou, Zhen-Yi Cai, Da-Bin Lin, Jian-Min Wang,Comments: 24 pages, 7 figures, 1 tableSubjects: astro-ph.GA astro-ph.HECreated: 2026-06-21; Updated: 2026-06-23; Datestamp: 2026-06-23
We investigate whether embedded stellar-mass BLACK HOLEs (sBHs) in ACTIVE GALACTIC NUCLEus (AGN) disks can leave observable optical/UV variability signatures through migration-trap-driven MAGNETic heating. This mechanism operates when sBHs migrating toward torque-balance radii pile up near migration traps, triggering localized, stochastic MAGNETic RECONNECTion that heats the disk atmosphere. It is potentially important because it provides a physical source of non-coronal disk heating and directly links optical/UV continuum variability to otherwise hidden compact-object populations. By coupling a one-dimensional sBH population synthesis model with a corona-heated accretion-disk reprocessing variability framework, we show that migration traps concentrate sBHs at preferred radii and generate localized, stochastic RECONNECTion heating. The resulting heating is self-regulated: sBH pile-ups enhance the RECONNECTion rate, while gap opening reduces the local gas density and partially suppresses the RECONNECTion power. This heating produces excess short-timescale optical/UV variability, flattened short-term structure functions, and deviations from the standard $τ\proptoλ^{4/3}$ lag-wavelength relation, which describes the time delay between variability at different wavelengths for a standard thin accretion disk. These signatures are strongest at low-to-moderate Eddington ratios, and related observations could provide indirect evidence for embedded compact-object populations in AGN disks.
[abstract 8 / 75] Yes (score: 6) - Title: Prospects for the detection of gamma rays using Cherenkov telescopes enhanced by a ground array observatoryAuthors: C. Alispach, A. Araudo, A. Bakalová, M. Balbo, V. Beshley, J. Blažek, J. Borkowski, T. Bulik, F. Cadoux, S. Casanova, A. Christov, J. Chudoba, L. Chytka, P. Čechvala, P. Dědic, Y. Favre, M. Garczarczyk, L. Gibaud, T. Gieras, E. Głowacki, P. Hamal, M. Heller, M. Hrabovský, P. Janeček, M. Jelínek, V. Jílek, J. Juryšek, V. Karas, B. Lacave, E. Lyard, D. Mandát, W. Marek, S. Michal, J. Michałowski, M. Miroń, R. Moderski, T. Montaruli, A. Muraczewski, S. R. Muthyala, A. L. Müller, A. Nagai, K. Nalewajski, D. Neise, J. Niemiec, M. Nikołajuk, V. Novotný, M. Ostrowski, M. Palatka, M. Pech, M. Prouza, P. Schovánek, T. Schulz, V. Sliusar, J. Srba, Ł. Stawarz, R. Sternberger, M. Stodulska, J. Świerblewski, P. Świerk, J. Štrobl, T. Tavernier, P. Trávníček, I. Troyano Pujadas, J. Vícha, R. Walter, K. Ziȩtara, R. Conceição, L. Gibilisco, M. Pimenta, B. Tomé,Comments: 9 pages, 10 figures. Published in Astroparticle PhysicsSubjects: astro-ph.IM astro-ph.HECreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
We study through detailed simulated data and their optimized analysis the expected performance of the Single-Mirror Small-Size imaging atmospheric Cherenkov Telescopes (SST-1M) potentially located inside a high-altitude array of Water-Cherenkov Detectors (WCDs) inspired by the current foreseen design of the Southern Wide-field Gamma-ray Observatory (SWGO). For such a hybrid setup, we show an improvement in the flux sensitivity above 10 TeV by about 60% for monocular and 30% for stereoscopic SST-1M observation, due to the improved gamma/hadron separation when additional parameters from the WCD array are used. We also discuss further benefits of the hybrid gamma observatory concept and its technical challenges.
[abstract 9 / 75] Yes (score: 6) - Title: Little Red Dots as Supermassive Analogs of SS 433Authors: Shuying Zhou, Mouyuan Sun, Xihan Ji, Ya-Ping Li, Luis C. Ho, Roberto Maiolino, Zhen-Yi Cai, Hai-Cheng Feng, Manqi Fu, Wei-Min Gu, Tong Liu, Junfeng Wang, Jianfeng Wu, Yongquan Xue,Comments: 21 pages, 10 figures, comments welcomeSubjects: astro-ph.HE astro-ph.GACreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
High-redshift little red dots (LRDs) are compact sources characterized by V-shaped spectral energy distributions (SEDs), broad emission lines, and often prominent Balmer breaks. Their high number density and apparently large BLACK HOLE masses suggest that they are essential to the early evolution of galaxies and supermassive BLACK HOLEs (SMBHs); however, the nature of their central engines remains uncertain. Here, we propose that LRDs are the supermassive, high-redshift analogs of the hyper-Eddington accreting Galactic microQUASAR SS~433, viewed at high inclinations. By scaling the hyper-Eddington accretion physics from stellar-mass BLACK HOLEs to supermassive scales, we show that the observed LRD features, including X-ray weakness, soft optical SEDs, apparent sub-Eddington accretion ratio, and Balmer breaks, emerge naturally from the self-shielding geometry of a puffed-up accretion disk. In this framework, the broad-line regions are ionized by anisotropic radiation escaping from the inner disk, analogous to the unseen UV/X-ray emission revealed by the W50 nebula in SS 433. Their low-inclination or lower-accretion-rate counterparts would appear as little blue dots (LBDs) or normal ACTIVE GALACTIC NUCLEi. Our model predicts that the Balmer break strength positively correlates with the broad-line width, that the emission lines are more variable than the optical continuum, that LRDs are intrinsically more luminous than observed, and that LBDs are more variable than LRDs. This unified-scale model redefines LRDs as the essential laboratories for observing the rapid accretion-driven growth that shaped the early assembly of galaxies and their central SMBHs.
[abstract 10 / 75] Yes (score: 6) - Title: XRISM Time-resolved Fe K$α$ Spectroscopy of NGC 4395: Time-variable Inner-disk EmissionAuthors: Taiki Kawamuro, Satoshi Yamada, Hirofumi Noda, Yoshiyuki Inoue, Shoji Ogawa, Misaki Mizumoto,Comments: 16 pages, 11 figures, accepted for publication in the ApJLSubjects: astro-ph.HE astro-ph.GACreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
We report the first XRISM observation of the low-mass AGN in the nearby dwarf galaxy NGC 4395 ($M_{\rm BH}\sim10^{4-5}\,M_\odot$), complemented by a simultaneous NUSTAR observation. We constrained the continuum by jointly fitting the XRISM/Resolve (2-12 keV) and NUSTAR (3-30 keV) spectra while excluding the Fe K band (5.5-7.5 keV). Relative to this baseline continuum, the time-averaged Resolve spectrum revealed an unresolved neutral Fe K$α$ core with a velocity width of $\lesssim$110 km s$^{-1}$ and an adjacent redward wing. The red wing was well reproduced by an additional RELATIVISTICally broadened Fe K component. Furthermore, time-resolved spectroscopy with $\approx$87 ks bins showed that the diskline profile varied significantly over the $\sim$400 ks observation. This evolution can be interpreted in terms of changes in the inner radius of the line-emitting region, together with a possible inclination modulation with a period of $\approx$210 ks. If interpreted as Lense-Thirring precession of a tilted inner flow, the observed period would favor the low end of the BLACK HOLE mass estimates ($M_{\rm BH}\approx9\times10^3\,M_\odot$) and imply a moderate spin ($a\gtrsim0.6$). These results highlight the capability of XRISM to track RELATIVISTIC disk dynamics in AGNs.
[abstract 11 / 75] Yes (score: 6) - Title: Observations of a Possible Transient Magnetically Arrested Accretion State in a Nearby Quasar: OQ208Authors: Brian Punsly, Cormac Reynolds, Paola Marziani, Gary J. Hill, Alexander B. Pushkarev, Carlo Stanghellini, Frank Schinzel, Christopher O'Dea, Gregory R. Zeimann, Andrew Biggs, Jian-Min Wang, Pu Du, Alberto Floris, Mauro D'Onofrio, Levi Malmstrom,Comments: To appear in ApJSubjects: astro-ph.GACreated: 2026-06-22; Updated: 2026-06-23; Datestamp: 2026-06-23
OQ208 is a nearby, partially obscured QUASAR (z=0.077) that is a young, bright, parsec scale radio source. We assemble archival and new high frequency VLBA and VLA observations and optical spectra to form a data-set spanning 39 years. Radio light curves covering 58 years were also compiled. We utilize new spectrophotmetry to calibrate previous spectroscopy using forbidden narrow lines that are expected to be stable on much longer time scales. VLBA and VLA observations of a light-year scale bright nuclear flare at 15.4~GHz and 22~GHz reveal a rise (fade) beginning in mid-1996 (early-2000). Quasi-contemporaneously, from 2/7/1997-6/3/2000, the H$α$ broad line equivalent widths (EWs) and fluxes dropped dramatically. In the context of the tendency of radio loud QUASARs to have a depressed extreme ultraviolet (EUV) continuum (the main source of ionizing flux for H$α$) relative to radio quiet QUASARs at matched UV luminosity (the EUV deficit of radio loud QUASARs), this may not be a coincidence. Analytic models previously developed to explain the relationship between JET power and the EUV deficit are consistent with (but not direct observational proof of) the small EWs being a consequence of transient MAGNETically arrested accretion states from $\sim1997-2001$. The 22 GHz VLBA nucleus gradually fades, in 2023 the flux density is $<5\%$ of its value in 2000. The environs of the nucleus also fade at 22 GHz, but in a time delayed fashion.
[abstract 12 / 75] Yes (score: 5) - Title: A broadband view of the thermal and non-thermal emission from the embedded massive star cluster RCW 38Authors: Giada Peron, Andrea Bracco, Giovanni Morlino, Silvia Mantovanini, Elena Amato, Daniele Galli, Marco Padovani,Comments: Submitted to A&A. Comments are welcomeSubjects: astro-ph.HE astro-ph.SRCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
Gamma-ray emission has now been detected from a variety of source classes in the Galaxy, including clusters of young massive stars. RCW 38, a very young embedded massive star cluster, is a case of particular interest: its gamma-ray emission detected up to hundreds of GeV, provided the first observational evidence of high-energy particle acceleration powered exclusively by stellar winds. In this work, we aim to characterize the emission mechanisms responsible for the gamma-ray flux in RCW 38 and to provide estimates of the acceleration efficiency, as well as the fraction of accelerated electrons compared to protons, $K_{ep}$. We present the most comprehensive multi-wavelength study of a single star cluster to date. Our analysis ranges from MHz radio observations obtained with the GLEAM-X survey from the Murchison Widefield Array (MWA) to GeV gamma-ray data from FERMI-LAT, and includes GHz and THz measurements from Parkes, Planck, and IRAS. We model the thermal and non-thermal emission of RCW 38 using an eight-parameter model constrained by the Markov chain Monte Carlo method. Our results support an interpretation in which the gamma-ray emission from RCW 38 is produced by hadronic interactions with the host molecular cloud. We derive robust constraints on the electron-to-proton ratio, with $K_{ep} \lesssim 10^{-3}$, and on the acceleration efficiency, estimated to be $\gtrsim$1%, consistent with the values required to explain the cosmic-ray composition, and in particular its $^{22}$Ne anomaly. These results strengthen the idea that stellar clusters play a significant role as contributors to cosmic-ray protons in our Galaxy at least up to energies of a few TeV. Future investigations with the next generation of ground-based detectors will determine whether they also play a relevant role at higher energies, particularly in the context of the cosmic-ray knee.
[abstract 13 / 75] Yes (score: 5) - Title: Linear Tearing Growth and Onset of Relativistic Magnetic Reconnection in the Presence of Shear Flows and a Guide FieldAuthors: Sarah Peery, Yi-Hsin Liu,Comments:Subjects: physics.plasm-phCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
It has been shown in non-RELATIVISTIC tearing theory that shear flows will slow the linear phase of tearing instability and can delay onset of MAGNETic RECONNECTion. We find using kinetic particle-in-cell simulations that shear flow as well as guide field strength affect the onset time of RELATIVISTIC MAGNETic RECONNECTion. To model this we develop a numerical solver for the growth rate of the RELATIVISTIC linear tearing instability, including effects of the motional electric field which has not previously been done. We find slowing of growth due to both shear flows and guide field, and at higher flow shear, transition through an intermediate regime to linear Kelvin-Helmholtz instability.
[abstract 14 / 75] Yes (score: 5) - Title: FERMI bubbles detected in $\sim$100 TeV neutrinosAuthors: Uri Keshet, Ilya Gurwich,Comments: 10 pages, 9 figuresSubjects: astro-ph.HECreated: 2026-06-21; Updated: 2026-06-23; Datestamp: 2026-06-23
The FERMI bubbles have been identified as a collimated bipolar outflow emanating from the Milky-Way center, tracing strong forward shocks which extend $\sim10$ kpc from the Galactic disk, originating from a $\sim10^{56\pm1}$ erg outburst. These shocks are sufficiently strong, extended, and energetic to produce a detectable flux of $\gtrsim 10$ TeV neutrinos, especially in their denser north and east, but early IceCube data were insufficient for identifying the signal. We find that IceCube high-energy starting events (HESE 12-year) correlate with the $\textit{FERMI}$-LAT sky map outside the Galactic plane ($>3σ$). Testing for neutrinos coincident with the bubble shells, localized using $\textit{eROSITA}$ data, we detect ($>4σ$) both bubbles at high ($|b|>30^{\circ}$) latitudes, with a local excess ($>5σ$) mainly in their X-ray bright eastern shells. The signal matches the anticipated secondaries of RELATIVISTIC ions carrying $\sim 10^{54.5}$ erg (with factor $\sim3$ uncertainty) in each bubble, shock-accelerated to $>$PeV energies. The results verify the strength of the shocks, suggesting an ion acceleration efficiency of order $\sim10\%$. We also present preliminary evidence for neutrinos from the even larger shells of the eROSITA bubbles, which encapsulate their younger FERMI-bubble counterparts, carrying a similar energy and confined by shocks nearly as strong.
[abstract 15 / 75] Yes (score: 4) - Title: Impact of the EPOS.LHC-R hadronic interaction model on the Centaurus A ultrahigh-energy cosmic-ray scenarioAuthors: Silvia Mollerach, Esteban Roulet,Comments: matches published versionSubjects: astro-ph.HECreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
We discuss the impact of the recent EPOS.LHC-R hadronic interaction model on the scenario in which most of the COSMIC RAYs with energies above 5 EeV originate in the nearby Centaurus A RADIOGALAXy. The heavier composition inferred from this hadronic model has important implications for the interpretation of the spectral features and for the anisotropies. In particular, the amount of H and He present above the ankle is now very suppressed. The elements of the CNO group from the source play a predominant role in the instep region just above the ankle, while the elements of the Si and Fe groups contribute significantly in the suppression region of the energy spectrum above 50 EeV. The lack of He from the source above the ankle also leads to a smaller expected anisotropy around the Cen A direction at energies of 10 to 20 EeV. The expected dipolar anisotropy in different energy bins above 4 EeV is well consistent with the measurements for appropriate values of the extragalactic turbulent MAGNETic field and source lifetime. The overall fit to the different observables improves considerably with the new hadronic model. A new method is introduced to extract the information on the COSMIC RAY masses from that of the depth of the maximum development of the air showers, which significantly improves the existing method.
[abstract 16 / 75] Yes (score: 4) - Title: Ballistic Surfing Acceleration as a Coherent Mechanism for Electron Acceleration in Galaxy Cluster ShocksAuthors: Ji-Hoon Ha, Krzysztof Stasiewicz,Comments: 10 pages, 3 figures, Accepted for publication in MNRASSubjects: astro-ph.HE physics.plasm-phCreated: 2026-06-18; Updated: 2026-06-23; Datestamp: 2026-06-23
Radio relics in merging galaxy clusters are widely interpreted as SYNCHROTRON emission from RELATIVISTIC electrons accelerated at large-scale shocks. However, the efficiency of diffusive shock acceleration (DSA) is expected to be suppressed in the low-Mach-number, weakly turbulent environments of cluster mergers; furthermore, recent theoretical insights suggest that DSA may not constitute a viable physical mechanism for such environments. In this work, we investigate ballistic surfing acceleration (BSA) as an electrodynamically grounded alternative for electron energization that bypasses the need for prescribed diffusion coefficients. We formulate BSA under typical cluster shock conditions, deriving the balance between coherent acceleration by the convective electric field and radiative losses from SYNCHROTRON and inverse-Compton cooling. This equilibrium defines the maximum reachable electron energy and constrains the resulting steady-state spectrum. By forward-modeling the associated SYNCHROTRON emission and comparing it with integrated radio observations of the `Sausage' (CIZA J2242.8+5301) and `Toothbrush' (1RXS J0603.3+4214) relics, we find that the observed spectral curvature and high-frequency steepening are consistent with BSA-limited energies, provided that active acceleration involves only a minute participation fraction ($10^{-9}$-$10^{-8}$) of the radiating electrons. Despite this high selectivity, BSA effectively produces Lorentz factors of $γ\sim 10^4$-$10^5$. Our results suggest that radio relics serve as prime astrophysical laboratories for probing coherent acceleration, with the BSA framework providing a robust and physically consistent explanation for electron energization in cluster shocks.
[abstract 17 / 75] Yes (score: 4) - Title: A HINSA view of cosmic-ray ionization in IC 348 and NGC 1333: evidence for a strong low-energy cosmic-ray disparityAuthors: Gan Luo, Marco Padovani, Daniele Galli, Thomas G. Bisbas, Brandt A. L. Gaches, Di Li, Marko Krčo, Ningyu Tang,Comments: 12pages, 12 figures, A&A acceptedSubjects: astro-ph.GA astro-ph.HECreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
The cosmic-ray ionization rate (CRIR) is one of the fundamental parameters influencing the chemical and dynamical evolution of molecular clouds. Although observations in recent years have revealed high CRIR values in massive star-forming regions and in the vicinity of protostars, the sources and acceleration mechanisms of COSMIC RAYs remain uncertain. In this work, we present our new estimates of CRIR using the HI narrow self-absorption (HINSA) technique towards two nearby low-mass star-forming clouds, IC 348 and NGC 1333. In both clouds, the CRIR decreases with increasing H$_2$ column density, but IC 348 exhibits values that are roughly an order of magnitude higher than those in NGC 1333. To interpret this contrast, we model the low-energy spectrum of CRs in a finite slab attenuation framework, using additional constraints from the high-energy CR spectrum inferred from FERMI $γ$-ray observations. The best-fit spectra reproduce the observed CRIR profiles and the contrast between IC 348 and NGC 1333 suggests an order of magnitude difference in low-energy CR populations, likely originating from local acceleration sources beyond protostars (e.g., stellar-wind termination shocks), and partly from the same sources responsible for the GeV $γ$-ray excess. Although uncertainties in cloud structure and gas density may affect the absolute CRIR values, they do not erase the pronounced disparity between the two regions.
[abstract 18 / 75] Yes (score: 4) - Title: Probing dipole and quadrupole anisotropy in Gamma-ray bursts from SWIFT datasetAuthors: Vedant Mokal, Shantanu Desai,Comments: 18 pages, 17 figures. Accepted for publication in UniverseSubjects: astro-ph.HE astro-ph.COCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
Testing the validity of the cosmological principle's assumption of large-scale isotropy remains crucial for modern cosmology. We investigate the angular distributions of GAMMA-RAY BURSTs using the GRB catalog from Neil Gehrels SWIFT Observatory (SWIFT) for an independent probe of isotropy. Using the HEALPix spherical harmonic decomposition, we estimate the dipole and quadrupole amplitudes and compare them against the null hypothesis obtained from 500 isotropic Monte Carlo realizations. Our results show 2.9$σ$ dipole and 7.2$σ$ quadrupole amplitude when applied to the raw data. To account for observational biases, we then create an exposure map using the pointing history, roll angle, and the partial coding fraction of the SWIFT Telescope. Reevaluating the null hypothesis using this map reduces the significance of these anisotropies to less than $1σ$. Therefore, our findings confirm statistical isotropy of the GRB sky using the SWIFT data, consistent with previous studies. We have also made the SWIFT exposure map publicly available.
[abstract 19 / 75] Yes (score: 4) - Title: Reconnection-induced electron energization in MAGNETospheric Kelvin-Helmholtz dynamicsAuthors: Silvia Ferro, Fabio Bacchini, Giuseppe Arrò, Francesco Pucci, Pierre Henri,Comments: Submitted to ApJLSubjects: physics.plasm-ph physics.space-phCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
The Kelvin-Helmholtz instability (KHI) is a major driver of multiscale plasma dynamics at velocity shear layers, where it can promote the formation of current sheets and the onset of MAGNETic RECONNECTion as well as drive plasma energization. While recent kinetic studies have shown efficient electron heating during nonlinear KH evolution, the connection between RECONNECTion dynamics and localized electron energization is still not fully understood. We investigate this link using two-dimensional fully kinetic simulations of KHI developing in a double-periodic system with two velocity shear layers and a uniform guide field, initialized from a finite-Larmor-radius equilibrium. During the nonlinear stage, initially coherent vortices evolve into layers populated by fragmented current sheets displaying RECONNECTion activity. The global energetics reveal species-dependent energization pathways. Ions act as the primary energy reservoir, transferring energy to the electroMAGNETic fields, while electrons receive the dominant net positive energy input. Electron energization is strongly anisotropic ($T_{\parallel,e} > T_{\perp,e}$) and localized within intermittent current sheets associated with enhanced field-particle energy exchange and elevated agyrotropy. These regions also show the development of suprathermal tails in the electron energy distributions, providing evidence for nonthermal electron energization. Despite opposite vorticity orientations, the two shear layers exhibit similar statistical behavior. Together, these results establish a direct connection between RECONNECTion-associated current structures and localized electron energization in collisionless KHI dynamics.
[abstract 20 / 75] Yes (score: 4) - Title: Little Red and Blue Dots: AGN-excited narrow lines, Lyman-$α$ emission, and resemblance to standard QUASARsAuthors: Sophia Geris, Roberto Maiolino, Xihan Ji, Guido Risaliti, Giorgio Lanzuisi, Francesco D'Eugenio, Yuki Isobe, Gareth Jones, Anishya Harshan, Matilde Brazzini, Ignas Juodžbalis, Jan Scholtz, Pierluigi Rinaldi, Hannah Übler, William Baker, Andrew J. Bunker, Marcella Brusa, Stefano Carniani, Stephane Charlot, Mirko Curti, Andrea Comastri, Emma Curtis Lake, Roberto Gilli, Kevin Hainline, Piero Madau, Stefano Marchesi, Giovanni Mazzolari, Lorenzo Napolitano, Eleonora Parlanti, Laura Pentericci, Cristina Ramos Almeida, Brant Robertson, Maddie S. Silcock, Roberta Tripodi, Giacomo Venturi, Cristian Vignali, Fabio Vito, Yongda Zhu,Comments: Submitted. 33 pages, 23 figures, 3 tablesSubjects: astro-ph.GA astro-ph.COCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
We present an analysis of a sample of 36 Little Red and Blue Dots (LRDs and LBDs) at $2.26
[abstract 21 / 75] Yes (score: 4) - Title: A grid of fast-rotating, chemically-homogeneous, SUPERNOVA and/or long-GRB progenitorsAuthors: M. Renzo, O. Gottlieb, H. S. Chan, J. A. Goldberg, A. Grichener, K. Sen, N. Shah, E. Farag, Matteo Cantiello,Comments: submitted to AAS, data available at https://zenodo.org/records/14286306, reproducible at https://github.com/mathren/CHE_LGRB_progenitors, comments welcome!Subjects: astro-ph.HE astro-ph.SRCreated: 2026-06-20; Updated: 2026-06-23; Datestamp: 2026-06-23
The understanding of the mechanism(s) by which massive stars collapse and possibly explode is rapidly maturing. Uncertainties in the structure of the stellar core at the onset of collapse are often dominant in numerical simulations, and a limited number of progenitor grids are available. This is especially true for explosions where rotation and MAGNETic fields play a significant or primary role. We present a grid of 113 single-star models with initial masses $M_{\rm ZAMS}=30-90\,M_{\odot}$ and initial rigid rotation $ω_{\rm ZAMS}=0.5-0.99\,ω_{\rm crit}$ computed at $Z=0.001$ with the open-source stellar evolution code \textsc{MESA}. We adopt a 128-isotope nuclear reaction network capable of following the weak reactions deleptonizing the core during and after silicon core burning. By construction, these models experience rotationally-induced chemically-homogeneous evolution, and reach the onset of collapse ($v_{\rm infall}\lesssim -300\,\mathrm{km\ s^{-1}}$) with large and structured amounts of angular momentum, possibly sufficient to form accretion disks on a proto-compact object. Therefore, these progenitor structures provide a homogeneous set of models with updated input physics and improved algorithmic accuracy to understand stellar explosions of (some types of) stripped-envelope SUPERNOVAe, possibly JETted and/or broad-lined, collapsars or MAGNETar-powered, and/or long $γ$-ray bursts.
[abstract 22 / 75] Yes (score: 4) - Title: EMU discovery of Thunder: a bow-shock PWN powered by PSR J1631-4722 escaping Nimbus SNR (G336.7+0.5)Authors: S. Lazarević, C. Maitra, A. Ahmad, R. Z. E. Alsaberi, S. Dai, D. Leahy, M. D. Filipović, P. G. Edwards, O. Kargaltsev, M. Abdelmaguid, J. D. Gelfand, J. West, S. Hutschenreuter, R. Brose, R. Kothes, V. Velović, C. Burger-Scheidlin, B. D. Ball, G. Graham, A. M. Hopkins, G. P. Rowell, S. F. Rahman, Z. J. Smeaton, S. Taziaux,Comments: 12 figures, 8 tables. Accepted for publication in ApJSubjects: astro-ph.HECreated: 2026-06-21; Updated: 2026-06-23; Datestamp: 2026-06-23
We report the discovery of a bow-shock pulsar wind nebula (PWN), dubbed Thunder, powered by the radio pulsar PSR J1631-4722 and projected within the Galactic SUPERNOVA remnant (SNR) G336.7+0.5 (Nimbus). The system was first identified in observations from the Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) survey and further characterised using MeerKAT Galactic Plane Survey data together with follow-up observations at 5.5 and 9 GHz obtained with the Australia Telescope Compact Array (ATCA). Assuming a distance of 7 kpc, the radio images resolve an elongated ~80 arcsec (2.7 pc) cometary nebula, indicative of a high velocity pulsar. An X-ray counterpart extending ~50 arcsec (1.7 pc) is detected in archival XMM-Newton data. The flat radio spectrum ($α$ = -0.27 $\pm$ 0.05) and hard X-ray photon index ($Γ$ = 1.6 $\pm$ 0.4) indicate SYNCHROTRON emission from RELATIVISTIC particles injected in the pulsar wind. Polarisation analysis reveals a highly ordered MAGNETic field aligned with the nebular flow, with fractional polarisation reaching up to 30% in the tail. An equipartition estimate gives a PWN MAGNETic-field strength of Beq $\approx$ 54-140 $μ$G. Pulsar timing over a ~2.2 yr baseline reveals strong timing noise and a small spin glitch with amplitude $Δν/ν$ = 1.10$\times$10$^{-8}$. The SNR shows no clear diffuse X-ray counterpart. The morphology and multiwavelength properties of the Nimbus-Thunder system, along with evolutionary models, constrain the system's age to approximately 30-45 kyr, placing the remnant in the late Sedov phase, approaching the transition to the radiative stage.
[abstract 23 / 75] (score: 3) - Title: Radial dust distributions and obscuring geometry in AGN from JWST/MIRI spectroscopyAuthors: Ruiyu Pan, Arkaprabha Sarangi,Comments: 20 pages, 9 figuresSubjects: astro-ph.GA astro-ph.HECreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
We forward-model rest-frame $8$--$20\,μ\mathrm{m}$ JWST/MIRI MRS spectra of 25 ACTIVE GALACTIC NUCLEi (AGN) with a three-dimensional radiative-transfer library in order to compare radial dust-density laws of the form $n(r)\propto r^{-p}$ over $p=0.5$--$2.0$. Within our tempered grid-based comparison, the model scores do not identify a single radial profile that is preferred for all sources. Instead, 20 of the 25 sources have their largest normalized tempered weights at $p\leq1$, while five have their highest scores at $p\geq1.5$, suggesting that both more extended and more centrally concentrated effective MIR-emitting dust distributions may be represented in the sample. The silicate feature shows a second systematic trend: absorption minima remain close to the canonical $9.7\,μ\mathrm{m}$ wavelength, whereas emission peaks are shifted redward by about $1\,μ\mathrm{m}$, consistent with a combination of radiative-transfer effects and dust processing in the illuminated inner regions. By contrast, the effective obscuring-geometry parameters are more tightly clustered within the adopted grid: the fitted opening-angle values cluster at $30^\circ$--$40^\circ$, and 24 sources have the intermediate radial-extent grid value $Y = 100$. These results suggest that variations in the radial dust distribution and effective dust properties are important contributors to the observed MIR spectral diversity, while the fitted opening-angle parameter is comparatively clustered within the adopted model framework.
[abstract 24 / 75] (score: 3) - Title: Pulsar electrodynamics inferred from frequency-dependent circular POLARIZATION diversityAuthors: Shunshun Cao, Yanjun Guo, Jinchen Jiang, Kejia Lee, Weiyang Wang, Renxin Xu,Comments: 13 pages, 10 figures, published by A&ASubjects: astro-ph.HECreated: 2026-06-22; Updated: 2026-06-23; Datestamp: 2026-06-23
The nature of coherent radio emission is still challenging even after more than half a century of pulsar discovery, but it is generally a consensus that single-pulse observations are essential for probing the MAGNETospheric dynamics, especially with the largest single-dish telescope FAST (Five-hundred-meter Aperture Spherical radio Telescope). This paper aims to explain the observed diversity of single pulse circular POLARIZATION, and to constrain the multiplicity and Lorentz factor of pulsar MAGNETospheric plasma, with the mode coupling model in the limiting POLARIZATION region. Assuming that circular POLARIZATION comes only from wave mode coupling, we apply a Bayesian analysis to the FAST observed single pulse circular POLARIZATION spectra, involving numerical solving of wave mode coupling equations, and analyze the posterior probability distribution functions of the parameters. Although the model fails to quantitatively fit most circular POLARIZATION spectra, circular POLARIZATION of different frequency evolution is reproduced. For three chosen pulsars, the Bayesian analysis constrains the multiplicity to be approximately $10^{0}\sim10^{2}$, and the Lorentz factor to be approximately $10^{0.5}\sim10^{2}$. Pulsar circular POLARIZATION could be induced by wave mode coupling. The plasma flow responsible for coherent radio emission carries only a very small fraction of the pulsar spin-down energy loss.
[abstract 25 / 75] (score: 3) - Title: Progenitor of the recoiling super-massive BLACK HOLE RBH-1 identified using HST/JWST imagingAuthors: Tousif Islam, Tejaswi Venumadhav, Digvijay Wadekar,Comments: 9 pages, 8 figuresSubjects: astro-ph.HE gr-qcCreated: 2026-06-18; Updated: 2026-06-23; Datestamp: 2026-06-23
Using a combination of \textit{Hubble Space Telescope} and \textit{James Webb Space Telescope} imaging, a runaway supermassive BLACK HOLE (RBH-1) was recently identified with an inferred velocity of $954^{+110}_{-126}\,\mathrm{km\,s^{-1}}$, likely ejected from a compact star-forming galaxy (denoted as GX) at $z \approx 0.96$. Assuming the runaway BLACK HOLE was the outcome of the gravitational-wave-driven merger of two BLACK HOLEs, we use its measured runaway velocity together with gravitational-wave recoil predictions from numerical relativity and BLACK HOLE perturbation theory to constrain the mass ratio and spin configuration of the progenitor SMBHs that overcame the final-parsec problem and merged $\sim 70$~Myr ago. We find that the progenitor binary must have been precessing, with a mass ratio $m_1/m_2\lesssim 6$, and that the more massive SMBH must have possessed a high spin (dimensionless spin magnitude $\sim 0.75$) in order to generate a recoil of this magnitude. This has important astrophysical implications as similar SMBH mergers can be an interesting source population for the upcoming LISA mission with signal-to-noise ratios $\gtrsim$ 1000. Furthermore, the progenitor SMBH properties imply that GX was likely formed through a major, gas-rich (``wet'') merger between two galaxies of comparable mass, with a mass ratio $\lesssim 4$.
[abstract 26 / 75] (score: 3) - Title: Investigating the Spectral Properties of Dual Nuclei in Galaxy Mergers from the GOTHIC survey: Supermassive Black Hole Growth, metal enrichment and Dual AGNAuthors: Prerana Biswas, Mousumi Das, Sudhanshu Barway, Françoise Combes, Anwesh Bhattacharya, Snehanshu Saha, C. P. Nehal,Comments: 16 pages, 14 figures. Submitted to MNRASSubjects: astro-ph.GACreated: 2026-06-18; Updated: 2026-06-23; Datestamp: 2026-06-23
Dual nuclei systems are galaxy merger remnants or closely merging galaxies that have two distinct stellar cores separated by ~ 10pc to 10kpc. They are important laboratories for probing the co-evolution of stellar populations, galaxy dynamics, and central BLACK HOLEs during the hierarchical assembly of galaxies. In this study, we present a spectroscopic analysis of a sample of dual nuclei from the GOTHIC survey, using the penalized pixel-fitting (pPXF) code. The sample consists of star forming nuclei pairs, dual ACTIVE GALACTIC NUCLEi (DAGN) and mixed pairs. Using the SDSS spectra, we extracted stellar kinematics, emission line fluxes, the STAR FORMATION history, metallicity of the nuclei, and derived important properties such as the supermassive BLACK HOLE (SMBH) masses, accretion rates and SMBH ratios. We compared different properties of the nuclei in the dual systems, such as stellar velocity dispersion, stellar masses, BLACK HOLE masses, age and metallicity. Our results show that the SMBH masses are higher for BHs in galaxy mergers compared to single nuclei for a given stellar mass, thus revealing that SMBHs grow during the galaxy merging process and not only due to the merger of SMBHs. Our study provides new observational constraints on the dynamical and evolutionary states of dual-nuclei systems, offering a deeper understanding of the role these systems play in galaxy evolution and central BLACK HOLE growth.
[abstract 27 / 75] (score: 3) - Title: Loss-Cone-Limited Dark Matter Accretion onto Early Black Hole SeedsAuthors: Brian Zhang, Grant J. Mathews,Comments:Subjects: astro-ph.CO astro-ph.GA gr-qcCreated: 2026-06-18; Updated: 2026-06-23; Datestamp: 2026-06-23
The rapid appearance of supermassive BLACK HOLEs at high redshift motivates a reassessment of non-baryonic growth channels. We develop a loss-cone framework for collisionless dark-matter (DM) capture by early black-hole seeds, with particular attention to phase-space depletion and refilling. The calculation combines Eddington-inverted NFW-like halos, a RELATIVISTIC direct-capture boundary, and an orbit-averaged Fokker-Planck treatment of angular-momentum transport. Primordial BLACK HOLEs (PBHs) are treated as massive perturbers whose refilling strength depends on both their abundance and individual mass. Collisionless refilling by triaxial or chaotic centrophilic orbits is included as a phenomenological upper-envelope channel. We show that ordinary stellar relaxation gives negligible DM-driven growth for the fiducial high-redshift seeds. PBH-driven granularity can yield order-of-magnitude growth in sufficiently compact halos, while triaxial or full-loss-cone supply can produce a rapid early burst. In the self-consistent calculations, however, the evolution generally becomes supply-limited. Once the accessible low-angular-momentum phase-space reservoir is depleted, the capture rate collapses and the black-hole mass saturates. Fixed-background NFW calculations therefore overestimate sustained growth, especially in the full-loss-cone limit. A TNG50-calibrated NFW benchmark gives negligible growth even under optimistic refilling assumptions. Collisionless DM capture is therefore unlikely to solve early SMBH growth in generic NFW-like halos, but it can provide a radiatively dark upper envelope in rare compact environments with efficient angular-momentum refilling.
[abstract 28 / 75] (score: 3) - Title: Rankine-Hugoniot conditions in Q-variables: a wave-aligned formulation of MHD discontinuitiesAuthors: Anna Krupka, Tijs Van Hoof, Tom Van Doorsselaere,Comments: 29 pages, 2 figures. Submitted to Physics of PlasmasSubjects: physics.plasm-phCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
The recently developed Q-variable formalism generalises the Elsässer representation by providing a wave-aligned representation applicable to a broad class of MAGNETohydrodynamic disturbances, including Alfvénic, fast, slow, and kink waves. While this framework has proven useful for the study of wave dynamics and turbulence, its behaviour in the presence of plasma discontinuities has not yet been established. In this work, we derive the complete set of Rankine-Hugoniot jump conditions in terms of the Q-variables by rewriting the ideal MHD equations in a form suitable for shock-frame jump analysis. This yields explicit jump relations for mass, momentum, MAGNETic flux, and energy. We then demonstrate analytically that these relations are exactly equivalent to the classical MHD Rankine-Hugoniot conditions. This reformulation provides a wave-aligned representation of MHD discontinuities and offers a natural framework for discussing directional wave content and branch-restricted limits when $α$, the wave-branch parameter entering the Q-variable definition, is chosen consistently with the relevant characteristic speed. The resulting formulation is well suited for the analysis of wave-shock interactions in MAGNETised plasmas, with potential applications to the solar wind, MAGNETospheric systems, and large-scale models of structured plasma environments such as UAWSOM.
[abstract 29 / 75] (score: 3) - Title: Effect of Noise on Spatio-Temporal Evolution of Current Filamentation Instability in Relativistic Beam-Plasma SystemsAuthors: Thulasidharan K, Vishwa Bandhu Pathak,Comments:Subjects: physics.plasm-phCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
The spatio-temporal evolution of the current filamentation instability in a RELATIVISTIC beam--plasma system is studied analytically and with two-dimensional particle-in-cell simulations. A partial differential equation for the transverse vector potential is derived for a sharp-front RELATIVISTIC beam entering cold, unMAGNETized plasma, including a second-order spatial derivative term that governs the spatial growth near the beam front. The equation is solved analytically for constant, linearly growing, and oscillatory initial noise when this term is neglected, and numerically when it is included, as no closed-form solution then exists. For constant initial noise, the numerical solution reproduces the simulated MAGNETic-field structure, unlike the analytical solution without the term. This shows that the longitudinal field modulation is intrinsic to the instability, present even for a noise with constant amplitudes. The noise profile as well can influence the spatial-temporal evolution of the instability, which we discuss further considering linearly growing and oscillatory noise. The field grows spatially behind the beam front and saturates at a length $L_{\mathrm{sat}}\propto(v_{0b}+2)v_{0b}/γ_{0b}^{3}$, where $v_{0b}$ and $γ_{0b}$ are the beam velocity and Lorentz factor, beyond which growth is purely temporal. The saturation length increases linearly in time at a constant rate $\mathrm{d}L_{\mathrm{sat}}/\mathrm{d}τ\approx0.42\,c$, matching the analytical estimate. The temporal growth rate remains unchanged, so the term modifies the spatial transport of the instability rather than its local amplification. For beam velocities above $0.6c$, the model deviates from the simulations as oblique modes and nonlinear filament dynamics outside the single-mode treatment become important.
[abstract 30 / 75] (score: 3) - Title: Subgrid Modelling for Relativistic Magnetohydrodynamics with Machine LearningAuthors: William Cook, Sebastiano Bernuzzi,Comments: 22 pages, 16 figures, 3 tablesSubjects: astro-ph.HE gr-qc physics.flu-dynCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
Resolving the impact of MAGNETic field instabilities in triggering small scale turbulent flow and the associated rearrangement of the field is of critical importance in understanding multimessenger observables in binary neutron star mergers, and angular momentum transport in neutron stars and accretion disks. Direct simulation of these instabilities are unfeasible, however large-eddy simulations can incorporate the impact of this turbulence with a subgrid model. We present the first machine-learning-based subgrid model for special RELATIVISTIC MAGNETohydrodynamics, trained using a neural network. We demonstrate its performance in online simulations of the 3D Kelvin-Helmholtz instability through both a priori and a posteriori tests. Evaluated in a low resolution simulation, our model captures MAGNETic field amplification of a simulation at 4 times the resolution with a speed-up of a factor 44. This demonstrates the applicability of such methods in general RELATIVISTIC simulations of neutron star mergers and other scenarios.
[abstract 31 / 75] (score: 3) - Title: Fast targeted gravitational-wave followup search for compact binary mergers using GSTLAL pipelineAuthors: Leo Tsukada, Noah Zhang, Surabhi Sachdev, Shomik Adhicary, Chad Hanna, Prathamesh Joshi, Divya Singh,Comments: 15 pages, 7 figuresSubjects: astro-ph.HE gr-qcCreated: 2026-06-20; Updated: 2026-06-23; Datestamp: 2026-06-23
We present a novel method to conduct targeted gravitational-wave searches for compact binary mergers using the GstLAL inspiral pipeline. By incorporating sky localization and timing information from external electroMAGNETic triggers, we enhance the sensitivity of the search for sub-threshold gravitational-wave signals associated with events such as short GAMMA-RAY BURSTs. Our approach modifies the standard likelihood ratio ranking statistic to include a sky localization prior, allowing for a more focused analysis on specific regions of the sky. We demonstrate the effectiveness of this method through injection studies, comparing the performance of the targeted search against the standard all-sky search configuration. The results show a significant improvement in detection efficiency for signals consistent with the provided sky location and timing, while maintaining control over false alarm rates. This targeted search framework enables rapid follow-up of electroMAGNETic transients, facilitating multi-messenger astronomy efforts in the era of advanced gravitational-wave detectors.
[abstract 32 / 75] (score: 3) - Title: Unified Mass-Scaled QPO Signatures of Kerr Sen Black Holes from Stellar Mass to Supermassive SourcesAuthors: Orhan Donmez, G. Mustafa,Comments: Comments and suggestions are welcomeSubjects: astro-ph.HE gr-qcCreated: 2026-06-21; Updated: 2026-06-23; Datestamp: 2026-06-23
In this study, we numerically investigate Bondi-Hoyle-Lyttleton (BHL) accretion around Kerr-Sen BLACK HOLEs and examine how the charge-related deformation of the spacetime affects the shock-cone morphology, the variation of the mass accretion rate, and the quasi-periodic oscillation (QPO)-like temporal behavior. The RELATIVISTIC BHL flow is solved numerically in the equatorial plane for two different BLACK HOLE spin parameters, a = 0.9 M and a = 0.5 M. From the numerically computed mass accretion rate signal, we calculate the power spectral density (PSD) and perform multi-component Lorentzian fits to identify the dominant QPO-like modes excited around the BLACK HOLE. The results show that the Kerr-Sen deformation shifts the characteristic frequencies, changes the coherence properties of the oscillation modes, and produces near-resonant harmonic structures close to 3:2 and 2:1. By using inverse mass scaling, the numerically computed frequencies are compared with observed QPOs from stellar-mass, intermediate-mass, and supermassive BLACK HOLE systems. In particular, reasonable agreement between the numerical simulation results and observations is found for the sources GRS 1915+105, IGR J17091-3624, M82 X-1, NGC 5408 X-1, RE J1034+396, 1H 0707-495, and ESO 113-G010. This comparative analysis indicates that Kerr-Sen BLACK HOLE shock-cone oscillations may provide a unified framework for interpreting timing features over a broad range of BLACK HOLE masses and may additionally contribute to constraining the mass and spin parameters of sources whose properties are not yet fully established observationally. These findings further imply that combined hydrodynamical and timing diagnostics constitute a promising approach for assessing the extent to which deviations associated with the Kerr-Sen geometry can be empirically distinguished from those of the Kerr spacetime.
[abstract 33 / 75] (score: 3) - Title: Characterization of Numerical Dissipation in Simulations of Magnetohydrodynamic TurbulenceAuthors: Yuyang Hua, Zhonghai Zhao, Bin Qiao,Comments: 32 pages, 12 figures, submitted to ApJSSubjects: physics.plasm-ph astro-ph.HE astro-ph.IM physics.flu-dynCreated: 2026-06-21; Updated: 2026-06-23; Datestamp: 2026-06-23
Comprehensive characterization of numerical dissipation is essential for high-fidelity simulations of MAGNETohydrodynamic (MHD) turbulence. In this work, we present an a posteriori framework for directly estimating numerical dissipation in MHD turbulence from simulation data without invoking a priori assumptions. Implemented in the open-source Python package PyMHD, the framework is applied to simulations of Alfvénic turbulence, turbulent small-scale dynamos, and MRI-driven turbulence, yielding a systematic characterization of the anisotropy and spectral properties of numerical dissipation across these regimes. The results indicate that numerical dissipation primarily dissipates energy transferred by the turbulent cascade at small scales, consistent with the conventional interpretation. However, its spectral properties are distinct from those of physical viscosity and resistivity, such that it cannot simply be represented by effective dissipation coefficients. In addition, numerical dissipation inherits the anisotropy of the underlying turbulence, and can even exhibit anomalous anti-dissipative behavior under certain circumstances. Moreover, this framework enables identification of the conditions under which physical dissipation dominates numerical dissipation across all scales, thereby providing practical guidance for achieving high-fidelity simulations of astrophysical MHD turbulence.
[abstract 34 / 75] (score: 3) - Title: Radio spectral properties and aging of two tailed RADIO GALAXies in a galaxy group at z=0.35Authors: Paula Vulić, Vernesa Smolčić, Alexis Finoguenov, Ghassem Gozaliasl, Hiddo Sunnz Bouwe Algera, Ivan Delvecchio,Comments:Subjects: astro-ph.COCreated: 2026-06-21; Updated: 2026-06-23; Datestamp: 2026-06-23
We present a study of two tailed RADIO GALAXies in the core of a massive, dynamically young galaxy group - an early group-group merger. Using VLA (3 GHz and 1.4 GHz), MeerKAT (1.35 GHz), and GMRT (610 and 325 MHz) observations, we investigate their radio spectral properties, spectral and dynamical ages. Radio morphologies show clear evidence of interaction with the intragroup medium (IGM). One galaxy is a wide-angle tail (WAT) source, while the other is most likely a head-tail (HT) galaxy. Both galaxies exhibit high radio luminosities, and we find spectral indices of $α=0.8\pm 0.1$ (WAT) and $α=0.6\pm 0.2$ (HT). Spectral index analysis reveals spectral steepening with distance from the core in both galaxies, with localized flattening in the WAT lobes and hotspots along the northern JET, and indications of such flattening in the middle of the HT tail. Spectral ages derived using Jaffe-Perola model are $33.80\substack{+7.63 \\ -7.23}$ Myr (WAT) and $20.86\substack{+10.07 \\ -17.17}$ Myr (HT), significantly lower than dynamical ages of $420\pm60$ to $700\pm100$ Myr (WAT) and $140\pm20$ Myr (and possibly up to $280\pm40$ Myr, for HT), yielding dynamical-to-spectral age ratios of $\sim12-20$ and $\sim7$ (and up to $\sim14$), respectively. The discrepancy may be reduced by using more complex dynamical age models, incorporating interactions with the IGM, which requires deeper X-ray observations of the group. Spectral age estimates may be affected by mixing of electron populations, and could be better constrained with future deep, high-resolution broad-band radio observations at both MHz and frequencies above 3 GHz. The combination of extended radio structures, spectral signatures of radiative aging with localized re-acceleration, and activity timescales up to hundreds of Myr indicates that galaxies are actively interacting with, and likely depositing energy into their environment.
[abstract 35 / 75] (score: 3) - Title: Finite-volume scheme for first-order viscoresistive RELATIVISTIC MAGNETohydrodynamicsAuthors: Ruben Lier, Jay Armas, Oliver Porth,Comments:Subjects: astro-ph.HE hep-thCreated: 2026-06-21; Updated: 2026-06-23; Datestamp: 2026-06-23
We present a numerical implementation of dissipative RELATIVISTIC MAGNETohydrodynamics based on Bemfica-Disconzi-Noronha-Kovtun (BDNK) theory, in which first-order corrections render the equations causal without introducing additional dynamical variables. We show how these corrections can be incorporated in a finite-volume scheme describing the coupled dissipation of energy, momentum, and MAGNETic field, with the latter treated as a one-form charge. While a minimal set of BDNK terms can convert diffusive equations into telegrapher-type equations, we find that in the ultra-RELATIVISTIC limit an additional correction is required for the system to behave in a stable and causal manner. With this set of equations, we develop an efficient method for primitive-variable recovery and validate the implementation through an analytical benchmark and various two-dimensional simulations.
[abstract 36 / 75] (score: 3) - Title: Black Hole Occupation Fraction: Dependence on Black Hole Mass Threshold, Environment, Resolution and RedshiftAuthors: Emanuele Contini, Jaekyoung Jang, Jinsu Rhee, Changjo Seo, Sukyoung K. Yi,Comments: 16 pages, 7 figures. Submitted to ApJ, comments welcome!Subjects: astro-ph.GACreated: 2026-06-22; Updated: 2026-06-23; Datestamp: 2026-06-23
We take advantage of the state-of-the-art semi-analytic model \texttt{FEGA25} \citep{contini2025}, run on merger trees extracted from three DARK MATTER-only cosmological simulations, to study the relation between the BLACK HOLE (BH) occupation fraction, $f_{\rm BH,occ}$, and galaxy stellar mass as a function of BH mass threshold, galaxy type, simulated volume, numerical resolution, sampled galaxy population, and redshift. \texttt{FEGA25} includes an improved treatment of ACTIVE GALACTIC NUCLEus feedback and does not impose a pre-existing BH seed population: BHs grow naturally through QUASAR and radio modes. Starting from the prerequisite that \texttt{FEGA25} reproduces the observed BH mass function from at least $z=2$ to the present day, our analysis leads to several results. We find that $f_{\rm BH,occ}$ increases with stellar mass, but that its normalization and shape depend strongly on the adopted BH mass threshold and on the relative contribution of central and satellite galaxies. The relative behavior of central and satellite galaxies depends on the simulation box and BH mass threshold, while the global relation should be interpreted as a population-weighted quantity. We also find significant box-to-box variations, reflecting the combined impact of numerical resolution, simulated volume, and sampled galaxy population. The redshift evolution is not universal: YS50 and the \texttt{NewCluster} zoom-in simulation show a trend qualitatively similar to that reported by \citet{tremmel2024}, whereas larger-volume boxes show the opposite behavior. Finally, comparison with other studies shows that the inferred occupation fraction is highly sensitive to BH mass threshold, simulated volume, numerical resolution, and sampled galaxy population.
[abstract 37 / 75] (score: 2) - Title: Post-Newtonian theory-inspired framework for characterizing eccentricity in gravitational waveformsAuthors: Tousif Islam, Tejaswi Venumadhav,Comments: 17 pages, 15 figures, software available at: https://github.com/tousifislam/gwModelsSubjects: gr-qcCreated: 2026-06-18; Updated: 2026-06-23; Datestamp: 2026-06-23
Characterizing eccentricity in gravitational waveforms in a consistent manner is crucial to facilitate parameter estimation, astrophysical population studies, as well as searches for these rare systems. We present a framework to characterize eccentricity directly from gravitational waveforms for non-precessing eccentric binary BLACK HOLE (BBH) mergers using common modulations that eccentricity induces in all spherical harmonic modes of the signals. Our framework is in the spirit of existing methods that use frequency modulations in the waveforms, but we refine the approach by connecting it to state-of-the-art post-Newtonian calculations of the time evolution of the eccentricity. Using 39 numerical relativity (NR) simulations from the SXS and RIT catalogs, as well as waveforms obtained from the post-Newtonian approximation and effective-one-body (EOB) formalism, we show that our framework provides eccentricity estimates that connect smoothly into the RELATIVISTIC regime (even up to $\sim 2M$ before merger). We also find that it is necessary to carry existing post-Newtonian calculations to an extra $0.5$PN order to adequately characterize existing NR simulations, and provide fits to the extra coefficient for existing simulations. We make the framework publicly available through the Python-based \texttt{gwModels} package.
[abstract 38 / 75] (score: 2) - Title: Data-driven extraction, phenomenology and modeling of eccentric harmonics in binary BLACK HOLE merger waveformsAuthors: Tousif Islam, Tejaswi Venumadhav, Ajit Kumar Mehta, Isha Anantpurkar, Digvijay Wadekar, Javier Roulet, Jonathan Mushkin, Barak Zackay, Matias Zaldarriaga,Comments:Subjects: gr-qc astro-ph.HECreated: 2026-06-18; Updated: 2026-06-23; Datestamp: 2026-06-23
Newtonian and post-Newtonian (PN) calculations suggest that each spherical harmonic mode of the gravitational waveforms (radiation) emitted by eccentric binaries can be further decomposed into several eccentricity-induced modes (indexed by $j=1$ to $j=\infty$), referred to as eccentric harmonics. These harmonics exhibit monotonically time-varying amplitudes and instantaneous frequencies, unlike the full eccentric spherical harmonic modes. However, computing or extracting these harmonics are not straightforward in current numerical relativity (NR) simulations and eccentric waveform models. To address this, Patterson \textit{et al} have developed a framework to extract the eccentric harmonics directly from effective-one-body formalism waveforms. In this paper, we build on the ideas presented in Patterson \textit{et al} and propose a data-driven framework, utilizing singular-value decomposition (SVD), that incorporates additional features based on PN intuition to ensure monotonicity in the extracted harmonics. We further demonstrate that the phase (frequency) of these harmonics is simply $jϕ_λ+ϕ_{\rm ecc}$ ($jf_λ+f_{\rm ecc}$) where $ϕ_λ$ ($f_λ$) is related to the secular orbital phase (frequency) and $ϕ_{\rm ecc}$ ($f_{\rm ecc}$) is an additional phase (frequency) that only depends on the eccentricity. We also provide simple analytical fits to obtain the harmonics as a function of the mean anomaly. These relations may prove useful in constructing faithful models that can be employed in cheap and efficient searches and parameter estimation of eccentric mergers. Our framework is modular and can be extended for any other eccentric waveform models or simulation frameworks. The framework is available through the \texttt{gwMiner} package.
[abstract 39 / 75] (score: 2) - Title: Hubble constant constraint using 117 FRBs with a more accurate probability density function for ${\rm DM}_{\rm diff}$Authors: Jiaming Zhuge, Marios Kalomenopoulos, Bing Zhang,Comments: Accepted for publication in ApJSubjects: astro-ph.CO astro-ph.HECreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
Fast radio bursts (FRBs) are among the most mysterious astronomical transients. Due to their short durations and cosmological distances, their dispersion measure (DM) - redshift ($z$) relation is useful for constraining cosmological parameters and detecting the baryons in the Universe. The increasing number of localized FRBs in recent years has provided more precise constraints on these parameters. However, the larger dataset reveals limitations in the widely used probability density function ($p_{\rm diff}$) for ${\rm DM}_{\rm diff}$, which refers to the diffuse electron term of FRB DM. In this project, we collect 117 of the latest, localized FRBs, discuss the effect of a more accurate $σ_{\rm diff}$, which is a parameter in $p_{\rm diff}$ and once thoughts as ``effective standard deviation'', and more clearly rewrite their likelihood to better constrain the parameters above. We find that the widely used approximation $σ_{\rm diff} \sim F/\sqrt{z}$ only works under contrived assumptions and shows the greatest deviation from the true standard deviation in low redshift. In general, one should use an accurate method to derive this parameter from $p_{\rm diff}$. Our method yields better constraints on $H_0Ω_b f_{\rm diff} = 2.813_{-0.258}^{+0.250}\;{\rm km/s/Mpc}$ or $H_0 = 66.889_{-5.459}^{+6.754} \;{\rm km/s/Mpc}$ when combining the FRB data with CMB measurements and taking $f_{\rm diff} = 0.84$. This fully analytical correction helps us better constrain cosmological parameters with the increasing number of localized FRBs available today.
[abstract 40 / 75] (score: 2) - Title: On the Reliability of Quasars as Cosmological Distance IndicatorsAuthors: Ariadna Montiel, Sofia Samario-Nava, Juan Carlos Hidalgo, Jose Ignacio Cabrera,Comments: Accepted for publication in MNRAS. 19 pages, 14 tables, 15 figuresSubjects: astro-ph.COCreated: 2026-06-18; Updated: 2026-06-23; Datestamp: 2026-06-23
We assess the viability of QUASARs as cosmological distance indicators based on the non-linear $L_X$--$L_{\rm UV}$ relation. We calibrate this relation in a model-independent way by anchoring QUASAR luminosity distances to cosmic-chronometer $H(z)$ measurements over $z\leq 1.43$, and construct a QUASAR Hubble diagram extending up to $z\simeq 7.5$. We compare a traditional stepwise approach, in which the calibration is fixed before cosmological inference, with a joint QSO+SN calibration--cosmology framework where calibration and cosmological parameters are sampled simultaneously. The stepwise analysis, supplemented with DESI DR2 BAO measurements and Planck compressed CMB distance priors, is used as a diagnostic benchmark, while the joint framework, with and without the SH0ES $H_0$ information, provides our main cosmological results. We selected a low-$z$ QUASAR subsample ($z<1.43$), matching the redshift range of the cosmic-chronometer calibration, and found calibration parameters consistent with previous studies. However, the stepwise cosmological constraints can become unstable once QUASARs are included, reflecting the incomplete propagation of calibration uncertainties and calibration--cosmology degeneracies. In contrast, the joint analysis yields self-consistent constraints because the QUASAR calibration parameters are fitted simultaneously with the cosmological parameters, allowing these uncertainties and degeneracies to be propagated into the final posteriors. Our results indicate that the current limitations of QUASAR cosmology are driven mainly by intrinsic scatter and possible sample-dependent effects in the $L_X$--$L_{\rm UV}$ relation, rather than by a fundamental inconsistency with standard cosmology.
[abstract 41 / 75] (score: 2) - Title: Accurate models for recoil velocity distribution in BLACK HOLE mergers with comparable to extreme mass-ratios and their astrophysical implicationsAuthors: Tousif Islam, Digvijay Wadekar,Comments: Models will be available through gwModels package: https://github.com/tousifislam/gwModelsSubjects: gr-qcCreated: 2026-06-18; Updated: 2026-06-23; Datestamp: 2026-06-23
Modeling the remnant recoil velocity (kick) distribution from binary BLACK HOLE mergers is crucial for understanding hierarchical mergers in ACTIVE GALACTIC NUCLEi or globular clusters. Existing analytic models often show large discrepancies with numerical relativity (NR) data, while data-driven models are limited to mass ratios of q<=8 (aligned spins) and q<=4 (precessing spins) and break down when extrapolated outside their training ranges. Using ~5000 of NR simulations from the SXS and RIT catalogs up to q=128 and ~100 BLACK HOLE perturbation theory simulations up to q=200, we present two classes of models: (i) gwModel_kick_q200 (gwModel_kick_q200_GPR), an analytic (Gaussian process regression) model for aligned-spin binaries. (ii) gwModel_kick_prec_flow, a normalizing-flow model for kick distribution from precessing binaries with isotropic spins. Our approach combines analytic insights from post-Newtonian theory with data-driven techniques to ensure correct limiting behavior and high accuracy across parameter space. Both gwModel_kick_q200 and gwModel_kick_prec_flow are valid from comparable to extreme mass ratios. Extensive validation shows all three models outperform existing ones within their respective domains. Finally, using both back-of-the-envelope estimates and 1404 detailed star cluster simulations incorporating our kick models, we find that the BLACK HOLE retention probability in low mass globular clusters can vary noticeably when the gwModel_kick_prec_flow model is employed. The models are publicly available through the gwModels package.
[abstract 42 / 75] (score: 2) - Title: Finite $V_{\rm 2Δ}$ puzzle in low-multiplicity pp collisions from ultra-long-range azimuthal correlations in the string-shoving modelAuthors: Antonio Ortiz, Dushmanta Sahu, Gyula Bencedi,Comments: 10 pages, 5 captioned figuresSubjects: hep-phCreated: 2026-06-18; Updated: 2026-06-23; Datestamp: 2026-06-23
Ultra-long range angular correlations have been recently reported by the ALICE collaboration in pp collisions at $\sqrt{s}=13$ TeV below ${\rm d}N_{\rm ch}/{\rm d}η=7$. The measurements have been performed as a function of the charged-particle multiplicity at midrapidity ($N_{\rm ch}$ in $|η|<0.8$), which is known to be strongly sensitive to local multiplicity fluctuations. The present work investigates the impact of the event-activity estimator on ultra-long range angular correlations. The study is conducted in the framework of PYTHIA8 with the string shoving mechanism since it gives a non-zero elliptic flow coefficient, $V_{2Δ}$. The analysis is conducted as a function of $N_{\rm ch}$, the number of parton-parton scatterings ($N_{\rm mpi}$) and flattenicity. Surprisingly, for ultra-long range correlations, pp collisions with $N_{\rm mpi}=1$ (diJETs) seems to be the most sensitive to string shoving. The effect diminishes with increasing $N_{\rm mpi}$. While in data, within uncertainties, $V_{2Δ}$ exhibits a weak multiplicity dependence; the string shoving mechanism gives a $V_{2Δ}$ that decreases with the increase in $N_{\rm ch}$. The present work therefore supports the picture stating that mechanisms such as string shoving might explain the low multiplicity limit, whereas, hydro becomes relevant in high-multiplicity pp collisions. This work also suggests that flattenicity might be more effective than $N_{\rm ch}$ to better handle non-flow effects.
[abstract 43 / 75] (score: 2) - Title: Tracking Summer Greenland Blocking: the Upstream Pathway Shapes Historical Extremes and Future ChangeAuthors: Michele Filippucci, Jacob Maddison, Simona Bordoni,Comments: Published paperSubjects: physics.ao-phCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
The representation and future evolution of summer Greenland atmospheric blocking in climate models is here investigated from a Lagrangian perspective using a novel Python package blocktrack. By applying the blocktrack algorithm to ERA5 reanalysis and a CMIP6 model ensemble, we identify and track blocking events over Greenland, and obtain their trajectories, intensities, duration and wave-breaking patterns. Greenland blocking (GB) events in ERA5 are then classified into two types based on their wave-breaking characteristics. These correspond to the previously identified upstream (anticyclonic wave breaking) and retrograding (cyclonic wave breaking) GBs. Upstream blocks, which originate in Northern Canada, exhibit stronger moisture transport before and during blocking onset and higher temperature anomalies than retrograding blocks, which follow an east-to-west trajectory and originate in the North Atlantic. Our analyses show how the recent observed increase in GB frequency, particularly in 2012, is primarily driven by upstream blocks. CMIP6 models generally fail to capture the observed increase and underestimate GB variability, especially for the upstream component. Projections under the SSP3-7.0 scenario show a decline in retrograding blocks but a possible increase in upstream blocks, depending on the detection index used. We discuss possible drivers of these changes, which include JET stream shifts, increased frequency of high-moisture transport events from low to high latitudes, surface temperature increases due to Atlantic Multidecadal Variability and Arctic Amplification. By analyzing block trajectories, this study demonstrates how Lagrangian diagnostics can provide novel insights into the dynamics of blocking events over Greenland.
[abstract 44 / 75] (score: 2) - Title: Local Analogs of Little Red Dots: Optical Variability and Evidence for an Active Galatic Nucleus OriginAuthors: Ruqiu Lin, Zhen-Ya Zheng, Junxian Wang, Luis C. Ho, Jorge A. Zavala, Zijian Zhang, Chunyan Jiang, Jiaqi Lin, Fang-Ting Yuan, Linhua Jiang, Tinggui Wang, Xiaer Zhang,Comments: 13 pages, 9 figures. Accepted for publication in ApJSubjects: astro-ph.GACreated: 2026-06-21; Updated: 2026-06-23; Datestamp: 2026-06-23
Little red dots (LRDs) draw extensive attention because of their unique observational characteristics and apparent overabundance in the early Universe, raising new insights into early BLACK HOLE formation and growth. Early studies show that LRDs exhibit weak variability in broad-band photometry and emission-line fluxes, suggesting a preference for super-Eddington accretion or disfavouring an AGN origin. However, the cadence of the current data, and therefore, the resulting light curves for LRDs, is limited, preventing us from placing strong constraints on their variability. Based on Zwicky Transient Facility (ZTF) light curves with a baseline of $\sim6$ years, we here study the optical variability of seven previously reported local analogs of LRDs at $z \sim 0.3$, offering an insight into LRDs from a low-redshift sample. Three out of seven local analogs show excess variances on all three bands of their light curves, and two of them can be fitted with the damping random walk model, supporting their AGN origins for the variability. The remaining sources show weak variance in at least one band, but no detectable variability at the current sensitivity level, exhibiting $\rm SF_\infty$ upper limits consistent with estimates from high-redshift (high-$z$) LRDs. Their non-detection of variability is likely due to the large photometric uncertainty. As an implication, by simulating long baseline light curves with the variability amplitude of local analogs and adopting JWST observation cadence, we investigate the limitation of the variability amplitude estimate for LRDs. Our mock observations imply that the current constraints on LRDs' variability are probably underestimated. This underestimation might be induced by the short temporal baseline of observations, as well as the intrinsic scatter of the empirical $M_{\rm BH}-τ$ relation.
[abstract 45 / 75] (score: 2) - Title: Recoil kicks from binary BLACK HOLE mergers in GWTC catalogs: implications for retention and hierarchical mergersAuthors: Tousif Islam,Comments: 13 pages, 8 figuresSubjects: astro-ph.HE gr-qcCreated: 2026-06-18; Updated: 2026-06-23; Datestamp: 2026-06-23
We infer recoil (kick) velocities for both individual binary BLACK HOLE (BBH) mergers and candidate intermediate-mass BLACK HOLE events, as well as for the BBH populations inferred from GWTC catalogs up to GWTC-5. We obtain informative recoil constraints for several events, including GW231028-153006 ($v_{\rm kick}=839^{+1018}_{-681}\,\mathrm{km\,s^{-1}}$) and GW231123-135430 ($v_{\rm kick}=974^{+944}_{-760}\,\mathrm{km\,s^{-1}}$), while finding that the majority of event-level recoil posteriors remain broad and only weakly informative. We further infer consistent population-level recoil distributions across GWTC-3, GWTC-4, and GWTC-5, with median kick velocities of approximately $300$--$330\,\mathrm{km\,s^{-1}}$. Using both event-level and population-level recoil estimates, we find typical retention probabilities of $\sim2$--$3\%$ for globular clusters, $\sim28$--$32\%$ for nuclear star clusters, $\sim25$--$29\%$ for dwarf galaxies, and $\sim92$--$94\%$ for elliptical galaxies. We also compute recoil-induced displacements and dynamical-friction return times, finding that retained remnants in globular clusters and nuclear star clusters can remain displaced from their host cores for extended periods. Our results show that retention alone is not sufficient to determine the prospects for hierarchical mergers: hierarchical-merger efficiency depends on both remnant retention and post-kick re-centering.
[abstract 46 / 75] (score: 2) - Title: Data-Driven Constraints on Magnetar Population: No Evidence for a Distinct White Dwarf ChannelAuthors: R. V. Lobato,Comments: Matches the published version in JHEAp: The revised version strengthens the statistical framework, validation, and physical interpretation, reinforcing the conclusion that current data do not support a distinct white-dwarf magnetar populationSubjects: astro-ph.HE astro-ph.SRCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
Magnetars are usually interpreted as highly MAGNETized neutron stars, yet a small subset of low spin-down sources has motivated alternative scenarios involving highly MAGNETized white dwarfs. We test whether the observed MAGNETar sample is consistent with a single neutron-star population or whether the data favor an additional compact-object channel. We combine exploratory machine-learning diagnostics with hierarchical Bayesian population modeling. First, we apply K-means clustering and principal component analysis in a five-dimensional feature space $(P,\dot{P},L_X,kT,|Z|)$, where $P$ is the spin period, $\dot{P}$ its time derivative, $L_X$ the X-ray luminosity, $kT$ the thermal spectral temperature, and $|Z|$ the absolute Galactic scale height. We then train a Random Forest classifier with leave-one-out cross-validation to identify the observables driving the empirical split. Subsequently, we construct a hierarchical Bayesian mixture model linking spin parameters to MAGNETic-field distributions through covariate-dependent mixing fractions. Posterior inference is performed with Hamiltonian Monte Carlo, and predictive performance is assessed using Pareto-smoothed importance sampling leave-one-out cross-validation. The exploratory analysis reveals a reproducible substructure: the Random Forest achieves $>95\%$ LOOCV accuracy, with $L_X$, $\dot{P}$, and $kT$ emerging as the dominant predictors. However, Bayesian model comparison shows no statistically significant preference for a two-population model. Instead, a few low spin-down sources receive intermediate posterior membership probabilities, suggesting transitional or outlying behavior rather than membership in a distinct class. Overall, current data do not require a separate white-dwarf MAGNETar population and are adequately described by a predominantly neutron-star population.
[abstract 47 / 75] (score: 2) - Title: Galactic Diffuse Gamma-Ray and Neutrino Emission from Cosmic-Ray Interactions in Stellar AtmospheresAuthors: Yanbo Wang, Zhenglong Wang, Rui Zhang, Yi Zhang,Comments:Subjects: astro-ph.HECreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
The Galactic diffuse gamma-ray emission is conventionally modeled as the product of cosmic-ray interactions with the interstellar medium. However, the cumulative contribution of stellar atmospheres acting as hadronic interaction targets remains an unexplored multi-messenger background. In this work, we present the first systematic evaluation of this stellar diffuse emission by coupling MESA stellar evolution profiles and MAGNETic-field-modulated cosmic-ray transport with a 3D Galactic population synthesis framework. We find that the cumulative stellar contribution to the Galactic diffuse gamma-ray flux is negligible at 1 TeV, and the associated diffuse neutrino flux ($\sim 10^{-16}\;\mathrm{TeV\;cm^{-2}\;s^{-1}\;sr^{-1}}$) remains orders of magnitude below current IceCube limits. Nevertheless, at ultra-high energies ($>10\;\mathrm{TeV}$), this emission establishes an irreducible local background that overtakes the strongly attenuated extragalactic isotropic gamma-ray background. Our results demonstrate that the Galactic stellar ensemble is a strictly sub-dominant background, indicating that stellar subtraction templates are not required for identifying Galactic PeVatrons or constraining DARK MATTER annihilation.
[abstract 48 / 75] (score: 2) - Title: Equilibrium of a simplified coil quasi-axisymmetric stellarator: Free boundary approachAuthors: Kassandra Salguero-Martínez, J. Julio E. Herrera-Velázquez,Comments: The paper has been rejected by Physics of Plasmas noting fundamental problems. The equilibria described in the paper are inconsistent with the bootstrap currents which arise in quasiaxisymmetric configurations. The paper is going through a major revision before being sent as a new submissionSubjects: physics.plasm-phCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
Inspired by the design for the simple Columbia Non-neutral Torus (CNT) proposed by Pedersen and Boozer (Phys. Rev. Lett. 88 205002(2002)), and later revisited by Yu et al. (J. Plasma Phys. 88 905880306 (2022)), this work explores axi-symmetric equilibria using two planar vertical field coils and two non-planar intertwined coils. Neoclassical optimization studies are performed in a single stage approach using the DESC stellarator equilibrium solver (Dudt and Koleman, Phys. Plasmas 27 (2020) 102513). The physical parameters used as input were the toroidal MAGNETic flux function $ψ$, the rotational transform $ι(ρ)$ as a function of the normalized flux function $ρ$ as the radial coordinate, the number of field periods $N_{FP}$, and an initial equilibrium assumption, given the major radius $R_0$ and the minor radius $a$. Once the equilibrium given by the coil configuration is defined, an optimization is made for quasi-symmetry. In this study, a triple product metric as defined by Dudt et al., (J. Plasma Phys. 89 (2023) 95589020) is used as a local error indicator, which is evaluated without resorting to Boozer coordinates. The goal is to optimize the effective ripple modulation amplitude $ε_{eff}^{3/2}$, thus decreasing the neoclassical transport in the low collisionality $1/ν$ regime. We show a sample of quasi-axisymmetric configurations obtained, both for the vacuum field and with finite pressure, which have reasonably good neoclassical transport in the sense of Boozer coordinates. In the best case scenarios the final rotational transfrom is inverted after optimization.
[abstract 49 / 75] (score: 2) - Title: Pitching Cosmic Curveballs: Environmental Effects on Extreme-Mass-Ratio Inspirals with Spinning SecondariesAuthors: Leif Lui, Lisa V. Drummond, Alejandro Torres-Orjuela,Comments: 6 pages, 5 figuresSubjects: gr-qc astro-ph.HECreated: 2026-06-22; Updated: 2026-06-23; Datestamp: 2026-06-23
Much like the aerodynamic deflection of a spinning curveball, a rotating secondary in an extreme-mass-ratio inspiral (EMRI) experiences Magnus and lift forces, in addition to the standard drag force, when traversing a gaseous environment. We present the first framework that incorporates these specific spin-coupled environmental effects (EEs) into the evolution of EMRI. Over the multi-year observation windows of space-based gravitational-wave (GW) detectors, these interactions imprint a unique, distinguishable dephasing signature on the signal. Crucially, a Fisher matrix analysis reveals that gas drag breaks the fundamental vacuum-projection degeneracy between the secondary's spin magnitude and inclination, thereby tightening parameter constraints. Thus, accounting for EEs is not merely a modeling necessity, but could potentially be a powerful tool for enhancing the detectability of the secondary's intrinsic spin, and could serve as a novel probe of accretion flows harboring massive BLACK HOLEs.
[abstract 50 / 75] (score: 2) - Title: Gas-induced perturbations on the gravitational wave in-spiral of live post-Newtonian LISA massive BLACK HOLE binaries: 0.1 disk aspect ratioAuthors: Mudit Garg, Alessia Franchini, Alessandro Lupi,Comments: 11 pages, 8 figures. Submitted to ApJ. Comments welcomeSubjects: astro-ph.GA astro-ph.HE gr-qcCreated: 2026-06-18; Updated: 2026-06-23; Datestamp: 2026-06-23
We perform 3D hydrodynamics simulations of an equal-mass quasi-circular live $10^6~{\rm M}_\odot$ massive BLACK HOLE binary (MBHB) embedded in a prograde, locally isothermal circumbinary disk (CBD) with $0.1$ aspect ratio. The binary evolution is driven by the gaseous torques and its dynamics is described with $2.5$ post-Newtonian corrections. This approach allows us to track the influence of the CBD on a gravitational-wave (GW) driven MBHB inspiral from $55$ to $46$ Schwarzschild radii, i.e., at its early evolution in the LISA band at redshift $z\sim1$. For the first time for the $0.1$ aspect ratio disk, we report the measurement of gravitational and accretion torques with and without concurrent GW emission. We also report how the morphology of the accretion time series onto the MBHB modestly alters when GW emission is the dominant binary evolutionary mechanism. Lastly, we find that the gas-induced orbital phase-shift is $0.12$ rad over $600$ orbital cycles, which LISA should detect at $z=1$. Our results have implications for multi-messenger astronomy, since observation of accretion rate modulation by LSST/Roman surveys and phase-shift by LISA will provide crucial information on the complex environment surrounding MBHBs.
[abstract 51 / 75] (score: 2) - Title: Old and Bright: The Remarkable Radio Brightening of the Engine-driven SN 2012au Several Years After Explosion Signals the Birth of a PWNAuthors: Eli Wiston, Raffaella Margutti, A. J. Nayana, Brian D. Metzger, Kohta Murase, Dan Milisavljevic, Itai Sfaradi, Ryan Chornock, Deanne L. Coppejans, Joe Bright, Garrett K. Keating, Giacomo Terreran, Mattias Lazda, Maria R. Drout, Michael Stroh, Lauren Rhodes, Ben Margalit, Jonathan Granot, Fabio De Colle, Michael Bietenholz, Daichi Tsuna, Samantha Wu, Tanmoy Laskar, Edo Berger, Daniel Patnaude, Collin T. Christy,Comments: 39 pages, 20 figures, 4 tables, Submitted to ApJSubjects: astro-ph.HECreated: 2026-06-18; Updated: 2026-06-23; Datestamp: 2026-06-23
We present the results from an extensive broad-band (radio to X-rays) observing campaign of the engine-driven Type Ib SN 2012au in the first 13 years of evolution. The early-time ($δt\leq{190}$ d) radio and X-ray evolution is well-described by conventional models of a forward shock interacting with a wind-like circumstellar medium ($ρ_{\rm{CSM}}\propto{r}^{-2}$). However, starting at $δ{t}\approx{6.7}$ yr, we detect a significant radio re-brightening. This late-time emission is dominated by a luminous component characterized by a broad and rapidly evolving spectral peak and a shallow optically thin spectral slope, $F_ν\proptoν^{-0.31\pm0.02}$. These properties imply a compact emitting region ($R\lesssim{10}^{16}$ cm) expanding at a remarkably slow velocity ($\lesssim{500}$ km/s) into a high-density environment ($\geq{10}^4 \rm{cm}^{-3}$), accompanied by a hard electron power-law index $p\approx{1.6}$. No soft or hard X-ray emission is detected at any epoch, indicating that high-energy radiation is either strongly absorbed or intrinsically absent. In the context of aspherical shock-CSM interaction models, these observations imply extreme properties of the CSM (geometry, density, total mass) that lack clear astrophysical motivation. Instead, we show that the emergence of radiation from a newborn Pulsar Wind Nebula (PWN) naturally explains the radio spectral evolution and high-energy limits, where the emission is governed by the adiabatic expansion of a relic pair plasma. We conclude that SN 2012au represents the most compelling candidate for a young, newborn PWN discovered to date, a scenario that can be directly tested with pending Very Long Baseline Interferometry (VLBI) observations.
[abstract 52 / 75] (score: 2) - Title: Radio Spectral Imaging and MHD Modeling of a CME-Driven Shock: Connecting Solar Type II Radio Bursts with Shock-Surface Magnetic GeometryAuthors: Peijin Zhang, Weihao Liu, Bin Chen, Ward B. Manchester, Surajit Mondal, Sijie Yu,Comments: 15 pages, 11 figures, 2 tables. Submitted to The Astrophysical JournalSubjects: astro-ph.SRCreated: 2026-06-18; Updated: 2026-06-23; Datestamp: 2026-06-23
Solar type II radio bursts are widely regarded as signatures of shock waves propagating in the solar corona and are of particular importance for understanding shock-driven particle acceleration processes. Type II radio bursts often exhibit complex multi-lane and split-band features. The detailed spectral, temporal, and spatial structures carry key information about the shock properties and evolution. However, the physical origin of the multi-lane and split-band features remains unclear, largely due to a lack of spatially resolved data and understanding of the concurrent shock morphology and its MAGNETic-field context. In this work, we combine radio imaging spectroscopy of a multi-lane, split-band type II burst event with a three-dimensional global MAGNETohydrodynamic simulation of the associated coronal mass ejection-driven shock using the Alfvén Wave Solar atmosphere Model-Realtime. In this event, the burst intensity evolves from fundamental-emission dominated to harmonic-emission dominated. Meanwhile, the preferential emission source region moves from the Earth-facing side to the limb or far side, coinciding with quasi-perpendicular shock regions with enhanced Mach numbers. The observed spatial offset between the fundamental and harmonic sources is generally aligned with the projected shock-surface MAGNETic field from the simulation, consistent with anisotropic scattering in a MAGNETized turbulent plasma. These results establish a physical connection between type II radio sources and coronal shock MAGNETic geometry, providing new insight into the origin of the multi-lane features and their diagnostics of coronal shocks.
[abstract 53 / 75] (score: 2) - Title: Out-of-Equilibrium Effects in Non-Radial Relativistic Stellar Perturbations: A Model-Agnostic Formulation and Mode AnalysisAuthors: Takuya Katagiri, Victor Guedes, Kent Yagi,Comments: 23 pages, 6 figuresSubjects: gr-qc astro-ph.HECreated: 2026-06-18; Updated: 2026-06-23; Datestamp: 2026-06-23
We present a systematic, model-agnostic analysis of out-of-equilibrium effects, including viscosity and thermal conductivity, in non-radial oscillations of RELATIVISTIC stars. Extending the Lindblom-Detweiler formalism, we construct, to our knowledge, the first general framework for linear, non-radial RELATIVISTIC stellar perturbations that incorporates generic nonequilibrium corrections to the perfect-fluid sector in both the even- and odd-parity channels. Our framework is formulated in terms of the tensorial structure and thermodynamic decomposition of generic corrections without relying on any specific constitutive relations, thereby allowing us to elucidate, at a structural level, how these effects enter the perturbation equations and contribute to geometric deformations and fluid fluctuations. As an application, we consider the Bemfica-Disconzi-Noronha-Kovtun fluid and perturbatively investigate shifts in the frequencies and damping times of modes connected to their perfect-fluid counterparts in the limit of vanishing transport coefficients. We also identify structural features of the closed eigenvalue problem that can give rise to additional mode families. Our formalism provides a unified framework for analyzing how different RELATIVISTIC fluid theories modify the structure of non-radial stellar perturbations.
[abstract 54 / 75] (score: 2) - Title: An open-source numerical tool for rational orbits and gravitational radiation in static spherically symmetric spacetimesAuthors: Dan Li, Shiyang Hu, Chen Deng, Shijie Tan, Guansheng He,Comments: 18 pages, 8 figuresSubjects: gr-qcCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
Timelike orbits constitute a crucial probe for exploring the intrinsic properties of curved spacetimes, and the carried gravitational radiation signals provide a direct window into strong field gravity. In this paper, we develop a versatile computational framework based on Mathematica and the OpenMP parallel architecture to simulate the rational orbits of timelike particles and their gravitational radiation in static spherically symmetric spacetimes. Specifically, requiring only the user defined covariant metric, this numerical tool can efficiently calculate rational orbits across various configurations, as well as the corresponding gravitational wave POLARIZATION states and characteristic strains. The package presented here offers a highly efficient and comprehensive one-stop solution for investigating the properties of curved spacetimes and their potential observational signatures. To demonstrate the reliability and capability of our code, we apply it to the Schwarzschild spacetime as a test case, illustrating the functionality of the code across several key aspects, including the effective potential, stable orbital regions, rational and irrational orbits, and gravitational wave signals. Furthermore, we show that the gravitational waves emitted by an extreme mass ratio inspiral system composed of an intermediate mass BLACK HOLE and the Galactic Center supermassive BLACK HOLE have the potential to be identified by future space detectors.
[abstract 55 / 75] (score: 2) - Title: Wave-Energy Partition Governs Weak Collisional Damping in Cold PlasmasAuthors: Yanzeng Zhang, Xianzhu Tang, Ge Zhuang,Comments:Subjects: physics.plasm-phCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
Weak dissipation can control wave propagation, mode competition, and instability thresholds in plasmas, yet the physical origin of large branch-to-branch differences in collisional damping is often obscured by dielectric-tensor calculations. We show that weak collisional damping in cold plasmas is governed by wave-energy partition. In the one-rate cold-plasma model, the damping rate of a collisionless eigenmode is exactly the collision frequency multiplied by the fraction of the total wave energy stored in plasma motion. This result recasts the standard perturbative damping formula into a compact and physically transparent law, immediately explaining why field-dominated branches such as whistlers can be much less damped than the collision frequency, whereas quasi-electrostatic modes can exhibit damping of comparable magnitude. Analytic examples for Langmuir, transverse electroMAGNETic, whistler, and extraordinary waves show that the energy-partition form classifies weak collisional damping across distinct branches and provides a simple diagnostic for mode competition in multibranch plasma-wave systems.
[abstract 56 / 75] (score: 2) - Title: Test Particle Study of EDI Driven Electron Transport in a Hall Thruster Using PIC Derived Electric FieldsAuthors: Zhongping Zhao, Kunpeng Zhong, Yinjian Zhao,Comments:Subjects: physics.plasm-phCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
Electron transport in a Hall thruster is investigated at the test particle level using prescribed electric fields derived from the electron drift instability (EDI) resolving three dimensional particle-in-cell (PIC) simulation. Four primary electric field configurations are considered: static averaged field, full PIC field, proper orthogonal decomposition (POD) reconstructed field, and a simplified analytical Ey field. Two additional control cases, the MAGNETic-field-only case and the denoised PIC field, are also included. Transport statistics show that the averaged field produces only weak axial cross field transport. In contrast, the full PIC field produces clear fluctuation driven transport, characterized by pronounced negative axial displacement, enhanced channel entry, finite channel residence, particle energization, and appreciable anode directed loss. POD analysis shows that the transport relevant EDI electric field structures are distributed over multiple coupled modes, and that a moderate truncation order of approximately 20 modes is required to recover the main transport signatures. The analytical Ey model separately examines the influence of azimuthal electric field fluctuations on axial electron transport and shows that fluctuation amplitude is a primary determinant.
[abstract 57 / 75] (score: 2) - Title: Semi-local Floquet theory for active azimuthal MAGNETic modulation of Hall-thruster high-frequency instabilitiesAuthors: Yinjian Zhao, Changzheng Hu,Comments:Subjects: physics.plasm-phCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
A semi-local Floquet extension of a uniform-field kinetic electron drift instability (EDI) dispersion relation is developed to assess prescribed azimuthal MAGNETic-field modulation as a linear pre-screening tool for Hallthruster high-frequency instabilities. The uniform kinetic response is used as a local spectral kernel, while a sinusoidal MAGNETic modulation couples Floquet sidebands and replaces the scalar dispersion condition by a finite matrix dispersion problem. The numerical procedure combines scalar uniform-field predictors, determinant correction, singular-value diagnostics, sideband-weight analysis, and truncation checks. Because a single Floquet root contains multiple physical wave numbers, stability is assessed with the upper growth envelope over the Bloch zone rather than with an individual projected azimuthal wave-number branch. Parameter scans over modulation wavelength and amplitude show that sinusoidal azimuthal MAGNETic modulation broadens the coupled spectrum and redistributes unstable growth among low-wave-number modified-two-stream-like and cyclotron-resonant ranges. Some long-wavelength, moderate-to-large-amplitude cases reduce integrated positive growth measures, but these reductions are not accompanied by robust suppression of the peak growth envelope. No tested case produces a finite stable Bloch interval. Within the present cold-ion semi-local Floquet model, prescribed azimuthal MAGNETic modulation is therefore better interpreted as a spectral-redistribution mechanism than as a robust linear stabilization mechanism by itself.
[abstract 58 / 75] (score: 2) - Title: Flow mechanisms governing oscillation in a sonic fluidic oscillatorAuthors: Chris J. Nicholls, Michael R. Fenelon, Yang Zhang, Louis N. Cattafesta,Comments: Submitted to Experiments in Fluids, June 2026Subjects: physics.flu-dynCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
Two factors that influence the oscillation mechanism of a sonic fluidic oscillator are investigated: the geometry of the feedback channel connections (control ports) and the influence of flow restrictions in the oscillator outlets. Phase-averaged planar PIV measurements are performed inside the oscillator, synchronised with unsteady pressure measurements, and analysed using space-only proper orthogonal decomposition (POD). The POD analysis reveals two coupled modes: a Sweeping Mode capturing lateral JET displacement and a Bending Mode capturing JET curvature during switching, the latter being the primary driver of outlet mass flux modulation. Flow separation at the control port entrances is shown to throttle the feedback flow and progressively limit oscillation strength at higher inlet flow rates. Restrictive outlet paths induce a differential back pressure that is shown to cause the JET to separate from its attachment wall and bend towards the splitter tip (`secondary separation'). The secondary separation reduces the differential outlet mass flux and introduces a flow curvature that limits the upstream propagation of the back pressure and thus shields the primary JET attachment. The consequence of these effects is that strong oscillations are sustained down to the smallest outlet apertures investigated. The principal contribution is to demonstrate that the assumed coupling between upstream JET attachment and outlet flow split is broken when the outlet aperture is reduced, with significant implications for the design of fluidic oscillators operating with downstream flow impedances.
[abstract 59 / 75] (score: 2) - Title: Geometric numerical discretization of electroMAGNETic quasineutral modelsAuthors: Nishant Narechania, Emil Poulsen, Eric Sonnendrucker,Comments:Subjects: physics.plasm-phCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
In this work, the geometric electroMAGNETic Particle-in-Cell (PIC) framework, GEMPICX, is extended to solve the quasineutral, fully kinetic Vlasov-Maxwell equations on dual grids using mimetic finite differences. The discrete action principle is derived, taking into account the duality between the grids. The temporal derivative of the electric field does not directly appear in the dynamical system for the quasineutral model. Hence, a discretized curl-curl equation is used to implicitly obtain the electric field at every time-step. This also circumvents the need to obtain electric potentials. A Lagrange multiplier is used to maintain the discretized divergence of the current density at machine zero.
[abstract 60 / 75] (score: 2) - Title: Relativistic effects in extreme-mass-ratio inspirals within scalar clouds: Eccentric and inclined orbitsAuthors: Qi-Xuan Xu, Richard Brito, Riccardo Della Monica, Rodrigo Vicente, Chen Yuan,Comments: 30 pages, 11 figuresSubjects: gr-qc astro-ph.HE hep-phCreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
We study extreme-mass-ratio inspirals (EMRIs) evolving in a scalar cloud environment that may form through superradiant instabilities, using a fully RELATIVISTIC perturbative framework that allows for eccentric and inclined orbits. EMRIs, consisting of a stellar-mass compact object inspiraling into a supermassive BLACK HOLE, are key sources for space-based gravitational-wave detectors such as LISA. Previous RELATIVISTIC studies of EMRIs in scalar clouds have been restricted to circular, equatorial motion. Here, instead, we focus on a Schwarzschild BLACK HOLE background to incorporate eccentricity and orbital inclination. By computing the scalar energy and angular momentum scattered off to spatial infinity and absorbed at the event horizon, we show that orbital eccentricity can induce a dense spectrum of resonances near the last stable orbit, associated with strong RELATIVISTIC apsidal precession. We further find that orbital inclination can significantly modify the orbital energy and angular momentum losses. In particular, we identify a critical inclination angle below which, at sufficiently small orbital radii, there is a net transfer of energy from the scalar cloud to the orbit. Moreover, for sufficiently large eccentricities, resonances associated with RELATIVISTIC apsidal precession persist across the full range of inclinations, although their structure changes significantly between prograde and retrograde orbits. These results provide a foundation for future studies of EMRIs in scalar cloud environments on fully generic orbits around spinning BLACK HOLEs.
[abstract 61 / 75] (score: 2) - Title: The $M$-$σ$ Relation Has to BreakAuthors: Omri Nitzan, Re'em Sari,Comments: 10 pages, 3 figures. Submitted to ApJLSubjects: astro-ph.GACreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
We revisit the growth of central BLACK HOLEs via tidal disruption events (TDEs) and plunges of stellar-mass BLACK HOLEs (sBHs). Our model incorporates the current understanding of mass segregation, where sBHs sink to the center, enhancing the rates of both TDEs and plunges. We demonstrate that in dense cluster cores, with densities exceeding $10^6\,\mathrm{M_\odot\,{pc}^{-3}}$, seeds of initial mass $M_0\gtrsim100\,M_\odot$ undergo runaway growth. This runaway terminates once the BLACK HOLE radius of influence surpasses the core radius, or equivalently, most of the core mass has been consumed. This typically results in an intermediate-mass BLACK HOLE (IMBH), within a few $\mathrm{Gyr}$. Subsequent growth proceeds as a power law. In contrast to observed supermassive BLACK HOLEs (SMBHs), which tightly follow the famous $M \propto σ^β$ with $β\cong5$, our derived sBH accretion rates, integrated over a galactic lifetime, predict final masses of $M\approx10^5\,M_\odot \times(σ/50\mathrm{km\;s^{-1}})^{2.5}$. While our prediction for the contribution of plunges to the growth of the IMBH is robust, the TDE contribution can be negligible if only a small fraction of their mass is actually accreted or up to 3 times higher than the plunges contribution if half a stellar mass gets accreted in each event. Below $M\sim10^5\,M_{\odot}$ this accreted star and sBH mass exceeds the extrapolation of the observed $M$-$σ$ relation. This predicts that the $M$-$σ$ scaling must flatten below $M \sim 10^5\,M_{\odot}$ to a shallower, $2.26<β<2.5$ profile. If confirmed by observations, this would indicate capture-driven growth.
[abstract 62 / 75] (score: 2) - Title: Getting Tilted: Random Walk of Binary Black Hole Spin-Orbit Alignment in Dense Star ClustersAuthors: Maia A. S. Martinez, Christopher E. O'Connor, Fulya Kıroğlu, Frederic A. Rasio,Comments: 25 pages, 8+1 Figures, submitted to ApJ. Comments welcome!Subjects: astro-ph.HECreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
It is commonly assumed that the spin-orbit angles of binary BLACK HOLEs (BBHs) originating from dense stellar environments rapidly converge to an isotropic distribution following a number of strong gravitational encounters. We challenge this assumption by modeling the evolution of the BBH orbital angular momentum orientation through successive binary--single encounters as a random walk on the unit sphere, yielding an exact solution for the orientation distribution after $n$ encounters and a closed-form expression for the number of encounters required to reach isotropy. To characterize the step distribution, we conduct a large suite of Newtonian point-particle scattering experiments with an equal-mass binary, varying the mass of the single, and obtain semi-analytic expressions for both the mean step size and the full distribution of steps. Applying these results to BBHs with initially aligned spins, as may arise from the evolution of primordial massive binaries, we find that spin-orbit alignment can survive several strong encounters before being erased. This has direct implications for the slight trend toward spin-orbit alignment reported in GWTC-5.0 as well as for the retention of hierarchical merger products, such as the components of GW231123.
[abstract 63 / 75] (score: 2) - Title: A new solution for the mass growth of Black Holes consistent with thermodynamicsAuthors: María F. La Rotta Wilches, Roger Coziol,Comments: 6 pages, 3 figuresSubjects: astro-ph.GACreated: 2026-06-19; Updated: 2026-06-23; Datestamp: 2026-06-23
The James Webb Space Telescope (JWST) has recently revealed evidence of supermassive BLACK HOLEs (SMBHs) forming in the cores of high redshift galaxies that grew in mass extremely rapidly during the first billion years of the universe. In this study we present a new solution where the growth mass factor of BHs, $γ(t) \propto \dot M_{BH}/M_{BH}$, varies with time, following the changes of radiative efficiency, $ε$, and Eddington ratio, $λ_{Edd}$, caused by the variation in accretion flow. By optimizing the accretion rate, $\dot M_{BH}$, we obtained a solution that is universal, that is, which applies to any BH at any redshift. This suggests that the mass of the BH is a thermodynamics state function, in good agreement with the no hair theorem and the four laws of mechanics of BHs.
[abstract 64 / 75] (score: 2) - Title: Plasma Flow Generation and Particle Acceleration from Expanding Magnetic BubblesAuthors: Yang Zhang, Brandon K. Russell, Geoffrey Pomraning, Lan Gao, Xiaocan Li, Adam Stainer, William Daughton, Chuanfei Dong, Liang Wang, Peiyun Shi, Kian Orr, Hantao Ji,Comments:Subjects: physics.plasm-ph astro-ph.HE astro-ph.SR physics.space-phCreated: 2026-06-20; Updated: 2026-06-23; Datestamp: 2026-06-23
Impulsive plasma dynamics in the laboratory are often driven by rising electric currents, yet their quantitative plasma response has not been well established. By means of fully kinetic particle-in-cell simulations and LASER-driven capacitor-coil experiments, we show that a rising current expels plasma, forming an expanding MAGNETic bubble and accelerating particles. The expansion front velocity scales with the Alfvén speed determined by the MAGNETic field at its inner edge and the plasma density at its outer edge. This mechanism establishes impulsive current drive as a fundamental way that generates plasma flows and accelerates particles in laboratory plasmas, with potential relevance to astrophysics.
[abstract 65 / 75] (score: 2) - Title: Determining Kerr BLACK HOLE spin and inclination from a segment of the critical curve in BLACK HOLE imagesAuthors: Kenta Hioki, Umpei Miyamoto, Tomohiro Harada,Comments: 34 pages, 8 figures, 2 tablesSubjects: gr-qc astro-ph.HECreated: 2026-06-20; Updated: 2026-06-23; Datestamp: 2026-06-23
We present a method for determining the spin parameter $a/M$ and inclination angle $i$ of a non-extremal Kerr BLACK HOLE from segments of the critical curve identified in BLACK HOLE images. Although the critical curve itself is not directly observable, higher-order photon rings accumulate near it, and in realistic observations localized portions of the resulting brightness enhancement may be available for identifying segments of the critical curve. We introduce standardized segments of the critical curve and define three observables that characterize their geometry. We show that these observables uniquely determine $(a/M,i)$, together with an auxiliary parameter $r_{nl}\in[0,1]$ specifying the location of the identified segment along the critical curve, within the domain considered. Thus, even a segment of the critical curve contains sufficient geometric information to constrain the BLACK HOLE spin and inclination without reconstructing the full critical curve. The framework is naturally suited to realistic observations and may be extended to more general rotating BLACK HOLE spacetimes.
[abstract 66 / 75] (score: 2) - Title: Factors governing the existence of an abrupt transition to superrotation in an idealized GCMAuthors: Corentin Herbert,Comments:Subjects: physics.ao-phCreated: 2026-06-20; Updated: 2026-06-23; Datestamp: 2026-06-23
Some numerical simulations of very warm climates suggest that the Earth's atmosphere may undergo a transition to a state of equatorial superrotation, where the zonal-mean zonal wind in the tropics is westerly. However, major uncertainties remain about the circumstances under which such a transition could happen. A natural first step towards reducing these uncertainties is to better understand the dynamical processes involved in the transition in idealized setups. However, simple numerical experiments have reported very different responses to tropical diabatic heating in different models, with both a continuous and an abrupt transition to superotation. In this paper, we investigate the mechanisms controlling the nature of the transition. We show that in an idealized Held-Suarez framework, it is governed by both the meridional temperature gradient and the bottom friction coefficient. These two parameters control a competition between two feedback mechanisms: a positive tropical wave-JET mechanism, and a negative feedback mechanism related to absorption of extratropical waves near their critical latitudes in the tropics.
[abstract 67 / 75] (score: 2) - Title: Resonant Pitch-Angle Scattering Of Runaway-Electrons by Externally-launched Helicon Waves in the DIII-D TokamakAuthors: Hari Choudhury, Jeffrey Lestz, Carlos Paz-Soldan, Alexander Battey, Nils Leuthold, Andrey Lvovskiy, Claudio Marini, Jayson Barr, William Heidbrink, Donald Spong, Shawn Tang, Bart Van Compernolle, Qile Zhang, Yanzeng Zhang, Xianzhu Tang,Comments:Subjects: physics.plasm-phCreated: 2026-06-20; Updated: 2026-06-23; Datestamp: 2026-06-23
Resonant wave-particle interactions between externally launched helicon waves (also known as whistler waves) and runaway electrons (REs) have been demonstrated on the DIII-D tokamak. In this work we extend the initial results reported in Choudhury, H. et al. Phys. Rev. Lett. 136, 025101 (2026) by exploring the effects of antenna alignment with the edge MAGNETic field, toroidal wave propagation direction, and coupled power on RE scattering in the quiescent RE experimental scenario. Two distinct experimental configurations have been investigated: one in which the antenna aligns well with the edge background MAGNETic field, known as the ideal antenna configuration, and one with misalignment, known as the non-ideal case. Previously, it had been found that helicon power in the ideal antenna configuration prevented RE growth despite the normalized toroidal electric field remaining high enough to drive exponential RE growth in the absence of helicon power. In this paper, we show that scattering via the normal Doppler resonance (n=1) effectively limits the growth of the RE population in both the ideal and non-ideal antenna configurations, with evidence of a power threshold in the latter case. In contrast, launching waves that favour the anomalous Doppler resonance (n=-1) is observed to enhance rather than reduce the RE population. In addition, fast MAGNETic measurements reveal rising-tones in the 30-60 MHz range during helicon-off periods, which are not observed prior to helicon power. Finally, the challenges of using launched helicon waves to scatter post-disruption RE beams are discussed. Collisional damping and a large vacuum gap between the plasma and antenna on the outboard side present significant obstacles to helicon waves propagating into the plasma core.
[abstract 68 / 75] (score: 2) - Title: Shape-Preserving Evolution of the Global Ultraviolet Quasar Luminosity Function to $z\simeq7.5$Authors: Wenjie Wang, Zunli Yuan, Yu Luo, Longhua Qin,Comments: 25 pages, 10 figures, submitted to ApJSubjects: astro-ph.COCreated: 2026-06-21; Updated: 2026-06-23; Datestamp: 2026-06-23
We present a global unbinned-likelihood analysis of the rest-frame ultraviolet (UV) QUASAR luminosity function (QLF) over $0.1\le z\le7.5$, using a final analysis sample of 70,960 Type~1 QUASARs selected from the homogenized compilation of Kulkarni et al. (2019). We test a shape-preserving luminosity and density evolution (LADE) framework, in which the local luminosity function (LF) shape is fixed and the redshift evolution is described by separate density- and luminosity-evolution factors. For a double-power-law (DPL) local LF, we search 81 LADE models built from nine density-evolution and nine luminosity-evolution functions, and compare them with two flexible double-power-law (FDPL) reference models. The fiducial shape-preserving LADE model gives the lowest Akaike information criterion (AIC) and Bayesian information criterion (BIC) values among the main models considered, and 12 DPL-based LADE models have lower AIC and BIC values than both FDPL reference models. Repeating the model-grid analysis with a modified-Schechter local LF gives the same preferred evolutionary structure, indicating that the result is not driven only by the assumed local LF shape. The fitted evolution functions further show that the luminosity-evolution component is the more stable part of the LADE decomposition: it rises rapidly to $z\simeq2$--3 and then flattens or slowly declines. The density-evolution component is more model dependent, but the preferred LADE models consistently require a declining effective normalization toward high redshift. Taken together, we conclude that a shape-preserving framework offers a statistically efficient and compact empirical description of the global UV QLF.
[abstract 69 / 75] (score: 2) - Title: Tearing Instability in Gyrotropic MHD: Effects of Equilibrium Pressure AnisotropyAuthors: Grzegorz Kowal, Gabriel L. Ferreira-Santos, Diego A. Falceta-Gonçalves,Comments: 29 pages, 6 figuresSubjects: physics.plasm-phCreated: 2026-06-21; Updated: 2026-06-23; Datestamp: 2026-06-23
Weakly collisional plasmas are widespread in astrophysics and can sustain pressure anisotropy, yet most analytical tearing-mode scalings assume an isotropic equilibrium. We develop a linear theory of resistive tearing in nonideal gyrotropic MHD for a force-free Harris current sheet characterized by perpendicular plasma beta $β_0$ and parallel-minus-perpendicular beta difference $Δβ_0$. In the ideal outer region, anisotropy changes the far-field decay rate, the matching parameter $Δ'$, and the upper wavenumber cutoff for localized tearing, $α\equiv ka<α_c=\sqrt{\mathcal{A}/\mathcal{R}_0}$, with $\mathcal{A}=1-Δβ_0/2$ and $\mathcal{R}_0=1+\frac{1}{2}[(γ_\parallel+γ_\perp-2)β_0+γ_\parallelΔβ_0]$. In the resistive inner layer, anisotropy enters the leading momentum balance through $\mathcal{A}$. We derive modified FKR and Coppi branches and, by matching them at their crossover wavenumber, obtain $γ_{\max}τ_A\sim\mathcal{A}^{1/2}\mathcal{R}_0^{-1/4}S^{-1/2}$. Thus the classical Lundquist-number exponent is retained, while the prefactor depends on the equilibrium anisotropy, plasma beta, and gyrotropic closure. PSECAS eigenvalue calculations support the Coppi branch and are consistent with the FKR branch when a fitted finite-wavelength approximation for $Δ'$ is used. Within the localized-mode and pressure-positive domain, positive $Δβ_0$ generally suppresses tearing and broadens the inner layer, whereas negative $Δβ_0$ enhances growth and shifts the fastest mode to larger wavenumber. This work identifies how prescribed equilibrium pressure anisotropy modifies both ideal outer matching and resistive inner-layer dynamics in the gyrotropic-MHD regime.
[abstract 70 / 75] (score: 2) - Title: On the Tully-Fisher Relation for Active Galaxies -- I: Evidence of Larger ScatterAuthors: Justin H. Robinson, Mitchell Revalski, Misty C. Bentz, D. Michael Crenshaw, Hélène M. Courtois, Veronica Lahue, Julian Falcone, Rachael L. Merritt, Ishita Chintala, Thomas Kay, Mira Menon, Naveen Ali, Bradley Clemons, Atul Gautam, Thomas Gregoire,Comments: Accepted for publication in ApJ. 20 pages, 4 figuresSubjects: astro-ph.GACreated: 2026-06-21; Updated: 2026-06-23; Datestamp: 2026-06-23
We present an investigation of the Tully-Fisher (TF) relation solely for galaxies hosting an ACTIVE GALACTIC NUCLEus (AGN). Using 22 galaxies with primary, z-independent distances, we find that active galaxies exhibit significantly larger scatter about all TF relations compared to each respective calibration for (largely) inactive galaxies. The larger scatter persists despite removal of the AGN contamination from the photometry of the Type 1 AGNs via 1) careful surface brightness decompositions or 2) employing SEDs to constrain the light contribution of the AGN. These results suggest that the influence of an AGN on its host galaxy's surface brightness may extend beyond the nucleus. We also calculate the percentage difference between TF and primary distances, and find that TF-based distances are biased towards overestimation of the primary distances to active galaxies by anywhere from 5-10 percent for the optical/near-infrared and approximately 15 percent for distances predicted from inverting the Baryonic TF (BTF) relation. As TF-based distances (especially the I-band) are relied on heavily for analysis and modeling of the local peculiar velocity (Vpec) field, we suggest that active galaxies be removed from future Vpec modeling samples.
[abstract 71 / 75] (score: 2) - Title: Polarization Angle Geodesics in PSRs B1133+16 and B2016+28Authors: M. M. McKinnon,Comments: Accepted for publication in ApJ; 33 pages and 11 figuresSubjects: astro-ph.HECreated: 2026-06-21; Updated: 2026-06-23; Datestamp: 2026-06-23
Recent models of pulsar POLARIZATION predict that the position and ellipticity angles of the POLARIZATION vector can trace portions of a small or great circle on the Poincare sphere. A great circle can arise from a transition in dominance of orthogonal POLARIZATION modes, where the relative intensity of the modes changes with pulse longitude. A small circle may be caused by a rotation of the vector, where the phase difference between the modes changes with pulse longitude or wavelength. Observations of PSRs B1133+16 and B2016+28 are reanalyzed to search for these POLARIZATION features within their pulse profiles. The POLARIZATION angles observed in part of PSR B1133+16 are shown to follow a great circle on the Poincare sphere. The angles observed across the pulse of PSR B2016+28 follow an arc that resembles a portion of a great circle that has been altered by the pulsar's rotation. The observations are interpreted within the context of three different POLARIZATION models. All three models produce similar results for both pulsars and indicate that the observed geodesics are caused by mode transitions. The arc observed in PSR B2016+28 can also be interpreted as a vector rotation, provided the modes are elliptically polarized. The observations and accompanying analysis show that mode transitions are not restricted to the equatorial plane of the Poincare sphere and that arcs and partial circles may be more common than previously recognized.
[abstract 72 / 75] (score: 2) - Title: Remarks on atmospheric effect of D-foam in light of muon puzzleAuthors: Chengyi Li,Comments: 5 latex pages, no figure, accepted versionSubjects: hep-ph astro-ph.HE gr-qcCreated: 2026-06-22; Updated: 2026-06-23; Datestamp: 2026-06-23
In our recent paper arXiv:2509.00552, we used a stringy model for quantum space-time foam to suggest that the so-induced subluminal Lorentz violation~(LV) for photons would not lead to experimentally unacceptable changes in the developments of particle showers initiated by cosmic $γ$-rays in the Earth's atmosphere, in contrast to other approaches to LV. The result indicated, nonetheless, at the same time that the foam can mildly modify the electroMAGNETic cascades under certain conditions, by suppressing pair creation on nuclei by primary photons. In this addendum, we consider how this modification affects the detection of extensive air shower~(EAS) initiated by an ultrahigh-energy cosmic-ray particle~(viz., a primary hadron), like proton with $E \sim 10^{19}~\textrm{eV}$, given that secondary photon subshowers following $π^{0}$ decays could be similarly influenced. We argue that fewer electrons would reach the detector and hence the energy of the primary particle may be underestimated due to foam effects, enhancing in such a way the muon content in EASs. This opens up the possibility of interpreting the alleged ``excess'' of muons, as reported by Auger and Telescope Array collaborations recently and many other experiments on high-energy COSMIC RAYs, with a quantum-gravitational effect. Future observations are anticipated to confirm whether this anomaly really exists.
[abstract 73 / 75] (score: 2) - Title: Twisting Small-$x$ Gluon Tomography with Orbital Angular MomentumAuthors: Wei Kou, Xurong Chen,Comments: 8 pages, 5 figuresSubjects: hep-ph hep-thCreated: 2026-06-22; Updated: 2026-06-23; Datestamp: 2026-06-23
We propose an orbital-angular-momentum-resolved extension of small-$x$ gluon tomography in hard diffractive diJET deep inelastic scattering. In the standard plane-wave setup, the elliptic correlation between the diJET relative momentum and the target recoil probes the elliptic component of the small-$x$ gluon Wigner distribution through a fixed transverse readout. We show that replacing the plane-wave lepton current by a twisted wave-packet current promotes this readout into a tunable OAM--Bessel projection kernel. The exchanged virtual photon is not treated as an asymptotic vortex particle; the OAM dependence enters through the transverse structure of the lepton electroMAGNETic current. The resulting observable is a family of $M$-resolved elliptic correlations $A_2^{(M)}(q_T,R_γ)$, where $q_T$ denotes the transverse Bessel scale of the projection kernel, not the transverse momentum of the exchanged photon. We derive the normalized linear response and show that it contains a subtraction from the deformation of the total diffractive rate. Consequently, the elliptic response can vanish while the diffractive rate remains finite. This finite-rate null is a normalized projection zero of the response to the target elliptic gluon component, not a disappearance of diffraction. It is not available as a tunable mode zero in the standard single plane-wave readout, and provides an external projection basis in which the response to the same small-$x$ elliptic geometry can be probed with either sign or tuned to zero.
[abstract 74 / 75] (score: 2) - Title: Are most detected tidal disruption events partial?Authors: Megha Sharma, Daniel J. Price, Alexander Heger, Katie Auchettle,Comments: 19 pages, 15 Figures, accepted to ApJSubjects: astro-ph.HECreated: 2026-06-22; Updated: 2026-06-23; Datestamp: 2026-06-23
During a tidal disruption event (TDE), a star loses mass due to the tidal gravitational forces of the BLACK HOLE. In a partial tidal disruption event, a stellar remnant is left behind. Several dozen TDEs have been detected so far, including repeating partial events. We use the Phantom smoothed particle hydrodynamics code to model the disruption of a 1 Msun star around a 10^6 Msun BLACK HOLE for impact parameters resulting in less than equal to 50 % mass loss. We only consider zero energy orbits. Our simulations show that the mass fallback rate can exceed the Eddington limit for beta greater than or equal to 0.8, allowing debris to obscure the accretion disc by forming a reprocessing layer, similar to full TDEs. The mass fallback rate is shallower than t^{-5/3}, tracking closer to t^{-9/4}. Assuming thermal emission from the debris, that shock heating is trapped, that electron scattering dominates the opacity, and a color correction f_{col} of 1.7, we find temperatures of ~10^4 K, optical bolometric luminosities of ~ 10^{42-44} erg/s and blackbody radii ranging from 10-100 au for our simulations. We compare our values with observations and find support for the previous argument that some TDEs classified as full disruptions might actually be partial. Moreover, our results explain the detected optical/UV TDEs. We also find that our zero energy partial TDEs have properties similar to the repeating partial TDEs such as ASSASN-19dj, ASSASN-14ko, ASSASN-18ul, ASSASN-22ci, AT2020vdq and AT2022dbl. In the beta=0.8, isentropic simulation where radiation is assumed to escape, we find X-ray luminosities of ~ 10^{44-45} erg/s and radii lower than the inner most stable circular orbit.
[abstract 75 / 75] (score: 2) - Title: Periodic Timelike Motion and Gravitational Wave Signatures around a Magnetically Charged Black Hole Surrounded by QuintessenceAuthors: R. H. Ali,Comments:Subjects: gr-qcCreated: 2026-06-22; Updated: 2026-06-23; Datestamp: 2026-06-23
We investigate timelike geodesics and gravitational wave signatures of periodic motion around a static MAGNETically charged BLACK HOLE arising from nonlinear electrodynamics and immersed in a quintessence background. We analyze the effective potential for massive particles, determine the marginally bound and innermost stable circular orbits, and classify the resulting bound trajectories using the zoom-whirl taxonomy $(\mathit{z},\mathit{w},\mathit{v})$. We show that the quintessence parameter $c_q$ systematically shifts the orbital radii, conserved quantities, and turning-point structure associated with representative periodic families. We then model the gravitational radiation emitted by periodic extreme-mass-ratio inspirals within the numerical kludge approximation. The resulting waveforms exhibit the characteristic burst-like structure of zoom-whirl motion, while variations in the quintessence coupling parameter modify the phase evolution, burst timing, and harmonic content of the signal. The corresponding Fourier spectra display a discrete comb-like structure, and the characteristic strain is concentrated in the millihertz band relevant for space-based detectors such as LISA. These results indicate that a quintessence background can leave systematic imprints on periodic orbit dynamics and on the associated time and frequency-domain gravitational wave observables.
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