High Energy Astrophysical Phenomena
Gravitational waves from primordial black holes passing by neutron stars: observational prospects for the Galactic center
Nicolas Esser, Juan García-Bellido and Peter Tinyakov
We investigate the gravitational wave (GW) signals emitted by planetary-mass
primordial black holes (PBHs) passing nearby or traversing
neutron stars (NSs). While previous studies mainly focused on the detailed waveforms of the signals, we estimate the rate of PBH-NS gravitational-wave events originating from the
Galactic center and compute the probability of detecting a signal over 10 years of LIGO-Virgo-KAGRA observations. We examine in detail the case of PBHs bound to NSs, focusing on eccentric orbits that give rise to repeated GW bursts emitted in correlated series, each burst corresponding to a periastron passage. Despite the enhancement from the large number of bursts produced by a single PBH-NS pair, the total number of signals produced in this way remains subdominant to those due to random unbound encounters of PBHs with NSs. We also find that both types of signals have a very small probability $P\lesssim 10^{-8}$ to be detected in a 10 year period.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Polarisation Singularities of Gravitational Waves
Claire Rigouzzo, Sebastian Golat, Alex J. Vernon et al. (+3 more)
Departure from idealised plane waves gives rise to intricate
geometric structures in wave fields. One such structure is the polarisation singularity, which emerges when multiple monochromatic waves interfere (such as would be the case for
stochastic backgrounds), producing loci of purely circular or linear polarisation. In this work, we extend the theory of polarisation singularities to gravitational waves and higher
spin fields. Building on the electromagnetic description, we formulate the gravitational analogue of polarisation singularities and show that they are generic features of gravitational waves. Their dimension, however, depends on the
spin of the field. We illustrate these results with simulations of plane-wave interference and analyse the resulting singularity densities.
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All authors Claire Rigouzzo, Sebastian Golat, Alex J. Vernon, Kyan Louisia, Eugene Lim, Francisco J. Rodriguez-Fortuno
Earth and Planetary Astrophysics
Worlds Next Door. III. Indirect Evidence for Enhanced Atmospheric Metallicity and/or the Presence of Water Clouds in the Nearest Jupiter-analog $\epsilon$ Eri b
Aniket Sanghi, James Mang, Jorge Llop-Sayson et al. (+12 more)
We present the most sensitive direct imaging search for the nearest ($d = 3.2$ pc) Jupiter-analog
exoplanet, $\epsilon$ Eri b, with JWST/NIRCam coronagraphy between 4-5 $\mu$m (F444W). We achieve a 5$\sigma$ contrast sensitivity $\approx3.0\times10^{-7}$ ($\Delta \approx 16.3$ mag) in the F444W filter at the expected
planet separation of $\approx$1". This is the deepest 4-5 $\mu$m contrast performance achieved for any JWST/NIRCam observation to date at these separations (and $>10\times$ better than ground-based limits). Yet, the
planet remains elusive to imaging. We update the
star's age to $1.1\pm0.1$ Gyr, older than previous age estimates, using the latest gyrochronology relations. This significantly impacts $\epsilon$ Eri b's inferred effective temperature ($T_{\rm eff}$), which is now expected to lie between 150-200 K based on evolutionary models for a 1 $M_{\rm Jup}$
planet. Using cloud-free Sonora Flame Skimmer models and custom PICASO patchy cloud models in the above $T_{\rm eff}$ range, we find that the F444W non-detection of $\epsilon$ Eri b can be explained by a metal-enriched atmosphere and/or an atmosphere containing water ice clouds. Both possibilities suggest that $\epsilon$ Eri b's atmosphere is strikingly similar to that of Jupiter in our
Solar System. Alternatively, if we do not enforce the dynamical mass ($0.98 \pm 0.09\;M_{\rm Jup}$), a
solar metallicity, cloud-free, $\lesssim0.81\;M_{\rm Jup}$
planet would be consistent with the NIRCam upper limit based on the Sonora Flame Skimmer evolutionary models. Finally, we place limits on the size of a potential ring system using the NIRCam/F210M data and discuss the opportunity to directly image $\epsilon$ Eri b with additional JWST observations, the Roman Coronagraph Instrument, the ExtraSolar Coronagraph on the Lazuli Observatory, and EELT/METIS.
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All authors Aniket Sanghi, James Mang, Jorge Llop-Sayson, Eric Mamajek, William Thompson, Ankan Sur, Charles Beichman, Geoffrey Bryden, Andras Gaspar, Jarron Leisenring, Dimitri Mawet, Caroline Morley, Jean-Baptiste Ruffio, Schuyler Wolff, Marie Ygouf
High Energy Astrophysical Phenomena
Large-amplitude modulations and hours-timescale variability in the early X-ray light curve of a tidal disruption flare
A. Malyali, A. Rau, P. Baldini et al. (+11 more)
We present new X-ray, optical, and UV observations of the
tidal disruption event candidate eRASSt J234402.9-352640, (hereafter J2344). Between 50 and 60 days after peak optical brightness, J2344 exhibited large-amplitude modulations in its 0.2-2 keV emission, when the flux repeatedly dimmed and re-brightened by a factor of ~6, over a ~3-day timescale. These modulations exhibited harder-when-brighter behaviour but were not detected in high-cadence observations obtained 60-70 days and 170-200 days after peak optical brightness, when the system instead exhibited
stochastic X-ray variability over timescales of hours. We discuss the different physical mechanisms responsible for such exotic X-ray variability and explore the possibility that the modulations in J2344 were caused by the Lense-Thirring precession of the inner
accretion flow around the disrupting black hole.
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All authors A. Malyali, A. Rau, P. Baldini, A. Franchini, A. G. Markowitz, A. Merloni, G. E. Anderson, A. J. Goodwin, D. Homan, M. Krumpe, Z. Liu, J. C. A. Miller-Jones, I. Grotova, A. Kawka
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Universality of the Blandford-Znajek emission in stationary and axisymmetric spacetimes
Filippo Camilloni and Luciano Rezzolla
The Blandford-Znajek (BZ) mechanism is widely recognised as the most compelling process to extract rotational energy from an accreting black hole and power the emission of relativistic jets. We explore the universality of this process for generic black-hole spacetimes within the Konoplya-Rezzolla-Zhidenko formalism and find that the lowest-order contribution to the BZ power is invariant across different black-hole spacetimes. We also show that at the next-leading-order, different black-hole spacetimes will lead to different BZ luminosities. As a result, while slowly rotating black holes cannot be distinguished via measurements of their jet power, rapidly rotating ones have the potential of providing information on the strong-field properties of the spacetime when independent measurements of the BZ luminosity and of the black-hole angular velocity are available.
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Astrophysics of Galaxies
Zooming in on the circumgalactic medium with GIBLE: Cloud-scale simulations with cosmological initial conditions
Rahul Ramesh, Dylan Nelson, Drummond Fielding et al. (+1 more)
We conduct simulations of $\sim$kpc-scale cool clouds in the circumgalactic medium (CGM), using initial conditions sampled from a highly resolved cosmological magneto-hydrodynamical zoom-in of a Milky Way-like
galaxy. We select ten distinct cold clouds with masses of $m_{\rm{cloud}}$ $\sim$ $10^{4.5-5}$ M$_\odot$, originally resolved at a mass resolution of $m_{\rm{gas}}$ $\sim$ $200$ M$_\odot$. To further resolve small-scale features and physics, we implement a targeted refinement scheme within spherical regions co-moving with each cloud, thereby boosting the local mass resolution by a factor of 1000, reaching $m_{\rm{gas}}$ $\sim$ $0.2$ M$_\odot$ (spatial resolution, $r_{\rm{gas,cloud}}$ $\sim$ $O(\rm{pc})$). The selected clouds have diverse properties, across a broad parameter space, resulting in heterogeneous
evolution. For the clouds we study, radiative cooling is the dominant physical process enabling cloud survival, while
magnetic fields play a comparatively smaller role. The motion of these clouds is governed not only by drag forces that decelerate them, but also by acceleration from momentum exchange with the complex background velocity field, which can cause them to move faster than ballistic projectiles set by their initial velocities. Our results suggest that the non-trivial details of realistic cosmological initial conditions – specifically the complex density, temperature, and velocity fields – may play an important role in subsequent cloud
evolution, and that sampling the output of an existing large-scale simulation provides a self-consistent approach to capture these effects without ad hoc assumptions.
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All authors Rahul Ramesh, Dylan Nelson, Drummond Fielding, Marcus Brüggen
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Black hole scalar sirens in the Milky Way
Daniel Gavilan-Martin, Olivier Simon, Dhashin Krishna et al. (+3 more)
Hypothetical light scalar particles trigger the superradiant instability around spinning black holes (BHs), causing clouds of scalars to grow around the BH. In the presence of sufficiently strong particle self-interactions (characterized by the decay constant $f$), scalars are ejected from BH orbits, resulting in coherent, non-relativistic emissions that continuously carry away the BH's angular momentum. Parameters exist for which cloud growth is much faster, and scalar depletion is much slower, than the age of the
Galaxy. This defines a distinct class of astrophysical sources of scalars, which we call BH scalar sirens – BHs that persistently emit scalars effectively forever. We compute the scalar background from the expected population of $N_\text{BH}\sim 10^{8}$ isolated
stellar-mass BHs in the Milky Way, which are sirens for scalars in the mass range $10^{-13}$–$10^{-11}\,$eV and $f\lesssim 10^{14}$–$10^{9}\,$GeV. This provides a detection target independent of early-universe scalar production or cosmological initial conditions. The generated observable signals are up to two orders-of-magnitude larger than those expected from a misaligned
cosmic scalar in this mass range. The energy spectrum of emitted scalars is distinctly broader and at higher velocities (up to $\sim 10^{-1}c$) than that of virialized dark matter, and encodes the mass and
spin distributions of the BH population. While
stellar-mass Milky Way BHs are our primary target, our framework extends to supermassive, intermediate-mass and light BHs. Given the difficulty of directly observing populations of isolated BHs, scalar emissions offer a novel probe of these otherwise invisible objects, highlighting the potential for joint discovery between scalars and BHs, and broadly motivating searches for scalars over many orders-of-magnitude in mass.
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All authors Daniel Gavilan-Martin, Olivier Simon, Dhashin Krishna, Derek F. Jackson Kimball, Dmitry Budker, Arne Wickenbrock
High Energy Astrophysical Phenomena
Hydrodynamical simulations of helium-ignited binary white dwarf mergers
Vrutant Mehta, Vishal Tiwari, Ruediger Pakmor et al. (+2 more)
Type Ia
supernovae (SNe Ia) are common luminous astrophysical transients. SNe Ia serve as distance indicators for measuring the expansion rate of the universe and play important roles in
galactic nucleosynthesis. However, ambiguities persist regarding the nature of their
stellar progenitors and explosion mechanisms. The recent discovery of
Gaia hypervelocity white
dwarfs (WDs) has provided direct evidence in support of helium-ignited double degenerate SNe Ia. In this study, we investigate the outcomes of helium-ignited double-degenerate WD mergers by performing a set of 3D hydrodynamical simulations with two different codes: AREPO and FLASH. We consider two distinct binary WD systems close to helium ignition, evolving each with both codes while keeping initial conditions fixed. The first binary WD model produces a double detonation of the primary WD and the hypervelocity ejection of the surviving secondary, similar to the canonical dynamically driven double degenerate double detonation (D6) scenario. In the second model, the secondary also undergoes a core detonation, resulting in the complete disruption of both WDs. Notably, despite utilizing distinct numerical solvers,
nuclear reaction networks, and mesh strategies, AREPO and FLASH produce broadly consistent outcomes for both sets of initial conditions. While the nucleosynthetic yields differ due to the different
nuclear reaction networks employed, the overall agreement between the simulations demonstrates the robustness of the numerical modeling of this scenario. Our results strongly support the viability of both the D6 and quadruple detonation channels for at least some SNe Ia. We explore the prospective observational signatures of this channel, including in the X-rays using XRISM's RESOLVE.
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All authors Vrutant Mehta, Vishal Tiwari, Ruediger Pakmor, Divyanshu Singh, Robert Fisher
Earth and Planetary Astrophysics
TESS Planet Occurrence Rates Reveal the Disappearance of the Radius Valley Around Mid-to-Late M Dwarfs
Erik Gillis, Ryan Cloutier and Emily Pass
We present the deepest systematic search for
planets around mid-to-late M
dwarfs to date. We have surveyed 8134 mid-to-late M
dwarfs observed by TESS with a custom built pipeline and recover 77 vetted transiting
planet candidates. We characterize the sensitivity of our survey via injection-recovery and measure the occurrence rate of
planets as a function of orbital period, instellation, and
planet radius. We measure a cumulative occurrence rate of $1.10\pm0.16$
planets per
star with radii $>1\, R_\oplus$ orbiting within 30 days. This value is consistent with the cumulative occurrence rate around early M
dwarfs, making M
dwarfs collectively the most prolific hosts of small close-in
planets. Unlike the bimodal Radius Valley exhibited by close-in
planet population around FGK and early M
dwarfs, we recover a unimodal
planet radius distribution peaking at $1.25\pm0.05 \, R_\oplus$. We additionally find $0.954\pm0.147$ super-Earths and $0.148\pm0.045$ sub-Neptunes per
star, with super-Earths outnumbering sub-Neptunes 5.5:1, firmly demonstrating that the Radius Valley disappears around the lowest mass
stars. The dearth of sub-Neptunes around mid-to-late M
dwarfs is consistent with predictions from water-rich pebble
accretion models that predict a fading Radius Valley with decreasing
stellar mass. Our results support the emerging idea that the sub-Neptune population around M
dwarfs is composed of water-rich worlds. We find no hot Jupiters in our survey and set an upper limit of 0.012 hot Jupiters per mid-to-late M
dwarf within 10 days.
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Astrophysics of Galaxies
Revisiting the Perseus Cluster III: Role of Aspherical Explosions on its Chemical Composition and Extension to Metal-Poor Stars and Galaxies
Shing-Chi Leung, Henry Yerdon, Seth Walther et al. (+2 more)
The Perseus Cluster has been precisely measured by the legacy Hitomi
telescope on the Si-group (Si, S, Ar, Ca) and Fe-group elements (Cr, Mn, Ni). These element abundance ratios provide insight into the typical behaviour of
supernovae. In Paper II, we presented new massive
star explosion models at various
metallicity, assuming spherical explosions. We show that while the fitting is improved, some features (e.g., Ni/Fe) remain to be improved. In this article, we extend our calculation to an aspherical explosion using the jet-induced explosion mechanism. The detailed pre- and post-explosion chemical profiles are calculated with a large post-processing network to capture the production of odd-number elements (V, Mn, Cu) and iron-group elements. We further explore how the jet-driven explosions create the diversity of models which could be compatible with the observed diversity in terms of $^{56}$Ni-mass vs ejecta mass, Ti-V relation, and
stellar abundances. Finally, we apply the new collapsar models in the
Galactic Chemical
Evolution context. We study how the
galactic stars, including the Zn-enriched
star HE 1327-2326, can put constraints on the relative rates of collapsar and some of its model parameters. We show that collapsar could lead to significant changes in some elements, e.g., Zn. Our study shows that the collapsar is a necessary component to explain multiple elemental trends observed in the Milky Way
Galaxy.
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All authors Shing-Chi Leung, Henry Yerdon, Seth Walther, Ken'ichi Nomoto, Aurora Simionescu
Solar and Stellar Astrophysics
Revisiting the Perseus Cluster II: Metallicity-Dependence of Massive Stars and Chemical Enrichment History
Shing-Chi Leung, Seth Walther, Henry Yerdon et al. (+2 more)
The legacy Hitomi
telescope has delivered the precise measurements of the chemical abundances in the Perseus Cluster, covering the Si-group (Si, S, Ar, Ca) and Fe-group elements (Cr, Mn, Ni). In Paper I (Leung et al., ApJ 2025), we examined the role of convection parameters and presented new core-collapse
supernova (CCSN) explosion models at
solar metallicity, which fit the observed abundance pattern. In this article, we extend our calculation for the
stellar evolutionary models and CCSN models of the initial mass $15 - 60M_{\odot}$ and the
metallicity $Z = 0 - Z_{\odot}$. The detailed pre- and post-explosion chemical profiles are calculated with a large post-processing network to capture the production of $\alpha$-chain elements (e.g., Si, S, Ar), odd-number elements (e.g., P, K, Cl), and iron-group elements (e.g., Mn, Ni). We study the role of CCSNe in the production of these elements. We compare the
galactic chemical
evolution model based on the nucleosynthesis yield of the new massive
stars and other yield tables from the literature. For each
supernova yield, we perform parameter surveys and search for configurations that produce the best-fit model and best-rate model using the Perseus Cluster as the reference. From the survey, we study how individual chemical elements affect the contributions of massive
stars and Type Ia
supernovae in the
cosmic chemical enrichment
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All authors Shing-Chi Leung, Seth Walther, Henry Yerdon, Ken'ichi Nomoto, Aurora Simionescu
Astrophysics of Galaxies · Cross-listed from hep-ph
Ruling Out Spiky WIMP Dark Matter using Indirect Searches
Dibya S. Chattopadhyay, P. S. Bhupal Dev and Yago Porto
The dark matter (DM) density profile in the innermost region of the
Galaxy remains an open question. In particular, while adiabatic growth of the supermassive black hole Sgr A$^\ast$ at the
Galactic Center (GC) can induce a 'spike' in central DM density, the existence of such a spike is still under debate. Here we present new constraints on the spike slope $\gamma_{\rm sp}$ using conventional DM indirect detection searches. We first recast existing
photon and
neutrino line searches, which include the contribution from the GC region, into constraints on the thermally-averaged DM annihilation cross section $\langle\sigma v\rangle$ in the presence of a DM spike. We then derive new bounds on the spike profile for a generic Weakly Interacting Massive Particle (WIMP) DM scenario, where the thermal freeze-out mechanism fixes the annihilation cross-section at $\langle\sigma v\rangle\sim (2-3) \times 10^{-26}~{\rm cm}^3~{\rm s}^{-1}$. We find that, for DM annihilation to
photons, existing
Fermi-LAT and MAGIC data place strong constraints on spike profiles at the GC over a broad range of WIMP DM masses, from 10 GeV to 100 TeV, for
photon branching fractions down to $\sim 10^{-2}$, and remain sensitive to values as small as $\sim 10^{-4}$ in parts of the parameter space. For the
neutrino channel, we use the recent IceCube data to constrain the existence of an extremely steep spike in the $\mathscr{O}(1-10)$~TeV DM mass range. Our analysis can be easily extended to other annihilation channels.
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Instrumentation and Methods for Astrophysics
Reconstruction of cosmic-ray direction and energy in radio arrays using deep ensemble graph neural networks
Arsène Ferrière, Aurélien Benoit-Lévy, Olivier Martineau-Huynh et al. (+1 more)
Using advanced machine learning techniques, we developed a method to reconstruct the arrival direction and energy of ultra-high-energy
cosmic rays from the voltage traces they induce on ground-based
radio detector arrays. In our approach, triggered
antennas are represented as a graph structure, which serves as input for a graph neural network (GNN). By incorporating physical knowledge into both the GNN architecture and the input data, we improve the precision and reduce the required size of the training set with respect to a fully data-driven approach. This method achieves an angular resolution of 0.092 degrees and an electromagnetic energy reconstruction resolution of 16.4% on simulated data with realistic noise conditions. We also employ uncertainty estimation methods to enhance the reliability of our predictions, quantifying the confidence of the GNN's outputs and providing confidence intervals for both direction and energy reconstruction. Finally, we investigate strategies to verify the model's consistency and robustness under real-life variations, with the goal of identifying scenarios in which predictions remain reliable despite domain shifts between simulation and reality.
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All authors Arsène Ferrière, Aurélien Benoit-Lévy, Olivier Martineau-Huynh, Matías Tueros
Astrophysics of Galaxies
Extreme Emission Line Galaxies in CEERS Are Powered by Star Formation, not AGN
Kelcey Davis, Madisyn Brooks, Jonathan R. Trump et al. (+28 more)
We present a spectroscopic study of photometrically identified extreme emission-line
galaxies (EELGs) with observed-frame equivalent widths (EWs) >5000 A of either H alpha or H beta + [OIII] in the CEERS legacy deep field utilizing JWST NIRSpec spectroscopy from the CAPERS, RUBIES, THRILS and CEERS surveys. This master sample allows for performance tests of photometric selections and unveils what types of sources, either AGN or young
star formation, were producing excessive ionizing radiation in the early Universe. We identify AGN through broad H alpha emission-lines and report 6 new broad-line AGN at 3.5<z<7 identified by the deep (~8 hr) G395M THRILS survey. We investigate the photometrically selected EELGs in a color-color plot designed for “Little Red Dot” selection and demonstrate that it effectively removes AGN with non-extreme lines from the sample. EELGs with and without broad lines show similar optical line ratios. We compare emission-line morphology to EWs and continuum morphologies and find that [OIII] morphology is more compact at higher EW. ~10% of photometrically selected EELGs have broad Balmer lines, jumping to 35% in deep spectroscopy which indicates a significant fraction of photometrically selected EELGs may host AGN. However, many AGN selected as EELGs have incorrectly high photometric EWs. For sources with extreme emission-line EWs that pass our photometric criteria and host an AGN, we find that the narrow H alpha component dominates over the broad, especially in the highest-EW sources. This implies that even when an AGN is present, it does not dominate the extreme emission.
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All authors Kelcey Davis, Madisyn Brooks, Jonathan R. Trump, Vital Fernández, Taylor A. Hutchison, Rebecca L. Larson, Anthony J. Taylor, Elizabeth J. McGrath, Guillermo Barro, Anton M. Koekemoer, Pablo Arrabal Haro, Mark Dickinson, Bren E. Backhaus, Nikko J. Cleri, Steven L. Finkelstein, Ananya Ganapathy, Raymond C. Simons, Ricardo O. Amorín, Alexander de la Vega, Norman A. Grogin, Michaela Hirschmann, Weida Hu, Jarrett L. Johnson, Jeyhan S. Kartaltepe, Dale Kocevski, Mario Llerena, Ray A. Lucas, Madeline A. Marshall, Fabio Pacucci, Laura Pentericci, Phoebe R. Upton Sanderbeck
High Energy Astrophysical Phenomena
A precessing jet from a supermassive black hole: multi-wavelength observations of S5 1044+71
M. Cerruti, P. A. Duverne, G. Ganesaratnam et al. (+3 more)
The bright gamma-ray blazar S5 1044+71 has been identified as showing very significant quasi-periodic oscillations in the
Fermi-LAT data in recent studies, with a periodicity of about 3 years. With the completion of a new gamma-ray cycle, we aim to revisit the periodicity in
Fermi-LAT data, and analyze all available multi-wavelength (MWL) data to search for possible correlations and time-lags. These observations will be used to test for the compatibility of the observed periodicity with a precessing jet from the supermassive black hole. We analyze data from
Fermi-LAT, NuSTAR, Swift, AstroSat, ASAS-SN, ZTF, Pan-STARRS, and NEOWISE. In addition we present an analysis from historical observations from Palomar and Pulkovo. Single-band spectral variability, MWL correlations, and cross-correlations are computed. We then model the
Fermi-LAT light curve with a precessing jet model, providing constraints on the geometry of the system and the
evolution of the Doppler factor. The latter is used as a geometrical constraint in the modeling of the spectral energy distributions. We confirm previous claims on the existence of a periodic gamma-ray signal. We detect significant spectral variability in gamma-ray, X-rays, and optical/UV data. We detect significant correlation between low-energy (infrared/optical/ultraviolet) data and gamma-rays, with a correlation index of about 1; the correlation between X-rays and gamma-ray is milder, with a correlation index of about 0.3. We do not detect any significant time-lag between bands. The
Fermi-LAT light curve is successfully fit by a precessing jet model. The fit to the spectral energy distributions indicate that S5 1044+71 is a typical blazar, in which the gamma-ray emission is located beyond the broad-line region. All MWL observations we present in this work are consistent with the existence of a precessing relativistic jet from the supermassive black hole.
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All authors M. Cerruti, P. A. Duverne, G. Ganesaratnam, P. Goswami, H. X. Ren, N. Sahakyan
High Energy Astrophysical Phenomena
A White Dwarf Tidal Disruption by an Intermediate-Mass Black Hole as the Progenitor of Ultra-long GRB 250702B
Chengchao Yuan, Ning Jiang and Zi-Gao Dai
The recent detection of GRB 250702B, the longest gamma-ray burst observed to date with
prompt emission lasting $\sim 2.5\times 10^4$ seconds, challenges the conventional collapsar model. Its remarkable features–including an extraordinary X-ray
flare at $\sim 1.3$ days post-detection, a late-time transition from steep to shallow decay in the X-ray afterglow, and hard spectra extending from keV to MeV energies–point to a novel progenitor. Here we show that these multiwavelength signatures can be consistently explained by a relativistic jet powered by successive partial
tidal disruptions of a white
dwarf (WD) by an intermediate-mass black hole (IMBH). By modeling the time-dependent
accretion rate from repeated partial disruptions and the resulting jet
evolution, we show that the external forward and reverse shocks account for the long-term X-ray, near-infrared, and
radio afterglow, whereas the luminous X-ray
flare originates from internal energy dissipation caused by collisions between fast and slow relativistic ejecta associated with the final complete disruption. Our findings establish IMBH-WD
tidal disruption events as a viable engine for ultra-long GRBs.
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Solar and Stellar Astrophysics
Dyson spheres on H-R diagram
Amirnezam Amiri
The construction of Dyson spheres, megastructures designed to capture the total radiative output of
stars, can be one of the most compelling techno-signature scenarios for advanced extraterrestrial civilizations. By considering
equilibrium temperatures, we investigate the luminosities and fluxes of Dyson spheres built around two promising classes of host
stars: white
dwarfs and red M-
dwarfs. Using radiative balance arguments and representative
stellar parameters, we compute the temperature-radius relationship for full energy interception and place these hypothetical structures on the Hertzsprung-Russell (H-R) diagram to assess their observational signatures. Our results show that Dyson spheres around white
dwarfs produce cooler and fainter blackbody emissions, peaking in the near- to mid-infrared, while those around M-
dwarfs radiate more strongly but at longer wavelengths. In both cases, the
equilibrium temperature decreases as R_ D^-1/2, while the total luminosity and observed bolometric flux remain fixed by the
stellar output. These findings highlight the astrophysical suitability of low-luminosity
stars as Dyson sphere hosts and provide practical constraints for future techno-signature searches using infrared surveys.
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Cosmology and Nongalactic Astrophysics
Imprints of primordial magnetic fields in gravitational collapse during early structure formation
Jennifer Schober, Molly Abramson, Sayan Mandal et al. (+2 more)
Context.
Primordial magnetic fields (PMFs) generated in the early Universe might have left observable imprints on present-day large-scale structure. However, the spatial scales on which
primordial signatures are able to survive the nonlinear processes that accompany structure formation remain unclear. Aims. The aim of this study is to investigate the
evolution of the statistical properties of PMFs during the onset of gravitational collapse. Methods. We performed a suite of high-resolution direct numerical simulations of isothermal self-gravitating, magnetized gas clouds. By varying the viscosity, we probed different Reynolds-number regimes and follow the coupled
evolution of gravitational collapse and magnetohydrodynamic
turbulence. Results. At sufficiently high Reynolds numbers,
turbulence generated during collapse triggers the onset of a small-scale dynamo, which amplifies
magnetic energy below the Jeans scale and modifies the
magnetic energy spectrum significantly. The question of whether dynamo amplification dominates the
magnetic field
evolution is determined by the competition between the dynamo growth time and the free-fall time. Conclusions. Our results highlight the importance of resolving the Jeans scale and the associated turbulent inertial range in cosmological magnetohydrodynamic (MHD) simulations to accurately capture the interplay between gravitational compression and dynamo amplification and to assess which structures retain
memory of
primordial fields.
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All authors Jennifer Schober, Molly Abramson, Sayan Mandal, Salome Mtchedlidze, Tina Kahniashvili
High Energy Astrophysical Phenomena
Variability of the X-ray obscuring wind in Mrk 335 with XMM-Newton/RGS
Daniele Rogantini, Erin Kara, Luigi Gallo et al. (+10 more)
Transient X-ray obscuration in Seyfert 1
galaxies likely arises from clumpy
accretion-disk winds near the broad-line region (BLR), but the wind structure and short-timescale variability are difficult to measure because high-resolution spectra are often suppressed during deep low states. We analyse a coordinated XMM-Newton/NuSTAR campaign on Mrk 335 in June 2021, with long-term Swift monitoring, capturing the source in an intermediate-flux state with strong RGS absorption features. We model the broadband SED to determine the ionising continuum for self-consistent photoionisation modelling of the RGS spectra. The stacked RGS spectrum requires three photoionised absorbers with log xi ~ 3.69, 2.97, and 1.91, outflowing at |v_out| ~ 5800, 3200, and 2100 km/s, respectively. Their properties are consistent with the three-phase obscurer reported in 2009, indicating that a similar multi-phase obscuring wind can persist over decade timescales. Using five consecutive RGS observations, we track the wind
evolution on day timescales and find strong variability in column density and ionisation in all phases, together with smaller but coherent velocity changes. During a
flare, the low-ionisation phase shows a significant drop in opacity, while in the subsequent epoch all phases show increased
outflow velocities, suggesting a possible connection between continuum variability and changes in the line-of-sight absorber. The high-ionisation phase responds most directly to changes in ionising luminosity, while the lowest-ionisation phase shows at most a delayed response. Order-of-magnitude constraints place the obscurer at BLR scales, ~10^3-10^5 Rg, with kinetic power potentially reaching the percent level of L_bol for plausible assumptions on geometry and clumpiness.
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All authors Daniele Rogantini, Erin Kara, Luigi Gallo, S Komossa, Peter Kosec, Christos Panagiotou, Dan Wilkins, Ehud Behar, Joheen Chakraborty, Dirk Grupe, Missagh Mehdipour, Ciro Pinto, Irina Zhuravleva
Solar and Stellar Astrophysics
Tidal Synchronization of Binaries in Pleiades
Li Wang, Chenyu He, Chengyuan Li et al. (+1 more)
Tidal interactions in close binaries play a key role in the long-term rotational and orbital
evolution. The distributions of circularization across open clusters (OCs) place strong observational constraints on
tidal dissipation in binaries. However, direct observational constraints on synchronization among binaries in OCs remain limited. For the 125 Myr OC Pleiades, this work combines cluster membership from
Gaia Data Release 3, rotation periods from the K2 mission, and orbital solutions of the binary population from a long-term spectroscopic survey, to investigate the degree of
tidal synchronization in each binary by comparing the pseudo-synchronization period to the rotation period of the primary
stars. Among 42 binaries with reliable orbital periods Porb and rotation periods, we identify seven tidally synchronized systems with Porb < 8.6 days, including one early-type system and six late-type systems. For binaries with longer Porb, primaries generally are super-synchronized, and most systems are eccentric. We find a synchronization transition near Porb ~ 8.6-14 days, comparable to the known circularization period (Porb ~ 7.2 days) in the Pleiades, which suggests similar critical period scales for synchronization and circularization in this coeval population. Synchronization depends much more strongly on mass ratio than on primary mass. Most synchronized systems in Pleiades have high mass ratios and are likely to evolve into double white
dwarf systems. Tides likely impose strong rotational braking on close early-type binaries, while their influence on late-type close binaries is weaker, and their
spins largely follow the single-
star sequence.
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All authors Li Wang, Chenyu He, Chengyuan Li, Gang Li
Earth and Planetary Astrophysics
Elevated Eccentricities in the Radius Valley Hint at Water-Rich Mini-Neptunes
Sho Shibata and Andre Izidoro
While recent
planet-formation models broadly reproduce the observed population of super-Earths and mini-Neptunes, as well as the bimodal radius distribution (the “radius valley”), it remains unclear whether all these
planets share a common rocky composition (a single popoulation of
planets) or instead comprise two distinct populations – rocky
planets and icy
planets (two populations of
planets). The inferred eccentricity-radius relation, which shows a modest peak near the radius valley, provides a useful diagnostic for distinguishing between these scenarios. Here we use N-body simulations to examine how the radii and eccentricities of close-in
planets depend on the masses and orbital configurations of their progenitor protoplanets. We find that final planetary eccentricities scale with the system initial Safronov number. In two-population systems, energy equipartition between rocky and relatively more massive icy protoplanets creates a strong eccentricity contrast between the two groups, which appears as a peak near the radius valley. This signature does not appear if planetary systems are composed exclusively of rocky
planets (with or without H-rich atmospheres), as assumed in photoevaporation and core-powered mass loss models. Because the eccentricity-radius relation traces a dichotomy in the underlying protoplanet mass distribution – most plausibly arising from formation at different disk locations – our results suggest that a significant fraction of mini-Neptunes are water-worlds. The observed radius and eccentricity distributions may reflect a mixture of systems that host exclusively rocky
planets, systems dominated by icy
planets, and systems with both rocky and icy
planets.
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High Energy Astrophysical Phenomena
The Axion-Photon Mixing and the Extragalactic Magnetic Background: Plateau Regimes, Resonances, and Non-Gaussian Boosts
Andrea Addazi, Yi-Fu Cai, Salvatore Capozziello et al. (+2 more)
We present an analytical treatment of
Axion-Like-Particle (ALP)–
photon mixing with extragalactic background light (EBL) attenuation for constant, Gaussian-
stochastic, and non-Gaussian
magnetic field configurations–with direct implications for Very High Energy (VHE) gamma-ray observations such as LHAASO, HAWC, and CTA experiments. For constant fields, we derive exact probabilities and identify a perturbative plateau regime where
photon survival scales as quartic order of
magnetic field, isolating the four-point
magnetic correlation as a sensitive probe of non-Gaussianity. For Gaussian
stochastic fields, we obtain–for the first time–analytical formulas for non-exponential-decay components in the strong-attenuation regime. Contrary to the widely used domain-like model,
photon survival is suppressed by 4-6 orders of magnitude, while both conversion and survival probabilities exhibit distinct multi-peak structures from mass-equal resonance,
stochastic resonance, and EBL attenuation. Extending to non-Gaussian fields, we show that non-Gaussianity can enhance
photon survival by several orders of magnitude relative to the Gaussian case, potentially explaining the unexpectedly VHE
photon event observed by LHAASO. Our results demonstrate that
stochastic magnetic fields cannot be reduced to domain-like coherence without losing essential physics, and that VHE gamma-ray spectra encode observable information about both the power spectrum and non-Gaussian structure of intergalactic
magnetic fields–critical as next-generation observatories push toward PeV sensitivities.
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All authors Andrea Addazi, Yi-Fu Cai, Salvatore Capozziello, Qingyu Gan, Gaetano Lambiase
High Energy Astrophysical Phenomena
Spectral Universality of Turbulent Fluctuations in Relativistic Flows
Alexander G. Tevzadze
We develop a Lorentz-covariant framework for projecting spacetime spectra into temporal spectra of stationary turbulent fluctuations in relativistic flows. For self-similar spacetime spectra, we derive a universal scaling relation, $\alpha = \beta - D$, where $\alpha$ is the temporal spectral index, $\beta$ the spacetime homogeneity exponent, and $D$ the effective dimensionality of spectral support. We further demonstrate that this universality breaks down when spacetime homogeneity is violated. Temporal spectra in relativistic flows are thus intrinsically nonlocal observables, requiring a covariant projection framework that establishes a general principle for spectral inference in relativistic
plasma turbulence and high-energy
plasma flows.
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High Energy Astrophysical Phenomena
The extremely low-luminosity Type Iax SNe 2022ywf and 2023zgx
Barnabás Barna, Dominik Bánhidi, Tamás Szalai et al. (+25 more)
We present the optical follow-up of SNe 2022ywf and 2023zgx, two examples from the Iax subclass of thermonuclear
supernova (SN) events. With peak absolute magnitudes of $M_\mathrm{V} = -13.7$ and $-14.4$ mag, respectively, both objects belong to the extremely low-luminosity (EL) population of the class. A common origin of SNe in the Iax subclass is still under debate since the distribution of certain observables may indicate that the extremely low-luminosity explosions form a distinct population. We aim to estimate the physical properties of the two EL objects, including mapping the ejecta structure. We perform spectral
tomography on the spectral series of SNe 2022ywf and 2023zgx around their maxima to map the physical properties of the ejecta. Together with the analysis of BgVriz photometry, a wide range of observables can be studied to investigate their distribution against luminosity. The constrained chemical abundances of the ejecta are compared to the predictions of the hydrodynamic simulations with similar peak luminosities. Constant abundances provide a good match for the distribution of chemical elements for both SNe 2022ywf and 2023zgx. The discrepancies compared to the least luminous pure deflagration model N5def_hybrid are minor, especially at post-maximum epochs. The two SNe also share similar characteristics in their constrained density structures, as well as the
evolution of the photosphere. The analysis supports the assumption that pure deflagration models can reproduce the main characteristics of SNe Iax, even for the EL population. The presented indirect observational evidence indicates that these objects show similar intrinsic properties to the relatively luminous Iax sample and fit into the velocity distribution of the subclass.
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All authors Barnabás Barna, Dominik Bánhidi, Tamás Szalai, Joseph P. Anderson, Teresa Boland, K. Azalee Bostroem, Ting-Wan Chen, Joseph Farah, Mariusz Gromadzki, Griffin Hosseinzadeh, D. Andrew Howell, Cosimo Inserra, Saurabh W. Jha, Lindsey A. Kwok, Colin Macrie, Curtis McCully, Erika Mochnács, Tomás E. Müller-Bravo, Megan Newsome, Estefania Padilla Gonzalez, Jeniveve Pearson, Tanja Petrushevska, David J. Sand, Manisha Shrestha, Nathan Smith, Shubham Srivastav, Giacomo Terreran, József Vinkó
Solar and Stellar Astrophysics
Sulfur fractionation in coronal plumes as observed by Solar Orbiter/SPICE
Slimane Mzerguat, Miho Janvier, Eric Buchlin et al. (+4 more)
Coronal plumes are bright, narrow structures rooted in coronal holes that contribute to the
solar wind. Their composition, particularly elemental fractionation as a function of first ionization potential (FIP), provides diagnostics of
plasma properties and
magnetic connectivity. Earlier plume studies of fractionation using low-FIP elements reached conflicting conclusions. Intermediate-FIP elements may provide additional diagnostic insight, since their fractionation is thought to involve processes beyond those affecting low-FIP species. We investigate sulfur (intermediate-FIP element) in plumes to assess the presence of fractionation, its
evolution, and its relation to wave activity. We analyzed
Solar Orbiter observations of two plumes in an equatorial coronal hole during March–April 2024, using Spectral Imaging of the Coronal Environment (SPICE) to derive the sulfur-to-nitrogen ratio. EUV imaging and magnetograms provided additional context. Data were processed with the open-source Python tool Spectral Analysis Fitting Framework and Reduction of Noise (SAFFRON). Both plumes showed sulfur fractionation that remained constant within uncertainties. The fractionated
plasma was co-located with strong
magnetic footpoints, in contrast with the surrounding interplume
plasma. These results provide the evidence for sulfur fractionation in plumes and suggest, consistent with the ponderomotive force model, wave dynamics in the chromosphere as a driver.
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All authors Slimane Mzerguat, Miho Janvier, Eric Buchlin, Deborah Baker, Andy S.H. To, David M. Long, Natalia Zambrana Prado
Solar and Stellar Astrophysics
Searching for low-mass stars with magnetically-induced hyper-inflated radii
D. J. Mullan and J. MacDonald
Precise empirical estimates of
stellar radii have revealed that the radii of certain low-mass
stars are inflated relative to
stellar structure predictions: the largest inflations occur in magnetically active
stars. Theoretically, the radii of magnetically active
stars are in some cases found to be 'hyper-inflated' to roughly double the radius of a non-
magnetic star with equal mass. Here we ask, do data exist which could allow us to search for empirical evidence in support of hyper-inflated
stars? A photometric study of 44 eclipsing binaries in the Kepler field by Cruz et al. may help us in our search. The Cruz et al. study, although subject to large uncertainties, hints at the presence of hyper-inflation in some of the 88
stars in their sample. Their data enable us to set theoretical limits on the maximum strength Bc of
magnetic fields inside their sample
stars. According to our magneto-convective model, the average empirical inflations found from analysis of the Cruz et al. data can be replicated if Bc approx. 10 kG inside
stars with masses greater than ~ 0.6 MSun. On the other hand, in
stars with masses less than about 0.4 MSun, our model predicts that the average empirical inflations of the
stars may approach hyper-inflated status. Such
stars may require significantly stronger internal fields, i.e. Bc approx. 100-300 kG. High-resolution spectroscopy of the Kepler binaries could help to confirm or refute our conclusions.
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Astrophysics of Galaxies
Distribution functions for spheroids
James Binney
Galaxy models comprising several components (including dark matter) that are bound by the self-consistently generated gravitational field are readily constructed from distribution functions (DFs) that are analytic functions of the action integrals J. We explain why such models have unphysical velocity distributions unless the DFs of hot components satisfy certain conditions as J_\phi -> 0. We show how DFs for both isotropic and radially biased spherical systems can be constructed with specified f(J). We show how to construct DFs for flattened systems with significant velocity anisotropy. Construction of self-consistent models rather than populations that are confined by an external potential leads to the conclusion that radially-biased spherical systems are generically unstable to quadrupolar perturbations. Chaos is likely key to maintenance of these constraints during adiabatic disc growth.
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Earth and Planetary Astrophysics
TEPCat: The Transiting Extrasolar Planet Catalogue
John Southworth
Transiting extrasolar
planets are extraordinarily valuable for understanding the characteristics and formation of
planets, because they are the only
exoplanets whose physical and orbital properties can be measured to high precision. Thousands are now known, and it is important to maintain a database of them for use by the scientific community. TEPCat performs this task: it is a critical compilation of the physical and observable properties of the known transiting planetary systems. This work introduces the motivation for TEPCat, its scope, contents, and implementation. Example plots of interesting quantities are constructed. The classification of
planets and of the eclipse features in their light curves is discussed. TEPCat is maintained and freely available online at https://www.astro.keele.ac.uk/jkt/tepcat/
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Astrophysics of Galaxies
Sanjeev Kumar, A.K. Awasthi and Mahesh Kumar
We present a computational framework for
galactic evolution based on a coupled
stochastic nonlinear oscillator, implemented with the
Stochastic Hopf Engine. Gas density ($G$) and
star formation rate ($S$) co-evolve through a supercritical
Hopf bifurcation, capturing the transition from quiescent stability to merger-driven starbursts. Scatter in dark matter
halo properties, modeled as multiplicative noise via the Euler–Maruyama method, broadens the bifurcation into a regime where noise-induced bursts occur below the deterministic threshold. Simulations reveal a periodic signature, the
Galactic Heartbeat, emerging as a deterministic limit cycle validated by the data3 resonance peak in the
star-formation spectrum. A radial reduction yields an effective Fokker–Planck equation for burst amplitude; its stationary solution matches numerical PDFs, providing statistical closure. Including differential shear $\Omega(r)$ and spatially varying bifurcation fields reproduces spiral morphologies and AGN-driven quenching. Driving the growth parameter sub-critical ($r_{agn} < 0$) yields “Red and Dead” cores via attractor collapse. Dark matter
halo scatter suppresses mean
star formation while enhancing intermittency, offering a minimal yet interpretable framework linking local feedback and global potentials to macroscopic
galactic evolution.
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Instrumentation and Methods for Astrophysics
A High-Throughput AES-GCM Implementation on GPUs for Secure, Policy-Based Access to Massive Astronomical Catalogs
Samuel Lemes-Perera, Miguel R. Alarcon, Pino Caballero-Gil et al. (+1 more)
The era of large astronomical surveys generates massive image catalogs requiring efficient and secure access, particularly during pre-publication periods where data confidentiality and integrity are paramount. While Findable, Accessible, Interoperable, and Reusable (FAIR) principles guide the eventual public dissemination of data, traditional security methods for restricted phases often lack granularity or incur prohibitive performance penalties. To address this, we present a framework that integrates a flexible policy engine for fine-grained access control with a novel GPU-accelerated implementation of the AES-GCM authenticated encryption protocol. The novelty of this work lies in the adaptation and optimization of a parallel tree-reduction strategy to overcome the main performance bottleneck in authenticated encryption on GPUs: the inherently sequential Galois/Counter Mode (GCM) authentication hash (GHASH). We present both the algorithmic adaptation and its efficient execution on GPU architectures. Building on optimized GPU AES kernels from recent work in cryptographic acceleration, this work presents the first integration of these techniques into a high-throughput, FITS-aware encryption framework specifically designed for large-scale astronomical data, combining cryptographic authentication, dual-key access control, and direct compatibility with the standard astronomical Python ecosystem. Our implementation transforms the sequential GHASH computation into a highly parallelizable, logarithmic-time process, achieving authenticated encryption throughput suitable for petabyte-scale image analysis. Our solution provides a robust mechanism for data providers to enforce access policies, ensuring both confidentiality and integrity without hindering research workflows, thereby facilitating a secure and managed transition of data to public, FAIR archives.
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All authors Samuel Lemes-Perera, Miguel R. Alarcon, Pino Caballero-Gil, Miquel Serra-Ricart