Current date: 2026-03-03
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Datestamp limit: 2026-03-03 (0 days ago)
Created/updated limit: 2026-02-24 (7 days ago)
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Number of records retrieved: 1146
Keyword score statistics
score 14 -- 1 abstracts
score 11 -- 1 abstracts
score 8 -- 2 abstracts
score 7 -- 1 abstracts
score 6 -- 2 abstracts
score 5 -- 5 abstracts
score 4 -- 7 abstracts
score 3 -- 11 abstracts
score 2 -- 30 abstracts
in total -- 60 abstracts
Articles that appeared on 2026-03-03
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[abstract 1 / 60] Wow! (score: 14)
- Title: Properties and Possible Physical Origins of $γ$-ray Emission in Extreme Synchrotron BlazarsAuthors: Ji-Shun Lian, Jia-Xuan Li, Ze-Rui Wang, Rui-Qi Huang, Hai-Ming Zhang, Jin Zhang,Comments: 34 pages, 7 figures, 4 tables, Published in ApJSubjects: astro-ph.HECreated: 2026-02-28; Updated: 2026-03-03; Datestamp: 2026-03-03
Extreme SYNCHROTRON BLAZARs, characterized by a first peak in their broadband spectral energy distributions (SEDs) at frequencies exceeding $10^{17}$ Hz, often exhibit a second peak beyond 1~TeV. These sources serve as ideal laboratories for studying particle acceleration and radiation mechanisms in RELATIVISTIC JETs. In this work, we systematically analyze the $\sim$16-year FERMI-LAT observational data for 25 extreme high-SYNCHROTRON-peaked BL Lacs (EHBLs). The results indicate that the majority of these sources display stable or low flux levels in the GeV band, with only 6 sources showing significant variability at a confidence level exceeding 5$σ$. The time-averaged spectra over the 16-year period for most EHBLs are well described by a hard power-law model, with photon indices predominantly clustered between 1.7 and 1.8. Using FERMI-LAT data in conjunction with multiwavelength observations compiled from the literature, we construct broadband SEDs for these EHBLs and fit them with a one-zone SYNCHROTRON + SYNCHROTRON-self-Compton (SSC) model. We find that this simplified theoretical framework is sufficient for modeling the observed SEDs of most of these EHBLs, albeit requiring relatively higher electron energies compared to other $γ$-ray emitting HBLs, and at times under-representing the UV emission. Based on the SED fitting results, we investigate the physical properties of the emission regions in these EHBLs and compare them with those of other $γ$-ray emitting HBLs. Consistent with other GeV--TeV $γ$-ray-emitting BL Lacs, the JETs in these EHBLs are marked by low radiation efficiency and low MAGNETization.
[abstract 2 / 60] Wow! (score: 11) - Title: Constraining the SYNCHROTRON peak and estimating the VHE brightness of a sample of extreme high SYNCHROTRON peak BLAZARsAuthors: Federica Sibani, Stefano Marchesi, Ettore Bronzini, Marco Ajello, Michele Doro, Lea Marcotulli, Elisa Prandini, Cristian Vignali,Comments: 21 pages, 17 figures. Accepted for publication in A&ASubjects: astro-ph.HECreated: 2026-02-27; Updated: 2026-03-03; Datestamp: 2026-03-03
We present the results of a multi-wavelength study of a population of X-ray bright ($\rm log(F_{0.2-12 \ keV})>-12.5$), non-$γ$-ray detected high and extreme high SYNCHROTRON peak (HSP, EHSP; $\rm log(ν_{\rm peak,\ Hz})>16$) BL Lacs to $i$) put stronger constraints on the SYNCHROTRON peak location and shape and $ii$) model their expected behaviour in the very high-energy band. First, we performed an X-ray spectral analysis, using XMM-Newton, Chandra, SWIFT-XRT, and eROSITA data, and fitting the spectra using both a power law and a log parabola model. Out of 78 sources in the initial sample, 17 were best described by a log parabola model, a result that supports a scenario where the SYNCHROTRON peak falls in the X-ray band. Among these 17 sources, we further selected the 10 objects dominated by the JET emission, with no significant contamination of the host galaxy. We performed a $γ$-ray analysis of \lat\ data for these objects, obtaining upper limits providing information on their flux in the 100 MeV - 300 GeV energy range. We then modelled the broadband SED of these objects with JetSeT using two models: one assuming a log parabola for the electron distribution and the other one with a broken power law electron distribution, using parameters consistent with those describing the emission of the prototypical EHSP 1ES 0229+200. We found the models to be generally consistent with the available multi-wavelength detections and upper limits. Furthermore, they confirmed that a subsample of sources could display relevant emission in the TeV energy range, even potentially reaching the threshold for detectability by the Cherenkov Telescope Array Observatory.
[abstract 3 / 60] Wow! (score: 8) - Title: Jet launching from the Kerr BLACK HOLE MAGNETosphere: An electrogeodesic approachAuthors: Jibril Ben Achour, Ileyk El Mellah, Eric Gourgoulhon,Comments: 37 pages, 4 figuresSubjects: astro-ph.HE gr-qcCreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
The launch of RELATIVISTIC JETs of plasma on astrophysical to cosmological scales is observed in a variety of astrophysical sources, from ACTIVE GALACTIC NUCLEi to X-ray binaries. While these JETs can be reproduced by general RELATIVISTIC MAGNETo-hydrodynamics (GRMHD) and particle-in-cells (GRPIC) simulations of the dynamical Kerr MAGNETosphere, the development of analytic models to describe the physics of the JETs has remained limited. A key challenge is to analytically describe the individual trajectories of accelerated charged particles, which ultimately build up the JET and emit radiation. In this work, we provide a first simple but fully analytical model of JET launching from the Kerr MAGNETosphere based on the motion of charged particles. To that end, we use the integrability of electrogeodesic motion in the Kerr monopole MAGNETosphere to study the ejection of charged particles near the poles. This enables us to derive (i) a criterion for the rotation axis to constitute a stable latitudinal equilibrium position, thereby representing an idealized JET, (ii) the expression for the MAGNETic frame-dragging effect, and (iii) the condition for an asymptotic observer to measure blueshifted particles emanating from the BLACK HOLE surroundings. Our study reveals that particles can be accelerated only in a specific region whose maximal radius depends on the spin and MAGNETization of the BLACK HOLE. Alongside these results, we provide a detailed review of the construction of test MAGNETospheres from (explicit and hidden) symmetries of the Kerr geometry and the condition for the separability of the electrogeodesic motion in a test MAGNETosphere, which serves as a basis for the model studied in this work.
[abstract 4 / 60] Wow! (score: 8) - Title: Electron-positron Pair Production in Global GRMHD Simulations of Black Hole Accretion FlowsAuthors: Ho-Sang Chan, Jason Dexter, Mitchell C. Begelman,Comments: 19 pages, 12 figures, accepted by MNRAS for publicationSubjects: astro-ph.HE gr-qcCreated: 2026-02-28; Updated: 2026-03-03; Datestamp: 2026-03-03
We present global, three-dimensional general RELATIVISTIC MAGNETohydrodynamic simulations of accreting BLACK HOLEs that incorporate pair physics. Pairs are modeled as a passive scalar that maintains a constant temperature. For high accretion rate models, we observe a maximum pair fraction of $\sim \mathcal{O}(0.01)$, consistent with those inferred from some X-ray binaries, and identify a `pair void' extending to a few gravitational radii from the BLACK HOLE. Pair fractions peak in the midplane just outside the plunging region and within a thin strip at the base of the corona. For moderate to high accretion rate models, pairs are near equilibrium close to the disk midplane, where the scattering optical depth is high and pair equilibrium timescales are short, and could be comparable to the Coulomb collision timescale. This suggests the possibility of a pair-regulated coronal temperature. In contrast, the upper corona and JETs, where the scattering optical depth is relatively low and pair equilibrium timescales are long, are populated with pairs that may exceed their equilibrium value by orders of magnitude. These pairs are transported by advection from the disk, which dominates over local pair processes. This result highlights advection as a significant source of pair injection, which may be relevant for certain X-ray binaries exhibiting $γ$-ray signatures. The pair density along the MAGNETically dominated poles exceeds the Goldreich-Julian density in some models.
[abstract 5 / 60] Wow! (score: 7) - Title: The Double-Episode Jet Genesis of the eROSITA and FERMI BubblesAuthors: Ruiyu Zhang, Fulai Guo, Shaokun Xie, Ruofei Zhang, Shumin Wang, Guobin Mou, Xiaodong Duan,Comments: Updated MHD simulations and added multi-wavelength analysis. Comments are welcomeSubjects: astro-ph.HE astro-ph.GACreated: 2026-03-01; Updated: 2026-03-03; Datestamp: 2026-03-03
The FERMI and eROSITA bubbles are giant gamma-ray and X-ray lobes in the Milky Way, extending up to $\sim$50° and ~$\sim$80° in galactic latitude, respectively, yet their origins remain debated. Using three-dimensional MAGNETohydrodynamic simulations, we investigate a scenario in which two temporally separated episodes of ACTIVE GALACTIC NUCLEus (AGN) JETs launched from the Galactic center produce the bubbles, with each structure bounded by a forward shock. Our simulations reveal that the first JET pair, launched 15 Myr ago, forms the outer eROSITA bubbles (extending to $\sim$18 kpc), while the second, launched 5 Myr ago, creates the nested FERMI bubbles ($\sim$10 kpc height). This model broadly reproduces the observed elongated morphology, multi-band X-ray surface brightness distribution, O VIII/O VII line ratios, radio ridge structures, and gamma-ray emissions of the bubbles. Cosmic-ray electrons are accelerated \textit{in situ} at the shock fronts, explaining the sharp edges and nearly uniform gamma-ray surface brightness distribution of FERMI bubbles. The results suggest that the eROSITA and FERMI bubbles encode a time-resolved record of episodic AGN activity in the Galactic center, providing a physically motivated framework for interpreting their multi-wavelength properties.
[abstract 6 / 60] Yes (score: 6) - Title: Short-duration GRB 250221A Afterglow Driven by Two-Component Jets from the merger of a compact starAuthors: Xiao Tian, Hou-Jun Lü, Xiao-Xuan Liu, Xiao-Fei Dong, Jia Ren, Wen-Long Zhang, En-Wei Liang,Comments: 14 pages, 5 figures, and 1 table, matched with the published verisonSubjects: astro-ph.HECreated: 2026-02-28; Updated: 2026-03-03; Datestamp: 2026-03-03
GRB 250221A is a short GAMMA-RAY BURST (GRB) at redshift $z=0.768$, with a duration of 1.8 s and no extended emission in either SWIFT/Burst Alert Telescope or Konus-Wind bands. A remarkable rebrightening feature in both optical and X-ray bands was observed at $\sim$0.6 days after the burst trigger, but no SUPERNOVA or kilonova signature was detected. The burst properties and empirical correlations or distributions (e.g., duration, spectral hardness, location in the Amati correlation, $\varepsilon-$value, $f_{\rm eff}$ parameter, and physical offset) favor a compact binary merger origin. However, a dense circumburst medium with $n\sim 80\rm~cm^{-3}$, obtained by adopting the energy injection into a JET to interpret the late-time rebrightening is inconsistent with the compact binary merger origin. In this paper, we propose a two-component JET model to explain the multiwavelength afterglow observations of GRB 250221A, in which the RELATIVISTIC narrow JET ($\rm θ_{c} \sim 3.8^\circ$) produces the prompt and the early decay afterglow emission, while the mildly RELATIVISTIC wide JET ($\rm θ_{w} \sim 4.4^\circ$) dominates at later times, resulting in the observed rebrightening feature. If this is the case, one can obtain a lower medium density with $n\sim 0.72\rm~cm^{-3}$ which is a little bit higher than that of short GRBs in merger environments, but falls into the reasonable and acceptable range. Finally, a possible kilonova emission is also discussed within the scenario of compact star merger origin of GRB 250221A.
[abstract 7 / 60] Yes (score: 6) - Title: Episode-wise spectro-polarimetry of GRB 220107A: Testing the hypothesis of evolving radiation mechanismsAuthors: Rahul Gupta, Rushikesh Sonawane, Shabnam Iyyani, D. Frederiks, Judith Racusin, Tanmoy Chattopadhayay, A. J. Castro-Tirado, A. F. Valeev, Soumya Gupta, Mayuresh Tembhurnikar, A. Ridnaia, D. Svinkin, S. B. Pandey, Dipankar Bhattacharya, Vidushi Sharma, Varun Bhalerao, G. C. Dewangan, Santosh Vadawale, R. Sánchez-Ramírez, Anastasia Tsvetkova,Comments: 16 pages, 10 figures, 6 tables, accepted for the publication in Astronomy and AstrophysicsSubjects: astro-ph.HECreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
We investigate the spectro-polarimetric properties of the long-duration GRB~220107A, which exhibited two distinct emission episodes separated by a 40 s quiescent gap, to test whether such multi-episode bursts show evidence for evolution in their underlying radiation mechanisms. We analyzed prompt emission data from AstroSat/CZTI, FERMI/GBM, and Konus-Wind, performing spectro-polarimetric analysis for each emission episode. The time-integrated POLARIZATION analysis shows no significant detection (PF$ < 38 \%$, $2σ$). Time-resolved analysis reveals clear spectral evolution between the two episodes, with episode 1 exhibiting a hard low-energy photon index and episode 2 showing substantial spectral softening ($α\sim -0.72$). Regarding POLARIZATION: Episode 1 shows a low POLARIZATION upper limit (< 52\%), consistent with expectations for photospheric emission dominated by quasi-thermal Comptonization in a baryon-rich outflow. Episode 2 also shows overall low POLARIZATION (PF$ < 55 \%$, $2σ$), though sliding-window analysis yields a marginally elevated signal (PF$= 70 \pm 30\%$, BF = 2.8) between T0+76 to T0+88 s. The robust spectral softening between episodes could arise from sub-photospheric dissipation, optically thin SYNCHROTRON radiation in small-scale MAGNETic fields, or if the tentative POLARIZATION enhancement proves intrinsic, it would favor SYNCHROTRON emission in large-scale ordered MAGNETic fields. The spectral evolution of GRB 220107A, combined with our polarimetric constraints, demonstrates the diagnostic potential of time-resolved spectro-polarimetry for constraining GRB prompt emission physics. We present GRB 220107A as a test case illustrating how future higher sensitivity observations could discriminate between competing emission models for multi-episode bursts. Our results emphasize both the promise and current limitations of prompt phase polarimetry.
[abstract 8 / 60] Yes (score: 5) - Title: Eclipsed X-ray Bursts from Magnetar SGR J1935+2154 and the Fireball MeasurementsAuthors: Sheng-Lun Xie, Aming Chen, Yun-Wei Yu, Shao-Lin Xiong, Hua Feng, Shuang-Nan Zhang, Zi-Gao Dai, Wang-Chen Xue, Ming-Yu Ge, Xiao-Bo Li, Liang-Duan Liu, Jia-Cong Liu, Wen-Jun Tan, Chen-Wei Wang, Shu-Xu Yi, Peng Zhang, Yan-Qiu Zhang, Zhen Zhang, Chao Zheng, Xiao-Ping Zheng,Comments:Subjects: astro-ph.HECreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
In theory, burst activity of the MAGNETar can lead to the formation of fireballs trapped by the MAGNETic field and corotating with the star. However, the smoking-gun observational evidence of the fireball is elusive. We envisage that the fireball emission should occasionally be eclipsed by the MAGNETar, especially when the burst duration is comparable to the MAGNETar's spin period. In this work, we first discover a peculiar type of burst whose light curve has a plateau-like feature among the long bursts of the MAGNETar SGR J1935+2154 detected by GECAM and FERMI/GBM. Then, based on these bursts, we identified four burst candidates with eclipse-like characteristics. By fitting their light curves with the eclipse fireball model, the viewing angle of the MAGNETar relative to its spin axis is estimated to be $17^\circ \pm 10^\circ$, and the distances from the fireballs to the MAGNETar are found to be more than 5 times the MAGNETar's radius, indicating that the fireballs are suspended in the MAGNETosphere rather than adhering to the MAGNETar surface. Furthermore, we find that this configuration is well consistent with the implication of the cyclotron resonance scattering feature we found in their spectra. Our results suggest that some intermediate X-ray bursts may originate from MAGNETic RECONNECTion within the MAGNETosphere rather than the starquake.
[abstract 9 / 60] Yes (score: 5) - Title: GRB 230204B: GIT Discovery of a Fast Fading Afterglow Associated with an Energetic GRB from a Massive-Star ProgenitorAuthors: Vishwajeet Swain, Varun Bhalerao, Harsh Kumar, Mehul Goyal, Ankur Ghosh, Utkarsh Pathak, Poonam Chandra, Tomas Ahumada, G. C. Anupama, Suman Bala, Sudhanshu Barway, Joshua S. Bloom, Dimple Dimple, Viraj R. Karambelkar, Mansi M. Kasliwal, Kuntal Misra, Josiah Purdum, Divita Saraogi, Jesper Sollerman, Aswin Suresh, Stefan J. van der Walt, Gaurav Waratkar,Comments:Subjects: astro-ph.HECreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
We present a comprehensive multi-wavelength study of a bright GAMMA-RAY BURST GRB 230204B, analyzing both prompt and afterglow emissions. This GRB is highly energetic, with an isotropic equivalent energy emission $E_{\mathrm{iso}} \sim 2.2 \times 10^{54}\ \mathrm{erg}$, released during the prompt emission. The GROWTH-India Telescope discovered a bright afterglow ($m_r = 15.55$) that faded rapidly ($\propto t^{-1.82}$). The prompt emission shows strong thermal photospheric emission, along with a non-thermal high-energy component. We explore the evolution of these components and find them to be consistent with theoretical expectations. Afterglow modeling reveals an energetic JET $E_{tot} \gtrsim 10^{52}\ \mathrm{erg}$ expanding into a wind-type medium viewed nearly on-axis, suggesting a massive star progenitor with strong winds. We also explore correlations between the prompt emission and afterglow that may help to understand the complete picture of GRB progenitors.
[abstract 10 / 60] Yes (score: 5) - Title: Simultaneous JWST, NUSTAR, and VLA Monitoring of Sgr A*: A Unified Picture of the Variable IR, X-ray and Radio EmissionAuthors: F. Yusef-Zadeh, M. Wardle, R. G. Arendt, C. O. Heinke, C. J. Chandler, H. Bushouse, G. A. Moellenbrock, J. M. Michail,Comments: 27 pages, 14 figures, accepted ApJLSubjects: astro-ph.HECreated: 2026-02-28; Updated: 2026-03-03; Datestamp: 2026-03-03
Flux variability is a fundamental channel of information from Sgr A* because of its direct probe of processes occurring within an accretion disk under strong gravity. We present simultaneous IR, X-ray and radio observations of Sgr A* on 2024 Apr 05 using JWST, NUSTAR, and VLA. We report the detection of a strong X-ray flare with a luminosity of $\sim5.2x10^{35}$ erg/s coincident with a bright near-IR flare, and a brightening in radio about an hour later. We investigate the candidate physical mechanisms for the X-ray flare emission and conclude that this can best be explained by inverse Compton scattering of near-IR flare radiation. We propose a dynamic scenario analogous to a coronal mass ejection in which a MAGNETic flux rope is ejected from Sgr A*'s inner accretion flow with a current sheet extending down from the rope to the bulk of the accretion flow. Reconnection within the sheet produces oppositely directed flows of accelerated particles moving upwards towards the rope and downwards towards the accretion flow. Infrared radiation from the approaching energetic electrons is enhanced by beaming and up-scattered by thermal electrons in the accretion flow to produce the strong X-ray flare. Meanwhile, the RELATIVISTIC electrons moving in the opposite direction away from the disk experience weaker MAGNETic fields so radiate at longer wavelengths by feeding into the MAGNETic flux tube and adiabatically cooled during its subsequent expansion. This physical picture attempts to unify the origin of the variable emission from Sgr A* at IR, X-ray and radio/submm wavelengths.
[abstract 11 / 60] Yes (score: 5) - Title: Meissner Effect in Kerr--Bertotti--Robinson SpacetimeAuthors: Haryanto M. Siahaan,Comments: 11 pages, no figureSubjects: gr-qcCreated: 2026-02-28; Updated: 2026-03-03; Datestamp: 2026-03-03
We establish the black-hole Meissner effect for extremal Kerr--Bertotti--Robinson (Kerr--BR) BLACK HOLEs, which are exact solutions of the Einstein--Maxwell equations describing a rotating BLACK HOLE immersed in a uniform Bertotti--Robinson electroMAGNETic universe. Using the near-horizon framework of Bičák and Hejda, we prove that for a purely MAGNETic external BR field the horizon-threading MAGNETic flux vanishes in the static limit of the near-horizon geometry, i.e.\ as the twist parameter $k\to 0$ when $Ba\to 1^-$, thereby establishing the Meissner effect analytically. The proof relies on two exact identities that hold at extremality for all values of the external field: $Ω_x|_{r_e}=0$ and $Ω_r|_{r_e}=B^2 a$, both consequences of the double-root structure of the horizon function $Δ$. Together they force the azimuthal gauge potential $A_ϕ|_{r_e}$ to become independent of the polar angle in the static limit, reducing to a pure-gauge constant on the horizon $S^2$ and expelling all MAGNETic flux. The Kerr--BR result is contrasted with the Kerr--Melvin family, where the static limit occurs at a finite interior field strength, and with the Melvin--Kerr--Newman--Taub--NUT spacetime, where the NUT parameter is known to prevent expulsion. An independent geometric argument based on the logarithmic divergence of the proper throat length corroborates the result, and its implications for Blandford--Znajek JET suppression near extremality are discussed.
[abstract 12 / 60] Yes (score: 5) - Title: Outflow from unMAGNETized shocked radiative transonic accretion disk around a BLACK HOLEAuthors: Arghya Chaudhuri, Apurba Ghosh, Sudip K Garain,Comments: 18 pages, under review in RAA, comments are welcomeSubjects: astro-ph.HECreated: 2026-03-01; Updated: 2026-03-03; Datestamp: 2026-03-03
We study outflow from an unMAGNETized, shocked accretion disk around a non-rotating super-massive BLACK HOLE using multidimensional hydrodynamics simulation with radiative cooling. We aim to investigate whether such shocked accretion flow can launch sustained collimated bipolar outflow reaching out to thousands of gravitational radii even in the absence of MAGNETic field and if yes, what terminal velocity can they achieve. We present the results of a few simulations of geometrically thick accretion flow with increasing specific angular momentum on a vertically elongated cylindrical domain. We show that bipolar outflow from a region very close to the BLACK HOLE is originating and propagating vertically out to our simulation domain boundary at around 2651 Schwarzschild radius. The outflow attains a terminal velocity with a maximum value found to be 0.14c and the outflow rate depends on the angular momentum value of the accreting material. We also compute the self-Comptonized bremsstrahlung spectra for all the disk-JET runs.
[abstract 13 / 60] Yes (score: 4) - Title: A possible wave-optical effect in lensed FRBsAuthors: Goureesankar Sathyanathan, Calvin Leung, Olaf Wucknitz, Prasenjit Saha,Comments: Accepted in A&A. 7 pages, 4 figuresSubjects: astro-ph.HE astro-ph.COCreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
Context: Fast Radio Bursts (FRBs) are enigmatic extragalactic bursts whose properties are still largely unknown, but based on their extremely small time duration, they are proposed to have a compact structure, making them candidates for wave-optical effects if gravitational lensed. If an FRB is lensed into multiple-images bursts at different times by a galaxy or cluster, a likely scenario is that only one image is detected, because the others fall outside the survey area and time frame. Aims: In this work we explore the FRB analog of QUASAR microlensing, namely the collective microlensing by stars in the lensing galaxy, now with wave optics included. The eikonal regime is applicable here. Methods. We study the voltage (rather than the intensity) in a simple simulation consisting of (a) microlensing stars, and (b) plasma scattering by a turbulent interstellar medium. Results: The auto-correlation of the voltage shows peaks (at order-microsecond separations) corresponding to wave-optical interference between lensed micro-images. The peaks are frequency dependent if plasma-scattering is significant. While qualitative and still in need of more realistic simulations, the results suggest that a strongly-lensed FRB could be identified from a single image. Conclusions: Microlensing could sniff out macro-lensed FRBs
[abstract 14 / 60] Yes (score: 4) - Title: Revisiting Very High Energy Gamma-Ray Absorption in Cosmic Propagation under the Combined Effects of Axion-Like Particles and Lorentz Invariance ViolationAuthors: Longhua Qin, Jiancheng Wang, Chuyuan Yang, Huaizhen Li, Quangui Gao, Ju Ma, Ao Wang, Weiwei Na, Ming Zhou, Zunli Yuan, Chunxia Gu, Guangbo Long,Comments: Allready accepted by ApJSubjects: astro-ph.HE hep-phCreated: 2026-03-01; Updated: 2026-03-03; Datestamp: 2026-03-03
Very-high-energy (VHE; $E \gtrsim 100$ GeV) gamma rays are expected to experience strong attenuation during cosmological propagation due to electron-positron pair production on the extragalactic background light (EBL). Recent observations of GRB 221009A (z = 0.151), including photons up to $\sim 18$ detected by LHAASO and a $\sim 300\ \mathrm{TeV}$ event reported by Carpet-3, suggest a higher-than-expected transparency of the Universe at extreme energies. These observations cannot be explained by standard EBL absorption alone; moreover, neither Lorentz invariance violation (LIV) nor photon-axion-like particle (ALP) oscillations, when considered in isolation, appear sufficient to account for the survival of such photons over cosmological distances. In this work, we propose a joint propagation scenario that incorporates photon-ALP mixing in astrophysical MAGNETic fields together with subluminal quadratic LIV corrections to the $γγ$ pair-production threshold. Applying this framework to the broadband gamma-ray spectrum of GRB 221009A, we show that ALPs with coupling ($g_{aγ} = 1.685 \times 10^{-10}\mathrm{GeV}^{-1}$ ) and mass ($m_a = 9.545 \times 10^{-8}\mathrm{eV}$), combined with a quadratic LIV energy scale ($E_{\rm LIV,2} = 1.30 \times 10^{-7} E_{\rm Pl}$) adopted from the literature, can significantly enhance the photon survival probability in the energy range (10\text{-}300) TeV. The resulting enhancement exceeds that obtained from either ALP mixing or LIV effects alone. These results indicate that a combined ALP-LIV scenario may provide a viable interpretation of the extreme-energy gamma-ray observations of GRB 221009A and highlight the potential of VHE gamma-ray measurements as probes of physics beyond the Standard Model.
[abstract 15 / 60] Yes (score: 4) - Title: Constraining the Fraction of LIGO/Virgo/KAGRA Binary Black Hole Merger Events Associated with Active Galactic Nucleus FlaresAuthors: Liang-Gui Zhu, Lei He, Xian Chen, Wen Zhao,Comments: 13 pages and 4 figures; Accepted for publication in The Astrophysical Journal (ApJ)Subjects: astro-ph.HE astro-ph.IM gr-qcCreated: 2026-03-01; Updated: 2026-03-03; Datestamp: 2026-03-03
The formation channels of binary BLACK HOLE (BBH) mergers detected by the LIGO/Virgo/KAGRA (LVK) network remain uncertain. While BBH mergers occurring inside ACTIVE GALACTIC NUCLEus (AGN) disks may interact with surrounding gas and generate observable optical flares. We test this scenario by quantifying the spatial and temporal correlation between BBH events in GWTC-4.0 and AGN flares identified from six years of the Zwicky Transient Facility (ZTF) DR23 data. Using 80 BBH mergers selected for adequate localization, redshift reach, observing-epoch overlap, and ZTF sky coverage, we construct a likelihood for the flare-associated fraction, $f_{\rm flare}$, that combines each event's 3D localization with a locally estimated flare number density derived from a 3D Voronoi tessellation, while explicitly accounting for survey boundaries and incomplete catalog coverage. Adopting a 200-day post-merger time window for potential counterparts, we infer $f_{\rm flare} = 0.07_{-0.05}^{+0.24}$ (90\% confidence level). This non-zero maximum-likelihood value is driven primarily by GW190412, for which a single flare candidate (J143041.67+355703.8) is consistent in both time and spatial position. The candidate's light curve is limited to two data points during its peak, so it remains classified only as a candidate AGN flare. Excluding GW190412 yields results consistent with no association and an upper limit of $f_{\rm flare} < 0.17$ at 90\% confidence level. The intrinsic properties of GW190412 and the characteristics of the candidate host AGN are broadly consistent with theoretical expectations for the AGN-disk formation channel, motivating continued, targeted electroMAGNETic follow-up of well-localized and highly asymmetric BBH mergers in current and upcoming time-domain surveys.
[abstract 16 / 60] Yes (score: 4) - Title: FRB scattering statistics through the CGM are sensitive to morphology and intermittencyAuthors: Dylan L. Jow, Calvin Leung,Comments:Subjects: astro-ph.GA astro-ph.HECreated: 2026-02-27; Updated: 2026-03-03; Datestamp: 2026-03-03
The small-scale properties of circumgalactic gas in ordinary galaxies drive its bulk properties: the mass loading of cold neutral gas in galactic outflows affects their bulk momentum; gas cooling processes on small scales affect the spatial distribution of gas in the cool (T~$10^4$K) circumgalactic medium (CGM). However, hydrodynamical simulations have yet to resolve the CGM on such small scales. Spectroscopy remains our primary probe of the small-scale CGM, with which sub-parsec scales are challenging to resolve. Fast radio bursts (FRBs)--microsecond to millisecond duration radio pulses--are temporally broadened ("scattered") by gradients in the electron density transverse to the line of sight, often generated by fluctuations on the smallest spatial scales. This makes FRB scattering a powerful, complementary, and scalable probe of the small-scale CGM. We show that the distribution of scattering timescales introduced by density fluctuations within a single, foreground halo--the tau distribution function, or TDF--is sensitive to the small-scale spatial morphology of the gas. The TDF is readily measurable and is analogous to areal covering factors reported in QUASAR absorption statistics. We compute the TDF in two regimes: scattering from a turbulent, volume-filling medium ("volumetric scattering") distributed along the line of sight; and scattering from discrete structures localized along the line of sight ("intermittent scattering"). Within these regimes, the TDF is sensitive to whether the cool gas comprises primarily spherical, filamentary (1D), or sheet-like (2D) structures. This work sets the stage for upcoming observations which will use hundreds of sight-lines through nearby halos to probe the small-scale CGM, and points out a novel science case for FRB detectors like MeerKAT, Parkes, FAST, and the DSA-2000, which are exquisitely sensitive over a narrow field of view.
[abstract 17 / 60] Yes (score: 4) - Title: High-resolution observations of small-scale activity in coronal hole plumesAuthors: Ziwen Huang, L. P. Chitta, L. Teriaca, R. Aznar Cuadrado, H. Peter, S. K. Solanki, T. Wiegelmann, F. Plaschke,Comments: 16 pages, 11 figuresSubjects: astro-ph.SRCreated: 2026-02-28; Updated: 2026-03-03; Datestamp: 2026-03-03
Plumes have been proposed to channel MHD waves and the solar wind into the heliosphere. High-speed propagating disturbances (PDs), though well detected in plumes, cannot yet be clearly assigned to MHD waves or to mass flows. Additionally, plume bases as observed in the extreme ultraviolet are riddled with small-scale transients that could be related to the PDs. We study three plumes within an equatorial coronal hole observed by the EUV High Resolution Imager of the Extreme Ultraviolet Imager on board Solar Orbiter. The properties of the small-scale brightenings at the plume bases are investigated to interpret their nature and possible relation with PDs. We process images with the Difference of Gaussians method to highlight the target brightenings, which are further identified with two different approaches. In the 30-min observation, 50 brightenings are visually selected, which also help set thresholds for automatic detection, where we find 451 brightenings. Their properties, including velocities on the plane of sky (PoS), are analyzed statistically. Potential field extrapolation based on the MAGNETic field data from the Polarimetric and Helioseismic Imager on board Solar Orbiter is used for correcting the PoS velocity to the real velocity along the MAGNETic field. We observe that the majority of the base brightenings are small-scale, short-lived, and slightly elongated at the plume bases. They display intricate movements, with most exhibiting velocities in the PoS of less than 10 km/s. Their 3-dimensional velocities are found to be substantially lower than (and difficult to reconcile with) the speeds of PDs. A direct link between base brightenings and PDs remains inconclusive. We propose two possibilities for base brightenings: they may be related to wave-driven Type I spicules or originate from interchange RECONNECTions. Further investigation is required to validate these hypotheses.
[abstract 18 / 60] Yes (score: 4) - Title: Accretion Geometry of Black Hole X-ray Binaries: Insights from X-ray ObservationsAuthors: Honghui Liu,Comments: 52 pages, 7 figures, Accepted for publication in Astrophysics and Space ScienceSubjects: astro-ph.HECreated: 2026-02-28; Updated: 2026-03-03; Datestamp: 2026-03-03
The accretion-ejection activities of BLACK HOLEs play a vital role in shaping the Universe. Bright and recurrent BLACK HOLE X-ray binaries are ideal objects for studying accretion physics across a wide range of accretion rates, providing insights into the understanding of their supermassive counterparts. This short review summarizes X-ray techniques capable of measuring accretion geometry, our current understanding, and open questions. In particular, X-ray spectroscopic studies indicate that the accretion disk can extend close to the innermost stable circular orbit in the bright hard state. Some hints of disk-corona-JET connections are also discussed.
[abstract 19 / 60] Yes (score: 4) - Title: Predicting the Peak Energy of SWIFT Gamma-Ray Bursts Using Supervised Machine LearningAuthors: Wan-Peng Sun, Si-Yuan Zhu, Da-Ling Ma, Fu-Wen Zhang,Comments: 12 pages, 16 figures, 5 tables. Accepted for publication in Astronomy & AstrophysicsSubjects: astro-ph.HECreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
Gamma-ray bursts (GRBs) are among the most energetic explosive phenomena in the universe, and their peak energy ($E_{\rm p}$) is a key physical quantity for understanding the prompt emission mechanism. However, due to the limited energy coverage of the SWIFT satellite, a large fraction of SWIFT GRBs lack reliable measurements of the peak energy. Therefore, developing an accurate and efficient method to predict $E_{\rm p}$ is of great importance. In this work, we propose a method based on the SuperLearner framework that integrates multiple supervised machine learning algorithms to predict $E_{\rm p}$ of SWIFT/BAT GRBs. We use the SWIFT/BAT observational data from December 2004 to September 2022 as training features, and adopt the peak energies of 516 GRBs jointly detected by SWIFT and either FERMI/GBM or Konus-Wind as training labels. After training and testing multiple supervised models, the final SuperLearner ensemble yields a more robust and reliable predictive model. In 100 iterations of 5-fold cross validation, the predicted $E'_{\rm p}$ values show a tight correlation with the observed $E_{\rm p}$, with an average Pearson correlation coefficient of $r = 0.72$. Compared with previous Bayesian estimates, our model provides predictions that are likely closer to the true values. Based on the trained model, we further predict the peak energies of 650 SWIFT GRBs, significantly increasing the number of GRBs with known peak energies and providing new statistical support for constraining GRB emission mechanisms and energy origins.
[abstract 20 / 60] (score: 3) - Title: Measurement of ion acceleration and diffusion in a LASER-driven MAGNETized plasmaAuthors: J. T. Y. Chu, J. W. D. Halliday, C. Heaton, K. Moczulski, A. Blazevic, D. Schumacher, M. Metternich, H. Nazary, C. D. Arrowsmith, A. R. Bell, K. A. Beyer, A. F. A. Bott, T. Campbell, E. Hansen, D. Q. Lamb, F. Miniati, P. Neumayer, C. A. J. Palmer, B. Reville, A. Reyes, S. Sarkar, A. Scopatz, C. Spindloe, C. B. Stuart, H. Wen, P. Tzeferacos, R. Bingham, G. Gregori,Comments:Subjects: physics.plasm-phCreated: 2026-02-28; Updated: 2026-03-03; Datestamp: 2026-03-03
Here we present results from an experiment performed at the GSI Helmholtz Centre for Heavy Ion Research. A mono-energetic beam of chromium ions with initial energies of $\sim 450$ MeV was fired through a MAGNETized interaction region formed by the collision of two counter-propagating LASER-ablated plasma JETs. While LASER interferometry revealed the absence of strong fluid-scale turbulence, acceleration and diffusion of the beam ions was driven by wave-particle interactions. A possible mechanism is particle acceleration by electrostatic, short scale length kinetic turbulence, such as the lower-hybrid drift instability.
[abstract 21 / 60] (score: 3) - Title: Radiation-dominated polar emitting region of an accreting X-ray pulsar -- I. Polarization- and spectrum-dependent structure, and the emergent continuumAuthors: M. I. Gornostaev,Comments:Subjects: astro-ph.HECreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
The radiation-dominated polar emitting region of an accreting X-ray pulsar is simulated numerically in the framework of a three-dimensional (geometrically two-dimensional) model. The radiative transfer within the emitting region and the structure of the latter are calculated with the use of the self-consistent algorithm developed earlier. The MAGNETic scattering cross sections dependent on the photon energy and POLARIZATION have been incorporated. Second-order bulk Comptonization over entire emitting region, induced Compton scattering, the switching of the POLARIZATION modes, free-free processes, the cyclotron emission because of electron-proton collisions, and a realistic shape of the accretion channel have been taken into account. The case of a dipole MAGNETic field is considered. It is shown that the induced Compton effect can play a notable role in establishing the electron temperature in the post-shock zone. Within the model shock wave, a higher electron temperature is achieved than in the post-shock zone by means of the bulk-heating mechanism. The photons gaining the energy in the shock wave and above it due to bulk motion effects and the thermal Doppler effect are responsible for the formation of high-energy regions in the emergent continuum of the POLARIZATION modes.
[abstract 22 / 60] (score: 3) - Title: Spacetime in motion: an evolving RELATIVISTIC binary BLACK HOLE metric for GIZMOAuthors: Giacomo Fedrigo, Alessandro Lupi, Alessia Franchini, Matteo Bonetti,Comments: Accepted for publication in A&ASubjects: astro-ph.HE astro-ph.IMCreated: 2026-02-27; Updated: 2026-03-03; Datestamp: 2026-03-03
The last evolutionary stages of massive BLACK HOLE binaries prior to coalescence is dominated by the emission of gravitational waves, which will be probed by the future Laser Interferometer Space Antenna. If gas is present around the two BLACK HOLEs, however, the associated electroMAGNETic emission can provide additional information about the binary properties and location before the merger event. For this reason, a proper characterisation of the electroMAGNETic emission during these phases is of fundamental importance, and requires a detailed description of the gas dynamics close to the event horizon of the two BLACK HOLEs, only achievable via numerical simulations. Within this context, we present the implementation of the Superposed Kerr-Schild dynamic metric in the RELATIVISTIC scheme in the meshless code GIZMO. Our code can now simulate BLACK HOLE binaries approaching merger with high computational efficiency and accuracy, taking into account RELATIVISTIC effects on the gas. To validate our implementation, we perform two tests. First, we explore the case of a RELATIVISTIC Bondi flow around a binary, finding very good agreement with numerical relativity simulations. Then we explore the case of an inviscid RELATIVISTIC circumbinary disc, comparing our results with a similar simulation run assuming Newtonian gravity. In this second case, we find moderate differences in the mass accretion rate and in the inflow dynamics, which suggest that the presence of a non-Keplerian potential and of apsidal precession in the orbiting gas trajectories may produce stronger shocks and boost angular momentum transport in the disc. Our work highlights the importance of accounting for RELATIVISTIC corrections in accretion disc simulations around BLACK HOLE binaries approaching merger, even at scales much larger than those currently probed by numerical relativity simulations.
[abstract 23 / 60] (score: 3) - Title: HST view of NGC 5044: Constraints on Filament Widths, Magnetic Support, Multiphase Structure, and Comparison with Cluster EnvironmentsAuthors: Prathamesh Tamhane, Ming Sun, William Waldron, Kokoro Hosogi, Patricia da Silva, Huan Le, Massimo Gaspari, Francoise Combes, Norbert Werner, Gerrit Schellenberger, Andrew Fabian, Rebecca Canning, Laurence David, Megan Donahue, Mark Voit,Comments: Accepted for publication in PASA. 18 pages, 12 figures and 2 tablesSubjects: astro-ph.GACreated: 2026-02-27; Updated: 2026-03-03; Datestamp: 2026-03-03
We present new Hubble Space Telescope (HST) imaging of ionised filaments in the brightest group galaxy NGC 5044. These filaments extend several kiloparsecs and have widths of $\sim$50--120 pc, with some as narrow as those in cluster cores and others broader, reflecting the lower confining pressure in groups. Filament width ($W$) scales with ambient pressure ($P$) as $W \propto P^{-0.4}$. Combining HST, ALMA, and MUSE data, we measure column densities and MAGNETic field strengths. Equipartition fields decline from $\sim$40 $μ$G at the centre to $\sim$20 $μ$G at 5 kpc, about 2--3 times weaker than in clusters. Dynamical stability requires stronger radial fields ($\sim$10$^2$ $μ$G), consistent with simulations and MAGNETic draping, though such high values exceed Faraday Rotation Measure limits. Turbulence and COSMIC RAYs also contribute support. Group and cluster filaments are stable against gravitational collapse, and ultraviolet imaging reveals no STAR FORMATION in NGC 5044 ($<$10$^{-3}$ M$_\odot$ yr$^{-1}$). NGC 5044 hosts an ionised gas core within its Bondi radius with $n_e \propto r^{-1}$ and filling factor $f \gtrsim 3 \times 10^{-3}$, that is connected to the extended filaments, suggesting a channel for gas inflow toward the BLACK HOLE. Group and cluster filaments likely share a common origin, with MAGNETic fields and AGN feedback preserving their structure. Ambient pressure and dust survival regulate molecular gas formation. Lower-pressure groups favour broader, more diffuse filaments with sporadic molecular clumps and weaker dust shielding, whereas higher-pressure clusters host narrower strands with stronger molecular-ionised gas alignment. We predict that (i) filament width scales with ambient pressure, (ii) filament-coincident Faraday rotation structures emerge at $\leq 0.1$ kpc resolution, and (iii) molecular/ionised gas co-spatiality is weaker in groups than in clusters.
[abstract 24 / 60] (score: 3) - Title: Giant radio pulses in the MAGNETar XTE J1810-197 detected with the IAR's telescopesAuthors: S. B. Araujo Furlan, G. E. Romero, E. Zubieta, G. Gancio, F. García, S. del Palacio, C. O. Lousto,Comments: 12 pages, 12 figures, proposed for acceptance in Astronomy & AstrophysicsSubjects: astro-ph.HECreated: 2026-02-27; Updated: 2026-03-03; Datestamp: 2026-03-03
[...] We observed XTE J1810-197 between 29 September 2022 and 14 July 2023 with the radio telescopes at the Argentine Institute of Radioastronomy (IAR). We searched for single pulses in time series at a DM range of 100-400 pc cm-3 , with a threshold in signal-to-noise ratio (S/N) of 8. [...] We found 249 giant pulses at a DM mean value of 178.8$\pm$0.1 pc cm-3 . We measured peak flux densities up to 119 Jy, and fluences up to 58 Jy ms. We fitted a power law distribution to the flux density, obtaining an index of -4.0$\pm$0.3. We observed a maximum rate of approximately 15 pulses per hour on 20 February 2023, followed by an abrupt disappearance of transient radio emission, indicating a transition to a less active state. The brightest single pulses are limited to a $\sim$2$\%$ of the rotational phase and have similar fluence values to the reported intermediate FRB-like bursts of SGR 1935+2154. No significant X-ray activity in the MAXI data was detected during the radio observing period. This is the first study of single radio pulses of a MAGNETar using IAR data, showing the potential of the upgraded telescopes for investigating the transient radio sky. The properties of the single pulses detected here show the MAGNETar transient nature and capability to emit high-luminosity pulses. We compared the detected emission to FRB-like bursts and single pulses emitted by SGR 1935+2154. Even though the mechanism producing all the events should be coherent, the luminosity of the events, features on the dynamic spectra, and the difference between being phase confined or not, indicate that XTE J1810-197 presents GP emission, while SGR 1935+2154 only shows normal single pulses or FRB bursts. This could indicate that the conditions for producing each type of event differ.
[abstract 25 / 60] (score: 3) - Title: The Hall Term and Anomalous Resistivity Effects in Neon Gas-Puff Z-PinchesAuthors: A. Rososhek, C. E. Seyler, E. S. Lavine, D. A. Hammer,Comments:Subjects: physics.plasm-phCreated: 2026-02-27; Updated: 2026-03-03; Datestamp: 2026-03-03
In this paper, we compare experimental and numerical simulation results to benchmark the PERSEUS code against gas-puff $Z$-pinch implosions on COBRA. We then use the code to investigate the structure of the plasma sheath. To this end, we study the morphology of the implosion, focusing on non-MAGNETohydrodynamical (MHD) effects such as electron drifts governed by the Hall term within the growing MAGNETo-Rayleigh-Taylor instability (MRTI). The spatial wavelength of MRTI is better reproduced when both the Hall term and an anomalous resistivity driven by the electron drift are included. Additionally, cathode-anode gap polarity effects are more accurately captured when the Hall term is turned on. The plasma sheath structure, which includes both the accelerating piston driven by the MAGNETic pressure and the shockwave ahead of it, matches interferometric measurements in width only when a current-driven anomalous resistivity model is used. This anomalous resistivity is assumed to be driven by the lower-hybrid-drift instability, which generates small-scale turbulence with typical wavelengths < 30μm.
[abstract 26 / 60] (score: 3) - Title: Evgeny P. Velikhov (1935-2024)Authors: Günther Rüdiger,Comments: 31 pages, 12 figuresSubjects: physics.hist-ph astro-ph.HECreated: 2026-03-01; Updated: 2026-03-03; Datestamp: 2026-03-03
The master student at Lomonosov University in Moscow E.P. Velikhov formulated 1959 the theory of MAGNETorotational instability, which dominates current astrophysics. A meteoric career made him later the science, nuclear and disarmament advisor to Gorbachev and Yeltsin. This article describes the interactions between Velikhov and the PROMISE team from Potsdam and Dresden-Rossendorf when it came to experimentally testing the theory in the laboratory in the 2000s. At an MHD conference in Catania, Sicily, he offered the public the use of small, transportable Russian nuclear power plants anywhere in the world until the fusion machines currently under development had finally solved the energy problem.
[abstract 27 / 60] (score: 3) - Title: Rugged MAGNETo-hydrodynamic invariants in weakly collisional plasma turbulence: Two-dimensional hybrid simulation resultsAuthors: Petr Hellinger, Victor Montagud-Camps,Comments:Subjects: physics.plasm-ph astro-ph.SRCreated: 2026-03-01; Updated: 2026-03-03; Datestamp: 2026-03-03
Aims. We investigated plasma turbulence in the context of solar wind. We concentrated on properties of ideal second-order MAGNETo-hydrodynamic (MHD) and Hall MHD invariants. Methods. We studied the results of a two-dimensional hybrid simulation of decaying plasma turbulence with an initial large cross helicity and a negligible MAGNETic helicity. We investigated the evolution of the combined energy and the cross, kinetic, mixed, and MAGNETic helicities. For the combined energy and the cross, kinetic, and mixed helicities, we analysed the corresponding Kármán-Howarth-Monin (KHM) equation in the hybrid (kinetic proton and fluid electron) approximation. Results. The KHM analysis shows that the combined energy decays at large scales. At intermediate scales, this energy cascades (from large to small scales) via the MHD non-linearity and this cascade partly continues via Hall coupling to sub-ion scales. The cascading combined energy is transferred (dissipated) to the internal energy at small scales via the resistive dissipation and the pressure-strain effect. The Hall term couples the cross helicity with the kinetic one, suggesting that the coupled invariant, referred to here as the mixed helicity, is a relevant turbulence quantity. However, when analysed using the KHM equations, the kinetic and mixed helicities exhibit very dissimilar behaviours to that of the combined energy. On the other hand, the cross helicity, in analogy to the energy, decays at large scales, cascades from large to small scales via the MHD+Hall non-linearity, and is dissipated at small scales via the resistive dissipation and the cross-helicity equivalent of the pressure-strain effect. In contrast to the combined energy, the Hall term is important for the cross helicity over a wide range of scales. The MAGNETic helicity is scantily generated through the resistive term and does not exhibit any cascade.
[abstract 28 / 60] (score: 3) - Title: ALMA High-J CO Spectroscopy of High-Redshift Galaxies. II. 0.03" Resolution CO Kinematics Reveal Super-Eddington Accretion in a Dust-Obscured Galaxy at z=3.111Authors: Ken-ichi Tadaki,Comments: Submitted to ApJ. 14 pages, 8 figures. Figure 1 presents 0.03" resolution ALMA CO(11-10) and CO(7-6) maps. Companion catalog paper: arXiv:2602.23521Subjects: astro-ph.GA astro-ph.HECreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
We present ultra-high-resolution (0.03"~230 pc) Atacama Large Millimeter/submillimeter Array (ALMA) observations of the hyperluminous dust-obscured galaxy W2305-0039 at z=3.111, targeting the CO J=7-6 and J=11-10 lines. The CO(11-10) emission is extremely compact and exhibits anomalously high excitation relative to CO(7-6) within the central <500 pc. X-ray-dominated region models successfully reproduce this excitation, providing strong evidence for intense X-ray irradiation by a deeply obscured ACTIVE GALACTIC NUCLEus (AGN), while photodissociation-region models fail to match the observed ratio. Forward modeling of the nuclear CO(11-10) position-velocity diagram yields a dynamical black-hole mass of log(M$_{\rm BH}$/M$_{\odot}$) = 8.3$^{+0.7}_{-0.6}$ and an intrinsic gas velocity dispersion of $277~^{+16}_{-14}$ km s$^{-1}$. Combined with the AGN luminosity from infrared spectral energy distribution decomposition, these measurements imply a highly super-Eddington accretion state with $λ~_{\rm Edd}~\gtrsim 4$. Our results provide dynamical evidence that the most rapid phases of black-hole growth can occur within a compact, heavily obscured nuclear region. Extending ALMA beyond its current 16 km maximum baselines will be essential for pushing such dynamical measurements to tens-of-parsec scales and resolving the black-hole sphere of influence in massive galaxies at $z \gtrsim 6$.
[abstract 29 / 60] (score: 3) - Title: Atmospheric-Pressure Ar/Air Plasma Jet-Induced Degradation of Azo Dyes in Aqueous Solutions: Kinetic and Mechanistic InsightsAuthors: Mohammed Shihab, Alaa El-Ashry, Seham A. Ibrahim, Sarah Salah, Abdelhamid Elshaer, Nabil El-Siragy, Atef A. Elbendary,Comments:Subjects: physics.plasm-phCreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
Atmospheric-pressure non-thermal plasmas are promising platforms for advanced oxidation in water treatment, yet quantitative coupling between reactive species delivery, solution chemistry, and molecular fragmentation remains unclear. We investigate degradation of two structurally related azo dyes using an Ar plasma JET in a plasma-liquid discharge configuration with an immersed counter-electrode to enhance interfacial coupling. Plasma exposure generated a reactive oxygen and nitrogen species environment and strong acidification, increasing proton concentration up to 49-fold. UV-Vis analysis showed rapid chromophore decay, achieving 0.88 and 0.94 removal within 40 min. Biphasic kinetics indicated a transition from radical-flux-controlled to transport-influenced regimes. Fluorescence and Raman spectroscopy confirmed transient oxidized intermediates and progressive pi-conjugation breakdown, elucidating plasma-driven oxidative fragmentation mechanisms.
[abstract 30 / 60] (score: 3) - Title: Cross-sphere Coupling and Source Inversion of Ionospheric Disturbances Associated with the 2025 Myanmar Strike-slip Earthquake from BeiDou GEO and Multi-GNSS ObservationsAuthors: Jianghe Chen, Pan Xiong, Qingshan Ruan, Xiaoran Zhang, Yuqi Lin, Xuemin Zhang, Ting Zhang, Kaixin Wang, Xuhui Shen,Comments:Subjects: physics.geo-phCreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
Focusing on the M7.9 earthquake in Myanmar in 2025, this study comprehensively utilizes data from BeiDou geostationary satellites of the Chinese Continental Crustal Movement Observation Network and multi-system Global Navigation Satellite Systems (GNSS). The spatiotemporal evolution characteristics and physical mechanisms of pre-seismic ionospheric anomalies and co-seismic ionospheric disturbances were systematically analyzed. By employing the moving interquartile range method combined with solar-terrestrial environmental parameters, a negative Total Electron Content (TEC) anomaly associated with the seismogenic region was identified three days before the earthquake. The equatorial conjugate structure of this TEC anomaly revealed a multi-path coupling effect between the lithosphere, atmosphere, and ionosphere. The extraction of Coherent Ionospheric Disturbance (CID) signals based on wavelet transform and band-pass filtering indicated that the co-seismic ionospheric disturbances were dominated by acoustic-gravity waves in the 2-8 mHz frequency band, propagating at a speed of approximately 1.2 km/s, and exhibiting an asymmetric pattern in the southeast direction. A spatial density-weighted method for locating the source of ionospheric disturbances was proposed, elucidating the joint control mechanism of fault strike-slip motion, geoMAGNETic field modulation, and equatorial electroJET on the disturbance energy. The results confirm that the high spatiotemporal resolution of BeiDou GEO satellites and multi-system GNSS significantly enhances the capability to capture weak ionospheric anomaly signals associated with earthquakes. These results provide additional observational constraints on space-based Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) processes and may contribute to the development of ionosphere-based earthquake monitoring techniques.
[abstract 31 / 60] (score: 2) - Title: Surrogate-based multilevel Monte Carlo methods for uncertainty quantification in the Grad-Shafranov free boundary problemAuthors: Howard Elman, Jiaxing Liang, Tonatiuh Sánchez-Vizuet,Comments: In memory of Prof. Howard C. Elman, esteemed friend, mentor, and outstanding computational scientistSubjects: physics.comp-ph cs.NA math.NA physics.plasm-phCreated: 2026-03-01; Updated: 2026-03-03; Datestamp: 2026-03-03
We explore a hybrid technique to quantify the variability in the numerical solutions to a free boundary problem associated with MAGNETic equilibrium in axisymmetric fusion reactors amidst parameter uncertainties. The method aims at reducing computational costs by integrating a surrogate model into a multilevel Monte Carlo method. The resulting surrogate-enhanced multilevel Monte Carlo methods reduce the cost of simulation by factors as large as $10^4$ compared to standard Monte Carlo simulations involving direct numerical solutions of the associated Grad-Shafranov partial differential equation. Accuracy assessments also show that surrogate-based sampling closely aligns with the results of direct computation, confirming its effectiveness in capturing the behavior of plasma boundary and geometric descriptors.
[abstract 32 / 60] (score: 2) - Title: Examining the influence of anisotropy on the fundamental mode of nonradial oscillation in neutron stars on a complete general RELATIVISTIC schemeAuthors: José D. V. Arbañil, Gabriel O. Cavalheiro, Victor B. T. Alves, Juan M. Z. Pretel, César O. V. Flores, César H. Lenzi,Comments: 24 pages, 4 figuresSubjects: gr-qc astro-ph.HECreated: 2026-02-28; Updated: 2026-03-03; Datestamp: 2026-03-03
The anisotropic influence on the $f$-mode frequency of oscillations and dimensionless tidal deformability of neutron stars are analyzed by employing the nonradial oscillation equations for the complete general relativity frame and tidal deformability equations, which are derived and modified from their standard form to introduce the anisotropic factor. The fluid inside the compact star obeys an equation of state constructed by matching microscopic nuclear and perturbative QCD calculations through a piecewise polytropic interpolating scheme. For the anisotropic function, we use a local anisotropy, which is regular along the whole star and is null both at the center and on the star's surface. We show that the $f$-frequency of oscillation and dimensionless tidal deformability change considerably with the anisotropy. Finally, we investigate the correlation between the dimensionless tidal deformability of the GW$170817$ event with the anisotropy.
[abstract 33 / 60] (score: 2) - Title: Condensation of area quanta ensembles with quantum statistics in Schwarzschild spacetimesAuthors: Ryley McGovern, Seth Major, Trevor Scheuing, Thomas Takis,Comments: v2: typos addressed, results unchanged, essentially published version, 20 pages, 2 figuresSubjects: gr-qcCreated: 2026-02-27; Updated: 2026-03-03; Datestamp: 2026-03-03
As is well known, near-horizon (equivalently high acceleration) observers in spherically symmetric BLACK HOLE spacetimes have a particularly simple form of the quasi-local energy. Using this energy and indistinguishable area quanta satisfying quantum statistics a statistical mechanical description of the Schwarzschild BLACK HOLE geometry for uniformly accelerating observers is developed. The resulting model has several phases including one with highly excited states, Bose-Einstein condensates, condensates distinct from the usual Bose gas, and degenerate FERMI gases. In the large area limit, relevant for comparison to the Bekenstein-Hawking entropy, the new condensed state is favored over Bose-Einstein condensation and the degenerate FERMI gas. The entropies of the phases, and the entropy of mixing, are computed. The resulting low-entropic condensed state, where the quanta are essentially all in the lowest Bose energy state, provides the framework for the quantization of near-horizon geometric fluctuations, which is explored in a companion paper.
[abstract 34 / 60] (score: 2) - Title: Inertial Frame Dragging as a Probe to Differentiate Kerr-Newman Naked Singularities from Black HolesAuthors: Arindam Kumar Chatterjee, Parthapratim Pradhan,Comments: 48 pages, 62 figures, 4 tables. Updated the introduction section and the plot captions. A small change is made in the section on observational aspectsSubjects: gr-qcCreated: 2026-02-28; Updated: 2026-03-03; Datestamp: 2026-03-03
We investigate inertial frame dragging and RELATIVISTIC precession in the Kerr--Newman spacetime and show how gyroscopic observables can operationally discriminate between Kerr--Newman BLACK HOLEs and Kerr--Newman naked singularities. We study a test gyroscope attached to a stationary observer and derive closed-form expressions for the Lense--Thirring, geodetic, and general spin-precession frequencies. A sharp qualitative distinction emerges: for Kerr--Newman BLACK HOLEs, the spin-precession frequency generically diverges as the horizon is approached (remaining finite only for the ZAMO family), whereas for Kerr--Newman naked singularities, the precession remains finite throughout the spacetime, with divergences confined to the ring singularity on the equatorial plane. Working with physically admissible stationary observers (including ZAMOs), we first construct the timelike geodesic motion and the fundamental orbital frequencies for equatorial circular orbits. Using these, we analyse the radial and vertical epicyclic frequencies, the ISCO shift induced by the charge parameter $Q$, and the associated periastron and nodal precession frequencies relevant to quasi-periodic oscillations (QPOs). We demonstrate that nonzero $Q$ produces systematic, and in rapidly rotating regimes nontrivial, modifications to the frequency hierarchy: $ν_{\rm nod}$ can develop a finite maximum at $r=r_p=\mathcal{O}(M)$, its peak amplitude decreases with increasing $Q$, and sign reversals may occur for sufficiently large charge and high spin, signalling a reversal of nodal-precession orientation. These results establish spin-precession behaviour as a robust strong-field probe of horizons versus exposed singularities, with potential implications for testing cosmic censorship using future high-precision precession/QPO measurements.
[abstract 35 / 60] (score: 2) - Title: Astrometric properties of reference frame sources as a function of redshiftAuthors: Zhiyun Zhang, N. Liu, Xiaxuan Zhang, I. Nurul Huda, Sufen Guo, Z. Zhu, J. -C. Liu, J. Yao, Z. -W. Wang, H. -F. Yu, D. -D. Zhang,Comments: 14 pages, 13 figures, accepted for publication in A&ASubjects: astro-ph.IMCreated: 2026-02-28; Updated: 2026-03-03; Datestamp: 2026-03-03
Previous studies based on the latest realisation of the International Celestial Reference Frame (ICRF3) have suggested a correlation between astrometric properties (such as the radio-optical offset) and redshift for ACTIVE GALACTIC NUCLEi (AGNs). We extend these investigations by using a large, all-sky sample of approximately 22,000 compact radio sources from the Radio Fundamental Catalogue (RFC) to examine this relationship in a systematic and statistically robust manner. We compiled redshifts for about 10,000 RFC sources over the range 0 < z < 5 by combining data from the Dark Energy Spectroscopic Instrument Data Release 1 and the Sloan Digital Sky Survey Data Release 17/19 with additional datasets from the NASA/IPAC Extragalactic Database. Cross-matching with Gaia Data Release 3 yielded a sample of 4,068 RFC objects with reliable spectroscopic redshifts and classifications, including galaxies and quasi-stellar objects (QSOs). We analysed the redshift dependence of their radio astrometric properties from very long baseline interferometry (VLBI) and their optical astrometric properties from Gaia. We find that the VLBI astrometric properties show no significant dependence on redshift within the achieved level of precision. In contrast, several optical astrometric quantities exhibit clear redshift-dependent behaviour. The median absolute radio-optical offsets decrease markedly over 0 < z < 0.5, where galaxies dominate the sample, decline more gradually over 0.5 < z < 1.3, and exhibit a mild increase at z > 1.3, where QSOs dominate. Similar behaviour is observed for several Gaia astrometric quantities, including astrometric uncertainties, proper motions, and G magnitudes. These behaviours can be largely explained by the dependence of Gaia astrometric performance on G magnitude and by the evolution of the G magnitude with redshift.
[abstract 36 / 60] (score: 2) - Title: Still The New Classical Relativistic Equation of Charge Motion in an ElectroMAGNETic FieldAuthors: Anatoliy V. Sermyagin,Comments: Comments: 7 pagesSubjects: physics.class-phCreated: 2026-02-27; Updated: 2026-03-03; Datestamp: 2026-03-03
The non-RELATIVISTIC Goedecke equation (1975), which describes the motion of a point charge taking into account the radiation reaction, has no "runaway" solutions. A "physical" method of covariant generalization of this equation is proposed, a special case of which is based on the Lorentz transformations in a coordinate--free covariant representation. Two equivalent forms of a new classical RELATIVISTIC equation of motion of a point charge are obtained. It is shown that the Abraham--Lorentz--Dirac (ALD) and the Mo--Papas (MP) equations are approximate consequences of the presented theory.
[abstract 37 / 60] (score: 2) - Title: Quasi-periodic Eruptions from Stellar-mass Black Holes Impacting Accretion Disks in Galactic NucleiAuthors: Kun Liu, Shang-Fei Liu, Zhen Pan, Hongping Deng, Rongfeng Shen, Cong Yu,Comments: 16 pages, 8 figures and 1 table. Submitted to AAS Journals. Comments are welcomeSubjects: astro-ph.HECreated: 2026-02-27; Updated: 2026-03-03; Datestamp: 2026-03-03
We investigate the origins of quasi-periodic eruptions (QPEs) in galactic nuclei using global three-dimensional meshless finite-mass (MFM) simulations. By modeling stellar and black-hole impactors traversing accretion disks under various inclinations and surface densities, we evaluate their consistency with the observed properties of QPEs. Stellar impacts produce highly asymmetric bipolar ejecta with forward outbursts dominating by over an order of magnitude in energy and luminosity due to the star blocking downstream flow and creating a low-density wake. This shock-compression mechanism often renders backward events unobservable, implying one detectable burst per orbit, and challenging the standard assumption of two bursts. It also fails to explain alternating long-short recurrence patterns and places several sources near or within twice the tidal disruption radius for solar-mass stars, raising severe stability concerns. Whereas a stellar-mass BLACK HOLE (sBH) gravitationally focuses and heats disk gas extending from its Bondi radius $R_{\rm B}$ to its Hill radius $R_{\rm H}$ during an impact, yielding nearly symmetric ejecta with mild contrasts. This gravitational-drag mechanism generates higher energy budgets at low inclinations due to enhanced mass accumulation. We suggest an ad hoc effective interaction radius $ R_{\rm eff} \simeq 0.5\, R_{\rm B}^{1/3} R_{\rm H}^{2/3} $ to quantify this trend. Our semi-analytical model confirms that sBH-disk collisions can power the full QPE energy range ($10^{44}$-$10^{48}$ erg), naturally accounting for periodicity, asymmetry, durations and diversity.
[abstract 38 / 60] (score: 2) - Title: Small hosts, big appetites: unveiling rapid and early low-mass BLACK HOLE growth in cosmological zoom-in simulations of dwarf galaxiesAuthors: Giulia Ortame, Martin A. Bourne, Sophie Koudmani, Debora Sijacki, Francesco D'Eugenio, Roberto Maiolino,Comments: 25 pages, 12 figures (including 4 appendices)Subjects: astro-ph.GACreated: 2026-02-27; Updated: 2026-03-03; Datestamp: 2026-03-03
Dwarf galaxies are ideal laboratories to probe the interplay between galaxy formation and the growth of BLACK HOLEs (BHs) in the early Universe. Mounting observational evidence reveals the presence of BHs in low-mass galaxies across cosmic time, with $\textit{JWST}$ uncovering a likely population of $\textit{overmassive}$ BHs at $2 \lesssim z \lesssim 11$. Simulations struggle to reproduce this high-redshift regime, motivating revisions to models of BH accretion and feedback from ACTIVE GALACTIC NUCLEi (AGN). To address this, we present high-resolution cosmological zoom-in simulations of a dwarf galaxy based on FABLE physics, introducing novel sink-based BH accretion models and relaxing the fiducial assumption of strong SUPERNOVA feedback. BHs accrete more efficiently in the sink-based runs compared to the `traditional' Bondi-based counterparts, with AGN feedback leading to early, rapid quenching maintained by fast, hot and metal-enriched outflows. These outflows pollute the outer circumgalactic medium, yielding flat metallicity gradients down to $z=0$. We further assess the performance of two widely used virial estimators and find significant departures from the true dynamical mass, especially during the high-redshift dwarf assembly. Since our galaxy is dark-matter-dominated at all times and radii, BH growth, tied to the baryon cycle, shows no clear correlation with global dynamical properties. Efficient AGN feedback, produced by overmassive BHs relative to extrapolated local $M_\bullet - M_\star$ relations, indicates that dormant BHs residing in local, quenched dwarfs might be the relics of some of the high-redshift $\textit{JWST}$ BHs.
[abstract 39 / 60] (score: 2) - Title: SIMPLIFI-Study of Interstellar Magnetic Polarization: A Legacy Investigation of Filaments. II. Enhancement of grain alignment near embedded protostars in the DR21 RidgeAuthors: S. Kumar, T. G. S. Pillai, G. V. Panopoulou, J. Kauffmann, L. N. Tram, S. Reissl, D. Clemens, V. J. M. Le Gouellec, M. Heyer, L. M. Fissel, P. F. Goldsmith, D. Seifried, G. A. P. Franco,Comments: 18 pages, figures, submitted to A&ASubjects: astro-ph.GACreated: 2026-02-27; Updated: 2026-03-03; Datestamp: 2026-03-03
Thermal dust continuum polarimetry is a powerful indirect probe of MAGNETic field geometry in dense molecular clouds while at the same time providing information on the alignment of dust grains with the MAGNETic field. The leading theory of grain alignment, Radiative Torque Alignment (RAT), has been successful in explaining a variety of observations, including the loss of POLARIZATION fraction toward high column densities. One prediction of RAT is that an increase in grain alignment efficiency should be observed in the environments surrounding protostars, due to radiation from the embedded source. However, observational confirmation of this prediction remains scarce. In this study, we sought to test the theoretical prediction of enhanced grain alignment near protostars in the high-mass star forming region DR21 using 214 $μm$ SOFIA/HAWC+ observations. We investigated the correlation of the POLARIZATION fraction of dust emission, $p$, and the POLARIZATION angular dispersion, $S$, with respect to total intensity. We also probed intrinsic dust POLARIZATION properties using the product $S\times p$ as a proxy. We detected significant POLARIZATION fractions even at the highest intensities, where strong dePOLARIZATION is typically expected. The POLARIZATION fraction-intensity trend flattens at $I > 1.6^{+0.3}_{-0.3} \times 10^4$ MJy/sr ($N_{H_2}$ $\sim 2\times 10^{23}$ ${cm}^{-2}$). We compared the observed trends with predictions from an analytical model of a centrally heated envelope surrounding an embedded luminous protostar. The predictions from the simple model agree well with the observed trends. Our results provide strong support for enhancement of grain alignment by local radiation from embedded sources.
[abstract 40 / 60] (score: 2) - Title: Comprehensive MHD modelling of ten successive CMEs driving a historic geoMAGNETic storm -- The 2024 Mothers Day eventAuthors: Shirsh Lata Soni, Anwesha Maharana, Sanchita Pal, Stefaan Poedts,Comments: 28 pages, 5 figures (3 appendix figures), 4 tablesSubjects: astro-ph.SRCreated: 2026-02-27; Updated: 2026-03-03; Datestamp: 2026-03-03
Interacting coronal mass ejections (CMEs) result in complex heliospheric structures that can dramatically enhance their geoeffectiveness compared to isolated events. A striking example of such complex structures is that of the Mothers Day event, which occurred during 10-14 May 2024, leading to the strongest geoMAGNETic storm in decades. It was driven by at least ten interacting CMEs accompanied by flare and filament eruptions from the solar western hemisphere. We aim to understand its solar and heliospheric origins, variation in plasma and MAGNETic characteristics, and predict its geoeffectiveness. Furthermore, we focus on bringing to the community the challenges and limitations faced during themodelling of such a complex, yet important environment. We use multi-point remote observations of CMEs and employ different methods to estimate their speeds and geometry. These parameters drive the 3D MAGNETohydrodynamic simulations of CME evolution and heliospheric propagation in the framework of the EUHFORIA model. The best-performing simulation reproduced the arrival time of the storm and peak intensity with a lead of 2 hours, and estimated the storm strength with about 70% accuracy. This work underscores the requirements and challenges involved in accurately modelling extreme events. The major bottleneck was to constrain the CME input parameters that dictate the accuracy of the data-driven simulations. Predicting the impacts of the complex heliospheric structures during this event required the modelling of the CME-CME interactions accurately. As a community, we need to invest more in observational infrastructure while improving the speed and accuracy of our MHD forecasting models.
[abstract 41 / 60] (score: 2) - Title: Fast Radio Bursts in the Era of the Vera C. Rubin Observatory's Legacy Survey of Space and TimeAuthors: C. W. James, B. Smith, K. Dage, A. L. Chies Santos, K. W. Bannister, M. Caleb, J. F. Crenshaw, A. T. Deller, K. G. Lee, L. Marnoch, K. M. Rajwade, S. D. Ryder, R. M. Shannon, B. Stappers, T. Zhang,Comments: 10 pages, 7 figures, 2 tablesSubjects: astro-ph.HE astro-ph.COCreated: 2026-02-27; Updated: 2026-03-03; Datestamp: 2026-03-03
Identifying the host galaxies of fast radio bursts (FRBs), and comparing their redshifts and dispersion measures, has unlocked a new probe of the cosmological distribution of ionised gas. However the necessary optical observations to identify FRB hosts, and measure their redshifts, are becoming increasingly onerous as the detection rate of precisely localised FRBs increases. Here we analyse the ability of the Legacy Survey of Space and Time (LSST), being conducted by the Vera C. Rubin Observatory, to identify FRB host galaxies, and the utility of LSST photometric redshifts for FRB cosmology. By combining a model of FRB host galaxy r-band magnitudes, $m_r$, with predictions for the FRB z-DM distribution, we create a method to predict the $m_r(z)$ distribution for the host galaxies of FRBs detected by radio surveys. We then predict these distributions for the coherent modes of the Australian Square Kilometre Array Pathfinder (ASKAP) and MeerKAT. We find that even a single visit with Rubin will be able to identify 65% of FRB host galaxies detected by ASKAP's coherent upgrade, `CRACO'; while the final 10 year co-added images will identify 81% of those from MeerKAT's tied array beams. We also simulate the impact of using photometric redshifts for a simplified analysis to determine $H_0$, finding that estimated photo-z errors result in a decreased precision of only 7% on $H_0$ for ASKAP's CRACO system. The impact of missing dim FRB hosts, which are likely at higher redshifts, is more significant, and might degrade sensitivity to $H_0$ by 47%, or 62% when combined with photo-z errors. All told, Rubin's LSST will be an incredibly powerful survey for facilitating FRB cosmology, although supplemental observations may be useful for particularly dim and distant host galaxies.
[abstract 42 / 60] (score: 2) - Title: Spatial instability analysis and mode transition of a viscoelastic JET in a co-flowing gas streamAuthors: Jiawei Li, Ming Wang, Kai Mu, Zhaodong Ding, Ting Si,Comments: It has been accepted for publication in Journal of Fluid MechanicsSubjects: physics.flu-dynCreated: 2026-02-28; Updated: 2026-03-03; Datestamp: 2026-03-03
Spatial linear instability analysis is employed to investigate the instability of a viscoelastic liquid JET in a co-flowing gas stream. The theoretical model incorporates a non-uniform axial base profile represented by a hyperbolic tangent, capturing the shear layer. The Oldroyd-B model discretized with Chebyshev polynomials is employed, and energy budget analysis is used to interpret underlying mechanisms.At low Weber numbers, the JET evolves axisymmetrically and the instability is governed by interfacial gas-pressure fluctuations; as the Weber number increases, the growing inertia drives a transition of the predominant mode from axisymmetric to helical. At weak elasticity, the instability is also primarily governed by gas-pressure fluctuations. As elasticity increases, the predominant mode transitions from axisymmetric to helical. This transition is accompanied by a migration of disturbance structures from the interface toward the JET interior and an enhanced coupling between velocity perturbation and the basic flow. These trends reveal a new predominant instability mechanism -- the elasticity-enhanced shear-driven instability -- which is distinct from capillary or Kelvin-Helmholtz instabilities in Newtonian JETs. A We-El phase diagram delineates the boundary between predominant modes, and experimental results obtained in a flow-focusing configuration validate the theoretical predictions.
[abstract 43 / 60] (score: 2) - Title: High-Energy Shock Breakout from Supernovae and Gamma-ray BurstsAuthors: Chris L. Fryer, Eric Burns, Joseph M. Colosimo, Michela Negro, Brendan O'Connor,Comments: 26 pages, 21 figuresSubjects: astro-ph.HECreated: 2026-02-28; Updated: 2026-03-03; Datestamp: 2026-03-03
Cosmic explosions play a critical role in a broad range of astrophysical fields. Although considerable progress has been made to understand the explosive engines and their progenitors, many of the details are not well understood. One of the most powerful electroMAGNETic probes of the explosive mechanism and the stellar progenitor is the first burst of photons emitted from this blastwave as it exits the stellar photosphere, known as shock breakout (SBO). Our understanding of SBO has evolved considerably in the past decade. Shock heating as the blastwave propagates through the star and circumstellar material can drastically alter this emission producing a much broader range of potential SBO signals than that predicted by standard analytical approaches. Here we present a semi-analytic approach to model this diverse SBO emission, focused on thermal Bremsstrahlung radiation, which more accurately captures the complexities in Nature over previous treatments. We calculate a range of signals for a range of SUPERNOVA and GAMMA-RAY BURST types. Our models demonstrate how we can use these signals to place constraints on the nature of the explosive engines and better understand the role SBO can play in prompt GAMMA-RAY BURSTs. We study the implications of these results to historic observations, Einstein Probe transients, and in the context of proposed missions. We find that stripped envelope events can be detected serendipitously with survey telescopes, but type Ia and II SBO detections require fast-pointing X-ray observations in response to early warning alerts from gravitational wave or neutrino detectors.
[abstract 44 / 60] (score: 2) - Title: Nonlinear MAGNETohydrodynamic modeling of ideal ballooning modes in high-$β$ Wendelstein 7-X plasmasAuthors: Yao Zhou, K. Aleynikova, Chang Liu, N. M. Ferraro,Comments: To appear in Phys. PlasmasSubjects: physics.plasm-phCreated: 2026-03-01; Updated: 2026-03-03; Datestamp: 2026-03-03
We present nonlinear MAGNETohydrodynamic (MHD) simulations of high-$β$ Wendelstein 7-X plasmas using the stellarator extension of the M3D-$C^1$ code, building on the recent work that shows benign saturation of ideal ballooning modes above the designed $β$ limit in the standard configuration [Y. Zhou et al, Phys. Rev. Lett. 133, 135102 (2024)]. First, we examine the results' sensitivity to the parallel thermal conductivity. It is found that while an increased parallel conductivity reduces the linear growth rate, the saturated pressure profile is barely affected. Second, we consider the dependence on the profile shape. It is shown that an equilibrium with a peaked pressure profile and lower $β$ is subject to more significant change than a broad profile with higher $β$ and a larger growth rate, suggesting that benign saturation, or nonlinear stability, is not guaranteed and not dictated by linear growth. Third, we study the influence of the MAGNETic configuration, with the equilibrium rotational transform varied by adjusting the planar coil current. With similar growth rates, similar magnitudes of profile change are found regardless of the presence of a low-order resonance, which implies that the saturation mechanism is not specific to a resonant or non-resonant mode. These results indicate that MHD stability should still be treated seriously in stellarator operation and design, for which nonlinear modeling using tools like M3D-$C^1$ can play an instrumental role.
[abstract 45 / 60] (score: 2) - Title: X-ray and Hα superflare on an RS CVn-type star, UX Arietis: Constraint on the flare location from radial velocity change during the flareAuthors: Sota Urabe, Yohko Tsuboi, Kosuke Namekata, Sakura Nawa, Hiroyuki Maehara, Noboru Nemoto, Yuta Notsu, Wataru Iwakiri,Comments: 12 pages, 12 figuresSubjects: astro-ph.SR astro-ph.HECreated: 2026-03-01; Updated: 2026-03-03; Datestamp: 2026-03-03
We report on a giant stellar flare from the RS CVn-type binary UX Arietis, detected with the Monitor of All-sky X-ray Image (MAXI) and followed by a 12-day optical spectroscopic campaign using the 3.8~m Seimei Telescope. The flare released $5 \times 10^{37}$~erg in X-rays (0.1--100~keV) and $(2$--$6) \times 10^{36}$~erg in the H$α$ line, placing it among the most energetic events of its kind. The H$α$ light curve showed sinusoidal modulation atop an exponential decay, consistent with reappearance of the flaring region due to binary rotation. At orbital phase 0, when the primary star is farthest from the observer, 40\% of the H$α$ flux was obscured, while at phase 0.5 the full emission was visible. This suggests the H$α$ emitting region is located at a relatively low latitude and is comparable in size to the stellar disk. Radial velocity modulation implies that the region lies at $\sim19\,R_{\odot}$ from the system's rotation axis, farther out than the stellar limb at $14.4\,R_{\odot}$. Photometric monitoring with the Chuo-university Astronomical Telescope revealed a large low-latitude starspot covering $\sim25\%$ of the surface. These findings are consistent with a scenario in which the flare occurred above the starspot, and the H$α$-emitting plasma was MAGNETically confined in a loop extending at least $5\,R_{\odot}$ above the stellar surface. From the MAXI data and assuming a radiatively cooling plasma, the electron density and volume are estimated to be $10^{10}$~cm$^{-3}$ and $1 \times 10^{35}$~cm$^3$, respectively. If cubic in shape, this corresponds to $7\,R_{\odot}$, consistent with the H$α$ region height. These results provide direct constraints on the geometry of the plasma and its spatial relationship with the starspot in one of the most energetic stellar flares ever observed.
[abstract 46 / 60] (score: 2) - Title: Structure-preserving Randomized Neural Networks for Incompressible Magnetohydrodynamics EquationsAuthors: Yunlong Li, Fei Wang, Lingxiao Li,Comments:Subjects: physics.flu-dyn cs.LG cs.NA math.NACreated: 2026-03-01; Updated: 2026-03-03; Datestamp: 2026-03-03
The incompressible MAGNETohydrodynamic (MHD) equations are fundamental in many scientific and engineering applications. However, their strong nonlinearity and dual divergence-free constraints make them highly challenging for conventional numerical solvers. To overcome these difficulties, we propose a Structure-Preserving Randomized Neural Network (SP-RaNN) that automatically and exactly satisfies the divergence-free conditions. Unlike deep neural network (DNN) approaches that rely on expensive nonlinear and nonconvex optimization, SP-RaNN reformulates the training process into a linear least-squares system, thereby eliminating nonconvex optimization. The method linearizes the governing equations through Picard or Newton iterations, discretizes them at collocation points within the domain and on the boundaries using finite-difference schemes, and solves the resulting linear system via a linear least-squares procedure. By design, SP-RaNN preserves the intrinsic mathematical structure of the equations within a unified space-time framework, ensuring both stability and accuracy. Numerical experiments on the Navier-Stokes, Maxwell, and MHD equations demonstrate that SP-RaNN achieves higher accuracy, faster convergence, and exact enforcement of divergence-free constraints compared with both traditional numerical methods and DNN-based approaches. This structure-preserving framework provides an efficient and reliable tool for solving complex PDE systems while rigorously maintaining their underlying physical laws.
[abstract 47 / 60] (score: 2) - Title: Feasibility of Negative Triangularity Equilibria in the SPARC TokamakAuthors: Narin Yüksek, Theodore Golfinopoulos,Comments:Subjects: physics.plasm-phCreated: 2026-03-01; Updated: 2026-03-03; Datestamp: 2026-03-03
We investigate the feasibility of negative triangularity (NT) plasma configurations in the SPARC tokamak, a compact, high-field device (up to 12.2 T) designed for positive triangularity (PT) operation. Using the FreeGS free-boundary equilibrium solver, we systematically explore the parameter space through 600+ equilibrium calculations spanning triangularity (-0.7-0.7) and elongation (1.0-2.1) while respecting SPARC's coil current limits and first-wall constraints and selecting a reduced-field 8 T operating point. We find that moderate NT double-null plasmas (delta = -0.35, kappa = 1.68) are achievable at 8 T with plasma currents of 2.1 MA. However, NT operation requires 43% plasma volume reduction (from 20.0 to 11.4 m$^3$) compared to the baseline PT design due to vessel walls optimized for PT conformity, and connection lengths are reduced by 40% due to geometric mismatch with the PT-optimized divertor. Central solenoid current requirements decrease by 54% in NT configurations, though specific shaping coils (PF3) require a factor of 5.5 higher currents. All equilibria satisfy fundamental MHD stability criteria with comfortable margins. Thus, while performance is degraded relative to baseline design, these results demonstrate SPARC's potential as a high-field experimental bridge between contemporary NT experiments and proposed NT reactor concepts, capable of testing whether NT's operational advantages (ELM-free operation, favorable impurity transport) persist under reactor-relevant conditions provided by SPARC.
[abstract 48 / 60] (score: 2) - Title: Turbulent Heating between 0.2 and 1 au: A Numerical StudyAuthors: Victor Montagud-Camps, Roland Grappin, Andrea Verdini,Comments:Subjects: physics.space-ph astro-ph.SR physics.plasm-phCreated: 2026-03-01; Updated: 2026-03-03; Datestamp: 2026-03-03
The heating of the solar wind is a key to understand its dynamics and acceleration process. The observed radial decrease of proton temperature in the solar wind is slow compared to the adiabatic prediction and it is thought to be caused by turbulent dissipation. To generate the observed 1/R decrease, the dissipation rate has to reach a specific level which varies in turn with temperature, wind speed, and heliocentric distance. We want to prove that MHD turbulent simulations can lead to the 1/R profile. We consider here the slow solar wind, characterized by a quasi-2D spectral anisotropy. We use the EBM (expanding box model) equations, which incorporate into 3D MHD equations the expansion due to the mean radial wind, allowing to follow the plasma evolution between 0.2 and 1 AU. We vary the initial parameters which are: Mach number, expansion parameter, plasma beta, and properties of the energy spectrum as the spectral range and slope. Assuming turbulence starts at 0.2 AU with a Mach number equal to unity, with a 3D spectrum mainly perpendicular to the mean field, we find radial temperature profiles close to 1/R in average. This is done at the price of limiting the initial spectral extent, corresponding to the small number of modes in the inertial range available, due to the modest Reynolds number reachable with high Mach numbers.
[abstract 49 / 60] (score: 2) - Title: Destruction of wall-bounded vortices using synthetic JET actuatorsAuthors: Frank A. Tricouros, Cameron Hoober, John C. Vaccaro, Tyler Van Buren,Comments: 22 pages, 13 figuresSubjects: physics.flu-dynCreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
We experimentally explore the effectiveness of a rectangular orifice synthetic JET actuator for wall-bounded vortex destruction. Vortex flows near a boundary often present unforeseen or undesired forcing on a neighboring surface due to the low pressure concentration within the vortex. Synthetic JETs -- primarily used for separation control, enhanced mixing, and induced turbulence -- offer a unique strategy for vortex mitigation due to the unsteady flow at the region of the orifice disrupting the coherence of the oncoming flow. In a flat plate boundary layer, we test multiple JET orifice configurations, vortex lateral position relative to the orifice, and vortex sizes. We find that each JET was capable of reducing the incoming vortex rotational coherence up to 70%. This disruption led to pressure recovery within the vortex wake region. The velocity wake of the vortex was more persistent (most JETs produced a wake of their own) though some cases were capable of accelerating the fluid while maintaining moderate rotation reduction and pressure recovery. These results indicate that synthetic JETs have the potential to mitigate a near wall vortex structure, particularly in scenarios where the position and size of the vortex are known.
[abstract 50 / 60] (score: 2) - Title: Identifying Compton-thick AGNs in the COSMOS II. Among mid-infrared selected AGNsAuthors: Xiaotong Guo, Qiusheng Gu, Guanwen Fang, Shiying Lu, Fen Lyu, Yongyun Chen, Nan Ding, Mengfei Zhang, Xiaoling Yu, Hongtao Wang,Comments: 11 pages, 7 figures, 2 tables. Submitted in Astronomy & AstrophysicsSubjects: astro-ph.GACreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
Compton-thick ACTIVE GALACTIC NUCLEi (CT-AGNs), defined by column density $\mathrm{N_H} \geqslant 1.5 \times 10^{24} \ \mathrm{cm}^{-2}$, are so heavily absorbed that their X-ray emission is often feeble, even undetectable by X-ray instruments. Nevertheless, their radiation is expected to be a substantial contributor to the cosmic X-ray background (CXB), predicting that CT-AGNs should comprise at least $\sim$30\% of the total AGN population. In the Cosmological Evolution Survey (COSMOS), the identified CT-AGN fraction falls far below theoretical expectations, indicating that a substantial population of CT-AGNs is hidden due to their low photon counts or their flux below the current flux limits of X-ray instruments. This work focuses on identifying CT-AGNs hidden in mid-infrared (MIR)-selected AGNs. First, we selected a sample of 1,104 MIR-selected AGNs that were covered but individually undetected by X-ray. Next, we reduced the X-ray data in the COSMOS and analyzed multiwavelength data in our sample to derive the key physical parameters required for CT-AGN identification. Using MIR diagnostics, we first find out 7 to 23 CT-AGN candidates. Their subsequent X-ray stacking analysis reveals a clear detection at $>3σ$ significance in the soft band and only $>1σ$ significance in the hard band. We fit the stacked soft- and hard-band fluxes with a physical model and confirm that these sources are absorbed by Compton-thick material. However, CT-AGNs constitute only 2.1\% (23/1104) of our sample, significantly below the fraction predicted by CXB synthesis models, indicating that a considerable population of CT-AGNs remains missed by our selection. A comparison of host-galaxy properties between CT-AGNs and non-CT-AGNs reveals no significant differences.
[abstract 51 / 60] (score: 2) - Title: Local Analogs of Little Red Dots: Optical Variability and Evidence for an AGN 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: 12 pages, 9 figures. Comments are welcomeSubjects: astro-ph.GACreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
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 52 / 60] (score: 2) - Title: Anisotropic matter and nonlinear electroMAGNETics BLACK HOLEsAuthors: Yun Soo Myung, Wonwoo Lee,Comments: 12 pages, 3 figuresSubjects: gr-qcCreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
It is shown that anisotropic matter BLACK HOLEs with two parameters $w$ and $K$ are identified as nonlinear electrodynamics (NED) BLACK HOLEs with power-index $s$ and charge term $ξ(s,q)$ by introducing a NED term. These NED BLACK HOLEs include constant scalar hair ($s=1$), charged quantum Oppenheimer-Snyder ($s=3/2$), and Einstein-Euler-Heisenberg ($s=2$) BLACK HOLEs derived from their known actions. Rotating NED BLACK HOLEs can be obtained from rotating anisotropic matter BLACK HOLEs when replacing $w$ and $K$ by $2s-1$ and $ξ(s,q)$. The extremal rotating NED BLACK HOLEs being the boundary between rotating charged NED BLACK HOLE and naked singularity are derived as functions of the rotation parameter $a(q)$.
[abstract 53 / 60] (score: 2) - Title: Superfluid Vortex Lines-Magnetic Flux Tubes Interaction and Braking Indices of PulsarsAuthors: Erbil Gügercinoğlu,Comments: Submitted to Universe Journal for the Special Issue "10th Anniversary of Universe: Studying the Strongly Interacting Matter in Nuclear Reactions from Intermediate to Ultra-Relativistic Energies"Subjects: astro-ph.HECreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
Braking of pulsars, or the law of their spin deceleration, is a manifestation of the combination of various processes occurring in the MAGNETospheres of neutron stars and their internal structural dynamics. The interaction of superfluid neutron vortex lines with superconducting MAGNETic flux tubes in the neutron star core plays a significant role in rotational evolution and MAGNETic field evolution through spin glitches and MAGNETic flux expulsion. In this study, the effect of this interaction on the temporal variation of the braking index of pulsars is investigated. The variation of the deviation from the $n=3$ value predicted by the generally accepted MAGNETic dipole formula with respect to physical parameters such as the MAGNETic field and the age of the neutron star has been elaborated, and applications have been made to pulsars with reliably measured braking indices.
[abstract 54 / 60] (score: 2) - Title: A Unified Explanation for JWST Little Red Dots and High-Redshift Low-Mass Disk-like Galaxies: Prolate Galaxies Viewed End-on vs Side-onAuthors: Yingjie Peng,Comments: Submitted. Comments are welcome. This is the twelfth paper in the "From Haloes to Galaxies" seriesSubjects: astro-ph.GA astro-ph.HECreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
Recent JWST surveys have revealed two puzzling high-redshift phenomena: (1) an unexpectedly large abundance of flattened, disk-like galaxies at z > 3, and (2) a rare population of compact, extremely red sources at z ~ 4-9 ("Little Red Dots," LRDs) that often show V-shaped SEDs and very broad Balmer lines. These findings lack a consensus interpretation and have motivated models ranging from dusty starbursts to obscured AGN and more exotic scenarios. We propose that both phenomena are linked by a simple geometric consequence of a third clue: mounting evidence from structural modeling and axis-ratio statistics indicates that many low-mass galaxies at z > 3 are intrinsically prolate (cigar-like), not oblate rotation-supported disks. In this picture, a substantial fraction of the flattened, disk-like morphologies reported at z > 3 arise from side-on and intermediate-angle projections of prolate systems, while the rare near end-on views appear extremely compact and high-surface-brightness, and are preferentially reddened by the maximal line-of-sight column, naturally matching key elements of LRD selection. The expected fraction of near end-on systems, $P_{\text{end}} = 1 - \cos(θ_{\text{max}})$, is ~1-3% for $θ_{\text{max}}$ ~ 10°-15°, consistent with LRD demographics in wide JWST fields. This orientation-based framework does not exclude AGN or starburst activity; rather, it explains LRD rarity as an orientation effect and provides a natural route to the large columns of gas/dust and scattering depths inferred in recent dense-gas and electron-scattering interpretations of LRD spectra, without fine-tuned new physics. The model makes falsifiable predictions to validate or rule out this geometric interpretation.
[abstract 55 / 60] (score: 2) - Title: Observational insights into Sr I 4607 Å scattering POLARIZATION with DKIST/ViSPAuthors: Franziska Zeuner, Ernest Alsina Ballester, Luca Belluzzi, Roberto Casini, David M. Harrington, Tanausú del Pino Alemán, Javier Trujillo Bueno,Comments: Accepted for publication in A&ASubjects: astro-ph.SRCreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
Scattering POLARIZATION signals in the Sr I 4607 Å spectral line are among the strongest originating from the solar photosphere, offering a powerful diagnostic of tangled MAGNETic fields in the 3--300 G range via the Hanle effect. However, measuring them with sub-arcsec resolution remains a significant challenge. We analyze spatially resolved quiet-Sun observations of these signals performed with the Visible Spectropolarimeter (ViSP) at the Daniel K. Inouye Solar Telescope (DKIST) and identify its current observational limits. We present high-resolution, high-precision spectropolarimetric observations in a spectral window including the Sr I 4607 Å line at various limb distances. We apply consistent instrumental corrections across all spectral lines, enabling the adjacent lines to serve as reliable references. At a limb distance of $μ= 0.74$, the signal-to-noise ratio is low but sufficient in the total linear POLARIZATION map to directly reveal sub-arcsec structures in the Sr I line for the first time, which can be attributed to scattering POLARIZATION. Disk-center measurements are still dominated by noise related to the current limitations of the observational setup. By combining high spatio-temporal and spectral resolution with exceptional polarimetric precision, DKIST enables measurements of solar photospheric scattering POLARIZATION at fine scales. However, current signal-to-noise limitations still hinder direct detection of disk-center scattering POLARIZATION and must be addressed before further progress can be made.
[abstract 56 / 60] (score: 2) - Title: B-fields And dust in interstelLar fiLAments using Dust POLarization (BALLAD-POL): VI. Grain alignment mechanisms in the massive quiescent filament G16.96+0.27 using dust POLARIZATION observations from JCMT/POL-2Authors: Saikhom Pravash, Thiem Hoang, Archana Soam, Qi-Lao Gu, Tie Liu, Pham Ngoc Diep, Le Ngoc Tram, Nguyen Bich Ngoc,Comments: 29 pages, 18 Figures, 4 Tables. Accepted for publication in ApJSSubjects: astro-ph.GACreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
Dust POLARIZATION induced by aligned non-spherical grains acts as an important tool to trace the MAGNETic field (B-field) morphologies and strengths in molecular clouds and constrain grain properties and their alignment mechanisms. The widely accepted grain alignment theory is the alignment induced by RAdiative Torques (RATs). In this work, we investigate grain alignment mechanisms in a massive, quiescent and filamentary Infrared Dark Cloud G16.96+0.27 using thermal dust POLARIZATION observation with JCMT/POL-2 at 850 $μ$m. We observe the so-called phenomenon of POLARIZATION hole attributed to the decrease in POLARIZATION fraction in denser regions of higher total intensity and gas density. Our study finds that B-field tangling effect is minimal to cause the POLARIZATION hole, and the dominant factor is the reduction in grain alignment efficiency in denser regions, consistent with RAT mechanism. To test RAT theory, we calculate various quantities describing grain alignment, including minimum size of aligned grains, MAGNETic and MAGNETic relaxation parameter, and show that RAT mechanism can explain observational data. Our study also reveals evidence for MAGNETically-enhanced RAT (M-RAT) mechanism required to explain the observed high POLARIZATION fractions of above 10 % in the outer regions of the filament. Finally, we perform detailed modeling of thermal dust POLARIZATION using $\mathrm{DustPOL\_py}$ based on M-RAT theory and find that the modeling could successfully reproduce the observational data when maximum grain size is around 0.45 $μ$m accompanied by an increase in grain axial ratio, along with the consideration of variations in the MAGNETic field's inclination angle with the line of sight.
[abstract 57 / 60] (score: 2) - Title: Radio Study of Vela X CocoonAuthors: Yihan Liu, Yu Zhang, C. -Y. Ng, Zijian Qiu, Sujie Lin, Lili Yang,Comments: 10 pages, 8 figuresSubjects: astro-ph.HECreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
The evolution of pulsar Wind Nebulae (PWNe) influences how high energy particles in the vicinity are generated and transport. The Vela PWN (only $\sim300$\,pc away), provides a rather rare case between young and well-evolved systems. We therefore performed new 6 and 16\,cm high-resolution observations of the Vela X Cocoon region with the Australia Telescope Compact Array (ATCA). The observations reveal a complex region with a $\sim0.5^\circ$ major curved filament extending to far south from the pulsar, as well as other intersecting filaments and wisps. Our spectral analysis hints its connection with the PWN. Our results also found strongly linearly polarized emission, ordered and tangential $B$-field to the filaments. We find the rotation measure (RM) and POLARIZATION fraction (PF) along the filament are anti-correlated with the total intensity. We develop a simple 3D model of a spiral filament to explain these, while the PF distribution requires external interpretations such as interaction with the reverse shock. Comparison with archival data suggests that large scale features like the major filament are generally stable and large motions near the X-ray filament, all these confirm the distinction between radio and X-ray features.
[abstract 58 / 60] (score: 2) - Title: A Template-Based Search for Large-Scale-Structure--Correlated Anisotropy in the Nanohertz Gravitational-Wave Background Using the Public NANOGrav 15-Year Data SetAuthors: Yun Fang,Comments: 15 pages,6 figuresSubjects: astro-ph.CO astro-ph.HECreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
Recent PTA analyses reporting evidence for a nanohertz common-spectrum process motivate targeted tests of whether any anisotropic component of the stochastic gravitational-wave background (SGWB) is correlated with the nearby large-scale structure (LSS), as anticipated for an astrophysical background dominated by supermassive BLACK HOLE binaries. We present the first Bayesian PTA likelihood analysis that embeds an externally observed, full-sky galaxy-survey LSS template directly as an overlap-reduction-function (ORF) component. Using the 2MASS Photometric Redshift (2MPZ) galaxy catalog, we construct low-multipole LSS--correlated ORF templates in two redshift slices ($0
[abstract 59 / 60] (score: 2) - Title: Low-$T/|W|$ instabilities in differentially rotating neutron stars resembling merger remnantsAuthors: Georgios Lioutas, Panagiotis Iosif, Andreas Bauswein, Nikolaos Stergioulas,Comments: 39 pages, 35 figures, submitted to PRDSubjects: astro-ph.HE gr-qcCreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
We construct constant rest-mass sequences of equilibrium models of differentially rotating neutron stars which resemble binary neutron star post-merger remnants. For a more realistic description of the post-merger remnant, we impose that each model carries approximately $95\%$ of the angular momentum that a binary system with the same total rest-mass has at the moment of merging, based on an empirical relation informed from neutron star merger simulations. We account for equation of state effects by employing two distinct microphysical descriptions for high density matter. We dynamically evolve the equilibrium models with a three-dimensional general RELATIVISTIC hydrodynamics code that employs the conformal flatness approximation. We investigate the connection between the occurrence of the instability and the existence of corotation radii within the stellar configurations and determine the instability window for both equation of state sequences. The occurrence of low-$T/|W|$ instabilities leads to pronounced gravitational wave emission in the range $0.13 \lessapproxβ\lessapprox 0.2$, while models outside this range exhibit less pronounced features in the gravitational wave spectrum. The prominence of gravitational wave emission is primarily determined by $β$, while the equation of state seems to have a more minor effect. We present correlations between the strength of the gravitational wave emission associated with the instability and properties of the equilibrium models. Stellar configurations modelled by different equations of state display differences in the timescales over which the various dynamical features develop, as well as whether they exhibit a pronounced $m=1$ deformation. Potential relations between the instability growth timescales and properties of the stellar models are studied.
[abstract 60 / 60] (score: 2) - Title: Interpreting map-based $E$/$B$ spectral properties of CMB foregroundsAuthors: Gilles Weymann-Despres, Léo Vacher, Michael E. Jones, Angela C. Taylor, Carlo Baccigalupi, A. J. Banday, Richard D. P. Grumitt, Nicoletta Krachmalnicoff,Comments: 22 pages, 16 figures. Submitted to MNRASSubjects: astro-ph.CO astro-ph.GACreated: 2026-03-02; Updated: 2026-03-03; Datestamp: 2026-03-03
Map-space $E$/$B$ decompositions of linear POLARIZATION are attractive for foreground and CMB analyses because they isolate the $B$-family patterns that contaminate primordial tensor searches from $E$-family patterns that trace coherent Galactic structures. However, the $E$/$B$ transform is non-fully-local and induces apparent spectral complexity in projected fields even when the underlying sky is spectrally simple in $\underline{P}=Q+iU$. We quantify this effect for SYNCHROTRON emission. We introduce a complex-parameter description of the frequency dependence of $\underline{P}$, its spin-preserving projections $\underline{P}_E$ and $\underline{P}_B$, and the scalar $\underline{S}=E+iB$, using complex log--Taylor and moment expansions (with simple transformation rules under $E$/$B$ projection) and linking their coefficients to spectral-index variations, line-of-sight mixing, SYNCHROTRON ageing, and Faraday effects. Using a toy model and a PySM template, we find that scalar combinations, especially $|E|$ and $|B|$, acquire the largest induced complexity, while $\underline{S}$ is less affected but lacks a directly interpretable amplitude and angle. By contrast, $\underline{P}_E$ and $\underline{P}_B$ retain a clear geometric meaning and exhibit only moderate spectral distortions, while satisfying the closure relation $\underline{P}=\underline{P}_E+\underline{P}_B$ (which extends to all spectral orders in the moment formalism). Finally, with three frequency channels, we compare low-order spectral truncations and propose diagnostics to test whether the data favour a single power law in $P$ or independent power laws in $(P_E,P_B)$. This work is intended to be of practical relevance for both Galactic science and CMB $B$-mode analyses and lays the conceptual foundation for a series of papers applying the framework to observational data.
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