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Physics Astrophysics High Energy Astrophysical Phenomena

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Wednesday 7 October

High Energy Astrophysical Phenomena

Evidence for a Similar Physical Origin Between Prompt Emission and X-Ray Flares of Gamma-Ray Bursts

Wen-Yuan Yu, Wen-Long Zhang and Hou-Jun Lü

Statistical properties of X-ray flares are highly similar to those of the prompt emission in gamma-ray bursts (GRBs), suggesting that they may share a common physical origin (e.g., central engine activity). However, comparable statistical studies of afterglow X-ray flares and prompt gamma-ray pulses that are not observed simultaneously remain incomplete. In this paper, by systematically searching for gamma-ray emission simultaneous with X-ray flares, we identify 38 GRBs containing 50 pulse–flare pairs, 19 of which have measured redshifts. We perform joint temporal and spectral analyses of the gamma-ray pulses and X-ray flares over their overlapping time intervals, and find that the spectrum of each pair can be well described by an absorbed power-law (PL), PL plus blackbody (PL+BB), cutoff power-law (CPL), and Band function. More importantly, by applying self-organized criticality (SOC) analysis to both the prompt gamma-ray pulses and the simultaneously observed X-ray flares, we find that the temporal parameters (e.g., waiting time, rise time, peak time, decay time, and duration) of the two components follow similar power-law distributions, with the largest absolute difference of $\Delta\alpha\sim0.36$ for the waiting time and much smaller differences ($\Delta\alpha\lesssim0.12$) for the other four parameters. For the isotropic energy derived from the subsample with measured redshifts, the difference between the two components is $\Delta\alpha\sim0.54$. These results suggest that the X-ray flares and the prompt emission are likely to share the same physical origin.
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High Energy Astrophysical Phenomena · Cross-listed from astro-ph.SR

ASTRAL: A Framework for Optimal Placement and Emulation of Stellar Evolution Models

Trevor Gravely, Marko Ristić and Brandon Barker

Generating dense grids of detailed stellar evolution simulations is computationally prohibitive, as resolving progressively complex nucleosynthesis chains and dynamical timescales incurs a rapidly increasing computational cost that scales with dimensionality and resolution. Existing simulation grids are sparse, heterogeneous, and often cover disparate regions of parameter space, limiting (direct) systematic comparison and broader generalization to downstream science analyses. We present ASTRAL (Active Simulation Tuning and Regression for Astrophysical Libraries), a publicly available framework for optimal placement and emulation of stellar evolution models. The ASTRAL framework builds surrogate models that provide a continuous representation of the parameter space which is populated by sparse simulation grids. Furthermore, ASTRAL interpolates across the simulation parameter space (e.g. zero-age-main-sequence mass) to predict stellar properties of stars with associated uncertainty estimates for systems not explicitly simulated. We show that ASTRAL significantly outperforms uniform placement in constructing emulation-ready model libraries that capture both global and local variability in the output features. We showcase the performance of our framework in the context of a simple, one-dimensional MESA model. Finally, we examine how our methodology can inform downstream applications by analyzing our emulator's predictive confidence when applied to supernova simulations. We emphasize that, while developed for stellar evolution, the ASTRAL framework is directly extensible to other simulation-driven domains where model evaluations are expensive and parameter spaces are high-dimensional.
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High Energy Astrophysical Phenomena · Cross-listed from physics.hist-ph

The contribution of Soviet scientists to the emergence of high-energy neutrino astrophysics: from the Cherenkov effect to underwater and in-ice telescopes

Bakhromzod Rizoi

The 2026 Nobel Prize in Physics was awarded to Francis Halzen @for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin.@ This article examines the Soviet contribution to the broader historical development of high-energy neutrino astrophysics. Four interconnected strands are distinguished: the physics of Cherenkov radiation and its application to cosmic rays; early proposals for large-scale neutrino detection underground and in natural water; the theory of atmospheric, cosmogenic, and astrophysical neutrinos; and the development of underground, underwater, radio, and in-ice detection techniques. The article shows that M. A. Markov s 1960 proposal was concerned primarily with atmospheric neutrinos and with detecting charged secondary particles through Cherenkov radiation in water, whereas the use of Antarctic ice was initially developed in the Soviet Union in the radio domain. The optical concept of a detector in deep polar ice was formulated by F. Halzen and J. G. Learned in 1988. The Pamir cosmic-ray school, the theoretical work of G. T. Zatsepin, V. A. Kuzmin, and V. S. Berezinsky, the Baksan Neutrino Observatory, Soviet participation in DUMAND, and the formation of the Lake Baikal neutrino program are considered separately. The Pamir material is included as historical and methodological context; it does not imply a direct experimental lineage from Pamir installations to IceCube. The historical links of these strands to IceCube are therefore different in character: conceptual and citation-based in some cases, methodological or institutional in others. This distinction helps separate documented continuity of ideas from the broader scientific context in which modern high-energy neutrino astronomy emerged.
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High Energy Astrophysical Phenomena

Axion effects on hybrid stars: earlier hadron-quark phase transition and larger quark-matter cores

Yu-Heng Liu, He Liu, Hong-Ming Liu et al. (+3 more)

We investigate the effects of axions on the properties of hybrid stars and the possible hadron-quark phase transition in their cores within the Maxwell construction. The hadronic phase is described by the improved isospin- and momentum-dependent interaction (ImMDI) model, while the quark phase is modeled by a three-flavor Nambu–Jona-Lasinio (NJL) model with an axion-modified Kobayashi-Maskawa-'t Hooft (KMT) interaction. Based on the obtained equation of state, we analyze the properties of hybrid-star matter, including the speed of sound and the polytropic index, as well as the structural characteristics of hybrid stars, including the mass-radius relation and the properties of the quark core. Our study shows that the axion field $a/f_a$ slightly stiffens the equation of state of quark matter but significantly shifts the hadron-quark phase transition to lower baryon densities. These two effects compete in influencing the equation of state of hybrid-star matter, and may even soften it, which is different from the effect of the vector coupling interaction. Consequently, the axion field has only a weak influence on the maximum mass of hybrid stars, but significantly increases the mass and radius of the quark core, especially for weak vector coupling. These results indicate that, within the present Maxwell construction, the primary role of the axion is to promote an earlier hadron-quark transition at low densities and to enlarge the quark core.
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All authors Yu-Heng Liu, He Liu, Hong-Ming Liu, Min Ju, Xu-Hao Wu, Peng-Cheng Chu

High Energy Astrophysical Phenomena

Polarised X-ray emission from the accreting millisecond pulsar SAX J1808.4-3658 during an X-ray outburst and a type-I X-ray burst

A. Papitto, A. Di Marco, M.C. Baglio et al. (+22 more)

Modelling the X-ray pulse profiles of accreting millisecond pulsars (AMSPs) is a key technique to constrain the masses and radii of neutron stars. To this end, measuring the properties of polarised X-rays provides crucial information on the system geometry. We present the significant detection by IXPE of linearly polarised 2-8 keV X-rays during the decay of the 2025 outburst of the 2.5 ms AMSP SAX J1808.4-3658, with an average polarisation degree of $2.9\%\pm0.5\%$ and a polarisation angle of $46{\deg}\pm5{\deg}$, broadly consistent with the direction observed in the optical band. This level of polarisation is similar to that found in the only other source of this class that has been targeted so far. By using a pulse-phase timing solution obtained with IXPE and NuSTAR, which confirms the long-term evolution of the pulsar spin and orbit, we did not find any significant pulse phase-resolved variability in the Stokes parameters. Interpreting the polarised X-rays as originating from hot spots on the NS surface indicates they are almost aligned with the spin axis. We also report an indication for linearly polarised emission with a degree of $16\%\pm6\%$ (2-6 keV) during the peak of a type-I thermonuclear X-ray burst, with an angle almost orthogonal to that of the persistent emission. If confirmed, this level would exceed expectations for X-rays reflected by a thin accretion disc.
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All authors A. Papitto, A. Di Marco, M.C. Baglio, D. Baldi Tomei, C. Ballocco, G. Illiano, R. La Placa, C. Malacaria, A. Bobrikova, J. Poutanen, T. Salmi, A. Sanna, A. Veledina, F. Ambrosino, L. Burderi, S. Campana, F. Coti Zelati, D. de Martino, T. Di Salvo, G.L. Israel, F. La Monaca, A. Marino, A. Miraval Zanon, M. Pilia, L. Stella

High Energy Astrophysical Phenomena

The Prompt Emission of Gamma-Ray Bursts from Population III Stars

Nathan Walker, Davide Lazzati, Tyler Parsotan et al. (+4 more)

Population (Pop) III stars, the first generation of stars in the Universe, have eluded direct detection for decades. The advent of the James Webb Space Telescope, with its unprecedented sensitivity to high-redshift sources, has renewed interest in the prospects for identifying these primordial stars. While previous studies have explored the direct detection of Pop III stars through gravitational lensing, here we investigate an alternative approach: identifying Pop III stars through gamma-ray bursts (GRBs) produced by the deaths of massive Pop III progenitors. We generate source-frame mock observables and find that, although Pop III and Pop I GRBs share many common properties, several observables can potentially distinguish between the two populations. In particular, light-curve timescales, isotropic-equivalent energies, peak energies, and the locations of GRBs in empirical prompt-emission correlations depend sensitively on the mass and explosion energy of the progenitor. We find that Pop III GRBs tend to exhibit longer characteristic timescales and higher isotropic-equivalent peak energies than their Pop I counterparts. Finally, we show that Pop III GRBs may provide a promising origin for the population of soft X-ray prompt emission recently detected by the Einstein Probe, offering a complementary avenue for probing the first generations of stars.
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All authors Nathan Walker, Davide Lazzati, Tyler Parsotan, Rosalba Perna, Matteo Cantiello, Jake Hassan, Brian Morsony

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Anisotropic Fluid Model for Massive Boson Stars: Spherically Symmetric Configurations

Ethan McKeever, Victor Guedes, Shu Yan Lau et al. (+1 more)

Boson stars are among the best-studied exotic compact objects and constitute one of the few black-hole mimickers for which both the formation mechanism and dynamical behavior can be investigated from first principles. Constructing boson star solutions is generally more challenging than constructing neutron star solutions, often requiring either extremely accurate initial guesses for the oscillation frequency or the use of computationally intensive relaxation methods to solve the field equations. In the strong-coupling limit, massive boson stars can be described effectively as perfect- fluid configurations, enabling their construction using methods analogous to those developed for neutron stars. In this paper, we relax the strong-coupling assumption and derive a phenomenological anisotropic-fluid model for spherically symmetric massive boson stars that remains applicable over a broad range of model parameters. We provide ready-to-use fits for both the anisotropy profile and the effective equation of state in terms of the central scalar-field amplitude and the ratio of the self-interaction coupling constant to the squared scalar-field mass. To validate the model, we compute the masses and radii of boson stars using a standard neutron-star construction approach and compare the results against full boson-star calculations. We find excellent agreement between the two methods, while the new approach reduces the computational cost by a factor of about 10. Our phenomenological fluid framework offers an efficient and accurate method for constructing spherically symmetric massive boson stars and computing their observable properties. We provide a ready-to-use Python implementation of the Tolman-Oppenheimer-Volkoff solver, allowing users to construct boson star configurations within the proposed framework.
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All authors Ethan McKeever, Victor Guedes, Shu Yan Lau, Kent Yagi

Tuesday 6 October

High Energy Astrophysical Phenomena

An All-Sky Search for Moving Gamma-Ray Sources with Fermi-LAT

Dou Lai and James Unwin

Nearby compact gamma-ray sources can move appreciably during the Fermi-LAT mission and thus evade searches that assume a stationary sky. Compact dark matter halos, dark matter spikes around primordial black holes (PBH), and evaporating PBH provide potential examples. We perform a novel all-sky search for steady point sources moving at 0.25 deg/yr-0.8deg/yr in ten years of 1-100 GeV Fermi-LAT data. For a transverse speed of 200 km/s, this angular range probes distances of roughly $3.0\times10^3$ AU to $9.7\times10^3$ AU. We find 577 candidate tracks, consistent with $533\pm27.0$ tracks in time-scrambled skies. We place a model-independent 90% upper limit of 80.8 recovered signal tracks. At peak calibrated sensitivity, this corresponds to fewer than 123 steady, full-sky sources with an incident $E^{-2}$ photon spectrum. We give the calibrated detection efficiency of the search to steady point sources and use it to derive illustrative constraints on both evaporating PBHs and PBHs surrounded by annihilating dark matter halos.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Toward a complete understanding of the properties of GW190521

Aasim Jan, Sophia Nicolella, Aaron Zimmerman et al. (+4 more)

Interpreting GW190521 remains challenging due to its exceptionally high total mass and correspondingly small number of observable gravitational-wave cycles, which gives rise to degeneracies between different physical interpretations. Motivated by the outstanding questions surrounding the event, we present a comprehensive reanalysis of GW190521 using waveform models drawn from multiple families, including a model that includes both eccentricity and spin-precession. We find evidence that the source was highly eccentric, with an inferred eccentricity of $0.81^{+0.05}_{-0.01}$ at 5 Hz, and show that non-eccentric interpretations arise from failing to probe the high-likelihood region at large eccentricities. We further demonstrate that when eccentricity is included in the analysis, there is no indication of spin precession, suggesting that the apparent precession in quasicircular analyses is at least partially driven by an eccentricity–spin-precession degeneracy. While all waveform models favor a comparable-mass binary, one model admits a secondary mode at more asymmetric masses. We find a robust probability $(\geq97\%)$ that the primary black hole lies within the pair-instability supernova mass gap ($\sim60-130\,M_\odot$), whereas the probability that the secondary lies in the gap depends on the waveform model. Through inference of GW190521-like injections, we show that the waveform systematics observed in the analysis of GW190521 could arise from the response of models to unmodeled eccentricity, rather than from intrinsic differences between waveform models. When analyzing a quasicircular spin-precessing injection similar to GW190521, we find no significant model dependence in the inferred parameters. Finally, because the inferred eccentricity lies beyond the calibration regime of current models, we test its robustness by recovering highly eccentric numerical-relativity waveforms.
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All authors Aasim Jan, Sophia Nicolella, Aaron Zimmerman, Deirdre Shoemaker, Katerina Chatziioannou, Richard O'Shaughnessy, Muhammed Saleem

High Energy Astrophysical Phenomena · Cross-listed from astro-ph.IM

A method for multimodal analysis of TAIGA experiment data using essential features

Alexander Kryukov, Julia Dubenskaya, Elena Fedotova et al. (+6 more)

The aim of processing and analyzing experimental data from physical experiments is to obtain physically significant information about the phenomenon under study. This goal is achieved by multi-stage processing of experimental data, during which noise associated with measurements is suppressed and the dimensionality of the input data is reduced. In this paper, we propose a new method based on the use of neural networks such as autoencoders to extract essential features. The special value of the proposed approach lies in the possibility of its application to the analysis of multimodal data received simultaneously from several installations. We will apply this approach to a multimodal data (MMD) of the experiment TAIGA. Currently, the analysis of the MMD is carried out independently for each installation separately. Therefore, the development of methods for the joint analysis of MMD from TAIGA-type installations is an urgent task in cosmic ray physics and gamma-ray astronomy. Based on Monte Carlo simulation, it is shown that the proposed method allows for effective MMD analysis. It can also be used for MMD analysis at other experimental complexes.
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All authors Alexander Kryukov, Julia Dubenskaya, Elena Fedotova, Elizaveta Gres, Stanislav Polyakov, Eugene Postnikov, Alexander Razumov, Pavel Volchugov, Dmitry Zhurov

High Energy Astrophysical Phenomena

Can LISA See Inside the Little Red Dots?

Samuel Gómez Gómez, Xisco Jimenez Forteza, Carlos Palenzuela et al. (+1 more)

The Little Red Dots (LRDs) are compact, broad-line sources that appear to contain accreting black holes (BHs) embedded in dense gas. Proposed models for their central environments (including quasi-stars, radiative BH envelopes and super-Eddington accretion discs) predict gas densities at the radii probed by an extreme-mass-ratio inspiral that differ by many orders of magnitude. We compute the inspiral of a $10$–$30\Msun$ BH for a range of LRD interior models, including environmental effects from the gas, and test with a mismatch criterion whether the resulting waveforms can be distinguished from vacuum and from one another. Dense interiors (Bondi-like free-fall cavities and radiative envelopes) produce measurable deviations from vacuum in essentially every detectable event. Convective quasi-star interiors are measurable for $\MBH\lesssim10^5\Msun$ and $z\lesssim0.6$, while a co-rotating disc leaves no measurable imprint. In favorable cases the models are also mutually distinguishable. None of the 14 JWST LRDs at $z>3.9$ would be detectable with a $10\Msun$ companion, but 30 of 31 LRDs at $z<0.9$ would be if their black holes are $\sim100$ times less massive than their virial estimates, and in many of them the interior's imprint would be measurable. Across the LRD population to $z=6$, a 4-yr LISA mission would yield $0.08$–$0.8$ detectable events for $10^5\Msun$ hosts and $10\Msun$ companions ($1.5$–$15$ for $30\Msun$) if LRD nuclei host inspirals at the rate of ordinary galactic nuclei. In dense clusters, where captures are plunges, this falls to $\lesssim10^{-4}$.
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All authors Samuel Gómez Gómez, Xisco Jimenez Forteza, Carlos Palenzuela, Rosalba Perna

High Energy Astrophysical Phenomena

Predictions for Short Gamma-Ray Burst Detections by COSI

Eliza Neights, Eric Burns, Nicolò Parmiggiani et al. (+21 more)

The Compton Spectrometer and Imager (COSI) is a soft gamma-ray telescope scheduled to launch in 2027. COSI will trigger onboard the spacecraft in response to short-duration transients, including gamma-ray bursts, and it will promptly disseminate alerts which include localizations to the community. This will enable rapid follow-up observations of the afterglow and associations with transients identified by other instruments. By simulating COSI observations of short gamma-ray bursts (sGRBs) and processing them with the trigger algorithm which will run onboard the spacecraft, we estimate the sensitivity of COSI to sGRBs. We then convolve this with a simulated set of sGRBs representing the intrinsic population in the universe to predict the rate that will be detected by COSI. We find that COSI is expected to trigger on $\sim$47-89 sGRBs per year with $\sim$7-10 localized to within 2.5{\deg}. With the gravitational wave sensitivity anticipated in the O5 run, we predict 0-3 joint detections with gravitational waves.
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All authors Eliza Neights, Eric Burns, Nicolò Parmiggiani, Yong Sheng, Savitri Gallego, Aldo Aguilar-Nadalini, Aaron C. Trigg, Sylvain Guiriec, Koothodil Abhijith Augustine, Matthew G. Baring, Anna L. Butterworth, Hsiang-Kuang Chang, Che-Yen Chu, Niccolò Di Lalla, Christopher Fryer, Hadar Lazar, Israel Martinez-Castellanos, Marion Sudvarg, Péter Veres, Steven E. Boggs, Dieter H. Hartmann, Carolyn A. Kierans, John A. Tomsick, Andreas Zoglauer

High Energy Astrophysical Phenomena

PEARLS: NuSTAR and XMM-Newton Extragalactic Survey of the JWST North Ecliptic Pole Time-Domain Field V: Unraveling X-ray Spectral Variability

Samantha Creech, Francesca Civano, Daniel Wik et al. (+13 more)

As one of the first deep time-domain surveys in the hard X-ray band, the NuSTAR campaign in the JWST North Ecliptic Pole Time Domain Field (NEP-TDF) offers a prime opportunity to measure variability in a faint population of Active Galactic Nuclei (AGN) in the medium-to-high redshift universe. In the X-ray band, AGN variability is generally caused by changes in the brightness of the corona ($F_{int}$ variability) or changes in the column density of obscuring material near the SMBH ($N_H$ variability). Broad-band spectroscopy ($\sim$0.5-24 keV) is required to reliably disentangle these two phenomena. With simultaneous NuSTAR and XMM-Newton coverage—as well as 1.8 Ms of Chandra monitoring—the X-ray surveys in the NEP-TDF are ideally situated for this purpose. This work presents the first spectral modeling of the 52 NuSTAR-identified sources discovered in the latter half of the campaign, as well as a spectroscopic variability study of the entire 112-source NuSTAR NEP-TDF catalog. Seven variable candidates are identified. We find that $\gtrsim 1000$ total counts split across many ($\gtrsim 10$) epochs are needed in order to detect variability. Additionally, variable sources are compared to the survey sensitivity in order to inform population synthesis models of how variations can affect the detectability of faint AGN, which dominate the SMBH accretion history. Lastly, the timescale of $N_H$ variability is investigated as a probe for the obscurer location. Significant variability is slightly more common on $> 100$ day timescales, suggesting that the torus may have only slight dominance in driving $N_H$ variability in faint AGN.
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All authors Samantha Creech, Francesca Civano, Daniel Wik, Núria Torres-Alba, Ross Silver, Xiurui Zhao, Tonima Ananna, Gibson Bowling, Norman A. Grogin, Anton M. Koekemoer, Peter Maksym, Sylvia Mesicek, Rafael Ortiz III, Payaswini Saikia, Steven Willner, Rogier Windhorst

High Energy Astrophysical Phenomena

A Newly Identified Transient Ultraluminous X-ray Source in M31

Ferdinand, Murray Brightman, Jean-Marie Hameury et al. (+9 more)

Ultraluminous X-ray sources (ULXs) are off-nuclear X-ray sources with luminosities exceeding the Eddington limit of typical stellar-mass compact objects. While most known ULXs are relatively persistent sources, transient ULXs have emerged as a distinct population that offer unique insight into extreme, super-Eddington accretion. We report the discovery and X-ray characterization of a newly identified transient ULX in M31. First detected serendipitously on 2021 June 9, the source reached a peak unabsorbed $0.3 - 10$ keV luminosity of $\sim10^{39}\ \rm erg\ s^{-1}$. Its spectral evolution suggests increasing advection at later epochs, opposite to the expected transition from a super-Eddington slim disk toward a standard thin disk during the decay of the outburst. The observed X-ray light curve can be reproduced using the disk-instability model of Hameury & Lasota, with characteristic timescales of $\sim41-61$ days. The inferred mass-accretion rate is super-Eddington for a $1.4\,M_{\odot}$ neutron star but approximately Eddington for a $10\,M_{\odot}$ stellar-mass black hole. Nearby optical sources from the Hubble Source Catalog suggest a possible giant donor with an age of $\log_{10}({\rm age/yr})\sim8.5$ and a mass of $\sim3.2\,M_{\odot}$, when compared with stellar isochrones with an assumed $A_V=1.58$. We estimate a transient ULX occurrence rate in M31 of $0.18\pm0.10\ {\rm yr^{-1}}$. This rate is lower than those reported for other galaxies in previous studies. M31 ULX-3 expands the small population of known transient ULXs in M31 and highlights the importance of continued, regular X-ray monitoring of nearby galaxies.
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All authors Ferdinand, Murray Brightman, Jean-Marie Hameury, Elias Kammoun, Dominic J. Walton, Matthew J. Middleton, Hannah Earnshaw, Felix Fürst, Wynn V. Jacobson-Galán, Jacob E. Jencson, Margaret Lazzarini, Mark T. Reynolds

High Energy Astrophysical Phenomena · Cross-listed from astro-ph.GA

Modeling the nanohertz gravitational wave background with the t-process: Improved frequentist analysis of gravitational-wave power

B. E. Moreschi, K. A. Gersbach, G. Shaifullah et al. (+2 more)

Pulsar timing array (PTA) collaborations have recently reported evidence for a gravitational wave background (GWB) signal in the nanohertz band, which most likely originates from the incoherent superposition of GWs emitted by a population of supermassive black hole binaries (SMBHBs). Since the number of binaries emitting in each frequency bin is finite, and since individual loud sources can dominate the GWB, the power spectral density (PSD) of the background is expected to deviate significantly from the smooth power law that describes an idealized population. PTA searches usually describe the PSD either with a power law or with a free spectrum model, which fits the PSD in each frequency bin as a free parameter. In this paper, we explore the t-process as a third model; it assumes a power law as the underlying spectrum but leaves each frequency bin free to deviate from it. We compare the performance of these three models on simulated datasets, injecting $100$ realizations of a realistic SMBHB population, to evaluate how well each model recovers a complex PSD. Using Bayesian and frequentist tools, we find that the t-process model gives the most precise PSD results, with uncertainties $43\%$ and $26\%$ narrower than those obtained with the power law and the free spectrum, respectively, while the improvement in accuracy is smaller. Moreover, using the t-process model, we compute isotropic and anisotropic signal-to-noise ratios with median gains of about $46\%$ over the power law and $65\%$ over the free spectrum in the first nine frequency bins. The t-process also returns lower anisotropy p-values and among the frequency bins with $p<0.01$, it allows to localize the loudest binary within the angular resolution of the sky maps in $14.3\%$ of the cases, compared to the $10\%$ for the power law and the $6.2\%$ for the free spectrum.
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All authors B. E. Moreschi, K. A. Gersbach, G. Shaifullah, S. R. Taylor, A. Sesana

High Energy Astrophysical Phenomena

Extreme Stellar Death and Galaxy Feedback at z = 2: A Rest-frame Ultraviolet Characterization of the Strongly Lensed Superluminous Supernova 2025wny

Willem B. Hoogendam, David O. Jones, Christopher J. Storfer et al. (+26 more)

We present photometric and spectroscopic follow-up observations of the strongly-lensed H-poor superluminous supernova (SLSN) 2025wny at $z = 2.0155$. We use integral-field Keck-II/KCWI spectroscopy to obtain rest-frame ultraviolet spectra spanning $11$ to $61$ days after maximum light. We use Pan-STARRS photometry to constrain the brightest image's magnification, finding $\mu_A=19.4\pm1.6$, a factor of $\sim$2-4 higher than mass-modeling estimates. We fit the Pan-STARRS photometry with a magnetar energy-injection model including $^{56}$Ni decay using the Modular Open Source Fitter for Transients (MOSFiT); the model can reproduce the near-maximum light curve with parameters typical of local universe SLSNe-I, including a magnetar spin period $P_{\rm spin}=4.1^{+0.7}_{-1.0}\,\mathrm{ms}$ and magnetic field $B_{\perp}=2.4^{+1.1}_{-0.8}\times10^{14}\,\mathrm{G}$; however, the late-time plateau suggests an additional power source. Spectroscopically, iron-group element line blanketing is virtually absent in the rest-frame UV spectra, and the absorption features match previously identified SLSN-I features from abundance tomography. Based on narrow ISM line metallicity estimates, SN 2025wny exploded in a sub-solar-metallicity galaxy. From host-galaxy lines in our rest-frame UV-to-optical spectrum we estimate high-velocity outflows of $\sim$575 km s$^{-1}$ and an exceptionally high Ly$\alpha$ escape fraction of $f_{esc}^{Ly\alpha}=0.23\pm0.03$. SN 2025wny matches lower-redshift SLSNe reasonably well. Upcoming surveys like LSST and Roman will discover additional high-redshift SLSNe, further testing whether SLSNe-I explosions remain consistent at the population level in the early universe.
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All authors Willem B. Hoogendam, David O. Jones, Christopher J. Storfer, Luca Izzo, Kyle W. Davis, Miranda Y. Kong, Katie Auchettl, Aadya Agrawal, David R. Aguilera-Dena, Kenneth C. Chambers, Siyuan Chen, Thomas de Boer, Ryan J. Foley, Matthew Grayling, Jason T. Hinkle, Jens Hjorth, Mark E. Huber, Chien-Cheng Lin, Thomas B. Lowe, Eugene A. Magnier, Kaisey S. Mandel, C. Tanner Murphey, Gautham Narayan, Gregory S. H. Paek, Kishore C. Patra, Haille M. L. Perkins, Armin Rest, Benjamin J. Shappee, Richard J. Wainscoat

High Energy Astrophysical Phenomena

Unveiling the Accretion Architecture of GS 1354–64: A Broadband X-ray and Polarimetric Study of its 2025–2026 Outburst

Kaushik Chatterjee

A comprehensive multi-satellite analysis of the dynamically confirmed black hole candidate GS 1354-64 during its highly active 2025-2026 outburst is presented. Leveraging simultaneous broadband spectroscopy, fast timing, and X-ray polarimetry, I map the evolution and geometry of the accretion flow. During the initial Compton-dominated hard state rise, strong, narrow Type-C quasi-periodic oscillations (QPOs) evolving from 0.08 Hz to 1.73 Hz with high fractional RMS (~8-10%) are detected, showing a strong anti-correlation with the inner disk radius (R_in) and a linear correlation with the coronal photon index (Gamma), supporting disk migration driving the precessional frequency while cooling the corona. An anomalous, highly ionized (Fe XXVI) equatorial disk wind is also observed, suggesting strong localized radiation pressure prior to the state transition. In the luminous, thermal-dominated soft state, individual-epoch reflection modeling indicated a rapidly spinning black hole (a* ~ 0.94-0.99) at inclination i ~ 45-53 deg; joint spectral modeling across these epochs refines this to i ~ 51 deg and a* ~ 0.998, with the disk pinned to the ISCO. The QPOs shifted to higher frequencies (~4.7-6.2 Hz) and weakened (RMS ~3-6%). Joint spectro-polarimetric modeling of this epoch reveals a steep, energy-increasing polarization degree, ruling out a spherical or lamppost geometry in favor of a highly asymmetric, radially extended slab-like corona. The suppression of the high-RMS QPO, combined with the strict energy-independence of the polarization angle, indicates the corona stabilized into an extended, symmetric slab, consistent with the collapse of the puffed-up spherical corona seen in the hard state.
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High Energy Astrophysical Phenomena

It Takes Two: nucleosynthesis in core-collapse supernova simulations of binary-star progenitors

Gaétan Jalin, Almudena Arcones, Evan P. O'Connor et al. (+2 more)

Binary interaction is common amongst massive stars and can significantly alter their pre-supernova structure and composition. This has important consequences for the nucleosynthetic yields and observable properties of the resulting supernovae. However, binary-evolved progenitors remain largely unexplored in modern neutrino-driven core-collapse supernova simulations. In this work, we present one- and two-dimensional core-collapse supernova simulations of single- and binary-star progenitors. We investigate the impact of binary interaction on the explosion and examine the effect of in-situ networks on the dynamics and resulting nucleosynthesis relative to post-processing approaches. Our progenitors highlight the impact of binary interaction on the pre-supernova core structure of the star and its significance for explodability. We find that binary progenitors are predicted to be generally more explodable than single stars with the same initial mass, indicating that the supernova outcome cannot be well correlated with the initial mass. However, a systematic comparison of the explosion outcomes of binary- and single-star progenitors from self-consistent simulations is still required to confirm this trend. Energy generation from nuclear reactions, as well as the abundances of key isotopes such as ${}^{56}$Ni, can be well approximated by a small $\alpha$-chain network. However, there are notable discrepancies in the production of Ti, Cr, and Fe isotopes which remain sensitive to the network size and thermodynamic history.
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All authors Gaétan Jalin, Almudena Arcones, Evan P. O'Connor, Andrea Ercolino, Norbert Langer

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Constraining the gravitational-wave breathing mode with LVK antenna patterns and GWTC data

Hong-Bo Jin and Yanyan Zheng

Metric theories of gravity admit a massless breathing scalar $b$ besides the tensor modes $+$ and $\times$. Many scalar–tensor models predict a much smaller breathing amplitude; gravitational quantum field theory (GQFT) instead allows $h_b$ comparable to the tensor amplitudes. We evaluate the LIGO–Virgo–KAGRA (LVK) antenna patterns with PyCBC, including Michelson suppression of $b$. Here $F_b$ is the breathing antenna pattern and $\mathcal{S}_b=\sum_d F_b^{d2}$ is the network breathing power. At the H1 zenith at the GW150914 epoch, $F_b\sim 5\times 10^{-6}$; for $72$ Gravitational-wave Transient Catalog (GWTC) events with packaged strain the median inclination gain in $\mathcal{S}_b$ is $\sim 34\times$. Ranking multi-detector GWTC events (network $\mathrm{SNR}\ge 8$, $\ge 2$ sites) by $\mathrm{SNR}\sqrt{\mathcal{S}_b^{*}}$ identifies loud O4 triggers and GW170817 as geometric targets. Parameter-estimation (PE) weighted $\mathcal{S}_b$ on twelve events shows that the true sky can suppress this ranking (GW170817) and that GW200129_065458, GW150914, and GW190814 have the highest PE-weighted $\mathcal{S}_b$ for $\xi$ in $h_b=\xi h_+$ (GR: $\xi\equiv 0$). An HLV design-noise injection grid gives $\ln B(\mathrm{GR}+b/\mathrm{GR})\approx 13$ ($4$) for $\xi=1$ ($0.5$) on an inclined sky ($\mathcal{S}_b\sim 0.18$); near zenith ($\mathcal{S}_b\sim 0.016$) the $\xi$ posterior remains unconstrained. The GWTC limits are semi-joint: masses and spins fixed at PE medians, while $d_L$, $\theta_{JN}$, sky, and $\xi$ vary within PE-informed priors. Eleven of twelve events are analyzed (GW170817 omitted: PE sky on the breathing null). None favors $\mathrm{GR}+b$; $|\xi|_{90\%}\approx 0.15$, $0.18$, and $0.23$ for GW150914, GW200129_065458, and GW200311_115853 disfavor $|\xi|\sim\mathcal{O}(1)$, while weaker bounds (including GW190814) still allow that scale.
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High Energy Astrophysical Phenomena

Assessing transitional pulsar candidates through a quantitative estimation of their light-curve similarity

D. F. Torres, C. R. García, F. Coti Zelati et al. (+5 more)

Transitional millisecond pulsars are often identified through X-ray light-curve morphology, especially by visual comparison with the prototype PSR J1023+0038. Such classifications remain qualitative and lack a calibrated notion of how much variability is already present within the prototype itself. We introduce a Dynamic Time Warping (DTW) framework that compares light curves through moving-window similarity distributions and calibrates candidate-prototype distances against the internal heterogeneity of PSR J1023+0038. In this formulation, a source is not simply asked to resemble one prototype observation, but to remain compatible with the range of morphologies exhibited by the prototype across observations. We apply the method to confirmed and candidate tMSPs and to a control sample of non-tMSP systems. The resulting similarity measure provides a reproducible ranking for tMSP-like behaviour and is therefore useful for candidate triage and archival searches. At the same time, the control sample shows that short-timescale accretion variability can partly mimic tMSP-like morphology, demonstrating that light-curve shape alone is a screening diagnostic rather than a definitive class identifier.
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All authors D. F. Torres, C. R. García, F. Coti Zelati, D. de Martino, G. Illiano, A. Papitto, A. Patruno, M. C. Baglio

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Line-of-Sight Acceleration-driven waveform corrections for unequal-mass compact binary coalescences

Mohd Asim Ansari, Avinash Tiwari, Sajad A. Bhat et al. (+2 more)

A constant line-of-sight acceleration (LOSA) of the centre-of-mass of a quasi-circular compact binary coalescence (CBC) leads to modulations in the gravitational-wave (GW) waveform at $-4$ post-Newtonian (PN) order. In our previous work, we calculated the phase and amplitude corrections only for the $(\ell,m) = (2,2)$ mode. The gravitational wave event GW190814 has recently attracted considerable attention because it has been suggested to provide evidence for a nonzero LOSA. However, several LOSA analyses of GW190814 employ higher-order-mode waveform models, such as IMRPhenomXPHM, while incorporating LOSA corrections only for the dominant (2,2) mode. This approximation assumes that their omission has a negligible impact on parameter estimation. In this paper, we present a self-consistent implementation of LOSA in a higher-mode waveform model by deriving the corresponding phase and amplitude corrections. We show that these corrections are essential for asymmetric binaries such as GW190814 and that neglecting them biases parameter inference. We also discuss inconsistencies in the derivation and implementation of LOSA corrections in waveform models in the literature that include higher-order modes.
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All authors Mohd Asim Ansari, Avinash Tiwari, Sajad A. Bhat, Aditya Vijaykumar, Shasvath J. Kapadia

High Energy Astrophysical Phenomena

The Potential Contribution of Radiative Supernova Remnants to the Local Cosmic Ray Spectrum

P. Cristofari, V. H. M. Phan, S. Recchia et al. (+1 more)

Recent observations of very-high-energy gamma rays from massive stellar clusters and microquasars have demonstrated that these systems can efficiently accelerate particles to very high energies, renewing the debate on the dominant sources of Galactic cosmic rays (CRs) and casting further doubt on the role of supernova remnants (SNRs), long considered the prime candidates. In these astrophysical environments, particle acceleration is generally thought to be driven by diffusive shock acceleration (DSA). The question of the duration of the phase in which DSA can efficiently take place is therefore essential to clarify the contribution of the various candidate CR sources. We aim at clarifying the contribution of SNRs to the Galactic CR spectrum, and the expected efficiency of DSA, especially accounting for possible particle acceleration during part of the radiative phase. We compute the total CR proton content at typical SNRs from DSA and reaccelerated pre-existing CRs, and discuss the importance of these two mechanisms throughout the adiabatic and early radiative phases. We find that if DSA and reacceleration take place during a fraction of the radiative phase, the total content of particles energized at SNRs can quickly overcome the typical budget required to account for the bulk of CRs. This suggests that the typical instantaneous efficiency, often defined as the fraction of fluid ram pressure converted into CRs would need to remain below $\lesssim 1$% for most of the SNR evolution. Moreover, the radiative phase can contribute to shaping the spectra injected from typical SNRs. We illustrate that the difference between SNRs from thermonuclear and core-collapse SNe could help account for the measured difference in the helium and proton of the local interstellar spectrum.
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All authors P. Cristofari, V. H. M. Phan, S. Recchia, S. Gabici

High Energy Astrophysical Phenomena · Cross-listed from astro-ph.EP

Reflex instabilities II: The reflex motion of the central object drives at least seven instabilities in accretion discs

Nathan Magnan, Michel Tagger, Clément Baruteau et al. (+3 more)

This series of papers studies the stability of accretion discs to the reflex motion of the central object under the gravitational pull of the disc itself. In this second paper, we use linear analysis to reproduce or discover seven distinct instabilities. We outline their defining characteristics and propose a classification. Of the four instabilities that had already been discovered, three are artificial: one does not survive the transition to modern surface density profiles such as power-laws, one is due to the location of the domain's boundaries, and one is due to the use of damping layers near the domain's boundaries. Only the SLING instability of Adams et al. (1989) and the three new 'cavity' instabilities seem capable of affecting accretion discs. All four can be described to a high degree of precision by WKB methods. They may drive eccentricity growth, affect planet migration, create spiral and crescent substructures in the absence of any planet, and boost accretion onto the central object. The issue is that the three artificial instabilities are extremely hard to avoid in simulations, and would bias the same observables. This suggests that our community may not have the tools to model the reflex motion of the central object yet.
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All authors Nathan Magnan, Michel Tagger, Clément Baruteau, Aurélien Crida, Jean-François Gonzalez, Héloïse Méheut

High Energy Astrophysical Phenomena · Cross-listed from astro-ph.EP

Reflex instabilities I: Boundaries makes grid-based disc simulations frame-dependent

Nathan Magnan, Michel Tagger, Clément Baruteau et al. (+3 more)

If the mass distribution within an accretion disc is asymmetric, it will exert a gravitational pull on its central object. The central object must then move away from the origin of the reference frame, resulting in atypical gravitational pulls on the disc. The goal of the present series of papers is to investigate the stability of this feedback loop. In this first paper, we report a surprising finding: the choice of reference frame affects the number and nature of the waves and instabilities contained in the analytical equations. To show this, we use a simple example: the modes discovered by Sanchez et al. (2025, Appendix A.3). We provide the first analytical description of those modes, we explain their physical mechanism, and propose to call them 'bracket modes' because they arise from the bracket side of an integration by parts. We show that the same disc can be stable in the stellocentric reference frame but unstable in the barycentric reference frame. This is because the boundaries of the simulation domain are frame-dependent. To avoid this, one must model the entire disc all the way from the central cavity to the outer edge. But this is prohibitively expensive, and some discs do not have a central cavity anyway. Our results suggest that extreme caution is required when interpreting simulations of asymmetric discs, and that our community may not have the tools to model the reflex motion of the central object yet.
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All authors Nathan Magnan, Michel Tagger, Clément Baruteau, Aurélien Crida, Jean-François Gonzalez, Héloïse Méheut

High Energy Astrophysical Phenomena

Predicting High-Energy neutrino emission from X-ray absorption in CSM-interacting SNe

Silvia Gagliardini, Simone Dall'Osso and Dafne Guetta

Core-collapse supernovae (CCSNe) interacting with a dense circumstellar medium (CSM) are promising sources of high-energy neutrinos. Most neutrino predictions rely on specific assumptions about the CSM density profile and progenitor mass-loss history. We develop a data-driven framework that connects X-ray observations directly to the expected neutrino signal. Using the temporal evolution of the hydrogen-equivalent absorbing column density, N_H(t), together with the shock velocity inferred from the X-ray plasma temperature, we reconstruct the CSM density profile and shock velocity evolution. We estimate the shock-breakout (SBO) epoch and the resulting neutrino emission, and apply the method to the nearby interacting supernovae SN 2023ixf and SN 2024ggi. For both sources, we compute the expected neutrino event rates for IceCube and KM3NeT/ARCA. We find that neutrino production is concentrated near SBO, when hadronic interactions are most efficient. This naturally defines a short time window, specific to each source, that maximizes the signal-to-background ratio. Our results demonstrate that X-ray observations can constrain at once both the expected neutrino signal and the optimal time window for its detection, providing an observationally-driven strategy for multimessenger searches of these shock-powered transients.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Line-of-sight Acceleration Driven Effects in Eccentric Compact Binary Coalescences

Mohd Asim Ansari, Avinash Tiwari, Sajad A. Bhat et al. (+2 more)

The line-of-sight acceleration (LOSA) effect, imprinted in the gravitational wave (GW) signal of an inspiralling compact binary by an external gravitational potential, is one of the most promising means of probing the environment of compact binaries on a single-event basis. However, this effect is potentially degenerate with other low-frequency effects, particularly the binary's orbital eccentricity. LOSA effects and orbital eccentricity can mimic each other if only one or the other (but not both) are accounted for in the waveform template. In this work, we present the (2, 2) mode, leading eccentric harmonic, frequency-domain phase correction incurred by an accelerating eccentric compact binary, and discuss inconsistencies pertaining to this phase correction in the literature. We show that the degeneracy between LOSA and orbital eccentricity can be resolved if both effects are modeled in the template. To demonstrate this, we inject a GW170817-like signal, with eccentricity and LOSA added to it, and recover the parameters of the injected signal assuming an A+ like noise power spectral density (PSD) of the LVK detector network. We find that the true LOSA and eccentricity parameters, along with other binary parameters, are recovered within the $90\%$ credible interval (CI). This study highlights the importance of incorporating LOSA in eccentric waveform models to robustly and reliably estimate LOSA and eccentricity.
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All authors Mohd Asim Ansari, Avinash Tiwari, Sajad A. Bhat, Sreejith Nair, Shasvath J. Kapadia

High Energy Astrophysical Phenomena

Probing turbulence in the ionized interstellar medium using young pulsars. I. Dispersion measure variations

S. J. I. Melfor, A. Parthasarathy, S. Johnston et al. (+9 more)

Temporal variations in the dispersion measure (DM) of pulsars probe fluctuations in the free-electron density of the ionized interstellar medium (IISM). While DM variations have been studied extensively in millisecond pulsars, young pulsars provide a complementary probe due to their lines of sight (LoSs) intersecting supernova remnants, pulsar wind nebulae, and other turbulent environments. However, systematic studies of DM variability in young pulsars remain limited. In this paper, We characterize the temporal DM variations of a large population of young pulsars to constrain the turbulence of the IISM along their LoSs and to investigate the physical origins of the observed variability. We analyzed 18 years of timing observations of 364 young pulsars obtained with the Murriyang/Parkes radio telescope, combining legacy data from the 21 cm Multibeam receiver with recent observations from the ultra-wideband low-frequency (UWL) receiver. Epoch-wise DM measurements were derived from sub-banded times of arrival, and the variability was characterized using linear trends and DM structure functions, which were compared with expectations for a Kolmogorov turbulence. Significant DM variations are detected in 89 pulsars in the UWL data and in 23 pulsars in the multibeam data, with 16 in the combined dataset showing significant trends. This represents one of the largest long-baseline studies of DM variability in pulsars. We find tentative evidence that the observed DM variations are predominantly consistent with Kolmogorov turbulence. PSRs J1105-6107 and J1829-1751 show estimated DM variations driven by periodic profile variability. We also identify 21 bright, slow pulsars exhibiting short-term DM variations that exceed expectations from the IISM.
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All authors S. J. I. Melfor, A. Parthasarathy, S. Johnston, A. Chalumeau, S. Dai, M. Kerr, M. E. Lower, R. N. Manchester, L. S. Oswald, S. Roch, C. A. Sobey, P. Weltevrede

High Energy Astrophysical Phenomena

X-ray spectral scaling of black hole mass in quasi-periodic eruptive source RX J1301.9+2747

Lev Titarchuk, Elena Seifina, Vadim Arefiev et al. (+2 more)

We present a spectral and timing analysis of X-ray emission from the actively accreting supermassive black hole (SMBH) in RX~J1301.9+2747 with prominent quasi-periodic eruptions (QPEs) using ASCA, ROSAT, XMM-Newton, and NICER observations. NICER detected renewed QPE activity from this source in 2024. We examined in detail the X-ray spectrum formation in this source during QPE outbursts applying the first-principal model, Bulk Motion Comptonization. We find an increase of the photon index $\Gamma$ with a mass accretion rate $\dot M$, the index saturation at $\Gamma_{sat}=2.7\pm 0.1$ at high $\dot M$ value during outburst peaks. Based on the derived $\Gamma-\dot M$ correlation, we apply the scaling technique for the first time to measure the black hole mass in RX~J1301.9+2747. The SMBH mass in this source was estimated to be between $4\times 10^5$ M$_ {\odot}$ and $7\times 10^6$ M$_ {\odot}$ for the inclination range from 0$^{\circ}$ to 70$^{\circ}$, which is adopted as a plausible range based on the AGN unified model assumption, applying HLX–1~ESO 243–49, OJ~287, and 1H~0707–495 as reference scaling sources. We also estimate a BH mass in RX~J1301.9+2747 applying a timing analysis, in which the Compton cloud size to be $\sim 10^{11}$ cm, estimated from the quasi-periodic oscillation frequency, $\nu\sim 10^{-4}$ Hz, indicates SMBH mass in RX~J1301.9+2747 is of order of $10^6$ M$_{\odot}$. Overall, the BH mass obtained by the scaling method in this source is consistent with previous measurements using other methods.
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All authors Lev Titarchuk, Elena Seifina, Vadim Arefiev, Diana Makhinya, Alexei Le

High Energy Astrophysical Phenomena · Cross-listed from astro-ph.CO

Evolution of neutrino distributions under repeated electron scattering

Jens Chluba, Bryce Cyr, Michiru Uwabo-Niibo et al. (+1 more)

We study the energy redistribution of neutrinos by repeated elastic scattering with an isotropic thermal bath of free electrons. Starting from the relevant Boltzmann collision integral, we formulate the evolution equations in terms of the neutrino–electron redistribution kernel derived in our companion work. The scattering kernel formulation retains recoil, relativistic kinematics and Pauli blocking, while reducing the calculation to a one-dimensional integral in the outgoing neutrino energy. To gain a better analytic understanding, we derive the corresponding Fokker–Planck (FP) limit of the collision operator in two independent ways and contrast it with the Kompaneets equation for photons. This shows that the different energy dependence of the weak cross section changes the drift and diffusion operators which causes the high-energy part of a neutrino distribution to evolve much faster than its low-energy part. We discuss the fermionic analogues of temperature-, chemical-potential- and $y$-type spectral distortions, and give approximate analytic solutions to the FP equation in several limiting cases. We also derive the analytic expressions for the relativistic scattering operator when Doppler terms dominate, allowing us to compute the relativistic Sunyaev-Zeldovich equivalent for neutrinos in the inefficient scattering limit. We compare these expressions to the full numerical result based on the detailed collision term. Finally, we set up conservative numerical schemes for both the FP equation and the scattering kernel, generalizing previous codes developed for studying the repeated Compton scattering of photons by relativistic electrons. Controlled line-injection experiments then illustrate when the diffusion approximation is accurate and where the non-locality of the redistribution kernel remains essential.
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All authors Jens Chluba, Bryce Cyr, Michiru Uwabo-Niibo, Masahide Yamaguchi

High Energy Astrophysical Phenomena · Cross-listed from hep-ph

The neutrino magnetic moment and supernovae with strong magnetic fields

Clément Ehrhardt, Maria Cristina Volpe, Miguel Ángel Aloy et al. (+1 more)

Despite several decades of searches, the neutrino magnetic moment remains unknown. If it is large, the neutrino evolution can be affected by its coupling to strong magnetic fields like the ones present in at least some core-collapse supernovae. We explore these effects for Majorana neutrinos. We first discuss a schematic model often employed and show the impact of resonant spin-flavor precession on the neutrino signal for a future galactic supernova. Then, we consider detailed simulations of a neutrino-driven supernova with 17 ${\rm M}_{\odot}$ leaving a neutron star and a magnetorotational supernova with 26 ${\rm M}_{\odot}$ with a black-hole remnant. We present predictions for the supernova neutrino fluxes and the event rates in presence of a non-zero neutrino magnetic moment, for the running JUNO and upcoming Hyper-Kamiokande experiments. Our results show a significant impact for transition magnetic moments of $10^{-14} ~\mu_B$ during the neutronization burst and the accretion phase for the neutrino driven supernova, and as small as $10^{-15} ~\mu_B$ at the early times for the magnetorotational supernova.
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All authors Clément Ehrhardt, Maria Cristina Volpe, Miguel Ángel Aloy, Martin Obergaulinger