High Energy Astrophysical Phenomena · Cross-listed from astro-ph.GA
An Off-Nuclear Tidal Disruption Event Discovered At Late Times: The Case Of TDE 2023mfm
Itai Sfaradi, Ryan Chornock, Yuhan Yao et al. (+24 more)
We present the discovery and analysis of the optically selected tidal disruption event (TDE) 2023mfm, which originates from a wandering massive black hole (MBH) in a massive ($\sim 10^{11} \,$M$_{\odot}$)
galaxy hosting a central low-luminosity active galactic
nucleus (AGN). Our analysis of the ZTF, Lick, Keck, Swift, Chandra, XMM-Newton, HST, and VLA observations reveals that TDE 2023mfm is a TDE-H from a $10^{6.2 \pm 0.5}\,$M$_{\odot}$ black hole which is offset by $0.66 \pm 0.02$" from the center of its host
galaxy, corresponding to a projected distance of $1.08 \pm 0.04$ kpc. TDE 2023mfm displays all the traits of optically selected TDEs. The emission remains hot, $T_{\rm bb} \sim 22,000 \pm 1,000$ K, for more than a month after peak, and the $g$-band light curve peaks at $\left( 2.24^{+0.10} _{-0.11} \right) \times 10^{43} \, \rm erg \, s^{-1}$ and stays above half-maximum luminosity for $47.8^{+3.7}_{-3.5}$ days. The late-time optical-to-UV emission observed with the HST suggests the presence of an unresolved stellar population with a stellar mass of $10^7-10^8\,$M$_{\odot}$ at the position of the TDE, possibly being a low-mass dwarf
galaxy or a stripped
galaxy from a previous minor merger. The
radio emission from TDE 2023mfm emerges at least a year after optical discovery, and we find it likely that it originates from a delayed outflow, however, further observations are needed to determine its true origin.
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All authors Itai Sfaradi, Ryan Chornock, Yuhan Yao, Erica Hammerstein, Jean Somalwar, Raffaella Margutti, Huei Sears, Robert Stein, Natalie LeBaron, Adelle J. Goodwin, Sjoert van Velzen, Matthew J. Graham, Kate D. Alexander, Nayana A. J., Edo Berger, Jonathan Carney, Yvette Cendes, Collin T. Christy, Walter W. Golay, Wenbin Lu, James C. A. Miller-Jones, Charlotte Ward, Eli Wiston, Tracy X. Chen, Mansi M. Kasliwal, Frank J. Masci, Jesper Sollerman
High Energy Astrophysical Phenomena
Bayesian Evidence for Inspiraling Hotspot Motion in the Galactic Center
Pablo Ruales, Maciek Wielgus, Delilah E.A. Gates et al. (+1 more)
During flaring episodes, polarimetric observations of the Galactic Center black hole Sagittarius A* (Sgr A*) reveal evolving, loop-like trajectories in the Stokes Q-U plane, the so-called Q-$U loops. Keplerian models of transiently energized orbiting features, hotspots, have been employed to reproduce these polarimetric signatures. In this work, we develop a
Bayesian framework to infer the time-dependent kinematics of the hotspot from polarized light curves, using a general prescription for its motion. We model the emitting region's trajectory as a continuous, piecewise sequence of K kinematic segments, each described by radial and azimuthal velocity parameters. We perform analyses with K=1,2,3 and compare these models to millimeter-wavelength ALMA observations of Sgr A* from 2017 April 11 that include two subsequent Q-U loops, extending the observational constraints on the kinematics. We examine the effects of the local
magnetic field geometry, spectral index, and kinematic profile of the hotspot's trajectory on the polarized signal. We find statistically significant evidence that the emitting region follows a non-geodesic inspiraling trajectory, and this preference over a strictly Keplerian orbit strengthens sharply when a longer data segment is modeled. The inspiraling non-Keplerian models are preferred to a purely Keplerian model based on both the
Bayesian log-evidence comparison and the reduced chi-square statistic. Our results offer new insight into the nature of flaring events in the Galactic Center and the episodically produced hotspots associated with them.
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All authors Pablo Ruales, Maciek Wielgus, Delilah E.A. Gates, Alejandro Cardenas-Avendano
High Energy Astrophysical Phenomena
Hierarchical Bayesian Inference on the intrinsic event rate of Type I gamma-ray bursts from the Fermi/GBM catalogue
Cao Tian-Yong, Yi Shu-Xu, Du Yun-Fei et al. (+2 more)
The intrinsic event-rate of Type I gamma-ray bursts (GRBs) as a function of
redshift, provides a probe for binary
neutron star (BNS) mergers population. However, the above-mentioned inference is complicated by instrumental selection effects, the lack of
redshift measurements for the majority of GRBs, and uncertainties in jet geometry. In this work, we applied a hierarchical
Bayesian inference framework to the Fermi/GBM Type I GRB catalogue to reconstruct the underlying event-rate population. This framework accounts for the selection effects and marginalizes over the limited-information posteriors of individual GRB
redshifts and jet structures. The population model uses parameterized luminosity function, distribution of jet structure parameters, the Madau-Dickinson
star-formation rate and a delay-time distribution of BNS mergers. The posterior distribution of the hyperparameters in the model are to be inferred, using a GPU-accelerated MCMC
algorithm. The intrinsic event rate density as function of
redshift is constrained up to $z=5$, which a local rate density of \(R_0 = 22.6^{+15.0}_{-10.6}\,{\rm Gpc^{-3}\,yr^{-1}},\), which is consistent with the latest gravitational-wave measurements.
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All authors Cao Tian-Yong, Yi Shu-Xu, Du Yun-Fei, Yorgancioglu S. Emre, Xiong Shao-Lin
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Black Hole Quasinormal Mode Resonances and Reconnections in Coupled Systems
Leah Jenks, Hayato Motohashi, Kazufumi Takahashi et al. (+2 more)
Black hole quasinormal modes (QNMs) provide a window into the underlying structure of black holes and the environments in which they arise. QNMs have particularly rich dynamics in coupled systems beyond general relativity, in which they are known to undergo avoided crossings, resonant excitation, and mode reconnections. Recent work has shown that reconnecting QNM trajectories can trace out a distinctive double spiral structure in the complex frequency plane. In this work, we study this phenomenology in a concrete model of perturbed dynamical Chern-Simons (dCS) theory, as well as in a minimal toy model. In the former, we characterize the exceptional points, avoided crossings and reconnections for several values of the perturbation parameters, and find that the limiting frequency of the double spiral endpoints is independent of the perturbation strength. We compute the excitation factors and find that they follow the scaling characteristic of a resonance between the scalar and gravitational modes. To determine whether these phenomena depend on the specific features of dCS, we construct a toy model of coupled degrees of freedom with square potential barriers, and find that we can reproduce the avoided crossings and reconnections, indicating that these phenomena can occur more generally in coupled systems and are highly sensitive to the system parameters.
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All authors Leah Jenks, Hayato Motohashi, Kazufumi Takahashi, Takuya Takahashi, Emanuele Berti
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Constraining dark matter using 20-year INTEGRAL/IBIS observations II: Sub-GeV dark matter
Jordan Koechler and Pedro De la Torre Luque
We present new constraints on sub-GeV dark matter (DM) annihilation and decay using twenty years of diffuse hard X-ray observations from the INTEGRAL/IBIS
telescope. By performing a joint analysis of the spectral and morphological information contained in the IBIS
dataset, we simultaneously fit Galactic longitudinal profiles and energy spectra, exploiting their complementary signatures to disentangle potential DM signals from the dominant astrophysical backgrounds. We use physically motivated background models combining inverse-Compton (IC) emission from Galactic
cosmic-ray electrons with thermal emission from unresolved accreting white dwarfs, and consistently include the secondary IC emission generated by DM-induced electron and positron populations propagated through the
Galaxy. We conservatively derive 95% upper limits on the annihilation cross section $\langle\sigma v\rangle$ and decay half-life $\tau$ for the $e^+e^-$, $\mu^+\mu^-$, and $\pi^+\pi^-$ final states across the mass range 1 MeV to 5 GeV. Our constraints are in the range $10^{-28}$ cm$^3$/s $\lesssim \langle\sigma v\rangle \lesssim 10^{-26}$ cm$^3$/s for annihilation and $\tau \gtrsim 10^{25}$ s for decay at DM masses of a few MeV, improving upon existing X-ray limits by up to two orders of magnitude over much of the mass range. Our bounds are translated into constraints on the kinetic mixing parameter $\epsilon$ of a dark
photon and the scalar-
Higgs mixing angle $\sin\theta$, and compared with existing indirect, direct and accelerator limits available, providing a comprehensive picture of the allowed parameter space for light portal DM.
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High Energy Astrophysical Phenomena · Cross-listed from astro-ph.SR
Discovery of over a thousand variable stars in Terzan 5 and Liller 1 with JWST
Kevin B. Burdge, Ilaria Caiazzo, Malina M. Desai et al. (+18 more)
The Bulge Fossil Fragments Terzan 5 and Liller 1 host some of the densest stellar environments in the
Galaxy, yet their variable
star populations have remained largely unexplored due to crowding and heavy obscuration. Here, we identify 1,315 variable sources in these two systems in what is to our knowledge the first JWST time-series variability census of a globular cluster-like object. By differencing consecutive non-destructive reads within each NIRCam integration, we transform sample-up-the-ramp imaging into an infrared movie sampled every 21 seconds. More than a century of observations has cataloged 5,604 variables, the majority of them pulsating
stars, across 151 Galactic globular clusters. Our census alone amounts to 23 percent of that total and contains more photometrically variable binaries than had previously been cataloged in all globular clusters combined. The field of Liller 1, with zero previously known variables, now hosts 915, nearly double the count in the runner-up $\omega$ Centauri. We detect dramatic infrared variability from the Rapid Burster, revealing the counterpart sought since 1976 (see Desai et al. 2026), and blindly recover a signal coincident with the prototype redback
pulsar PSR J1748-2446A at its
radio-timed orbital period, identifying the first optical or infrared counterpart to any of Terzan 5's
pulsars. More broadly, we present a technique that recovers group-level time-series photometry from JWST observations, enabling time-domain studies with an observatory whose field of view is naturally matched to the
Galaxy's densest stellar systems.
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All authors Kevin B. Burdge, Ilaria Caiazzo, Malina M. Desai, Cristina Pallanca, Vera L. Berger, Kaley Brauer, Matteo Correnti, Paul Draghis, Kareem El-Badry, Francesco R. Ferraro, Denis González-Caniulef, Kyle Kremer, Barbara Lanzoni, Dongzi Li, Jessica R. Lu, Geoffrey Mo, Mason Ng, Roger W. Romani, Kaitlyn Shin, Daniel R. Weisz, Giorgia Zullo
High Energy Astrophysical Phenomena
Discovery of the Infrared Counterpart of the Rapid Burster with JWST
Malina M. Desai, Kevin B. Burdge, Cristina Pallanca et al. (+8 more)
The Rapid Burster (MXB 1730$-$335) is the only known
neutron star to produce both Type I and Type II X-ray bursts, making it a key system for understanding
accretion physics onto
neutron stars. It resides in Liller 1, a dense, metal-rich stellar system whose crowded core and $\sim$11 magnitudes of visual extinction have concealed the Rapid Burster's optical/infrared (OIR) counterpart for nearly five decades. Here, we present infrared observations of Liller 1 obtained with JWST/NIRCam that, for the first time, reveal the unambiguous OIR counterpart to the Rapid Burster. Caught in an X-ray active state, the counterpart exhibits dramatic infrared variability, fading by $\sim$ 2.5 magnitudes in JWST's F200W band (1.755$-$2.227 $\mu$m) with strong fluctuations on minute timescales. These observations provide an infrared anchor for the Rapid Burster and open the way for future spectroscopy and simultaneous IR and X-ray monitoring to constrain the donor's spectral type and the system's
accretion physics.
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All authors Malina M. Desai, Kevin B. Burdge, Cristina Pallanca, Saul Rappaport, Francesco R. Ferraro, Barbara Lanzoni, Mason Ng, Paul Draghis, Emma T. Chickles, Ilaria Caiazzo, Deepto Chakrabarty
High Energy Astrophysical Phenomena
Fast radio burst - persistent radio source systems III. The relation between PRS luminosity and FRB rotation measure
D. Pelliciari, G. Bernardi, L. Bruno et al. (+5 more)
Fast
radio bursts (FRBs) are millisecond-duration
radio transients of extragalactic origin whose physical origin remains uncertain. A small fraction of FRBs are known to repeat, and some of them are associated with persistent
radio sources (PRSs), interpreted as synchrotron-emitting nebulae surrounding the FRB source. In the context of magnetar-based models, the rotation measure (RM) of an FRB is expected to correlate with the spectral luminosity of its associated PRS, providing a probe of the physical properties and
evolution of the nebula. We investigate the relation between FRB RM and PRS spectral luminosity, constrain the characteristic size of the PRS nebulae, and use the intrinsic scatter of the relation to investigate evolutionary scenarios for FRB–PRS systems. We analyse a sample of 50 FRB sources with known RM, including both PRS detections and spectral luminosity upper limits, using a
Bayesian MCMC framework that jointly accounts for detections and non-detections. We model the luminosity–RM relation as $L_\nu \propto \zeta_e \gamma_c^2 R^2 {\rm RM}^\beta$, constraining the characteristic nebular size $R$ and the RM scaling index $\beta$. For the full sample, we obtain $R = 0.016^{+0.115}_{-0.014}$ pc at $1\sigma$ confidence for a free $\beta$, while fixing the RM dependence to the canonical linear scaling, $\beta = 1$, gives $R = 0.008^{+0.058}_{-0.007}$ pc. The data mildly favour super linear RM scalings, although the inferred values of $\beta$ remain consistent with $\beta = 1$ within $2\sigma$. We find a substantial intrinsic scatter in the luminosity–RM relation, significantly larger than previous estimates based on confirmed PRSs alone. Interpreting this scatter within evolutionary models, our results favour scenarios involving efficient particle acceleration and/or rapid nebular expansion.
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All authors D. Pelliciari, G. Bernardi, L. Bruno, M. Pilia, P. Esposito, L. Beduzzi, A. Geminardi, O. Smirnov
High Energy Astrophysical Phenomena
Fast radio burst - persistent radio source systems II. A faint PRS associated with the nearby FRB 20181030A?
D. Pelliciari, G. Bernardi, B. Margalit et al. (+10 more)
Persistent
radio sources (PRSs) are the continuum counterparts of fast
radio bursts (FRBs), the latter being extragalactic transients of millisecond duration and Jy-level flux density. An FRB-PRS system is thought to be a flaring magnetar surrounded by an highly magnetized, baryon-loaded nebula. We aim to constrain the size of 20181030A-S1, a new PRS candidate, potentially associated with the repeating FRB 20181030A. The latter is localized with $\sim 1'$ uncertainties in the outskirts of NGC 3252, which is a spiral
galaxy at a luminosity distance of $20$ Mpc. We report very long baseline interferometric (VLBI) observations using the European VLBI Network at $1.7$ GHz of this PRS candidate at an angular resolution of $20$ milliarcseconds. Our observations reveal the presence of an unresolved
radio source (20181030A-S1) at the position of the PRS candidate, confirming its compactness at milli-arcsecond angular scales. A fit to the position of the point-source yields a peak flux density of $280 \pm 30$ $\mu$Jy and a transverse physical size constrained to be $R < 0.5$ pc at $68\%$ confidence level (CL). This flux density converts to a spectral luminosity of $(9 \pm 1) \times 10^{25}$ erg s$^{-1}$ Hz$^{-1}$, $\sim 3$ orders of magnitude lower than confirmed PRSs, making 20181030A-S1 the closest and faintest PRS candidate known. Its low luminosity and modest rotation measure are consistent with the $L_\nu-$rotation measure (RM) relation followed by confirmed FRB–PRS systems, supporting a common physical origin in magnetar-powered nebulae. We show how a magnetized wind nebula powered by an initially weak ($B_\star \simeq 10^{15}$ G) and young ($t_{\rm age} \simeq 15 - 150$ yrs) magnetar can account for both the observed spectral luminosity and RM of the system. Other possible origin scenarios for 20181030A-S1, in the case in which it is unrelated to the FRB source, are also discussed.
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All authors D. Pelliciari, G. Bernardi, B. Margalit, B. D. Metzger, C. Nanci, L. Bruno, M. Pilia, L. Beduzzi, C. Spingola, C. Stanghellini, P. Esposito, A. Geminardi, M. Giroletti
High Energy Astrophysical Phenomena
Fast radio burst - persistent radio source systems I. A 1.2 GHz search and catalog definition
D. Pelliciari, L. Bruno, G. Bernardi et al. (+5 more)
We present new $1.26$ GHz observations of 24 fast
radio bursts (FRBs; 9 repeaters and 11 one-offs), conducted with the upgraded Giant Meter Wave
Radio Telescope (uGMRT) at arc-second angular scale resolution, and combined them with literature data to construct an extended sample of 75 sources with either persistent luminosity measurements or upper limits. Our catalog is complete down to a $10^{29}$ erg s$^{-1}$ Hz$^{-1}$ luminosity threshold, which corresponds to the value of the first-discovered PRS, associated with FRB 20121102. We detect compact
radio emission in six FRB fields, two of which are previously known PRSs and four are new candidates. The four new candidates are associated with three new repeating FRBs and one apparently one-off source. We computed the PRS occurrence using the whole catalog of 75 FRBs and found that PRSs more luminous than $10^{29}$ erg s$^{-1}$ Hz$^{-1}$ are rare. Unless otherwise stated, all uncertainties and upper limits are reported at the $95\%$ confidence level (CL). If we only consider confirmed PRSs, we find an occurrence of $f_{\rm all} = 0.06^{+0.09}_{-0.03}$, while including PRS candidates as well yields $f_{\rm all} = 0.14^{+0.22}_{-0.08}$. We also compute the PRS occurrence in the two classes of FRBs: repeating and non-repeating. In the conservative case, i.e., when none of the new PRS candidates are considered to be associated with their FRBs, we find no preferred association between the PRSs and FRB class, with an occurrence of $f_{\rm r} = 0.14^{+0.20}_{-0.09}$ for the sample of repeating FRBs and $f_{\rm nr} \leq 0.12$ for the sample of one-off sources. In the inclusive case, i.e., when all the new candidates are considered confirmed PRSs, we find $f_{\rm r} = 0.27^{+0.21}_{-0.14}$ and $f_{\rm nr} = 0.03^{+0.14}_{-0.02}$, with marginal ($90\%$ CL) evidence that PRSs are preferably associated with repeating FRBs.
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All authors D. Pelliciari, L. Bruno, G. Bernardi, M. Pilia, P. Esposito, L. Beduzzi, A. Geminardi, O. Smirnov
High Energy Astrophysical Phenomena
Empirical determination of the Galactic neutron star–black hole merger rate using StarTrack models
Terrence Pierre Jacques, D. R. Lorimer, Nihan Pol et al. (+2 more)
The discovery of a
pulsar in a binary system with a black hole would provide a unique laboratory for testing general relativity in the strong-field regime and offer vital constraints on massive
star evolution. We assess prospects for the detectability of such systems by utilizing the
radio pulsar population and survey models within the modeling package PsrPopPy and, as a proof of principle, two evolutionary models with different treatments of common-envelope phases from the stellar population synthesis code StarTrack. For these two models, assuming the
radio pulsar beaming model proposed by Tauris and Manchester and accounting for the effects of orbital motion on
pulsar detectability, we calculate upper limits on the number of
neutron star–black hole systems in the
Galaxy and the corresponding merger rate given the lack of any
radio-detected
pulsar–black hole binary systems in current
radio surveys. For the most constraining model, we find a Galactic merger rate $< 4.3~\text{Myr}^{-1}$ (at 95% confidence). These results are extrapolated to the expected horizon distance for the fifth LIGO observing run, leading to LIGO detection rate estimates that are consistent with the latest values reported by the LIGO-Virgo-KAGRA collaboration. Our results indicate that the increased sensitivity of FAST, MeerKAT, and DSA offers the best prospects yet for uncovering this elusive population.
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All authors Terrence Pierre Jacques, D. R. Lorimer, Nihan Pol, M. A. McLaughlin, K. Belczynski
High Energy Astrophysical Phenomena
SN 2025qe: A case study of diversity in low-luminosity thermonuclear explosions
Hrishav Das, Anirban Dutta, Devendra K. Sahu et al. (+3 more)
We present optical photometric and spectroscopic observations of SN 2025qe, a Type Iax
supernova in IC 0529, monitored from $-10$ to $+150$ rest-frame days relative to $g'$-band maximum using the GROWTH-India and the Himalayan Chandra
Telescopes. SN 2025qe reaches a peak $g'$-band absolute magnitude of $M_{g'} \approx -16.16 \pm 0.15$ mag, placing it in the sparsely sampled luminosity gap between the brightest and faintest members of the SNe Iax class. The multiband light curves show pronounced wavelength-dependent broadening at late times, with the redder bands remaining brighter than in other SNe Iax. Semi-analytical (Arnett) modeling of the pseudobolometric light curve yields a synthesized $^{56}$Ni mass of $0.02\,M_\odot$, an ejecta mass of $0.45\,M_\odot$, and a kinetic energy of $7.0\times 10^{49}$ erg. Three-dimensional pure-deflagration models of Chandrasekhar-mass carbon-oxygen white dwarfs reproduce the peak luminosity and $^{56}$Ni yield but underpredict the slow, red post-maximum decline; models including energy input from a bound remnant better match the late-time
evolution, especially in the red bands. We model early-time spectra using TARDIS with a modified deflagration model and identify late-time spectral features using syn++. We qualitatively try to explain the persistent red-band flux with a two-component ejecta structure comprising a dense inner region, possibly including a bound remnant, and a density-enhanced outer shell that sustains redder emission. Together, the photometric and spectroscopic properties of SN 2025qe highlight the diversity of ejecta structure and
evolution among SNe Iax with similar peak luminosities, emphasizing the need for detailed observations and modeling of their ejecta.
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All authors Hrishav Das, Anirban Dutta, Devendra K. Sahu, G.C. Anupama, Prathamesh S. Kadam, Vishwajeet Swain
High Energy Astrophysical Phenomena
JWST unveils a dust-obscured supernova associated with a gamma-ray burst
B. Schneider, A. J. Levan, N. Sarin et al. (+22 more)
Recent observations have challenged the duration-based classification of gamma-ray bursts (GRBs), making the detection of an associated
supernova (SN) or kilonova crucial for conclusively identifying their progenitors. We investigate the origin of GRB 240825A at $z=0.659$, whose
prompt emission gave conflicting indications of a merger or collapsar origin and for which no SN was detected in deep ground-based observations. We analyze JWST/NIRSpec observations obtained 66.5 days (40.1 days in the rest frame) after the burst. We identify a SN signal using a pixel-by-pixel decomposition of the 2D spectrum and isolate it by jointly modeling the host and transient emission. We constrain the line of sight extinction from the afterglow spectral energy distribution and characterize the host through broadband photometry and nebular emission lines. Despite a dusty line of sight ($A_V=1.37\pm0.08$ mag), with tentative evidence of a 2175 Å bump, and a bright host
galaxy ($M_B=-20.5$ AB mag), we identify a point-like source at the GRB position with broad spectral features similar to those of SN 1998bw. The SN contributes $\sim$10-15% of the NIRSpec flux and would contribute only $\sim$1% of the total flux in a ground-based optical image at the same epoch. Its extinction-corrected luminosity is comparable to SN 1998bw, although it remains sensitive to the host subtraction and template assumptions. The host is an extended, dusty,
star-forming
galaxy with $\log(M_\star/M_\odot)=10.12\pm0.05$, SFR $=5.88\pm1.60\,{\rm M_\odot\,yr^{-1}}$, and a super-solar
metallicity of $12+\log({\rm O/H})=8.87\pm0.04$, above the
metallicity typically observed for collapsar GRB hosts. The detection of a dust-obscured SN firmly establishes the massive-
star origin of GRB 240825A and shows that JWST can uncover SNe in dusty, chemically enriched environments that were previously largely inaccessible.
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All authors B. Schneider, A. J. Levan, N. Sarin, N. A. Rakotondrainibe, B. P. Gompertz, V. Buat, J. T. Palmerio, D. B. Malesani, A. de Ugarte Postigo, A. Martin-Carrillo, A. Rossi, V. D'Elia, M. De Pasquale, D. Hartmann, P. Jakobsson, E. Le Floc'h, P. O'Brien, E. Pian, G. Pugliese, A. Raidani, R. Salvaterra, J. Sollerman, N. R. Tanvir, S. D. Vergani, D. Watson
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
The LZ event with a two-state dark matter halo
Vinicius Oliveira
The LUX-ZEPLIN (LZ) experiment has reported a single nuclear-recoil candidate at $E_R \simeq 248$keV. LZ interprets it in terms of inelastic dark matter that scatters endothermically from its ground state, $\chi_1 N \to \chi_2 N$. In pseudo-Dirac models the excited state $\chi_2$ can survive to the present day, and exothermic scattering, $\chi_2 N \to \chi_1 N$, is then also open. The published LZ intervals do not describe this case. We rebuild the LZ statistical inference and validate it against the published intervals. We then apply it to a
halo that contains a fraction $f$ of $\chi_2$. For $f \gtrsim 10^{-5}$–$10^{-2}$, depending on the mass splitting, the exothermic contribution dominates. For $f=1/2$ the cross section required by the candidate drops by factors of $80$ to $1.6\times10^4$ for $\delta = 250$–$350$~keV, and the kinematic cutoff of the endothermic signal disappears. A
benchmark that explains the event with $\chi_1$ alone lies a factor of $30$ above the upper limit when half of the
halo is $\chi_2$.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Parameter degeneracy and information loss in inverse flavor mapping for high-energy astrophysical neutrinos
Zi-Qiang Chen, Zhi-zhong Xing and Ye-Ling Zhou
Given a high-energy astrophysical
neutrino flux, its source flavor ratios $\eta = \{\eta^{}_e, \eta^{}_\mu, \eta^{}_\tau\}$ are correlated with the ones $f = \{f^{}_e, f^{}_\mu, f^{}_\tau\}$ measured at a
neutrino telescope via $f = P \eta$, where the elements of $P$ consist of four lepton flavor mixing parameters. But realistic inverse flavor mapping $\eta = P^{-1} f$ encounters unavoidable parameter degeneracy and information loss, especially in or near the $\det P = 0$ limit allowed by current
neutrino oscillation data. In this work we explore the parameter correlation condition for $\det P = 0$ including the $\mu$-$\tau$ reflection
symmetry case, formulate the corresponding constraints on $f^{}_e$ and $f^{}_\mu$ versus $\eta^{}_e$ and $\eta^{}_\mu$, and illustrate to what extent the source flavor distribution can be mapped by using the recent IceCube all-sky
neutrino flux data ranging from 5 TeV to 10 PeV under the assumption that the relevant sources have a common flavor composition.
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High Energy Astrophysical Phenomena
Investigating signatures of extinct PeVatron activity in supernova remnants IC 443 and W51 C
Silvia Celli and Giovanni Morlino
Context.
Supernova remnants (SNRs) are renewed sources of non-thermal particles and the main contributors of Galactic
cosmic rays (CRs). Recent ultra-high energy (UHE) gamma-ray data from middle-aged SNRs, such as IC 443 and W51 C, highlight the key role of these systems for particle acceleration. Understanding SNR contribution to PeV CRs requires a detailed modelling about how accelerated particles escape their shocks and are released inside the
Galaxy. Aims. We aim at critically assessing the SNR paradigm for the origin of Galactic CRs by investigating the expected secondary radiation produced by hadronic collisions of confined and escaping
protons in SNRs, and compare these to recent UHE observations. Methods. Through a time-dependent analytical model describing particle acceleration at the SNR forward shock, we investigate particle escape from the shock expanding into uniform environment and diffusing inside and outside the SNR. Results. Our results support the interpretation that the gamma-ray emission from W51 C and IC 443 is due to hadronic emission from both confined and escaping
protons, allowing us to derive robust constraints on the particle maximum energy, the
magnetic field amplification process, and the CR acceleration efficiency in these systems. Conclusions. We find that the acceleration efficiency is in the range 1 - 10% (2 - 12%) when the spectrum of accelerated particles is proportional to p^-4 (p^-4.3) and the in-situ
diffusion coefficient is suppressed by a factor of 3-10 compared to the average Galactic value. On the other hand, the particle maximum energy ever achieved falls, by a factor of a few, below the PeV energy required to explain the CR knee in the context of SNRs only.
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High Energy Astrophysical Phenomena · Cross-listed from astro-ph.SR
First results from PADRE/MeDDEA: X-rays from a flare and its CME
Muriel Zoë Stiefel, Säm Krucker, Olivier Limousin et al. (+22 more)
The MeDDEA hard X-ray spectrometer onboard NASAs PADRE CubeSat operates four flight-spare detectors from the Solar Orbiter/STIX instrument. This paper aims to evaluate the accuracy of the MeDDEA calibration and to demonstrate that MeDDEA data are ready for scientific exploitation. Using the first joint observations between MeDDEA and STIX, we investigate faint HXR emission associated with an escaping CME relative to the emission from the full
flare. The first large
flare observed by MeDDEA is analyzed, and the MeDDEA spectrum is compared with simultaneous observations from Fermi/GBM and ASO-S/HXI. From the Solar Orbiter viewpoint, the
flare is highly limb-occulted allowing STIX to isolate high coronal emission associated with the CME while MeDDEA observed the full
flare. We combined spectral fitting with HXR/EUV imaging from STIX, HXI, and AIA to investigate the locations and energetics of the
flare- and CME-associated HXR sources. The MeDDEA spectral observations are in agreement with FERMI/GBM and ASO-S/HXI within 10 percent in the energy range of 18-30 keV. The CME-associated
photon flux observed by STIX in the nonthermal range is faint at about 1 percent of the
flare photon flux. The energy content of the thermal component associated with the CME, on the other hand, is found to be of the same order of magnitude as the thermal energy of the
flare loop, at least for a filling factor of unity. Imaging information from STIX in combination with AIA reveals that the emission measured by STIX is located within the associated CME. We report that MeDDEA provides scientifically reliable spectral observations and is ready for scientific use.
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All authors Muriel Zoë Stiefel, Säm Krucker, Olivier Limousin, Niharika Godbole, Gwendoline Marc, Amir Caspi, Kyle Gregory, Ace Stratton, Diana Renaud, Aline Meuris, Laura A. Hayes, André Csillaghy, Pascal Saint-Hilaire, Juan Camilo Buitrago Casas, Christopher Smith, Savannah Sky Perez-Piel, Anton Tremsin, Elizabeth Warren, Bradley Pafchek, Eliad Peretz, Carlos Urdiales, Reynaldo Gonzalez, Chris M. Moeckel, Juan Carlos Martinez Oliveros, Steven Christe
High Energy Astrophysical Phenomena
Jet Forecast: Timing of Discrete Jet Ejections of Stellar-Mass Black Holes Anticipated via X-ray Properties
Toshihiro Kawaguchi and Kazutaka Yamaoka
The
radio – soft $\gamma$-ray data of the Galactic black hole binary XTE J1859+226 showed that discrete jets are launched when the inner radius of the
accretion disk ($R_{\rm in}$) rapidly approaches the innermost stable circular orbit (ISCO). Given the correlations among the X-ray fractional variability amplitude (rms), $R_{\rm in}$, and the X-ray hardness, previous phenomenological findings related to jet ejections (“jet line” and sharp drops of rms) also indicate that the rapid shrinkage of $R_{\rm in}$ down to the ISCO turns on the jet formation. In order to make clear how these properties appear in other objects, we investigated the X-ray and
radio data of XTE J1550-564, GX 339-4, and MAXI J1820+070. We found that all the four sources show drops of $R_{\rm in}$ and rms 1-10 days ahead of a jet activity, and exhibit no huge jumps of the
accretion rates prior to jet ejections. XTE J1859 and MAXI J1820 show the jet activities under sub-Eddington
accretion. Models for the jet production that require an enhancement of $\dot{M}$ or a super-Eddington
accretion rate are unlikely. Another behavior common to multiple sources is the curved shape of the rms–$R_{\rm in}$ correlation. Therefore, monitoring of $R_{\rm in}$ seems to be suitable to predict the timing of jet ejections. When both $R_{\rm in}$ and rms continuously decrease and when $R_{\rm in}$ is about to reach the ISCO, alerts can be circulated as a “jet forecast” for triggering Target-of-Opportunity observations.
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High Energy Astrophysical Phenomena
From Choked to Successful: The Role of Black Hole Spin in Collapsar Jet Breakout
Rushikesh Sonawane, Krishna Kumar and Shabnam Iyyani
Long gamma-ray bursts (LGRBs) are believed to originate from the core collapse of massive Wolf-Rayet (WR)
stars, leading to the formation of a spinning black hole that powers a relativistic jet. The
prompt emission is produced once the jet emerges from the stellar envelope. We perform 2D axisymmetric RHD simulations using the PLUTO code to model semi-self-consistent,
accretion-powered jets launched by Kerr black holes. For the two progenitor models, we adopt black hole masses of $4 M_{\odot}$ and $5 M_{\odot}$ corresponding to WR
stars of $10 M_{\odot}$ and $25 M_{\odot}$, respectively. Unlike previous studies, our simulations employ continuous jet injection, with the injected power linked to black hole
spin and
accretion through an empirical relation motivated by GRMHD simulations, enabling a controlled exploration of jet energetics over $10^{48}$-$10^{52}\,\mathrm{erg\,s^{-1}}$. We investigate jet breakout for WR progenitors of $10\,M_{\odot}$ and $25\,M_{\odot}$ and identify a critical
spin threshold: jets are choked for $a \leq 0.001$ and successfully break out for $a > 0.001$. The breakout time ($t_B$) shows a correlation with jet luminosity ($L_{\rm jet}$) and
spin ($a$), revealing three regimes: Newtonian ($a \lesssim 0.03$), relativistic ($a \gtrsim 0.3$), and intermediate. A dichotomy is observed in jet head velocity at breakout, with $\beta_h \gtrsim 0.8$ for high-
spin and $\beta_h \sim 0.35$-$0.8$ for lower
spins. In the Newtonian regime, simulations yield $t_B \propto L_{\rm jet}^{-0.48}$, steeper than analytical predictions, with systematically longer breakout times indicating modified jet-head scaling. In the relativistic regime, calibrated analytical models show improved agreement, with simulations indicating efficient jet propagation.
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High Energy Astrophysical Phenomena
Emission and cooling of a newborn quark star
Mikalai Prakapenia and Gregory Vereshchagin
It has long been believed that newborn
quark stars are inefficient emitters because the
quark plasma frequency is so high that it suppresses electromagnetic radiation across the entire spectrum up to energies of several tens of MeV. Here, we show that significant electromagnetic emission can instead originate from the electrosphere of a
quark star, where the
plasma frequency is much lower, approximately 40 keV. As a result, the cooling of a newborn
quark star is expected to proceed through two distinct observational epochs. During the first epoch, blackbody radiation is emitted from the photosphere of an optically thick relativistic wind generated near the electrosphere. Over the course of a few days following the
star's formation, the photospheric temperature decreases from several MeV to about 22 keV. During the second epoch, the blackbody spectrum evolves into a narrow feature centered around 40 keV, and the emission gradually fades. This spectral
evolution provides a characteristic signature of the electrosphere surrounding compact astrophysical objects and may be detectable with current or future X-ray observatories.
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High Energy Astrophysical Phenomena
Prompt and Afterglow Constraints on the Central Engine of GRB 240825A
Daban Mohammed Saeed, Rahim Moradi, Chen-Wei Wang et al. (+2 more)
GRB 240825A shows unprecedented temporal and spectral features that constrain the properties of its inner engine: (1) a
prompt emission three-component spectrum consisting of a Band function continuum, a quasi-thermal bump, and a hard MeV tail; and (2) an X-ray afterglow fitted by a power-law decay with index $1.29 \pm 0.02$; and (3) a $6.37 \pm 0.05$ Hz quasi-periodic oscillation (QPO) identified in the 100-300 keV band during the 2.07-3.25 s time interval, coinciding with the photospheric radiation phase. We compare two central-engine candidates: (a) a newborn millisecond magnetar undergoing multipolar
spin-down, free precession, and global magnetoelastic oscillations of its interior; and (b) a Kerr black hole powering a Blandford-Znajek jet subject to Lense-Thirring disk precession. In principle, both channels can reproduce the observed QPO frequency but impose different constraints on the energetics, temporal
evolution, and the origin of the oscillation. We first demonstrate that the X-ray afterglow is quantitatively reproduced by a hexapolar magnetar
spin-down model with an initial
spin period of $P_0 \simeq 1.38$ ms and a surface field of $B_{\rm hexa} \simeq 2.04 \times 10^{16}$ G. The decay index measures a braking index rather than the field multipolarity, does not exclude a fallback-regulated flow, and leaves $P_0$ and $B_{\rm hexa}$ uncertain by a factor of a few. In this scenario,
magnetic or magnetoinertial dynamics of the
star interior provide a plausible explanation of the QPO without invoking extreme stellar deformations. Although a black hole engine cannot be firmly excluded, the combined
prompt and afterglow observational properties of GRB 240825A favor a long-lived magnetar central engine.
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All authors Daban Mohammed Saeed, Rahim Moradi, Chen-Wei Wang, Brwa Shukur Ismael, Marco Muccino
High Energy Astrophysical Phenomena · Cross-listed from astro-ph.SR
Limits on eccentricity excitation by tidally enhanced mass loss in Wolf-Rayet binaries
Viktória Fröhlich and Zsolt Regály
Wolf–Rayet (WR) binaries frequently display high orbital eccentricities, and their eccentricity distributions are inconsistent with that of high-mass Galactic field binaries at high significance. This raises the question of whether these eccentricities are primordial or generated during the WR phase. We test whether a tidal enhancement of the mass-loss rate can pump the eccentricity of a WR binary on a sample of 14 WR systems. We model each system as a variable-mass two-body problem and integrate the orbital
evolution over the WR lifetime under three prescriptions: i) adiabatic isotropic mass loss, ii)
equilibrium-tide circularization, and iii) a tidally enhanced, pericenter-focused mass loss in which the companion-facing reduction of the effective surface
gravity raises the local Eddington parameter. Adiabatic mass loss can not change eccentricity and affects only the orbital separation, which increases by up to a factor of ~20. Tidal circularization is effective only in the tightest orbits, which are compatible with the observed systems only for high mass-loss rates, a regime in which any primordial eccentricity is erased. The tidally enhanced mass loss channel pumps the eccentricity by only $\leq10^{-4}$, three to four orders of magnitude below the observed values, and therefore cannot be the responsible mechanism. We conclude that the high eccentricities of WR binaries are predominantly primordial rather than generated by mass loss during the WR phase.
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High Energy Astrophysical Phenomena
Unexpected Gamma-ray Outburst from the CSS Radio Galaxy 3C 216
Stefano Ciprini and Federica Giacchino
While compact steep-spectrum (CSS)
radio galaxies, genuine young/intermittent-jet or frustrated-jet
radio galaxies trapped in gas-rich environments, are rarely detected in GeV gamma-ray energy bands, 3C 216 is an interesting exception. In 2023, the Large Area
Telescope (LAT) on board the Fermi Gamma-ray Space
Telescope detected an unexpected, rapid, and powerful GeV gamma-ray outburst from this CSS
radio galaxy, which was followed up by UV and X-ray observations from the Neil Gehrels Swift Space Observatory. During the outburst its spectral energy distribution is dominated by synchrotron and synchrotron self-Compton radiation, produced in the relativistic jet, suggesting a young
quasar classification.
Radio-band features, such as superluminal motion and a flat-spectrum core component, confirm that 3C 216 harbors a distinct blazar-like core, bent and viewed under a small angle to the line of sight. This is the unique large and energetic event from the source observed in 17 years of Fermi-LAT continuous all-sky and time-domain monitoring.
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High Energy Astrophysical Phenomena
Gravitational Waves from Core-Collapse Supernovae: Dependence on the Progenitor Star, Rotation Rate and Nuclear Equation of State
Jade Powell, Bailey Sykes and Bernhard Müller
We simulate 137 axisymmetric core-collapse
supernova explosions to systematically investigate the impact of different progenitor properties, rotation rates, and equations of state on the
supernova gravitational-wave emission. We use 15 different progenitor
stars, with masses ranging from $9.71\,\mathrm{M}_{\odot}$ to $36.61\,\mathrm{M}_{\odot}$, three equations of state, and three rotation rates, with durations extending up to 5.5\,s after bounce. We find substantial differences in the gravitational-wave emission between equations of state, with the CMF equation of state producing lower gravitational-wave amplitudes and a longer low frequency mode due to the standing
accretion shock instability that remains visible even at $\sim5$\,s post bounce. Rapid rotation also significantly alters the gravitational-wave signal, with more visible modes in the gravitational-wave emission, and lower energies due to later shock revival times. We include the gravitational-wave emission due to
neutrino memory, and show it can significantly improve the detectability of core-collapse
supernovae for observatories with improved low frequency sensitivity. We propose a recalibration of universal relations for the high frequency mode, using fits to our waveforms, that reduces the fit error at late times in the gravitational-wave signal. Finally, we investigate, for the first time, the impact of random seed perturbations on the gravitational-wave emission. We find that
stochastic perturbations can produce dramatic variations in gravitational-wave amplitude, and can alter the signal-to-noise ratio of a detection by as much as 62% for models close to the boundary between failed and successful shock revival.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Medium effects on neutron star modified and direct Urca cooling rates
B. X. Zhou, Jin-Biao Wei, Z. H. Li et al. (+2 more)
We study the effects of in-medium modification of the elementary cooling processes on observable properties of isolated
neutron stars. We then deduce the
neutron star mass distributions compatible with the cooling analysis and compare with current theoretical models. We conclude that current cooling data require fast direct Urca (DU) cooling, moderated by
proton superfluidity, to be active in most
neutron stars, and that the DU onset threshold must lie below canonical masses. In that case medium modifications of modified Urca (MU) rates are practically insignificant, but the $nn$ Bremsstrahlung rate plays a dominant role.
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All authors B. X. Zhou, Jin-Biao Wei, Z. H. Li, G. F. Burgio, H.-J. Schulze
High Energy Astrophysical Phenomena
Comment on "Fermi-LAT Galactic Center Excess Morphology of Dark Matter in Simulations of the Milky Way Galaxy"
Kevork N. Abazajian, Jason Kumar and Oscar Macias
Muru et al. [Phys. Rev. Lett. 135, 161005 (2025)] conclude from the HESTIA constrained simulations that the $\gamma$-ray morphologies of the Galactic Center Excess predicted by dark matter annihilation and by an old stellar population are essentially indistinguishable. Their "quadratic dark matter" maps, however, show the square of the mass projected along the line of sight, $\bigl[\int\rho\,s^{2}\,ds\bigr]^{2}$, rather than the annihilation integral $\int\rho^{2}\,ds$. Squaring a nonnegative map preserves its isophote shapes at corresponding intensity levels, as confirmed by the reported contour axis ratios. The corrected calculation on the same simulations does not support their conclusion.
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High Energy Astrophysical Phenomena
Discovery of a 62-min long-period transient with near-orthogonal rotator geometry
Scott D. Hyman, Natasha Hurley-Walker, Dale A. Frail et al. (+2 more)
We report the serendipitous discovery of J155543.7$-$563102 (hereafter LPT J1555$-$5631) with a period of 62.2 min in MeerKAT and ASKAP survey data. The source emitted bright (10-30 mJy), steep-spectrum ($\alpha\sim-1.5$), highly polarized
radio pulses during a 15-hr active window in May 2022, with no other quiescent or pulsed emission detected before or after over $\sim5$ years. The mean light curve exhibits two alternating pulses per cycle. A main pulse (MP) and an interpulse (IP) separated by $\Delta\phi=165.4^\circ$ with similar amplitudes, but different polarization properties: the wider MP (3.9%) is partially linearly and circularly polarized and shows a constant polarization position angle, while the narrow IP (1.1%) is $\sim$100% circularly polarized. We classify LPT J1555$-$5631 as a near-orthogonal rotator, for which emission from both
magnetic poles is visible during one rotation and the
magnetic and rotation axes are almost perpendicular. The 14.6$^\circ$ deviation from an antipodal separation and the nearly constant polarization position angle suggest that the emission does not arise from the standard dipolar polar-cap geometry of ordinary
pulsars, but instead originates within a broader, more complex magnetosphere. The observed properties of LPT J1555$-$5631 can be accommodated by extended emission regions, and favor coherent emission mechanisms such as the electron cyclotron maser instability, although they do not uniquely determine the progenitor or emission physics. If these inferences apply more broadly to the LPT population, they could account for why their beam widths are decoupled from rotation periods, the prevalence of flat polarization position angles, and may favor an elevated incidence of orthogonal rotators.
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All authors Scott D. Hyman, Natasha Hurley-Walker, Dale A. Frail, Emil Polisensky, W. D. Cotton