High Energy Astrophysical Phenomena
Suppression of spiral density waves in collisionless accretion flows
Stephen Majeski, Matthew W. Kunz and Jason Dexter
Spiral density waves are ubiquitous phenomena in differentially rotating flows. They are non-modal, non-axisymmetric perturbations that, due to shear in the background flow, possess time-evolving wavenumbers, frequencies, and amplitudes. In global simulations of optically thin, low-luminosity black-hole
accretion flows, the excitation of such waves leads to spiral patterns in the
plasma density that influence the morphology of the emission region. As such, the observed variabilities of such
accretion flows are expected to be affected by the behavior of spiral density waves. Thus far, investigations of spiral density waves in
accretion flows have exclusively used the assumption that the
accretion-flow
plasmas are in local thermodynamic
equilibrium (LTE) at all times. In reality, hot and diffuse
accretion-flow
plasmas are expected to deviate far from LTE, and should be modeled accordingly. Here, we employ a combination of kinetic and fluid models to describe spiral density wave propagation, damping, and excitation in a collisionless shearing sheet, which more accurately represents the
plasma conditions of low-luminosity
accretion flows than do models that assume LTE. We find that micro-physical
plasma instabilities are especially important in determining how spiral density waves behave, because the weak particle scattering that they induce leads to appreciable viscous damping. Observational implications of these results include reduced emission-region variability, which may improve agreement between Event Horizon
Telescope (EHT) observations and simulation/theory, as well as a reduction in emission-region pattern speeds compared to simulations employing LTE, which bears on the interpretation of eventual EHT movies.
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High Energy Astrophysical Phenomena · Cross-listed from astro-ph.GA
Separating the Optical to Near-Infrared Light of AGN and Their Host Galaxies
Callum Dewsnap, Pauline Barmby and Sarah C. Gallagher
The properties of
galaxies that host active galactic
nuclei (AGNs) offer clues to the conditions that enable
accretion onto supermassive black holes. A
galaxy's morphology can provide significant information on the evolutionary processes underway. By modeling the surface-brightness profiles of
galaxies that host AGN, we can characterize physical properties of the host
galaxy. With a sample of sources across a wide range of
redshifts, we can investigate how both the supermassive black hole and
galaxy evolve over time. Applying the best practices from previous work, we perform Sersic + point source fits of 96 X-ray-selected AGN in the Extended Groth Strip across up to 13 bands of James Webb Space
Telescope and Hubble Space
Telescope imaging using AstroPhot. We examine both parametric (Sersic) and nonparametric methods in tandem to best determine the physical properties of the host
galaxy. After separating the light of the host
galaxy and the AGN, we perform independent CIGALE model fits to photometric spectral energy distributions to estimate physical properties including the host
galaxy stellar mass and
star formation rate, and AGN disk luminosity. In the stellar-mass/
star-formation-rate plane, the AGN host
galaxies align with the population of massive non-AGN
galaxies in the control sample across all
redshifts. The AGN disk luminosities result in ratios of bolometric to X-ray flux within the expected range, 5-20:1. We provide an evaluation of the limitations of Sersic modeling to obtain
galaxy properties and provide recommendations on best practices for multi-band AGN+host
galaxy image decomposition with James Webb Space
Telescope imaging.
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High Energy Astrophysical Phenomena · Cross-listed from astro-ph.IM
Learning Approximate Isometric Embeddings for Efficient Template Placement
Alexandra Wernersson, Jessica Irwin, Melissa Lopez et al. (+1 more)
The sphere covering problem has broad applications in science however, exact solutions are computationally infeasible on curved, high-dimensional
manifolds because distances must be evaluated using a position-dependent metric. We present $\texttt{isobank}$, a normalizing flow that learns an approximately isometric coordinate transformation, such that Euclidean distances in the latent space approximate metric-induced proper distances in the physical parameter space. This enables template placement using Euclidean distance checks in the latent space, avoiding repeated metric evaluations during placement. We evaluate $\texttt{isobank}$ in the context of gravitational wave template bank construction, where the sphere covering problem corresponds to the template placement problem. On a five-dimensional eccentric binary parameter space, $\texttt{isobank}$ reaches 97% coverage at a maximum mismatch of $\mu=0.03$ with 23% fewer templates than the state-of-the-art
stochastic placement code $\texttt{mbank}$, which reaches 94% coverage. Coverage is measured on independent injections drawn uniformly over the masses,
spins and eccentricity, using the exact waveform match rather than the metric approximation. Training the flow takes about 2.5h and placing the bank under 1h on 32 CPU cores. $\texttt{isobank}$ is publicly available on Github https://github.com/Alexandra-Wernersson/isobank
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All authors Alexandra Wernersson, Jessica Irwin, Melissa Lopez, Sarah Caudill
High Energy Astrophysical Phenomena
Extending the Pulsar radio population through Quantum Vacuum Cherenkov Emission
Tales A. O. Gomes, Sergei V. Bulanov, Jaziel G. Coelho et al. (+3 more)
The presence of some
radio pulsars within and below the so-called “death valley” in the $P$–$\dot{P}$ diagram challenges the standard pair-cascade models based on
curvature radiation (CR) and resonant inverse Compton scattering (RICS) in
neutron star polar caps. We show that Cherenkov radiation from the
quantum vacuum, a strong-field
quantum electrodynamics (QED) phenomenon enabled by
vacuum polarization, constitutes a distinct pair-creation channel within the
vacuum gap model. Within this model, the acceleration length scale for Cherenkov
photon emission and the subsequent
photon mean free path are sufficiently short to ensure rapid conversion into $e^+e^-$ pairs. This process acts as a complementary pair-creation channel, remaining viable even in regimes where classical mechanisms become heavily suppressed. This leads to a new set of death lines in the $P$–$\dot{P}$ diagram that partially overlap with and extend beyond the CR and RICS death valleys, enlarging the viable parameter space for
radio-emitting
neutron stars. The result provides a physical basis for coherent
radio emission from long-period
neutron stars previously considered inactive, and offers a new window for testing non-linear QED with next-generation
radio facilities such as the Square Kilometre Array.
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All authors Tales A. O. Gomes, Sergei V. Bulanov, Jaziel G. Coelho, Martin Jirka, Alexander J. Macleod, J. A. Rueda
High Energy Astrophysical Phenomena
Neutrino flavor instabilities intermediate between slow and fast
Nicolas Viaux and Lucas Johns
The
neutrino flavor composition in
supernovae and
neutron star mergers is shaped by flavor instabilities, which are commonly classified into three types: slow (SFI), fast (FFI), and collisional (CFI). The focus here is on mixed-type instabilities combining attributes of the standard varieties. We examine instability growth rates in two-dimensional parameter spaces (“phase diagrams”) whose axes correspond to instabilities of pure type. We find critical curves connecting the pure-type instability onset points. We also exhibit qualitative trends in the growth-rate spectra $\gamma_{\bm{k}}$, emphasizing the occurrence of crossovers and phase transitions in the fastest-growing
Fourier mode $k_{\textrm{max}}$ and drawing
attention to the distinction between spatial-mean ($\bm{k} = 0$) and flavor-wave ($\bm{k} \neq 0$) instabilities. Our paper is a step toward understanding flavor instabilities as they actually occur in nature rather than in idealized limits.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Chaotic signatures in extreme-mass-ratio systems surrounded by bosonic environments
Qi-Xuan Xu, Kyriakos Destounis, Yin-Da Guo et al. (+2 more)
Extreme-mass-ratio inspirals are key gravitational-wave sources for testing strong
gravity and the environments of massive black holes. While orbital motion in Kerr black hole spacetimes is integrable, realistic black holes may be surrounded by environments that break integrability. We investigate conservative orbital dynamics around rotating black holes surrounded by scalar clouds using fully nonlinear numerical solutions and an analytical post-Newtonian model. Poincaré sections and rotation curves reveal finite-width resonant islands, providing evidence for non-integrability even when the cloud carries only a small fraction of the black-hole mass. We show that the post-Newtonian description reproduces the dominant resonance and its island width for weak clouds, but underestimates the width in the configurations with stronger, more compact clouds examined here. Moreover, we find that for a scalar cloud as massive as the black hole, the phase space exhibits wider resonant islands as well as scattered layers indicative of chaotic motion. Together with earlier work, these results show that environmental effects can generically break the integrability of geodesic motion, motivating further study of resonance crossings and their gravitational-wave signatures once radiation reaction is included.
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All authors Qi-Xuan Xu, Kyriakos Destounis, Yin-Da Guo, Richard Brito, Taillte May
High Energy Astrophysical Phenomena
Reginald Christian Bernardo
Rotational variations in
pulsars reflect either internal angular momentum exchange via equal and opposite torques (stationary
spin noise) or independent torques causing diffusive changes in total angular momentum (nonstationary
spin noise). We compare two models of a
radio-emitting crust and interior superfluid to test the stationarity of angular velocity fluctuations through observed
pulsar phases. We present results for three isolated
pulsars with measurable timing noise, demonstrating distinct inference outcomes. For PSR J1359-6038, the data mildly favor independent torques over equal-and-opposite torques, with an odds ratio of seven hundred to one. For PSR B1937+21, the analysis shows no clear preference between the models. For Vela in a pre-glitch interval, excess scatter and unexplained residual structure limit the interpretation.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Trace-anomaly decomposition and universal dark matter scaling in compact stars
Adamu Issifu, Constança Providência and Tobias Frederico
We investigate how dark matter (DM) admixture modifies the conformal properties and phase structure of dense
neutron-
star matter within a self-consistent single-fluid framework, with the global DM fraction $F_\chi=N_\chi/N_B$ fixing the local relation $n_\chi=F_\chi n_B$. We derive an exact decomposition of the total trace anomaly, $\Delta_{\rm tot}$, into microscopic contributions. For
collider-motivated
Higgs-portal
benchmarks, explicit
Higgs, vector-mediator, and contact-interaction contributions are negligible, while heavy nonrelativistic DM has an intrinsic trace anomaly close to the nonrelativistic limit, $\Delta_\chi\simeq1/3$. Consequently, the DM rest-mass energy fraction dominates the DM-induced modification of $\Delta_{\rm tot}$, producing a smooth upward shift of up to $\sim0.1$ for $F_\chi\sim0.2\%$. In the pressureless, comoving heavy-WIMP regime, we further identify a universal dark-sector scaling governed by the mass-loading parameter $\lambda=F_\chi m_\chi/m_N$: numerical calculations with different $(F_\chi,m_\chi)$ pairs at fixed $\lambda$ exhibit overlapping trace-anomaly, sound-speed, and mass–radius responses for a given baryonic equation of state. In hybrid
stars, DM leaves the coexistence pressure and chemical potential essentially unchanged, whereas first-order
hadron–
quark deconfinement produces sharp discontinuities in the squared sound speed $c_s^2$, $\Delta_{\rm tot}$, and $\Delta_{\rm tot}-\Delta_B$. The combined softening substantially reduces the maximum stellar mass, placing $F_\chi\sim0.2\%$ in tension with the observed $2\,M_\odot$
neutron stars. These results show that the trace anomaly and its density
evolution provide a sensitive diagnostic for distinguishing smooth DM-induced modifications of dense matter from genuine first-order deconfinement.
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High Energy Astrophysical Phenomena
The Impact of a Clumpy Ambient Medium on the Dynamics and Synchrotron Emission of AGN Jets
Ivan Almeida, Christian Fendt and Bhargav Vaidya
Relativistic jets from AGN are expected to propagate through an inhomogeneous ISM, but the role of small-scale gas inhomogeneities in shaping their early
evolution remains uncertain. We investigate this problem using 3D special-relativistic magnetohydrodynamic simulations with PLUTO, following a jet with a Lorentz factor of 10 propagating through a pc-scale medium. We compare a homogeneous ambient medium with two clumpy ambient-medium models, motivated by dense gas in the nuclear ISM, in which clouds occupy volume filling factors of $0.1$ and $1$ per cent. We compute synthetic synchrotron maps and spectra from Lagrangian macro-particles that have been accelerated by diffusive shock acceleration. Jet-cloud interactions deflect the flow, enhance shock formation, and produce a more asymmetric cocoon than in the homogeneous ISM case. Altogether, this results in a substantially stronger mass loading: the entrained mass increases from $0.43$ M$_{\odot}$ in the homogeneous run to $5.3$ and $8.8$ M$_{\odot}$ in the clumpy runs. The clumpy ISM also modifies the
turbulence and the material mixing within the jet cocoon. The dynamical differences we find translate into brighter and more irregular synchrotron emission. For the same injected jet, the models with a clumpy medium produce stronger frequency-integrated synchrotron emission than the homogeneous run, with the largest differences in the SED occurring from the sub-mm to the infrared/optical bands. Our results demonstrate that including a small-scale ISM structure provides a more complete description of the early dynamical
evolution of young AGN jets and their radiative properties.
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High Energy Astrophysical Phenomena
Intrinsic versus observation induced spin nonstationarity in pulsar timing
Reginald Christian Bernardo
Whether
spin noise of a
neutron star is stationary is, in two-component models, a question of whether stellar angular momentum is conserved internally or exchanged externally through independent
stochastic torques on the crust and superfluid. The question is posed in the two components' angular velocities, but
radio pulsar timing observes only the crust, through its rotational phase after a deterministic timing model is fitted. We develop a Gaussian process method for testing
spin noise stationarity directly with such phase data. Starting from the exact analytical phase means and covariances of a singular, nonstationary and a minimal, stationary two-component model, we show that the crust phase covariances are semiseparable and construct a likelihood that scales linearly with the number of observations, with the timing model marginalized analytically. We analyze simulated phase data from both models using full-state and crust-only observations, and after differentiation into local
spin frequencies. Integration, timing model removal and differentiation neither create nor destroy the distinction between stationary and nonstationary
spin noise, but determine how much survives in a finite, noisy data set. With both components observed, the models are distinguished decisively and the generating parameters are recovered. With the crust alone, both models describe the observed phase equally well over much of parameter space, and the Bayes factors are of order unity and prior-limited. The minimal model nonetheless ties the hidden superfluid phase to the observed crust phase through a single factor set by the superfluid inertia fraction, so an independent estimate of this fraction, as from glitches, turns it into a falsifiable prediction that a continuous gravitational wave observation of the interior could test.
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High Energy Astrophysical Phenomena
Stationarity and angular momentum conservation in pulsar spin noise
Reginald Christian Bernardo
We present an analysis of
pulsar spin noise based on physically-motivated two-component models of
spin wandering. We focus on two models, distinguished by their total angular momentum dynamics: a singular, nonstationary model with a diffusive total angular momentum, and a minimal, stationary model anchored on a conserved total angular momentum. We develop scalable Gaussian process methods and, using mock data, show that the two models are fully testable and distinguishable with full-state observations, i.e., simultaneous independent data on the crust and the superfluid rotational states. This paves a path to testing stationarity in
pulsar spin noise, potentially achievable with joint continuous gravitational wave observations and
radio timing of
pulsars. However, robust inferences and predictions are harder to achieve, and depend on the priors and data quality, when only one component is observationally accessible.
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High Energy Astrophysical Phenomena
Recycling serendipitous observations of XRISM for dark matter searches
Lidiia Zadorozhna, Denys Malyshev and Oleg Ruchayskiy
Searches for radiative decays of keV-mass dark matter have been limited by energy resolution. We propose a strategy for the XRISM/Resolve low count rate observations, and search the 3.48-3.56 keV band for a decay line from the Milky Way
halo. Despite a lower exposure, our bounds are stronger than those from XRISM observations of
galaxy clusters. We also identify a residual at E = 3.5311 keV with ~3sigma local significance, coincident with the previously reported unidentified feature, and having no plausible atomic or instrumental counterpart. These bounds will continue to tighten as additional pointings become available.
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High Energy Astrophysical Phenomena
Slingshot on compact binaries in the nuclear region of galaxies as the origin of large offset gamma-ray bursts
Juan C. Rodríguez-Ramírez, Viviane Alfradique, Clécio R. Bom et al. (+1 more)
A growing number of gamma-ray bursts (GRBs) have been observed at large projected offsets from the centres of their putative host
galaxies, sometimes extending to several tens of kiloparsecs. When the GRB is associated with a kilonova, a compact binary with at least one
neutron star is expected to be involved, and the cause of the offset can be attributed to the
neutron star natal kick. In this work, we explore an alternative mechanism: the gravitational scattering of compact binaries populating the nuclear region of the host
galaxy, by an intermediate-mass black hole or secondary supermassive black hole. We specifically consider populations of
neutron star-
neutron star (NS-NS),
neutron star-black hole (NS-BH), and
neutron star-white dwarf (NS-WD) binaries, and analyse the ejection of bound systems from the nuclear region through a gravitational-slingshot effect. We proceed analytically to derive the conditions for binary survival and to parametrise the post-encounter velocity. To quantify the associated merger offsets, we numerically integrate the post-slingshot trajectory of the binary centre-of-mass in host-
galaxy potentials that include the primary SMBH, the stellar component, and the dark-matter
halo, considering both elliptical-like and spiral-like
galaxy profiles. Our parameter sampling shows that NS-NS and NS-WD binaries typically merge farther from the galactic centre than NS-BH systems, with approximately 30-45% of successful ejections merging at three-dimensional distances exceeding 100 kpc; these extreme-offset mergers occur within $\sim$0.1-10 Gyr after ejection. These results motivate the analysed mechanism as a candidate channel for observed extreme-offset transients.
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All authors Juan C. Rodríguez-Ramírez, Viviane Alfradique, Clécio R. Bom, Davi C. Rodrigues
High Energy Astrophysical Phenomena
Disk-Like Matter Outflow from a Kerr-Type Wormhole: Possible Observational Manifestations and Magnetic Effects
Mikhail Piotrovich, Stanislava Buliga and Tinatin Natsvlishvili
We present a phenomenological study of a hypothetical compact object with a traversable 2 Kerr-type wormhole geometry connecting two asymptotically distinct regions. One mouth of the wormhole is assumed to reside in an active galactic
nucleus (AGN) environment with ongoing
accretion, while the second mouth is located in a comparatively quiescent galactic
nucleus without
accretion activity. In such a configuration, matter accreted near the AGN-side mouth may traverse the wormhole throat and emerge from the opposite mouth. Because the inflowing matter possesses angular momentum, the resulting outflow is expected to be predominantly equatorial, producing a disk-like structure fundamentally different from a conventional
accretion disk around a black hole. Several dynamical regimes are considered depending on the outflow velocity relative to the local escape and orbital velocities. Possible observational manifestations, thermal properties, recombination signatures, and
magnetic field effects are discussed. Special
attention is given to the possibility of jet formation in the absence of a conventional
accretion disk. We explicitly distinguish the weak-field, large-radius Newtonian classification used for the outer flow from the strong-field region near the throat, where the dynamics should be treated in a general-relativistic and magnetohydrodynamic framework. We further discuss the specific energy and angular momentum inherited from the inner edge of the
accretion flow, the possible modification of these quantities by
magnetic stresses and energy-extraction processes, and the effects of an intrinsic dipolar
magnetic field of the wormhole.
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High Energy Astrophysical Phenomena
Detection of kilosecond hard lags in the new pulsating ULX candidate NGC 7456 ULX-1
W. Leone, F. Pintore, C. Pinto et al. (+19 more)
Context. Ultraluminous X-ray sources (ULXs) are thought to be powered, in many cases, by super-Eddington
accretion onto compact objects. While soft X-ray lags have been detected in several ULXs, hard lags remain rare and poorly understood. Aims. We investigate the temporal and energy dependence of X-ray lags in NGC 7456 ULX-1 to constrain their physical origin and probe the super-Eddington
accretion flow. Methods. We analyzed the two deepest XMM-Newton observations, taken in 2018 and 2023. Hard (1-10 keV) and soft (0.3-1 keV) light curves were cross-correlated using adaptive-binning techniques optimized for Poissonian low-count data. We measured lags over consecutive 10 ks intervals and investigated their energy dependence. Spectra were modeled using thermal and Comptonization models. Results. We detect significant hard X-ray lags in both observations, with the hard emission delayed by $\sim 10^3$ s during phases of rapid flux variability. The delays are primarily driven by the lowest-energy
photons. Spectral modeling indicates a Comptonization-dominated flow comprising a cooler, extended outer region and a hotter, compact inner flow embedded in an optically thick wind. We interpret the delays as the combined effect of inward propagation of
accretion-rate fluctuations and
photon diffusion within the dense outflow. Fluctuations first enhance the soft-emitting outer regions and then propagate toward the hotter inner flow, where
photons undergo stronger Comptonization before escaping with a kilosecond delay. The small inferred inner emitting radius disfavors an intermediate-mass black hole accretor. Conclusions. The sign, amplitude, and energy dependence of the delays disfavor standard reverberation. Propagation-driven variability coupled with radiative transfer in optically thick winds appears to play a major role in shaping the timing properties of super-Eddington
accretion flows.
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All authors W. Leone, F. Pintore, C. Pinto, N. O. Pinciroli Vago, A. Sanna, A. Wolter, T. Di Salvo, R. Iaria, A. D'Aì, A. Anitra, R. Soria, P. Esposito, F. Barra, E. Ambrosi, S. Caserta, C. Salvaggio, R. Salvaterra, G. L. Israel, S. Banerjee, M. Marelli, G. Rodriguez-Castillo, L. Burderi
High Energy Astrophysical Phenomena · Cross-listed from astro-ph.SR
Solarprop 2.0: Modern charge-sign dependent solar modulation for everyone
Henning Gast
I present a greatly improved version of SOLARPROP, an open source framework for building models of charge-sign dependent solar modulation of
cosmic rays in the heliosphere. The transport equation of charged particles is solved by converting it to a set of
stochastic differential equations (SDEs). The code now includes the full set of SDEs in two spatial dimensions, allowing for
magnetic fields with latitudinal components, and it has been generalized to accommodate models in three spatial dimensions. Due to code parallelization and optimization, a speedup of up to three orders of magnitude with respect to the original version is achieved. Python bindings have been added for ease of use. The code has been validated against the results of several model calculations found in the literature. While excellent agreement is found in many cases, important differences are observed for two model implementations. Possible root causes for the differences have been investigated.
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High Energy Astrophysical Phenomena · Cross-listed from astro-ph.SR
Structure of Convective-Reactive Zone in a Supernova Progenitor
M. Mocak, C. Meakin, F. Rizzuti et al. (+5 more)
Convective-reactive events are phases of stellar
evolution where turbulent mixing and nuclear burning directly compete, since their timescales become similar within convection zones. During these events the convection zone structure is shaped by a complex and dynamic interaction of convective transport and nuclear burning of individual chemical elements, with
plasma streams connecting the entrainment regions with the burning layers. Here we analyse a 3D hydrodynamic simulation of an oxygen–neon shell merger in a massive pre-
supernova star. We study the emergent structure using the Reynolds-Averaged Navier-Stokes (RANS) mean-field composition transport equation. We find that the merged convective zone develops a complex,
turbulence-driven mixing structure of multiple nested convective-reactive shells, all contained within the single convection zone. Key controlling factors include not only the mean stratification and mixing, but also emergent collective behaviour of involved nuclear reactions for every chemical isotope. Almost all layers show a quasi-steady balance between burning and mixing. We categorise the various layers, and discuss/contrast with 1D stellar
evolution code treatments, highlighting some implications.
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All authors M. Mocak, C. Meakin, F. Rizzuti, S. W. Campbell, V. Varma, R. Hirschi, C. Georgy, W.D. Arnett
High Energy Astrophysical Phenomena
25 Years of Mrk 421 with XMM-Newton: Unveiling Structured Jets and Energy-Dependent Escape
Tek P. Adhikari, Gopal Bhatta, Sangeetha Kizhakkekalam et al. (+4 more)
We present a long-term X-ray spectral and timing analysis of the TeV blazar Mrk~421 based on nearly a quarter century of archival XMM-Newton/pn observations obtained between 2000 and 2025. Our sample comprises 76 epochs obtained with the pn instrument in both IMAGING and TIMING modes, allowing us to trace the source's variability and spectral
evolution. Mrk~421 exhibits flux variations by approximately an order of magnitude, with prominent flaring periods interspersed with low-activity states. A clear harder-when-brighter trend is observed, accompanied by scatter in the hardness ratio (HR), suggesting flux alone does not uniquely determine the spectral state. Fractional variability in the hard band ($2-10$ keV) correlates tightly with that in the soft band ($0.3-2$ keV), with a steeper slope indicating pronounced variability at higher energies. The flux distribution is non-Gaussian and lognormal-like, dominated by moderate flux levels with a tail of bright
flares. Spectral analysis shows that power-law model is not sufficient; 59 epochs are best described by a broken power-law (BPL) and 17 by a log-parabola (LP). This fluctuation between BPL and LP models suggests the emission region transitions between a distinct acceleration shockfront and downstream
stochastic turbulence. The spectral break energy of BPL remains predominantly clustered around $2$ keV across all flux states, while the average spectral steepening above the break is mild ($\Delta \Gamma \approx 0.19$), inconsistent with standard one-zone cooling models. Our results support structured jet scenarios or energy-dependent electron escape, providing key constraints on the long-term behavior of relativistic jets in high-synchrotron-peaked blazars.
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All authors Tek P. Adhikari, Gopal Bhatta, Sangeetha Kizhakkekalam, Navaneeth P K, Alex Markowitz, Zhicheng He, Santanu Mondal
High Energy Astrophysical Phenomena · Cross-listed from astro-ph.GA
Chemical complexity in feedback from supernova remnants: first detection of PO+ in IC443 and W44
G. Cosentino, F. Priestley, S. Scibelli et al. (+1 more)
Supernova remnant (SNR) may shape the physical and chemical properties of
star formation. By releasing refractory elements into the gas phase, they inject material of pre-biotic relevance into molecular clouds. Such elements may be inherited by planetary systems and become relevant for the emergence of life. We investigate the presence of P-bearing species in molecular clouds impacted by SNR-shocks. P is a crucial biological element, but its presence and reservoir in molecular clouds remain elusive. We present high-sensitivity 3 mm observations obtained with the IRAM 30m, toward the interaction sites between the SNRs W44 and IC443 and their associated molecular clouds. Focusing on PO+(2-1) and PN(2-1), we derive molecular column densities and abundances in local thermodynamic
equilibrium. We investigate the correlation between P-bearing species and the shock tracer Silicon Monoxide (SiO). We detect, for the first time, PO+ toward SNRs, with abundances X(PO+)~8e-12-5e-11, but no significant PN emission. PO+ toward both SNRs is associated with strong SiO emission, showing similar linewidths but velocity offsets, suggesting that PO+ preferentially traces the most compressed and more strongly ionised layers of the shock. By comparing the derived abundances with those reported in literature, we suggest that the PO+ abundance mainly depends on a combination of shock strength and shocked medium density. Our results indicate that P-chemistry in SNR shocks is shifted toward an ion-dominated regime, likely driven by enhanced
cosmic-ray ionisation rates. In this scenario, neutral species such as PN are efficiently destroyed, while ion-molecule reactions favour the production of PO+. This suggests that SNR shocks may play a role in processing P-bearing material and shaping gas-phase P chemistry in molecular clouds, with potential implications for the chemical inventory of
star-forming environments.
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All authors G. Cosentino, F. Priestley, S. Scibelli, F. Fontani
High Energy Astrophysical Phenomena
Superorbital Phase Evolution and Identification of New Anomalous Low State Candidates for Her X-1
Yi Chou and Jun-Lei Wu
The 35-day superorbital modulation of the X-ray binary Her X-1 was systematically investigated using a 35-year multi-instrument X-ray observational baseline. We developed a Rank-Searching method using the peak intensity of the main high state to identify anomalous low states (ALSs) with an objective and reproducible criterion. The method recovers the known ALSs, identifies two previously unrecognized candidate episodes, ALS 1991 and ALS 2015, and independently recovers the recently reported ALS 2025. We then characterized the long-term superorbital phase
evolution, identifying seven epochs that alternate between smooth and variable behavior. The smooth component is empirically described by a cubic trend, while the recurrent variable epochs have a characteristic timescale of approximately 3400 days. Within a first-order tilted-disk framework, the secular phase
evolution corresponds to an inferred cumulative disk-mass increase of $\sim1.8\%$ and an outer-disk-radius expansion of $\sim0.9\%$, while the short-term phase excursions can be reproduced by disk-mass variations of $\lesssim2.4\%$. A viscous
diffusion timescale of approximately 168 days provides a characteristic timescale for the short-term disk response. Finally, the stable phase relation and high profile similarity between the main and short high states indicate that the warped disk maintains a remarkably stable global geometry over the observational baseline.
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High Energy Astrophysical Phenomena
Eight Gamma-Ray Bursts Observed with the Fermi Gamma-ray Burst Monitor: Significant Quasi-Thermal Components and Conditional Jet Constraints
Ze-lian Du, Zhao-Yang Peng, Jia-Ming Chen et al. (+2 more)
The composition of gamma-ray burst (GRB) jets remains uncertain. We analyze eight Fermi Gamma-ray Burst Monitor (GBM) GRBs with reported
redshift information, selected from 126 events by prespecified fluence and spectral criteria. After excluding compound-model DIC evaluations classified as unstable by the posterior-stability tests, a stable added-blackbody (BB) comparison gives $\Delta\mathrm{DIC}>10$ in 203 of 215 accepted bins (60–100% per burst); independently, a multicolor-blackbody plus power-law (mBB+PL) decomposition gives $F_{\rm mBB}/F_{\rm tot}>0.5$ in 214 of 215 bins. The cutoff-power-law (CPL)–mBB correlations ($r=0.83$ and 0.78) exceed the Band–mBB correlations ($r=0.41$ and 0.48), demonstrating model dependence. Time-integrated BB fractions span 0.005–0.311, with six of eight below 0.12. We then apply the non-dissipative photosphere prescriptions of \citet{2013A&A...551A.124H} (H2013) and \citet{2015ApJ...801..103G} (G2015). After excluding boundary or physically inadmissible inversions, the H2013 numbers with $\epsilon_{\rm Th}>0.5$ are 1/2, 1/4, and 2/8 among valid solutions at $R_0=21$, 100, and 1000~km, respectively; the corresponding G2015 numbers with $\sigma_0<1$ are 0/1, 1/4, and 1/8. The large number of invalid solutions at small $R_0$ (six and seven at 21~km for H2013 and G2015) is itself evidence that those assumed radii are incompatible with the adopted inversion for most events. Among bursts having valid solutions at more than one radius, increasing $R_0$ generally lowers $\epsilon_{\rm Th}$ and raises $\sigma_0$. Thus launch radius, efficiency, and spectral decomposition dominate the conditional jet constraints; no universal jet class or unique non-thermal mechanism is inferred.
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All authors Ze-lian Du, Zhao-Yang Peng, Jia-Ming Chen, Yue Yin, Ting Li
High Energy Astrophysical Phenomena · Cross-listed from astro-ph.SR
1RXS J174320.1-042953: another polar with a red-shifted absorption component in emission line wings
Diego H. González-Buitrago, Ma. T. García-Díaz, Sergey Zharikov et al. (+5 more)
We present the results of a spectroscopic and multi-band photometric study of the
magnetic cataclysmic variable 1RXS J174320.1-042953. Multi-band photometry confirms a periodic modulation with an orbital period of $P_{\rm orb}=0.0864 \pm 0.0001$ days. Using the estimated secondary mass of $\sim0.15\,\mathrm{M_\odot}$ and, the X-ray-based white dwarf mass of $\sim0.75\,\mathrm{M_\odot}$, we obtain values of $q\sim0.2$ and a system inclination of $47^\circ\pm10^\circ$. The optical spectra of 1RXS J174320.1-042953 are dominated by strong, complex, asymmetric, and highly variable single-peaked emission lines of the Balmer series, \ion{He}{i}, and \ion{He}{ii}, which are characteristic of polar-type
magnetic cataclysmic variables. Doppler
tomography reveals no evidence of a Keplerian
accretion disc, supporting the classification of the system as a polar. The H$\beta$ and \ion{He}{ii} emission lines can be decomposed into at least two distinct components. The low-velocity components have semi-amplitudes of approximately 170 km s$^{-1}$ (H$\beta$) and 147 km s$^{-1}$ (\ion{He}{ii}), while the high-velocity components reach about 317 km s$^{-1}$ and 460 km s$^{-1}$, respectively. The low-velocity component is likely associated with the irradiated side of the secondary
star facing the white dwarf and/or the vicinity of the L$_1$ point, whereas the high-velocity component is related to the
accretion-stream structure. A redshifted absorption component in the emission-line wings is detected at orbital phases near $\phi \approx 0.0$, reaching velocities up to $\sim1400$ km s$^{-1}$ and likely produced by
accretion-stream material crossing the line of sight.
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All authors Diego H. González-Buitrago, Ma. T. García-Díaz, Sergey Zharikov, Gagik Tovmassian, A. Castro, E. J. Kotze, Yair Krongold, C. A. Negrete
High Energy Astrophysical Phenomena
High-energy neutrinos from shocked circumnuclear material around optically-bright and infrared-only tidal disruption events
Mainak Mukhopadhyay, Shigeo S. Kimura and Tatsuya Matsumoto
Tidal disruption events (TDEs) can launch sub-relativistic outflows that drive shocks into the surrounding circumnuclear material (CNM), providing a natural site for
cosmic ray (CR) acceleration and high-energy
neutrino production through hadronuclear ($pp$) interactions. We model this emission for optically bright and infrared (IR)-only TDEs, the latter motivated by a recently identified population of luminous IR transients with weak or absent optical counterparts, consistent with TDEs embedded in dusty, obscured nuclear environments. We semi-analytically compute the shock dynamics, CR acceleration and transport, and
neutrino production, including the radiative cooling and compression in dense environments. While optical TDEs remain inefficient $pp$
neutrino sources with comparatively small
neutrino yields, radiative compression in dense IR-only TDEs enhances the target density and allows the pp efficiency to approach the calorimetric regime, yielding up to $\sim 10\%$ of the observed diffuse
neutrino flux at $100$ TeV, given the rate uncertainties. The long-lasting
neutrino emission and low individual source yield motivate joint electromagnetically informed stacking searches. We forecast such searches for IceCube, IceCube-Gen2, KM3NeT, and HUNT, and conclude that a future $\sim 30\ {\rm km^3}$
neutrino observatory can reach $3\sigma$ sensitivity for nearby ($z \lesssim 0.4$) IR-only TDEs with multi-year search windows. Growing optical and IR TDE samples can therefore enable population-resolved searches that can test whether dense, obscured nuclear environments are efficient high-energy
neutrino sources.
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High Energy Astrophysical Phenomena
Towards Retrieval Augmented Generation in High-Energy and Astroparticle Physics
Jacky Kumar and Sajan Kumar
The high-energy and astroparticle physics literature has grown into an enormous body of knowledge. Gaining a comprehensive understanding of this literature is an important step in research, but is a challenging task. Before making meaningful advances, it is important to establish what has already been done and identify open questions. However, this process is becoming increasingly difficult given the sheer volume of publications. Conducting a focused literature survey on a narrow topic is particularly challenging. We develop an open-source
Retrieval Augmented Generation (RAG) pipeline to produce concise, targeted summary reports with citations, grounded in the database of arXiv papers, enabling researchers, editors, and referees to rapidly orient themselves within any corner of the field. Specifically, we embed approximately 230K hep-ph and astro-ph.HE papers to enable a hybrid
retrieval that captures both keyword matches and semantic similarity. The fused candidate set is then refined using a cross-encoder reranker. Following
retrieval, the papers are passed to a Large
Language Model (LLM), for which we use Google DeepMind's open-source Gemma-4-E4B model. The LLM first acts as a judge to evaluate the relevance and then synthesizes a coherent and grounded report with references. This modern AI-driven approach allows us to go beyond the capabilities of classical keyword search on arXiv or Inspire-HEP.
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