Current date: 2026-05-29
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Number of records retrieved: 831
Keyword score statistics
score 8 -- 1 abstracts
score 5 -- 4 abstracts
score 4 -- 6 abstracts
score 3 -- 7 abstracts
score 2 -- 17 abstracts
in total -- 35 abstracts
Articles that appeared on 2026-05-29
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[abstract 1 / 35] Wow! (score: 8)
- Title: A multi-technique search for year-scale $γ$-ray quasi-periodic modulation in the high-redshift FSRQ PKS~2052$-$47Authors: Sikandar Akbar,Comments: Published in JHEAPSubjects: astro-ph.HECreated: 2026-05-28; Updated: 2026-05-29; Datestamp: 2026-05-29
We investigate year-scale quasi-periodic oscillations in the $γ$-ray emission of the high-redshift flat-spectrum radio QUASAR PKS~2052$-$47 using monthly binned \emph{FERMI}-LAT data spanning MJD~54727.99--58507.99. To assess the statistical significance of periodic features embedded in red-noise-dominated variability, we apply several complementary timing techniques, including the Lomb--Scargle periodogram, weighted wavelet $Z$-transform, date-compensated discrete Fourier transform, REDFIT assuming an AR(1) process, and damped random walk modelling. The analyses reveal a dominant quasi-periodic modulation on a timescale of $\sim600$--630~d, together with a secondary longer-timescale feature near $\sim1050$--1110~d. Monte Carlo simulations show that the shorter-period signal exceeds the highest local confidence levels, while the longer modulation reaches $\gtrsim99$ per cent local significance in several tests; independent DRW-based simulations place both peaks above the $4σ$ envelope in the Lomb--Scargle analysis. Spectral-window diagnostics indicate that the detected periodicities are not artefacts of uneven sampling, and a sliding-window analysis shows that the QPO power is episodic across the $\sim11$~yr baseline. We discuss possible physical interpretations in terms of geometric Doppler modulation associated with JET precession or helical motion, accretion-driven instabilities, and SMBBH-induced dynamics.
[abstract 2 / 35] Yes (score: 5) - Title: FERMI-LAT View on Three Ultra-high-energy 1LHAASO Sources in the $52^{\circ}[abstract 3 / 35] Yes (score: 5)Authors: Linjie Liu, Xian Hou, Pierrick Martin, Chuyuan Yang,Comments: 17 pages, 3 figures, 4 tables. Published in ApJSubjects: astro-ph.HECreated: 2026-05-28; Updated: 2026-05-29; Datestamp: 2026-05-29
Using more than 17 yr of FERMI-LAT data, we performed a detailed investigation of the complex $52^{\circ}
arXiv:2605.29895 [pdf, ps, other]Little red dots (LRDs) are compact high-redshift objects, newly discovered by the James Webb Space Telescope. Although LRDs exhibit broad Balmer emission lines suggestive of the presence of ACTIVE GALACTIC NUCLEi (AGN), their spectral features differ significantly from those of ordinary AGN. Recent studies suggest that their characteristics can be explained if accreting supermassive BLACK HOLEs (SMBHs) are embedded within dense gaseous envelopes and surrounded by compact stellar clusters. In this scenario, stars in the cluster can scatter onto plunging orbits that intersect the envelope and collide with its surface. Here we investigate the observational properties of such star-envelope collisions as luminous transient events. We find that collisions involving red supergiants with radii of $\sim 10^{3}~R_\odot$, together with gaseous envelopes whose masses are comparable to those of the central SMBHs, are the most promising targets due to their high luminosities and long durations. For compact clusters with sizes of $\lesssim 10~{\rm pc}$, such massive stars can participate in star-envelope collisions within their lifetimes at event rates reaching $\sim 0.3~{\rm yr}^{-1}$ per LRD. We show that these transients are detectable with future wide-field surveys such as the Nancy Grace Roman Space Telescope if they occur at relatively low redshifts ($z \lesssim 1$). Detection of such transients would provide strong evidence for the envelope+stellar-cluster scenario of LRDs and offer a unique probe of the envelope mass, which is otherwise difficult to constrain from LRD spectra alone.
arXiv:2605.29909 [pdf, ps, other]Superluminous SUPERNOVAe (SLSNe) are a rare class of transients with peak luminosities 10-100 times greater than those of standard core-collapse SUPERNOVAe (SNe). The mechanisms powering their extreme brightness remain debated, with circumstellar medium (CSM) interaction, or energy injection from a central engine like a MAGNETar wind nebula being the most plausible scenarios. To further constrain the underlying mechanism, we carried out a systematic search for GeV gamma-ray emission using the FERMI-LAT telescope from a sample of nearby hydrogen-poor (Type I) and hydrogen-rich (Type II) SLSNe over the past 16 years. Among the sample, only SN 2017egm shows significant gamma-ray emission, with likelihood test statistic (TS) values of 26-33 (i.e., >5$σ$) depending on the adopted time window. The signal arises between 50 and 160 days after explosion and is well described by a power-law spectrum with index $Γ=2.17 \pm 0.23$. The emission is consistent both in terms of its light curve and its spectrum, with predictions from MAGNETar models requiring either low nebular MAGNETization or faster spin-down than dipole losses. The CSM shell interaction scenario can reproduce the observed flux level but not the observed timing of the gamma-ray signal. In addition, the observed ratio, $L_γ/L_{opt} \sim 1$, is inconsistent with theoretical expectations and not in line with ratio measurements in other interacting CSM-dominated objects (e.g., novae or SNe) where this ratio is less than $10^{-2}$. Our study strongly suggests that a central engine like a MAGNETar plays a key role in this SLSN and could explain the bulk of the optical and gamma-ray light curves properties. Finally, simulations of 50 hours of CTAO observations indicate that a SN 2017egm-like event would be detectable up to 140 Mpc in the MAGNETar model but not in the CSM model due to strong gamma-gamma absorption.
arXiv:2605.30025 [pdf, ps, other]The most promising candidate for short-duration GAMMA-RAY BURSTs (GRBs) is the merger of two neutron stars (NSs), which produces kilonovae (KNe) in the aftermath. This merging can result in a fast-spinning, highly MAGNETic NS, known as a millisecond MAGNETar, whose accretion processes can explain different phases in GRBs. The identification of a KN associated with the atypical long-duration GRB 211211A contradicted the classification schemes of the GRB progenitors. This study presents a comprehensive analysis of gamma- and X-ray observations, focusing on modeling X-ray data from a long-lived MAGNETar with two distinct fallback accretion rates ($\dot{M}\propto t^0$ and $\propto t^{\frac12}$) during the initial phase. The internal energy dissipation of the MAGNETar spin-down power, through the MAGNETization parameter, accounts for the long duration of the prompt gamma-ray episode observed in GRB 211211A. Furthermore, we provide a satisfactory explanation for the precursor and extended emissions following the prompt episode within the MAGNETar model with two fallback accretion rates. Although these accretion rates explain different characteristics, the model that incorporates a variable accretion rate offers a more accurate description. The current scenario for the GRB 211211A observations aligns with a compact binary merger that produces a long-lived MAGNETar instead of an immediate BLACK HOLE.
arXiv:2512.21885 [pdf, ps, other]We carried a detailed time and flux resolved X-ray spectral analysis of the high-SYNCHROTRON-peaked BLAZAR Mrk\,421 using simultaneous LAXPC20 and SXT observations. The 100\,s binned LAXPC20 light curve obtained during 3--8 January 2017 reveals pronounced flux variability. The source exhibits a fractional variability amplitude of $F_{\mathrm{rms}} = 0.210 \pm 0.005$ in the SXT band and $F_{\mathrm{rms}} = 0.316 \pm 0.006$ in the LAXPC20 band. During this interval, the source reached a peak LAXPC20 count rate of 122.94\,counts\,s$^{-1}$, while the peak count rate in the SXT light curve is 26.79\,counts\,s$^{-1}$. This enabled us to carry out flux-resolved spectroscopy by dividing the 100\,s binned LAXPC20 light curve into ten flux states (S1--S10), each spanning a width of 8\,counts\,s$^{-1}$. For each flux state, simultaneous SXT and LAXPC20 spectra were extracted and fitted jointly. We find that the spectra in these states are well described by a SYNCHROTRON-convolved broken power-law, which provides a better fit than a log-parabola model. The low-energy particle index (index before the break) is found to cluster around two discrete values across flux states indicating two spectra states in the source. The break energy consistently moves to high energy with increase in flux level in these states. Time-resolved spectroscopy (10-ks segments) confirms that the flux histogram is best modelled as a double lognormal distribution and the index histogram is double normal. Inclusion of two additional long observations spanning 2017-2019 shows the same double-state behaviour on longer timescales. Together, the results indicate that Mrk\,421 routinely occupies two dominant spectral; in a leptonic SYNCHROTRON framework this can be explained by Gaussian-like fluctuations in acceleration conditions producing lognormal flux states.
arXiv:2603.08119 [pdf, ps, other]Recent obeservations have revealed significant soft X-ray POLARIZATIONs from several quiescent MAGNETars, including the intriguing $90^°$ POLARIZATION angle (PA) swing as a function of photon energy for some sources. We present a general semi-analytical framework for calculating energy-dependent soft X-ray POLARIZATION signatures from MAGNETars, consistently incorporating both QED vacuum resonance in the atmosphere and resonant Compton scattering (RCS) in the MAGNETosphere. Starting from the polarized radiative transfer equation for RCS and treating vacuum-resonance-induced mode conversion as an input, we employ a first-order approximation in RCS optical depth to evaluate the effect of different MAGNETospheric plasma density (which depends on MAGNETic twist), drift velocity and temperature, and viewing geometry on the observed radiation. Our analysis reveals that MAGNETic twist and plasma drift velocity are the critical parameters controlling the impact of RCS on both the absolute POLARIZATION degree and its variation across the soft X-ray spectrum. We find that sufficiently strong RCS can wash out the PA swing caused by vacuum resonance. Furthermore, in addition to the QED vacuum resonance effect, significant RELATIVISTIC signatures arising from plasma drift velocity ($β_0 \gtrsim 0.5$) may introduce an extra $90^\circ$ PA swing in the spectrum. Our calculation framework, based on single-scattering approximation, bypasses the need for complex, multi-dimensional Monte Carlo simulations, providing an analytical pathway for modeling full-surface emission and rotational-phase-resolved radiation from MAGNETic neutron stars, in support of current and future X-ray POLARIZATION missions.
arXiv:2604.15673 [pdf, ps, other]Sgr A* exhibits a persistent negative circular POLARIZATION (CP) at 230\,GHz, offering a powerful probe of the MAGNETic field geometry in its accretion flow. Using a stationary semi-analytic radiatively inefficient accretion flow (RIAF) model in Kerr spacetime with polarized radiative transfer, we systematically analyze CP images for six poloidal MAGNETic field configurations across varying BLACK HOLE spins, inclinations, and field polarities. We find that CP production is dominated by Faraday conversion in radial, parabolic, quadrupole, and combined geometries, but by intrinsic emission in dipole and vertical fields. The radial and parabolic configurations produce the polarity-invariant net CP, while dipole and vertical fields yield the polarity-sensitive one. As the accretion disk is prograde with respect to the BLACK HOLE spin, the CP production across all six field geometries is found to be lower at high spin case, while the situation is more complicated in the retrograde case. Moreover, the net CP observed from edge-on views $V_{\rm net} \approx 0$ except for the quadrupole geometry. Comparing with ALMA data, the reversed-field model is excluded at high inclinations and then the MAGNETic field geometry of Sgr A* is constrained.
arXiv:2605.28928 [pdf, ps, other]A growing fraction of tidal disruption events (TDEs) exhibit radio emission that rises only years after the optical or infrared flare, indicating delayed outflow activity. In some events the outflow is inferred to be slow ($\sim 0.02 \, c$) and massive ($\gtrsim 0.01-0.1 M_{\odot}$), challenging models such as delayed JETs and disk state transitions. We propose a new mechanism for such delayed outflows: repeated collisions between a TDE accretion disk and a pre-existing stellar extreme-mass-ratio-inspiral (EMRI) orbiting the BLACK HOLE. In this scenario, the delay reflects the viscous time required for the initially compact TDE disk to expand and intercept the EMRI orbit, rather than delayed JET launching or off-axis viewing effects. Once star-disk collisions commence, repeated impacts eject outflows with velocities comparable to the orbital speed, $v_{\rm w} \sim 0.02-0.1c$. We develop a time-dependent model for the coupled evolution of the spreading disk and EMRI-induced mass-loss, identifying regimes where the outflow is dominated by disk material or ablated stellar debris. Depending on disk viscosity, orbital period, and collision efficiency, masses $\sim (10^{-3}-1) \, \rm M_\odot$ can be launched with energies up to $10^{51} \rm \, erg$, years after the TDE. These outflows produce radio emission through interaction with circumnuclear material or earlier TDE ejecta, consistent with observed late-time radio re-brightening. This model predicts a connection between delayed radio flares and EMRI-hosting systems, potentially including those exhibiting quasi-periodic eruptions (QPEs) powered by star-disk collisions, though the conditions for bright radio flares may not always match those necessary for detectable QPEs.
arXiv:2605.29022 [pdf, ps, other]GRB 221009A, the Brightest Of All Time (BOAT), presents a challenge for afterglow modelling due to its low Galactic latitude and consequent high line-of-sight extinction. This has led to a wide range of conflicting values for the optical spectral index and dust extinction in the literature. We present a re-analysis of the afterglow spectra, using VLT X-Shooter data at 0.5, 4, and 10.5 days, and JWST NIRSpec$/$MIRI data at 13.3 days post-burst. We fit the data with single and smoothly broken power-law models and perform a joint fit with a double smoothly broken power-law (DSBPL) across all epochs. Our analysis reveals a strong degeneracy between the assumed extinction and the inferred intrinsic spectral index, particularly in the optical, explaining the diversity of previous results. The joint DSBPL fit yields a total line-of-sight extinction of $A_{V} = 4.40 \pm 0.01$ and a blue continuum, with an intrinsic spectral index of $β= 0.447 \pm 0.001$. Although marginally preferred by the spectral fits, a wind medium can be rejected by the temporal evolution of the afterglow light curve. The fit spectral index and temporal decline are only consistent with a uniform density medium if an early JET break at $\sim 0.5-1.0$ days is invoked. Our results imply a hard electron distribution index of $p = 1.89 < 2$, challenging standard particle acceleration models and suggesting a narrow, energetic JET core dominates the early optical-to-X-ray emission.
arXiv:2605.29244 [pdf, ps, other]Magnetic RECONNECTion is a ubiquitous plasma phenomenon that plays a critical role in particle heating and energization. During RECONNECTion, the topology of MAGNETic field rearranges, depositing energy into the surrounding plasma through bulk flow, thermal heating, or non-thermal particle acceleration. While the pathways of this transformation from MAGNETic energy into kinetic have been studied extensively in recent years through theoretical or case-by-case observations, comprehensive statistical studies remain limited. In this paper, we present a statistical investigation using data from the Magnetospheric Multiscale (MMS) mission, and detail the particle energization mechanisms in MAGNETic structures found near RECONNECTing regions in turbulent Earth's MAGNETotail. We find that electrons with motion perpendicular to the MAGNETic field dominate $\vec{j}\cdot\vec{E}$ dissipation. In contrast to the conventional picture of unidirectional energy transfer to particles by laminar two-dimensional (2D) RECONNECTion, we find that energy exchange within MAGNETic structures during turbulent RECONNECTion tends to be bidirectional with only a small positive bias from electroMAGNETic fields to particles. Specific electron energization mechanisms are quantified, including those due to parallel electric field, FERMI energization from curvature drift, betatron heating from MAGNETic field inhomogeneity, and POLARIZATION drift.
arXiv:2604.26912 [pdf, ps, other]In this work, we investigate gravitational-wave signatures of a proposed subsolar-mass merger scenario resulting from fragmentation inside a collapsar accretion disk. This scenario has gained recent interest with the electroMAGNETic transient AT2025ulz, a possible superkilonova counterpart candidate to the sub-threshold gravitational wave event S250818k. One prediction of fragmentation is the formation of multiple smaller neutron-star fragments, some of which might merge hierarchically. Such mergers are expected not only to produce individual electroMAGNETic counterparts, but also, because of their repeated capture and merger dynamics, to impart kicks to the system and thereby drive orbital eccentricity. By performing numerical relativity simulations of hierarchical subsolar-mass compact-object mergers modeled as BLACK HOLEs in a disk-like geometry consistent with this scenario, we demonstrate the build-up of potentially large eccentricity for the final merger, of order $e \simeq 0.6$ initially, and show that, because of the short lifetime of the system, a substantial part of this eccentricity , up to $e\simeq 0.1$, can survive until the final neutron star -- BLACK HOLE merger in the general case. As a result, future detections of eccentricities in potential subsolar-mass gravitational-wave candidate events would be a strong indicator for a hierarchical formation scenario. In the extreme case, where we observe repeated mergers to lead to the formation of a solar-mass neutron star, the expected binary parameters can be in a regime similar to those of the eccentric neutron star -- BLACK HOLE merger event GW200105.
arXiv:2605.22913 [pdf, ps, other]We present a new FERMI-LAT analysis of the Galactic-center excess (GCE) designed to substantially reduce the dominant systematic uncertainties associated with interstellar-emission and source modeling in the inner Galaxy. Using an optimized multi-step fitting procedure together with an iterative source-finding pipeline, we achieve a markedly improved agreement between data and model, reducing fractional residuals to $\lesssim 10\%$ over a $40^\circ\times 40^\circ$ region centered on the Galactic center. We analyze a suite of GALPROP-based interstellar-emission models (IEMs) and complementary analysis variants (Galactic-plane masking, fits restricted to $1$-$10$ GeV, and weighted-likelihood fits) to quantify robustness. The reconstructed surface-brightness profile is strongly centrally concentrated and is well described by an approximately spherical generalized Navarro-Frenk-White morphology with inner slope $γ\simeq 1.15$. Bulge-tracing templates (nuclear bulge plus boxy bulge) fail to reproduce the full radial morphology, most notably for line-of-sight angles around $θ\simeq 1^\circ$-$2^\circ$ and at $θ\gtrsim 8^\circ$, whereas the DM-motivated component provides a good description over the full angular range. Moreover, the DM component remains highly significant across all IEMs and analysis choices, including fits that simultaneously include the bulge templates. We also provide an updated measurement of the GCE spectrum from $0.5$ to $1000$ GeV, confirming a peak at a few GeV and setting stringent constraints above tens of GeV, where we obtain only upper limits at the level $E^2Φ\lesssim 10^{-8}$ GeV cm$^{-2}$ s$^{-1}$ sr$^{-1}$. These results deliver a sharpened and systematically controlled characterization of the GCE morphology and spectrum, enabling more incisive tests of astrophysical and dark-matter interpretations.
arXiv:2605.28947 [pdf, ps, other]We present results on X-ray absorption and the dust grain chemistry in the diffuse interstellar medium (ISM), based on a new Cycle 25 Chandra High Energy Transmission Grating Spectrometer (HETGS) observational campaign targeting the BLACK HOLE transient GX 339-4. The X-ray source offers an optimal combination of moderate hydrogen column density and high X-ray flux, enabling the first detailed simultaneous fitting of the photoabsorption edges of Fe, O, Si, and Mg which are key elemental constituents of interstellar dust. We performed a joint spectral analysis of Chandra/HETGS data and archival observations from the Reflection Grating Spectrometer (RGS) on board XMM-Newton. We found that the dust grain chemical composition along this diffuse Galactic line of sight is best described by the silicate Mg-rich amorphous pyroxene (Mg0.75Fe0.25SiO3) and metallic iron. We also discuss the elemental abundances and depletions of Fe, O, Si, and Mg, and the presence of absorption features in the X-ray spectrum of this source associated with highly ionised plasma.
arXiv:2605.28948 [pdf, ps, other]The Hubble Space Telescope is the only high-resolution ultraviolet spectroscopic facility that will exist until the Habitable Worlds Observatory (HWO) achieves first light in the mid-2040s. We describe a coherent class of science, coupling rest-frame extreme-ultraviolet (EUV; 1--4 Ryd, 228--912 Å) absorption and continuum spectroscopy of intermediate-redshift QUASARs at $z = 1-2$, shifting the rest-frame EUV photons into the HST/COS far-UV bandpass. This science on QUASARs and gas in the IGM and CGM is doubly perishable. The COS detector sensitivity is declining, just as new QUASARs are found (Milliquas, UVQS, and soon Rubin, Roman, and Euclid). Thus, the window to reach UV-bright QUASARs at $z>1$ QSOs narrows with every deferred orbit. Expanding HST UV orbit allocations in the 2030s would deliver a step-change in warm-hot CGM/IGM science and produce the first systematic, empirical EUV SED census of QSOs. These datasets will serve as the foundational low-redshift anchor for HWO science. This recommendation makes the scientific and strategic case for an expansion of the HST/COS spectroscopic data base on intermediate redshift AGN in their rest-frame EUV.
arXiv:2605.29305 [pdf, ps, other]Extreme mass-ratio inspirals (EMRIs) are among the primary targets of future space-based gravitational-wave observatories, such as LISA, TianQin, and Taiji. Active galactic nucleus (AGN) disks provide a gas-rich environment in which stellar-mass BLACK HOLEs can migrate toward central supermassive BLACK HOLEs and form EMRIs. Previous studies of this ``wet'' channel have largely neglected stellar interactions within the disk. Here we show that binary formation, hierarchical mergers, and recoil kicks fundamentally regulate wet EMRI formation in AGN disks. Using semi-analytical AGN disk models combined with Monte Carlo simulations across supermassive BLACK HOLE masses of $10^5$--$10^7M_\odot$ and Eddington ratios of $10^{-3}$-1, we find that recoil kicks from mergers and binary--single interactions repeatedly lift stellar-mass BLACK HOLEs out of the disk plane, temporarily interrupting migration and strongly suppressing EMRI formation in much of parameter space. Detectable EMRIs are therefore preferentially produced in young AGNs, typically within $\sim$ 10-20Myr of disk formation, and often involve merger-grown secondary BLACK HOLEs. We predict LISA detection rates of $\sim$ 1-30yr$^{-1}$, with the observable population dominated by low-mass AGNs and sensitive to the poorly constrained demographics of faint active nuclei. Our results identify stellar interactions as a key ingredient in the evolution of compact objects in AGN disks and show that future EMRI observations can probe both AGN disk physics and the low-mass AGN population.
arXiv:2605.29306 [pdf, ps, other]Shadows cast in the COSMIC RAY (CR) muon sky by the Sun were located using muon data from the MINOS far detector in Northern Minnesota. The shadows were observed independently across three time periods; near solar minimum, near solar maximum, and over the entire 13 year span of the data. A distribution of muon positions for each shadow was then sampled to simulate CR motions near the Sun using the Parker spiral model of the Heliospheric Magnetic Field (HMF) and a dipole model of the GeoMAGNETic Field (GMF). The resulting particle distributions were then compared to their position with respect to the Sun. Results show that the Parker spiral model is most consistent with the solar minimum shadow and least consistent with the solar maximum shadow, as expected. The simple Parker spiral is more consistent with the data for a harder CR spectrum than is actually present, indicating the need for a more detailed HMF model. Plausible modifications to the Parker spiral model which would affect the overall shift of the Sun's CR shadow are discussed.
arXiv:2605.30175 [pdf, ps, other]Cluster analysis is a widely applied machine learning technique to understand the existing patterns in the population of GAMMA-RAY BURSTs (GRBs), in order to explore their physical sources. In the present scenario, the number of clusters corresponding to differentiable groups is still under conflict, in spite of numerous attempts with the state-of-the-art clustering procedures. This crucial unknown parameter needs to be evaluated, either directly or indirectly in terms of other tuning parameters, to produce the clusters in GRBs through implementation of an appropriate clustering algorithm. While most of the applied algorithms reached two physically explained groups of merger and collapsar predominated by the short and long bursts respectively, other statistical approaches violated this binary partition. However, physical establishment of any additional cluster(s) is not yet confirmed. Therefore, we propose a new algorithm, from a different stream of clustering referred to as `completely parameter-free', which carries out the classification of GRBs in a manner that has not been tried so far. It indicates two main groups, of short and long duration bursts from the BATSE sample, compatible with the merger-collapsar theory.
arXiv:2503.08793 [pdf, ps, other]We demonstrate that a symmetry of the local gyrokinetic model is broken when the safety factor q is almost (but not exactly) a rational number and MAGNETic shear is $\hat{s} \approx 0$. Tokamaks with such a q profile will spontaneously rotate due to turbulent momentum transport. Nonlinear gyrokinetic simulations indicate this mechanism is significantly stronger than all other drives of intrinsic rotation. It also generates intrinsic electric current that pulls q towards rational values, potentially aiding non-inductive current drive. This is likely important in the triggering of internal transport barriers.
arXiv:2508.21262 [pdf, ps, other]Microlensing by the stellar field in a strong-lensing galaxy can introduce wave-optics distortions into the waveforms of strongly lensed gravitational waves (SLGWs). If these signals are analyzed with waveform templates that do not include microlensing, the lensing-induced modulation may be misinterpreted as intrinsic source physics. In particular, microlensing can mimic spin precession, since both effects can produce beat-pattern-like features in the waveform. In this work, we study the degeneracy between stellar-field microlensing and spin precession, and ask to what extent microlensed SLGWs may show false evidence of precession. We analyze simulated SLGW events for two detector sensitivities, O5 and a lower-noise configuration with a power spectral density reduced by a factor of 4 (named O5 Plus), assuming binary BLACK HOLEs with parallel spins. We find that microlensing can indeed produce apparent evidence for precession, and that this effect becomes more visible at higher signal-to-noise ratios. Under O5 sensitivity, 4.88% of microlensed events lie above the one-sided Gaussian-equivalent 3$σ$ background threshold, corresponding to the 99.9th percentile of the unlensed-background distribution, while under O5 Plus sensitivity this fraction increases to 14.91%. We also find that the evidence for precession is positively correlated with the strength of microlensing. This correlation is weak under O5 sensitivity, but becomes clear under O5 Plus sensitivity. In addition, Type II (saddle-point) images show a stronger correlation than Type I (minimum-point) images. These results show that evidence for precession in GW data should be interpreted with care, as it may also arise from microlensing wave effects in SLGWs.
arXiv:2602.19566 [pdf, ps, other]Understanding the origin of collectivity-like signatures in small collision systems is a central open question in high-energy nuclear physics, and two-particle correlation functions offer unique sensitivity to the underlying-event (UE) dynamics that may drive such behavior in proton--proton (pp) collisions. In this work, the two-particle number ($R_{2}$) and transverse-momentum ($P_{2}$) correlation functions are studied in pp collisions at $\sqrt{s}=13$ TeV using PYTHIA 8, for final state charged hadrons within $|η|<0.8$ and $0.2
arXiv:2602.20316 [pdf, ps, other]The Sun is observed in unprecedented detail, enabling studies of its activity on very small spatiotemporal scales. However, the large volume of data collected by our telescopes cannot be fully analyzed with conventional methods. Popular machine learning methods identify general trends from observations, but tend to overlook unusual events due to their low frequency of occurrence. We study the applicability of unsupervised probabilistic methods to efficiently identify rare events in multidimensional solar observations and optimize our computational resources to the study of these extreme phenomena. We introduce Inspectorch, an open-source framework that utilizes flow-based models: flexible density estimators capable of learning the multidimensional distribution of solar observations. Once optimized, it assigns a probability to each sample, allowing us to identify unusual events. We apply this approach by applying it to observations from the Hinode Spectro-Polarimeter, the Interface Region Imaging Spectrograph, the Microlensed Hyperspectral Imager at Swedish 1-m Solar Telescope, the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory and the Extreme Ultraviolet Imager on board Solar Orbiter. We find that the algorithm assigns consistently lower probabilities to spectra that exhibit unusual features. For example, it identifies profiles with very strong Doppler shifts, uncommon broadening, and temporal dynamics associated with small-scale RECONNECTion events, among others. As a result, Inspectorch demonstrates that density estimation using flow-based models offers a powerful approach to identifying rare events in large solar datasets. The resulting probabilistic anomaly scores allow computational resources to be focused on the most informative and physically relevant events. We make our Python package publicly available at https://github.com/cdiazbas/inspectorch.
arXiv:2604.00121 [pdf, ps, other]We present an explicit multiscale algorithm for solving differential equations for problems with high-frequency modes that can be averaged over by separating and scaling the fast and slow dynamics within a single equation. We introduce a phased time integrator for cases where the boundaries of dynamical scales are known: one phase solves the unmodified equation, while the other freezes part of phase-space and slows down the evolution of the fast dynamics. This algorithm is applied to reduced kinetic models of plasmas in MAGNETic mirrors, which feature a distinct boundary between a region dominated by rapid particle transit and a region characterized by slow collisions. Two representative model problems are presented that decompose the dynamics of the MAGNETic mirror into a simpler, computationally inexpensive form. The model problems demonstrate a speedup by a factor of order $ω/ ν_c$, where $ω$ is the fast oscillation frequency and $ν_c$ is the slow damping rate. This is a 30,000$\times$ speedup for a case of practical interest.
arXiv:2604.11684 [pdf, ps, other]High-temperature superconducting (HTS) MAGNETs and other advances have led to renewed interest in MAGNETic mirrors for fusion energy. The non-Maxwellian nature of mirror plasmas necessitates kinetic modeling to predict, optimize and design mirrors. Explicit gyrokinetic full-f codes can be used to study instabilities and turbulent transport in tokamaks and mirrors, but they have been prohibitively expensive to integrate directly over the very long time scales required to compute kinetic plasma equilibrium. We demonstrate that these studies are now feasible thanks to novel multiscale methods delivering a 30,000X speed-up. The resulting kinetic equilibrium, electrostatic potential, and ion confinement time are consistent with analytic theory. This transformative capability opens the door to a new way of obtaining equilibria for mirrors, and we discuss how this technique may also accelerate calculations for tokamaks and stellarators. The models presented in this article address critical multiscale problems in modeling MAGNETic mirrors, opening a new research avenue for equilibrium studies using an explicit continuum gyrokinetic code.
arXiv:2605.03961 [pdf, ps, other]We compare images of core-collapse SUPERNOVA (CCSN) remnants (CCSNRs) and JET-shaped planetary nebulae (PNe) that have a narrow, faint zone extending from side to side, termed a pipe, with a hydrodynamical numerical simulation exploding a massive star with three pairs of JETs in the framework of the jittering JETs explosion mechanism (JJEM), and conclude that JETs shaped the pipes in these CCSNRs and PNe. We present two JET-shaped PNe with a pipe and three PNe with two opposite narrow JET-shaped lobes, and argue that in some cases the two opposite narrow lobes might merge to form one long, faint zone extending from side to side of the PN, namely, a pipe. From the qualitative similarity of the pipe morphology of the two CCSNRs we analyze with the pipe of the PNe, we suggest that JETs also shaped the pipe of these CCSNRs. We strengthen this conclusion with a three-dimensional hydrodynamic simulation that reproduces two opposite narrow lobes, similar to those observed in PNe with lobes. These lobes can merge later to form a pipe. This paper is another in a series that strengthen the case for the JJEM as the primary explosion mechanism of CCSNe by comparing CCSNR morphologies with those of JET-shaped PNe.
arXiv:2605.04173 [pdf, ps, other]We used very long baseline interferometry to constrain the orbit of the binary system 2MASS J05082729-2101444. We observed the system with the VLBA in three epochs at a frequency of 4.85 GHz, which provides an angular resolution of about 3 mas. We combined the three radio astrometric observations, 119 RVs (60 VIS and 59 NIR) obtained with the CARMENES high-resolution spectrograph over a period of 8.1 years, and a relative astrometric measurement of an archival H-band Keck NIRC adaptive optics image to fit the orbital motion of the binary system. The VLBA observations resolved the binary system and show emission from both stellar components, with similar flux-density levels (0.34-0.67 mJy), and showing slight temporal flux variations. The emission appears quiescent, with no significant circular POLARIZATION, and with no flare events. We obtained an orbital motion fit of the binary system, which shows an eccentric orbit (e = 0.71), an orbital period of 2.19 yr, and a semimajor axis of 26.964 mas (1.3 au). The VLBA observations made it possible to resolve the binary system and identify both stars as radio-loud sources. The combined fit shows that 2M0508-21 is an M-dwarf binary with a total dynamical mass of $0.459\pm0.007$ M$_{\odot}$, assuming Gaia's parallax. This mass is slightly higher than those estimated from the luminosity and theoretical evolutionary models. The upper limit of the circular POLARIZATION at 4.85 GHz ($\lesssim$10\%), the persistence of the quiescent emission, and the relatively low brightness temperatures are consistent with a gyro-SYNCHROTRON or SYNCHROTRON origin of the radio emission. Further VLBA observations are needed to obtain the individual masses of the stars, as well as to verify Gaia's parallax of the system. A complete characterization of the system will help improve evolutionary models for young objects at the substellar boundary.
arXiv:2605.25282 [pdf, ps, other]The simulation of extreme Mach astrophysical flows is traditionally viewed through the lens of deterministic positivity-preserving schemes. However, due to Kelvin--Helmholtz instabilities and shock anomalies, the multi-dimensional Euler equations admit a variety of non-unique entropy solutions in turbulent regimes. Here, we computationally explore the limits of weak-strong uniqueness of a Mach 2000 JET by defining the statistical solution as the pushforward of a probability measure through a vectorial lattice Boltzmann method operator. Utilizing optimized CUDA kernels, we compute an ensemble of 1000 Monte Carlo samples across a sequence of highly refined spatial grids of up to 3.2 million cells and subsequently post-process the empirical measures via memory-mapped CPU streaming. We contrast the strong sample-wise $L^1$ error divergence with the convergence of the probability measure in the 1-point Wasserstein distance via empirical Cauchy rates. Our results demonstrate that while individual flow realizations physically diverge due to chaotic shear-layer instabilities, the statistical solution converges to an admissible limit measure at a rate of 0.5. Consequently, we provide numerical evidence that the statistical solution to the considered problem is non-Dirac and remains stable in the extreme compressible regime.
arXiv:2605.27225 [pdf, ps, other]Version 5.0 of the Gravitational-Wave Transient Catalog (GWTC-5.0) adds new candidates detected by the LIGO Virgo KAGRA network of observatories through the second part of the fourth observing run (O4b: 2024 April 10 15:00:00 to 2025 January 28 17:00:00 UTC) and four days of the preceding engineering run (2024 April 6 to 2024 April 10). We find 161 compact binary coalescence candidates that are identified by at least one of our search algorithms with a probability of astrophysical origin $p_\mathrm{astro} \geq 0.5$ and that are not vetoed during event validation. We also provide detailed source property measurements for 104 candidates that have a false-alarm rate < 1yr$^{-1}$. Based on the inferred component masses, all these candidates are consistent with signals from binary BLACK HOLEs. Median inferred component masses in the new candidates range from 5.14$M_\odot$ (GW241109_115924) to 70$M_\odot$ (GW241116_151753). Improvements in detector sensitivity allow us to observe compact binary coalescences with increasing clarity: 5 binary-black-hole signals have network signal-to-noise ratio exceeding 30, with a maximum to date of 76.9 for GW250114_082203. Such loud signals enable more precise studies of properties of their astrophysical sources and tests of general relativity. We also present updated results up to the first part of the fourth observing run, identifying 229 candidates. This brings the total number of transients in the cumulative GWTC having $p_\mathrm{astro} \geq 0.5$ to 390, further expanding the size of the catalog and our view of the gravitational-wave universe.
arXiv:2605.28917 [pdf, ps, other]We study greybody factors, absorption cross sections and Hawking energy-emission rates for minimally coupled massless scalar, electroMAGNETic and massless Dirac test fields on the loop-quantum-gravity-inspired holonomy-corrected Schwarzschild BLACK HOLE. The geometry is controlled by a dimensionless holonomy parameter, and the radial wave equations are solved by direct numerical integration with first- and sixth-order WKB estimates as complementary checks. The scalar, electroMAGNETic and Dirac channels respond differently: the dominant scalar mode becomes more transparent, the electroMAGNETic threshold shifts slightly upward, and the dominant Dirac mode is only mildly modified. The scalar absorption cross section retains the universal low-frequency limit, the electroMAGNETic cross section changes mainly in the infrared, and the Dirac cross section develops a strongly suppressed low-frequency tail. Since the Hawking temperature falls monotonically, thermal suppression dominates the radiative output. Thus the holonomy correction enhances low-lying scalar transmission but suppresses Hawking radiation overall, with the electroMAGNETic sector most strongly quenched and the fermionic sector dominant once $α$ is appreciable.
arXiv:2605.28953 [pdf, ps, other]The possibility that Dark Matter (DM) is partially or totally constituted by stable Planckian remnants of light Primordial Black Holes (PBHs), suggested for instance by Loop Quantum Gravity (LQG), is investigated. Distinct phenomenological regimes are identified, including scenarios that trigger an early matter-dominated epoch. New constraints are derived on the initial PBH and final remnant abundances. We show that a significant initial abundance of PBHs lighter than $10^3$ kg would overproduce Planckian relics, implying that any observational evidence for such PBHs would challenge models with quasi-stable remnants. Conversely, the products of Hawking radiation from PBHs with masses between $10^3$ and $10^{12}$ kg impose that Planckian relics could only be a highly subdominant DM component. We identify a PBH mass around $10^3$ kg for which Hawking evaporation naturally reheats the Universe while the remnants entirely constitute the present-day DM. Such a scenario does not require fine-tuning the initial abundance of PBH of this mass, which could range from $10^{-10}$ to order one. These early-Universe cosmologies yield distinct observational signatures: scalar-induced gravitational waves sourced by primordial or Poisson fluctuations that are amplified by the early PBH-dominated era. Current and future observations of LIGO/Virgo/KAGRA, the Einstein Telescope and LISA, as well as probes of the effective number of RELATIVISTIC degrees of freedom, can be used to probe and constrain the initial PBH abundance and the present-day abundance of Planckian relics.
arXiv:2605.29187 [pdf, ps, other]Neutron star mergers are amongst the most promising sources for the joint detection of gravitational waves and electroMAGNETic signals. They are also potential sites for the production of r-process elements and probes of the equation of state of matter above nuclear saturation density. Neutrino-matter interactions during and after merger strongly influence the thermodynamic evolution and composition of the remnant and its outflows, thereby affecting kilonova emission and nucleosynthesis yields. However, existing merger simulations remain limited by significant approximations in the treatment of neutrino transport and interaction rates. In this work, we assess the thermodynamic conditions under which neutrinos decouple from matter and show the effect of charged-current absorption, quasi-elastic scattering on nucleons and nuclei, pair-production processes, and inelastic neutrino-electron scattering for electron neutrinos, electron antineutrinos, and heavy-lepton neutrinos in the different thermodynamical conditions sampled by a simulation using an energy-dependent Monte Carlo neutrino transport. We first estimate opacities in the post-merger remnant assuming neutrinos in equilibria with the fluid, and find results consistent with previous studies performed on simulations using a gray two-moment scheme. We note the very distinct regions in which nucleon-nucleon Bremmstrahlung and electron-positron annihilation are active (high and low density regions, respectively). We then evaluate opacities using the actual distribution function of neutrinos within a Monte Carlo simulation. We show greatly increased pair annihilation rates in cold, low-density regions, especially for heavy-lepton neutrinos. We also show that inelastic scattering on electrons, which has not been included in merger simulations so far, makes important contributions to the thermalization of heavy-lepton neutrinos.
arXiv:2605.29487 [pdf, ps, other]Super-Eddington accretion onto compact objects is expected to produce optically thick outflows with a funnel-shaped cavity that may collimate the emission. At inclinations higher than the grazing angle of the funnel, the central source is obscured. Accordingly, the observed emission is dominated by scattered and reflected radiation, which can therefore be strongly polarized. The detection of strong X-ray POLARIZATION in the Galactic X-ray binary Cygnus X-3 provides the first direct probe of this geometry. In this work, we present a systematic study of the inclination-dependent radiative signatures of such systems using a combination of semi-analytical methods and Monte Carlo simulations. Our treatment explicitly accounts for multiple scatterings and demonstrates that both the POLARIZATION degree and the degree of collimation are highly sensitive to the albedo of the funnel surface. We find that a low albedo (significant absorption) is essential for producing high POLARIZATION, yet it simultaneously suppresses the collimation of the emission. Conversely, a high-albedo medium (nearly pure scattering) can modestly collimate radiation, but at the cost of substantially reducing the POLARIZATION degree. We discuss our results in the context of Imaging X-ray Polarimetry Explorer observations of Cygnus X-3 and propose a physical scenario for its spectral state transitions, considering a combination of reflection from the funnel surface and scattering by a diffuse medium above the funnel. Our model provides a general framework for interpreting X-ray polarimetric signatures of obscured accretors.
arXiv:2605.29616 [pdf, ps, other]We present a comprehensive study of an infrared (IR) flare in the star-forming galaxy SDSS J010320.39+140152.5, which is selected from the sample of mid-IR (MIR) outbursts in nearby galaxies (MIRONG). Its MIR luminosity rose rapidly to a peak of $\sim5.4\times10^{43}$ \lum, maintained in the high state for about a year, and decreased continuously afterward. No optical variability was detected throughout the IR flare. Near-IR follow-up observations around the peak pinpointed the flare's location to spatially coincide with the galactic nucleus, with a $3σ$ upper limit of the offset of $\lesssim100$ pc. The IR spectral energy distribution (SED) of the flare is consistent with thermal emission of dust with temperatures of $\sim900$ K. Using a dust radiative transfer model, we inferred a peak UV luminosity of $\sim(4-10)\times10^{44}$ erg s$^{-1}$ and a total energy of $\sim(0.9-2)\times10^{52}$ ergs released. We ruled out the possibility of a SUPERNOVA, and prefer that the IR flare originated from an obscured tidal disruption event (TDE) rather than a changing-look ACTIVE GALACTIC NUCLEus (AGN). This flare stands as one of the most compelling cases to date for the emerging class of dust-obscured TDEs in recent years. They are missed by optical surveys, partly accounting for the observed bias in TDE host galaxies, and represent a crucial, yet often overlooked, component for a complete understanding of the TDE population.
arXiv:2605.30057 [pdf, ps, other]Weakly ionized plasmas can be found in the lower layers of the solar and stellar atmospheres and in structures such as prominences and spicules. A variety of density perturbations and bulk flows detected in these environments have been explained as the result of the ponderomotive force generated by nonlinear Alfvénic waves. In addition, the dissipation of the energy carried by these waves leads to heating of the plasma. Here, we use a two-fluid model to study the combined influence of Hall's current and elastic collisions between ions and neutrals on the propagation of linearly and circularly polarized transverse waves in weakly ionized plasmas. We derive analytical expressions for the damping and heating rates, showing their dependence on the strength of the collisional coupling and on the POLARIZATION state. We also perform numerical simulations to investigate the nonlinear generation of density perturbations and bulk flows related to the ponderomotive force and the energy dissipation by the ion-neutral interaction. We find that the nonlinear perturbations associated with the circularly polarized eigenmodes do not show the oscillatory motions typically caused by linearly polarized eigenmodes, but they retain the non-oscillatory bulk flows. We also briefly discuss how in weak coupling conditions the nonlinear dynamics of the neutral fluid is mainly driven by the wave energy dissipation while the ponderomotive force only directly acts on the charged fluid, resulting in different amplitudes of the longitudinal motions and the perturbations of density and temperature.
arXiv:2605.30192 [pdf, ps, other]Title: The Northern Cross Fast Radio Burst project: VI. The INCART public databaseAuthors: L. Bruno, G. Bernardi, M. Pilia, D. Pelliciari, A. Geminardi, F. Fiori, V. Galluzzi, G. Naldi, M. Trudu, A. Zanichelli,Comments: 8 pages, 6 figures. Accepted for publication in PASA. INCART is available here: https://ngc-frb-incart.ira.inaf.it/Subjects: astro-ph.HE astro-ph.COCreated: 2026-05-28; Updated: 2026-05-29; Datestamp: 2026-05-29Fast radio bursts (FRBs) are bright (Jansky-level) and short-duration ($\sim 1$ ms) flashes of extragalactic origin. Observations of single events have now been complemented by large-area surveys, delivering FRB catalogues and enabling the first population studies. The Northern Cross (NC) radio interferometer is one of the instruments performing observations of FRBs. In this work, we present the Italian Northern Cross Atlas of Radio Transients ({\tt INCART}), a public platform for the distribution of data products from the NC. {\tt INCART} makes available to the community the FRBs observed by the NC through manageable frequency-time series datasets and catalogues with best-fit physical parameters. The design of {\tt INCART} guarantees the possibility of scientific re-analysis of the FRB properties, in view also of future releases of the processing pipeline. Furthermore, {\tt INCART} focuses on long-term storage optimisation, which is a key aspect of state-of-the-art instrumentation. Public access to the FRB data from the NC maximises the legacy value of the collection, facilitates the synergy with other publicly-available catalogues, and fosters research group collaborations.
arXiv:2601.20471 [pdf, ps, other]
arXiv:2605.28081 [pdf, ps, other]