High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Resonant neutrino flavor conversion within dark matter spikes
P. S. Bhupal Dev, Elisa Gaido, Alejandro Ibarra et al. (+1 more)
We investigate how
neutrino–dark matter (DM) interactions modify the flavor composition of high-energy
neutrinos from active galactic
nuclei (AGNs). Coherent forward scattering in a DM spike around the central supermassive black hole can generate a flavor-dependent potential, inducing flavor conversion as the
neutrinos escape. We calculate the flavor composition at Earth for pion-decay and
muon-damped sources and find substantial departures from
vacuum-oscillation expectations. At
neutrino energies around $100\,\mathrm{TeV}$, the matter potential begins to compete with
vacuum oscillations when the coupling-weighted net DM number density reaches $|\epsilon_\alpha(n_\chi-n_{\bar\chi})|\sim10^{18}\,\mathrm{cm}^{-3}$. We compare our predictions with IceCube flavor triangle measurements under the illustrative assumption that the diffuse flux originates from AGNs with common
neutrino-production and DM-spike properties. Under this assumption, when the DM-induced potential acts on the
muon flavor and dominates the
vacuum terms at production, the $p\gamma$
muon-damped predictions lie outside the 95% MESE contour. High-energy
neutrino flavor measurements can therefore provide a novel probe of
neutrino-DM interactions in astrophysical environments.
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All authors P. S. Bhupal Dev, Elisa Gaido, Alejandro Ibarra, Yago Porto
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Tachyonic particle production in strongly supercooled phase transitions
Mateusz Kulejewski, Bogumila Swiezewska and Jorinde van de Vis
In strongly supercooled cosmological phase transitions, which generically lead to strong, observable gravitational-wave backgrounds, the scalar field typically transitions to a value well below the minimum of its potential. We study particle production caused by the subsequent
evolution of the field. Because some modes feature temporarily tachyonic masses, they can be efficiently produced, and a significant fraction of the energy density released in the phase transition can get converted to particles rather than gradient energy. This has consequences for the shape and amplitude of the gravitational-wave spectrum caused by the interactions in bubbles and sources a new, high-frequency signal. Moreover, it affects the bubble expansion velocity and equation of state, which can facilitate the formation of primordial black holes.
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Cosmology and Nongalactic Astrophysics
To USR or not to USR: An effective description of two-field dynamics
Samuel Sánchez López and Eemeli Tomberg
Single-field models of inflection point inflation experience a phase of ultra-slow roll (USR), leading to amplified
curvature perturbations. Recently, Lorenzoni et al. modified the scenario by adding a light spectator field, showing that it ruins USR by setting a floor for the first slow-roll parameter $\epsilon$. Mixing with isocurvature perturbations still amplifies the
curvature power spectrum. We offer an alternative point of view, arguing that the inflaton still undergoes effective USR. The spectator lifts the potential by a constant amount, and the inflaton perturbations follow single-field dynamics in the lifted inflection point potential, decoupling from the spectator perturbations. Mode mixing only affects the power spectrum dip, making it milder. We demonstrate this effective single-field behavior numerically for example models. Our results offer a simple way to study the models' parameter dependence.
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Solar and Stellar Astrophysics · Cross-listed from physics.space-ph
First Observation of a Polar Coronal Hole-like Fast Solar Wind Stream in the Sub-Alfvénic Solar Corona: an Analysis of Turbulence Properties
Riddhi Bandyopadhyay, Sujan Prasad Gautam, William H. Matthaeus et al. (+2 more)
Parker Solar Probe, near its 23rd perihelion in March 2025, sampled an extended interval of sub-Alfvénic solar wind likely originating from a large equatorial coronal hole. At heliocentric distances of approximately 10 solar radii, with speed mostly above 400 km/s, this interval is a first example of “polar coronal hole-like (PCH-l) fast" solar wind observed in the sub-Alfvénic solar corona. We characterize the
turbulence properties of this unique interval using Parker Solar Probe measurements. Despite being sampled well inside the nominal Alfvén surface, the
turbulence appears to be already well developed while remaining strongly transverse and highly imbalanced, exhibiting a large cross helicity. These observations provide new constraints on the development and
evolution of solar wind
turbulence within the lower corona.
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All authors Riddhi Bandyopadhyay, Sujan Prasad Gautam, William H. Matthaeus, Yeimy J. Rivera, Samuel T. Badman
Astrophysics of Galaxies
JWST Observations of Starbursts: The motion of dust - PAH kinematics of M82 and NGC 253 with JWST/MIRI spectroscopy
Fergus R. Donnan, Karin Sandstrom, Alberto D. Bolatto et al. (+27 more)
We present an analysis of dust kinematics in the local starburst
galaxies M82 (NGC 3034) and NGC 253 using Polycyclic Aromatic Hydrocarbon (PAH) features observed with JWST/MIRI spectroscopy. We are able to produce high-quality velocity maps of the 5.2 $\mu$m, 6.2 $\mu$m, and 11.3 $\mu$m PAH features, as well as numerous lines of molecular gas via H$_2$ rotational transitions and ionized gas from [NeII] and H recombination lines. Given the field of view and inclination, we trace a rotating disk in M82 where we observe a steep rise in the velocities followed by flattening, typical of
galaxy rotation curves. In NGC 253, however, the 6.2 $\mu$m and 11.3 $\mu$m PAH features trace the launching region of the outflow, firmly within the starburst region. We find the ionized gas also shows outflow contributions in NGC 253 while the warm molecular gas is dominated by rotation. Additionally, the molecular gas outflow velocities are lower than the ionized gas, with the 11.3 $\mu$m PAH feature consistent with the ionized gas rather than the molecular gas. We therefore suggest that PAHs are more closely associated with the ionized gas rather than the molecular at the base of the
galaxy outflow, where larger scale imaging shows comparable morphology between PAHs and HI. The 6.2 $\mu$m PAH feature has an even higher outflow velocity for both
galaxies, possibly suggesting preferential ionization of the PAHs within the faster-moving hot phase of the base of the outflow.
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All authors Fergus R. Donnan, Karin Sandstrom, Alberto D. Bolatto, Bruce T. Draine, Sara E. Duval, Ralf S. Klessen, Elisabeth A.C. Mills, Helena M. Richie, J.D.T. Smith, Sylvain Veilleux, Patricia A. Arens, Leindert A. Boogaard, Serena A. Cronin, Daniel A. Dale, Kimberly L. Emig, Rodrigo Herrera-Camus, Thomas S.-Y. Lai, Sebastian Lopez, Laura Lenkić, Rebecca C. Levy, Divakara Mayya, David S. Meier, Kaitlyn E. Sheriff, Utsav Siwakoti, Evan Skillman, Elizabeth Tarantino, Yu-Hsuan Teng, Vicente Villanueva, Fabian Walter, Paul P. van der Werf
Astrophysics of Galaxies
The molecular gas of four ram pressure stripped galaxies in the core of the Hydra I cluster
Clara C. de la Casa, Kelley M. Hess, Nikki Zabel et al. (+15 more)
We present new CO(1-0) measurements from ALMA and new HI measurements from MeerKAT in four ram pressure stripped (RPS)
galaxies in the core of the Hydra I cluster: NGC 3312, NGC 3314a, NGC 3314b and LEDA 753342. These deep data, with compatible spatial resolution in CO and HI ($\sim15''$, $\sim$4 kpc), help increase the low statistics of
galaxies observed in CO at extreme infall stage for probing how molecular and atomic gas behave under high ICM pressures. We studied the cold gas morphologies of these
galaxies, and found asymmetries in their detected CO disks with respect to their HI and optical disks. No stripped CO was found in the tails, which could support the scenario that H$_2$ displays morphological and velocity asymmetries in the disks before being stripped. We then compared the H$_{2}$/HI ratios and H$_{2}$ vs. HI deficiencies between the four Hydra I
galaxies, the xCOLDGASS sample dominated by field
galaxies and VIVA-VERTICO Virgo RPS
galaxies. LEDA 753342 ($\rm log~M_{\star}/M_{\odot} = 8.6$) is below the stellar mass limit of the reference samples ($\rm log~M_{\star}/M_{\odot} = 9$), but its $\rm M_{H_2}/M_{HI}$ and cold gas deficiencies are compatible with lower stellar mass field and Virgo cluster
galaxies. NGC 3312 and NGC 3314a are in an intermediate stage between field
galaxies and more advanced RPS Virgo
galaxies. NGC 3314b is more consistent with Virgo
galaxies more advanced in RPS, than with field
galaxies. We reason that LEDA 753342 is at a very early stage of RPS, that NGC 3314a and NGC 3312 are at a similar timescale of early but very active RPS with differences potentially due to unequal initial total baryonic mass and infall angles, and that NGC 3314b is the latest stage in RPS in the sample. These
galaxies display RPS across different evolutionary stages, and suggest that RPS starts affecting the CO reservoir before it starts being stripped from the
galaxy.
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All authors Clara C. de la Casa, Kelley M. Hess, Nikki Zabel, Emanuela Pompei, Yara L. Jaffé, Nazir Makda, Julia Healy, Johanna Hartke, Lourdes Verdes-Montenegro, Enrichetta Iodice, Sarah Blyth, Ralf Kotulla, Marie-Lou Gendron-Marsolais, Renée C. Kraan-Korteweg, Brenda Namumba, Amidou Sorgho, Roger Ianjamasimanana, John S. Gallagher
Solar and Stellar Astrophysics
PROSWIN: Probabilistic Solar Wind Speed Forecasting Using Deep Distributional Regression From Solar Images
Daniel Collin, Yuri Shprits, Luca Chiarabini et al. (+3 more)
Accurately predicting fast solar wind conditions is challenging, as uncertainties are large and unquantified by traditional single-value prediction models. In particular, the risks of high-speed solar wind streams (HSSs), which can cause damage to technological infrastructure, cannot be reliably assessed without probabilistic forecasts. We present PROSWIN, a probabilistic machine learning model that forecasts the hourly solar wind speed (SWS) at Earth with a four-day lead time. The approach combines solar images and magnetograms using a deep neural network coupled to a distributional regression
algorithm. Because standard error metrics underweight the relevance of HSS peaks, we further introduce the prediction score, a model-selection metric that jointly rewards timeline and HSS peak accuracy. On 14 years of data, our forecast achieves very well-calibrated uncertainties (<1% average deviation). Using the continuous ranked probability score (CRPS), a metric that assesses distributional accuracy, we obtain a timeline CRPS of 41.0 km/s, an HSS peak CRPS of 45.3 km/s, and a prediction score of 42.3 km/s. We find that the 171 Å channel is an important complement to the typically used 193 Å and 211 Å channels and that the prediction score for model selection improves the applicability of the model. Compared to selected models from the literature, ours is the only one that is accurate for both timeline and HSS peak values, rather than trading one off against the other. These results support the advantages of probabilistic over single-value solar wind models. The introduced methods are also transferable to other forecasting problems.
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All authors Daniel Collin, Yuri Shprits, Luca Chiarabini, Stefan J. Hofmeister, Nadja Klein, Guillermo Gallego
Earth and Planetary Astrophysics
Characterization of Planetary Systems with Astrometry
Gisela N. Ortiz-Leon
Astrometry is the oldest method used to search for extrasolar
planets. This technique provides key information about a planetary system, like the true mass of
planets and its three-dimensional orbital architecture. Nowadays, the space-based mission Gaia, on one hand, and ground-based interferometry at infrared and
radio wavelengths, on the other hand, can achieve astrometric accuracies of tens of micro-arseconds. Thanks to this unprecedented level of accuracy, the number of astrometrically discovered
exoplanets has started to grow. In this chapter, I review the basic principles for orbital characterization of unseen planetary companions using astrometric data. I also review the properties of the
exoplanets discovered so far with astrometric methods and comment on the contributions that this technique can make to the
exoplanet field.
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Astrophysics of Galaxies
Globular cluster candidates uncovered by VVVX and MUSE
P. Rodríguez Cuevas, B. Dias, D. Minniti et al. (+1 more)
The Milky Way has about 220 cataloged globular clusters. This number is far smaller than what is found in a similar
galaxy such as Andromeda, which has about 600 globular clusters. Two possible reasons for this large difference might be observational bias and cluster dissolution. The infrared photometric survey VISTA Variables in the Via Lactea Extended has discovered many globular cluster candidates toward the Galactic bulge that need confirmation. We confirm the globular cluster nature of four candidates from the Galactic bulge based on radial velocities from MUSE data. Following our previous experience and method, we searched for a peak in the radial velocity distribution by deconvolving the radial velocity distribution into its bulge, disk, and potential cluster components. For Minni 23, we confirm the previously found parameters: this is an old and metal-rich bulge globular cluster. Additionally, we found a radial velocity peak associated with the candidate globular cluster Minni 07, with $\mu_{RV,cl}=80^{+26}_{-22}$ ${\rm km\ s}^{-1}$, $\sigma_{RV,cl}=48^{+15}_{-15}$ ${\rm km\ s}^{-1}$. We also derived $A_V=1.5$ and [Fe/H]$\approx-0.27$ for Minni 07. On the other hand, we were unable to reliably confirm the globular cluster nature for the candidates Minni 10 and Minni 19 with the currently available data. The devised strategy has proven to be efficient for the proposed goals, and it is worth repeating it for the larger sample of candidate globular clusters.
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All authors P. Rodríguez Cuevas, B. Dias, D. Minniti, E. Garro
Astrophysics of Galaxies
Misaligned tidal tails in open clusters: a signature of the local spiral arm resonance
Andrés E. Piatti
Tidal tails of open clusters are traditionally expected to align with their orbital motion due to Galactic shear. However, recent observations suggest that a significant population of clusters exhibits misaligned tails, the origin of which remains poorly understood. I investigate the structural properties of tidal tails for a sample of 155 nearby open clusters within 1 kpc of the Sun to characterize the influence of non-axisymmetric Galactic perturbers on stellar stripping geometry.Using high-precision Gaia DR3 astrometry and the probabilistic membership, I trace the primary orientation and physical length of tidal tails. I distinguish between local and global perturbations by analyzing the spatial distribution of misalignment (DeltaPA) relative to the boundaries of the Local Arm and comparing results with recent test-particle simulations of barred and spiral potentials. I identify three distinct dynamical regimes. While the majority of the population is shear-aligned, a significant subset exhibits a spatially indifferent background misalignment (10deg < DeltaPA < 30deg) consistent with global Galactic bar torques. In contrast, a population of nascent tails (< 0.3 kpc) exhibits larger misalignments (DeltaPA > 40deg) with a unique spatial specificity, occurring exclusively within the inter-arm gaps (|d_arm| > 0.2 kpc). These significant misalignments could represent a transient dynamical phase occurring within the corotation resonance's zero-shear zone, where the radial gravitational forcing of the spiral potential dominates stellar exit trajectories by rotating the eigenvectors of the tidal tensor. This could identify nascent tidal tails as uniquely sensitive high-resolution tracers of the non-axisymmetric Galactic potential.
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High Energy Astrophysical Phenomena
Dark-matter relay for ultra-high-energy cosmic rays
Mikhail Sekretov
Astrophysical sources of ultra-high-energy
cosmic rays (UHECRs) remain unidentified, and no nearby
cosmic accelerators are established even for the highest-energy events. In addition, puzzling correlations of a fraction of UHECR flux with distant blazars were found by HiRes and, recently,
Telescope Array experiments. Here we propose that dark matter can provide a mechanism to effectively transfer UHECRs from distant sources: dark-matter particles are boosted by UHECRs near the source and pass their momentum to baryons close to the observer. The probability of this relay is not negligible because of the growth of dark-matter-baryon cross section with energy. We demonstrate that the effect is observable for fermionic dark matter of mass $m_{\mathrm{DM}} \sim 25$ MeV and discuss possible observational signatures of this mechanism.
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Cosmology and Nongalactic Astrophysics
Data-driven Galaxy Population Prior for Photometric Redshifts
Nikolas Frediani, Daniel Gruen, Luca Tortorelli et al. (+1 more)
Stage-IV cosmological surveys rely on well-characterised photometric
redshift distributions for constraining cosmological models, yet the projected weak
lensing requirements are about an order of magnitude more accurate than current state-of-the-art methods. Any photometric
redshift inference depends - explicitly or implicitly - on a prior over
galaxy SEDs, luminosities, and
redshifts. In this paper, we develop a purely data-driven approach for modelling the
galaxy population prior based on learning the distribution of
galaxy SEDs and evaluate its induced systematic uncertainties for photometric
redshift calibration. Under controlled conditions, we build a template-free model for
galaxy SEDs with minimal physical assumptions and assess how well it can reproduce the colour-
redshift relation. We train a generative model on a realistic population of noisy mock
galaxy spectra, simulated using the GalSBI-SPS
galaxy population model, to learn the joint distribution of intrinsic spectra, luminosities, and
redshifts. We employ a probabilistic autoencoder that compresses spectra into a low-dimensional latent space and performs neural density estimation with a normalising flow. The autoencoder can reconstruct the shape of
galaxy spectra with Gaussian noise of standard deviation $\sigma$ to $\sim0.1\,\sigma$ of the ground truth, thereby building a model for noiseless SEDs from noisy spectra only. We construct colour-selected tomographic bins with a self-organising map and compare the predicted mean
redshift. We find that deviations in each bin are smaller than the per-mille Stage-IV requirements, with $| \Delta \langle z \rangle |\lesssim 0.0007 (1+z)$. This work serves as a proof-of-concept that generative models can learn the prior of
galaxy observations accurately enough for upcoming surveys under controlled conditions.
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All authors Nikolas Frediani, Daniel Gruen, Luca Tortorelli, Jamie McCullough
Instrumentation and Methods for Astrophysics
The second Little UV Camera (LUVCam2) mission
Emily Hu, Suresh Sivanandam, Albert Lau et al. (+12 more)
The second Little UltraViolet Camera (LUVCam2) is a 80mm-diameter dual UV-optical space
telescope that will observe the UV
flares around low-mass
stars, with planned flight as a $\sim$1.4U payload aboard the 3U CubeSat BRNOsat in late 2027. We present the concept of operations, full system architecture, optomechanical, and electrical design for LUVCam2. LUVCam2 is the second technology demonstration for the LUVCam electronics board, with the first LUVCam (LUVCam1) still operating in low-Earth orbit (launched July 2024). The main upgrade of LUVCam2 is the use of the backside-illuminated GSENSE4040BSI CMOS sensor, promising significant improvement to UV
quantum efficiency over the frontside-illuminated model used in LUVCam1. Other upgrades to LUVCam2 include the incorporation of the LUVCam on-board computer onto the readout electronics, an integrated 1W heater and thermal control system, and novel operational capability for LUVCam2 to perform on-sensor
star-tracking using optical images of background
stars.
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All authors Emily Hu, Suresh Sivanandam, Albert Lau, Coby Silayan, Mark Barnet, Shaojie Chen, Gavin Hay, Nadim Hatoum, Aaron Tohuvavohu, Norbert Werner, Marianna Dafčíková, Filip Münz, Patrick Nkwari, Jakub Řípa, Andras Pal
Earth and Planetary Astrophysics
High-resolution optical spectroscopy reveals the distinctive volatile composition of the interstellar comet 3I/ATLAS
K. Aravind, E. Jehin, C. Opitom et al. (+9 more)
Comets preserve volatile material from the early stages of planetary-system formation. The discovery of the interstellar comet 3I/ATLAS enables a direct comparison between a comet formed around another
star and comets in the Solar System. We characterise the coma composition of 3I/ATLAS across perihelion using homogeneous high-resolution near-UV and optical spectroscopy with UVES on the ESO Very Large
Telescope, from August 2025 (r$_h$=3.14 au) pre-perihelion to February 2026 (r$_h$=4.34 au) post-perihelion. From flux-calibrated spectra, we measured OH, NH, CN, C$_3$, CH and C$_2$ emissions, derived production rates, examined abundance ratios and heliocentric-distance trends, constrained NH$_2$, and compared OH-based water production with estimates from forbidden oxygen lines. Gas production rates show broadly symmetric pre- and post-perihelion behaviour, with steeper heliocentric-distance dependences than typically observed in Solar System comets. NH and NH$_2$ are strongly depleted, indicating a severe deficiency of ammonia-related volatiles. The C$_2$/CN ratio indicates carbon-chain depletion and evolves with heliocentric distance, consistent with coma-driven effects such as hyperactivity rather than intrinsic compositional changes. Water production from forbidden oxygen lines exceeds OH-based estimates except near perihelion, suggesting varying contributions from H$_2$O and CO$_2$ to coma chemistry. Relative abundance correlations place 3I/ATLAS outside the canonical Solar System comet cluster and closest to strongly carbon-chain depleted comets, including G-Z-type comets, while showing strong depletion of NH- and C$_3$-bearing species relative to CN. 3I/ATLAS therefore extends the known diversity of cometary compositions, demonstrating that volatile reservoirs in other planetary systems can differ substantially from those sampled by Solar System comets.
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All authors K. Aravind, E. Jehin, C. Opitom, J. Manfroid, D. Hutsemékers, D. Bodewits, M. Bannister, R. C. Dorsey, L. Ferellec, H. Kawakita, M. Lippi, C. Snodgrass
High Energy Astrophysical Phenomena
Self-consistent modeling of energy-dependent synchrotron polarization in blazars with application to Mrk 421
Frederike Apel, Motseothata Tisang, Victor Barbosa Martins et al. (+3 more)
Observations of black hole jets closely aligned with our line of sight, known as blazars, have revealed that their X-ray emission can be significantly more polarized than in the optical bands. This chromatic polarization is often attributed to an energy-stratified jet. In blazars with X-ray emission dominated by electron synchrotron, the pitch angle between the
magnetic field lines and electron velocity might also affect the frequency dependence of the polarization degree, but this effect is generally neglected in state-of-the-art models. In this work, we model the polarization and spectral energy distribution of blazars, accounting for the system's temporal
evolution and pitch-angle-dependent electron synchrotron cooling. Our analysis investigates the impact of the
magnetic field structure and electron distribution on polarization and tests whether this can help explain its observed frequency dependence. By extending the numerical simulation code AM3, we incorporate a self-consistent calculation of electron synchrotron emission and simulate various
magnetic-field structures. We apply these models to Mrk 421 and compare them with observations. Finally, we present a time-dependent shock-in-jet model to investigate frequency-dependent polarization angle swings. Our results show how different
magnetic-field structures affect energy-dependent polarization signatures. In the case of Mrk 421, the data can be explained by a helical field in the jet. In the shock-in-jet scenario, the X-ray polarization angle changes by 70 degrees, while remaining almost constant in the optical/infrared. Our results demonstrate that a self-consistent treatment of the temporal
evolution of electrons is essential to model the polarized synchrotron emission from blazars and can naturally explain chromatic polarization signatures without requiring an energy-stratified jet.
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All authors Frederike Apel, Motseothata Tisang, Victor Barbosa Martins, Xavier Rodrigues, Markus Böttcher, Anna Franckowiak
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
A Simple Dark Matter Model to Explain the LZ Event and Galactic Center Excess
Caleb Gemmell, Dan Hooper and Gordan Krnjaic
We propose that the dark matter (DM) is a pseudo-Dirac
fermion with a mass of approximately $20-100$ GeV that couples inelastically to the Standard Model through a hadrophilic
spin-1 mediator, $V$, the gauge
boson of spontaneously broken baryon number. The two DM eigenstates, $\chi_{1}$ and $\chi_2$, acquire approximately equal abundances after thermal freeze-out and are depleted through the processes $\chi_1 \chi_1 \to VV$ and $\chi_2 \chi_2 \to VV$. Although the heavier state is unstable, for a mass splitting below the electron-positron threshold and sufficiently small mass mixing with the $Z$
boson, its lifetime can exceed the age of the universe, allowing both states to remain approximately equally abundant in the Galactic
halo. For a thermal-relic annihilation cross section, this model can produce a signal that is consistent with the observed features of the longstanding Galactic Center Gamma-Ray Excess (GCE). If $\delta \sim 1000$ keV, the same parameter space that explains the GCE can also explain the LZ event through exothermic $\chi_2 \to \chi_1$ downscattering off xenon
nuclei.
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Cosmology and Nongalactic Astrophysics
Constraining Inflation with Little Red Dots
Dionysios Karagiannis and P. Daniel Meerburg
Primordial non-Gaussianity is a direct probe of the physics of inflation. The tightest bounds still come from the
cosmic microwave background, but large-scale structure is rapidly catching up: its intrinsically three-dimensional maps contain far more modes, provided the tracer combines large volume, high
redshift, strong bias and sufficient number density. The Little Red Dots (LRDs) discovered by JWST plausibly offer all four. Inspired by recent work on BAO measurements using LRDs we forecast the joint
galaxy power spectrum and bispectrum of a $14{,}000\,{\rm deg}^2$ LRD spectroscopic survey over $4<z<9$, marginalising over $32$ nuisance parameters and including the non-Gaussian bispectrum covariance. We find $\sigma(f_{\mathrm{NL}}^{\mathrm{loc}})=0.32$, $\sigma(f_{\mathrm{NL}}^{\mathrm{equil}})=32$ and $\sigma(f_{\mathrm{NL}}^{\mathrm{orth}})=10$, improving on Planck by factors of $16$, $1.5$ and $2.3$. The local bound lies a factor of three below the $\sigma(f_{\mathrm{NL}}^{\mathrm{loc}})\simeq1$ threshold that separates broad classes of single- and multi-field inflation. LRD clustering therefore has the potential to become an important probe of inflation, and makes a strong case for future wide-field near- to mid-infrared spectroscopy.
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Solar and Stellar Astrophysics
Catalogue of Solar Radio Bursts Detected by the LOFAR LV614 Station at the Irbene Observatory during Solar Cycle 25
Jānis Šteinbergs, Dmitrii Kolotkov, Valery M. Nakariakov et al. (+3 more)
A catalogue (https://doi.org/10.5281/zenodo.20157853) of solar
radio bursts detected with the LV614 LOFAR station at the Irbene Observatory, Latvia, in the stand-alone mode from June 2022 to August 2025 in the 29-60 MHz frequency range is presented. Observations were conducted with the weekly cadence, one-second time resolution, and 0.195 MHz spectral resolution. The cumulative duration of the observation was 1125.2 h. For all analysed observations, bandpass calibration was applied using Cassiopeia A as a reference source. In total, the catalogue includes 335 solar
radio bursts.
Radio bursts of all five main types, I-V, were detected. Specifically, the catalogue contains parameters of 23, 8, 293, 6, and 5 bursts of Type I, II, III, IV, and V, respectively. The detected burst peak flux ranges from 0.3 SFU to 234 SFU. The catalogue provides information about the peak flux and frequency, and the estimated height of the source above the solar surface. For Type II and III bursts, we also give the estimations of the frequency drifts, with mean values $ 0.043 ~\mathrm{MHz\,s^{-1}}$ and $4.383 ~\mathrm{MHz\,s^{-1}}$, respectively. We also estimated the fit $df/dt = Af^a$, with the best fit parameters $A=0.78$ and $a=0.43$. The numbers of Type I and III events are found to decrease with the peak flux, with the power law indices about $-0.9$ and $-1.25$, respectively. For Type III, we estimated electron beam speed ranging from 0.005 to 0.477 of the speed of light for the fundamental frequency, and 0.008 to 0.794 of the speed of light for its second harmonic.
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All authors Jānis Šteinbergs, Dmitrii Kolotkov, Valery M. Nakariakov, Vladislavs Bezrukovs, Pietro Zucca, Jānis Kaminskis
Solar and Stellar Astrophysics
V844 Herculis: An Exceptional Intermediate Polar Hiding in an Ordinary Dwarf Nova
Anousha Greiveldinger, Peter Garnavich, Colin Littlefield et al. (+16 more)
We present time-series spectroscopy of the SU UMa-type dwarf nova V844 Her during quiescence. We discover high-velocity Balmer and He I emission features modulated at a period of 29.3$\pm$0.1 minutes. The spectroscopic periodicity is identical to the photometric period detected only during superoutbursts. Interpreting this as the result of
magnetic accretion onto the white dwarf, we identify V844 Her as an intermediate polar (IP). The
spin period of the white dwarf is most likely to be 29.3 minutes. In a few IP systems, optical modulation is seen at twice the
spin frequency, so we can not rule out that the
spin period is 58.6 minutes. The orbital period of V844 Her is only 1.31 hr, meaning that the system has the shortest binary period and one of the smallest orbit-to-
spin ratios of the confirmed IPs. We present extensive optical, ultraviolet, and X-ray observations of V844 Her during the 2023 superoutburst. Compared with quiescence, the XRT count rate decreases during superoutburst. While the enhanced mass transfer during the superoutburst likely increases X-ray production, we propose that the drop in the count rate comes from the loss of soft X-rays due to an additional column from the outbursting disk.
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All authors Anousha Greiveldinger, Peter Garnavich, Colin Littlefield, Mark R. Kennedy, Paula Szkody, Jordan Tweddale, Mark Whittle, Teófilo Arranz, Donald Collins, James DeYoung, Sjoerd Dufoer, Charles Galdies, Jean-Francois Gout, Franz-Josef Hambsch, Emmanuel Kardasis, David Messier, Arto Oksanen, Gary Poyner, Richard Sabo
Cosmology and Nongalactic Astrophysics
Gravitational-Susceptibility Dip Behind DESI's results: Addressing the Phantom Crossing by Local limit of Nonlocal Gravity
Aria Hemmatian, Yahya Mohammadi, Javad Tabatabaei et al. (+1 more)
The second data release of the Dark Energy Spectroscopic Instrument (DESI), based on more than fourteen million
galaxies and
quasars, prefers a dark energy component whose equation of state is dynamical. In the simplest two-parameter description of this behavior, the Chevallier–Polarski–Linder (CPL) parametrization, the data favor the quadrant $w_0>-1$, $w_a<0$, which implies that the equation of state crosses the phantom divide $w=-1$ at a
redshift $z\simeq0.4$. We show that the local limit of nonlocal
gravity, a teleparallel extension of general relativity governed by a scalar function called gravitational susceptibility $S(x)$, offers a natural explanation. In this model a cosmological constant is not allowed; dark energy is necessarily dynamical. The phantom crossing seen by an observer is an effective phenomenon generated by the time
evolution of $S(z)$. We establish a correspondence: to every general-relativistic dark energy model with equation of state $w(z)$, there corresponds a modified TEGR cosmology with $w=-1$ and a suitable susceptibility $S(z)$ that are indistinguishable at the level of the background expansion. We construct the susceptibility functions that reproduce the CPL behavior favored by DESI data, and we confront the model with the combined CMB,BAO, and SNe data using Boltzmann solver codes. The recovered susceptibility displays a characteristic low-
redshift dip with depth $\beta = -0.025 \pm 0.007$ at $z\simeq 0.4 $, and its derivative changes sign at a
redshift equal to the phantom-crossing epoch.
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All authors Aria Hemmatian, Yahya Mohammadi, Javad Tabatabaei, Shant Baghram
Astrophysics of Galaxies
Exploring the influence of reionisation-era galaxies on their local intergalactic medium using the Sherwood-Relics simulations
Hamish Anderson, Laura C. Keating, Luke Conaboy et al. (+3 more)
Recent surveys have detected excess flux in the Lyman-$\alpha$ forest of
quasar spectra several Mpc from high-
redshift line-emitting
galaxies, indicating a correlation between intergalactic medium (IGM) transmission and reionisation-era
galaxies. We examine the
galaxy-IGM connection using the Sherwood-Relics simulation suite, a set of hybrid radiation-hydrodynamic simulations that model the IGM at high
redshift. We simulate the Lyman-$\alpha$ forest and a population of mock [OIII] emitters using the survey specifications of JWST's ASPIRE programme. We measure the
evolution of the effective optical depth in regions close to
galaxies, and contrast this with a control sample probing the random IGM. We characterise the changing physical properties of the IGM to explain the observed sightline-to-sightline scatter in opacity between 5.4 < $z$ < 6.2. We find that the IGM is more opaque than average at small radii ($r$ $\leq$ 5 cMpc/$h$) close to
galaxies, as these regions are overdense. At larger radii (15 < $r$ $\leq$ 50 cMpc/$h$), the IGM is more ionised than average, due to the higher photoionisation rate near
galaxies. We find qualitative agreement with the observational results from ASPIRE, though we see large realisation-to-realisation scatter driven by
cosmic variance, as also seen in theoretical explorations of the
galaxy-Ly$\alpha$ transmission cross-correlation function. Our results generally agree with observations claiming that there is a large-scale ionisation bias around [OIII] emitters, supporting the idea that their role is significant in shaping the properties of the IGM during reionisation.
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All authors Hamish Anderson, Laura C. Keating, Luke Conaboy, Xiangyu Jin, James S. Bolton, Ewald Puchwein
Cosmology and Nongalactic Astrophysics
Mathieu Perron-Cormier, Kristine Spekkens, Nathan Deg et al. (+2 more)
Galaxy asymmetry is an efficient way to characterize
galaxy morphology in atomic hydrogen 21 cm emission detections. We propose a novel
Bayesian approach to calculate the probability of an underlying squared differences asymmetry in a noisy detection. This approach has a number of advantages, including the recovery of low asymmetry values where prior noise corrections failed. More importantly, our approach provides robust uncertainties on the asymmetry, enabling a wide variety of statistical studies of
galaxy populations. This method is generalized for convolved noise measures. We validate our method using a convergence test. Finally, we show how, when applied to the untargeted HI survey WALLABY, our method nearly triples the number of reliable measurements relatively to the previous state-of-the-art technique. This
Bayesian approach to measure asymmetry will therefore further unlock the statistical power of widefield
galaxy surveys.
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All authors Mathieu Perron-Cormier, Kristine Spekkens, Nathan Deg, Lawrence M. Widrow, Marcin Glowacki
Solar and Stellar Astrophysics
A VLBA survey of radio stars in the Orion Nebula Cluster: III. Inter-epoch variability analysis
E. T. O'Kelly, J. Forbrich, S. A. Dzib et al. (+1 more)
We present a multi-epoch Very Long Baseline Array (VLBA) survey of
radio sources in the Orion Nebula Cluster (ONC), updating the detection statistics and investigating inter-epoch variability. The
dataset comprises eight C-band (4-8 GHz) epochs targeting 575
radio sources previously identified in deep Very Large Array surveys. VLBA observations result in resolutions of milliarcseconds and are only sensitive to high brightness temperatures meaning only non-thermal emission is observed. We detect 226 unique
radio sources corresponding to a detection fraction of 39 per cent. The majority of sources (~83 per cent) are detected only once indicating that non-thermal emission associated with Young Stellar Objects (YSOs) is highly intermittent. To quantify variability, we use per-epoch peak flux densities and the variability factor (VF) defined as the ratio between the maximum and minimum fluxes. We identify 21 sources (~9 per cent of detected sources) that exhibit high variability defined as a change of flux density by at least a factor of five. We crossmatch with the COUP Chandra survey to identify sources as YSOs. We identify COUP counterparts for ~56 per cent of the detected sources. The remaining population cannot be explained solely by variability or background contamination, suggesting a population of
radio detected YSOs without X-ray counterparts. We find a clear correlation between
radio and X-ray luminosities consistent with the Güdel-Benz relation, the empirical relation between non-thermal
radio and thermal X-ray emission for magnetically active
stars.
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All authors E. T. O'Kelly, J. Forbrich, S. A. Dzib, J. Vargas-González
Earth and Planetary Astrophysics
NGTS clusters survey - VII. An Enigmatic Short-Period Circumsecondary Disk Candidate in Orion
Niamh Mallaghan, Ernst J. W. de Mooij, Christopher A. Watson et al. (+31 more)
Young stellar systems provide key insights into the processes governing
star/
planet formation, often exhibiting complex and evolving photometric variability. In this paper, we present an analysis of the object around NOI 105872, observed by the Next Generation Transit Survey (NGTS) to eclipse a young ($4.1\pm0.4$ Myr) M-type
star in the Orion Nebula Cluster. The system displays deep, asymmetric eclipses with a period of $\sim0.69$ days, alongside variability in morphology. We combine photometric observations spanning approximately a decade from multiple ground- and space-based facilities to investigate the nature of this system. We explore a range of physical scenarios to reproduce the eclipse profiles and their
evolution. After analysis, our preferred explanation is a circumsecondary disk surrounding a companion in orbit around the M-type primary. We adopt a six-parameter disk model and fit the eclipse profiles independently to each
dataset. The best-fitting solution yields a disk radius of $\sim 0.005 \mathrm{au}$ or $0.98 R_{*}$, with broadly consistent orientations across epochs, but with variations that may be attributed to disk precession or intrinsic stellar variability. Constraints from the Hill radius imply a companion mass consistent with a very low-mass stellar companion. These results establish NOI 105872 as a candidate for a circumsecondary disk system in a young stellar environment. Continued photometric monitoring and spectroscopic follow-up will be essential to confirm this interpretation. If confirmed, systems such as NOI 105872 provide valuable
benchmarks for understanding disk dynamics, companion formation, and the origin of complex eclipse phenomena in young
stars.
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All authors Niamh Mallaghan, Ernst J. W. de Mooij, Christopher A. Watson, Edward Gillen, Matthew Kenworthy, Louise D. Nielsen, David R. Anderson, Matthew P. Battley, Edward M. Bryant, Matthew R. Burleigh, Benjamin M. J. Cadell, Sarah L. Casewell, Alexander Chaushev, V. S. Dhillon, Elsa Ducrot, Jorge Fernandez Fernandez, Samuel Gill, Michael Gillon, Michael R. Goad, Faith Hawthorn, Katlyn L. Hobbs, James McCormac, Maximiliano Moyano, Catriona A. Murray, Toby Rodel, Suman Saha, Ramotholo R. Sefako, John Southworth, Mathilde Timmermans, Amaury H. M. J. Triaud, Jose Vines, Richard G. West, Peter J. Wheatley, Tafadzwa Zivave
High Energy Astrophysical Phenomena
Neutrino Astronomy at High Energies - An Experimental Review
Christian Spiering
Neutrino astronomy at high energies is an emerging field but still in a state of infancy. It is barely a dozen years ago that a diffuse flux of extraterrestrial
neutrinos with energies in the TeV and PeV ranges was detected and even fewer that first individual sources could be identified. A new window to the universe has been opened after four decades of efforts to realize the gigantic instruments that made that breakthrough possible. This review describes the road towards the present, reviews the actual status of the field and sketches future developments.
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Earth and Planetary Astrophysics
Molecules in the shadows of the protoplanetary disk HD 143006: Evidence for C/O $\gtrsim 1$ from simultaneously modeling fourteen ALMA lines
S. E. van Terwisga, P. Woitke, A. M. Weiss et al. (+2 more)
The inner disk of the T Tauri
star HD 143006 is inclined and casts a broad shadow on a large portion of the outer disk. We use this extraordinary geometry to study the impact of stellar ultraviolet (UV) irradiation on disk chemistry, temperature, and line formation. We present new ALMA observations of this disk in CO, $^{13}$CO, C$^{18}$O, CN, HCN, HCO$^+$, CS and C$_3$H$_2$ and combine these with previously-published data to get a rich
dataset, which is modeled with ProDiMo models for the illuminated and shadowed side by including an optional inclined inner disk to partially block stellar illumination of the outer disk. The observed line flux contrasts between the illuminated and the shadowed disk sides are small. We explain this by introducing “equilibrated models” which consider a slow heating/cooling relaxation of gas parcels orbiting in and out of the shadow. We fit the radial line intensity profiles of all 14 ALMA lines for both halves of the disk, the SED beyond 20$\,\mu$m, and two ALMA continuum images, with an overall reduced $\chi$ of about 2.3, in one combined model. Line intensities only increase slightly on the illuminated side because the gas warms up slowly, although fast UV photochemistry significantly reduces the observable molecular concentrations. For the lines of N$_2$H$^+$ and CS, which probe deeper layers where the gas and dust temperatures are coupled, slow UV-desorption of ices such as NH$_3$ and H$_2$S plays a crucial role. This can result in a brightening of these lines on the shadowed side. The carbon-to-oxygen ratio in the outer disk of HD 143006 is slightly greater than one ($\sim 1.05$). The disk mass is fitted to be as low as $0.0012 M_{\odot}$, but almost equally well-fitting models with a fixed disk mass of $0.021 M_\odot$ can be obtained after re-adjusting the disk shape, dust, and gas heating/cooling parameters. (abridged)
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All authors S. E. van Terwisga, P. Woitke, A. M. Weiss, A. D. Bosman, L. Trapman
Earth and Planetary Astrophysics
Transport and Thermochemical Kinetics of Alkali Species in Hot Jupiter Atmospheres: Implications for Magnetic Models
D. A. Christie, T. M. Evans-Soma, N. J. Mayne et al. (+4 more)
Interactions between the planetary
magnetic field of a hot Jupiter and the winds within its atmosphere are moderated by the electron and ion abundances. For a solar
metallicity atmosphere at pressures between 10 and $10^{-4}$ bar, the primary sources for these charged species are expected to be the potassium and sodium atoms, and models of
magnetic effects in hot Jupiter atmospheres have typically assumed that charged species exist within the atmosphere in their
equilibrium abundances. In this work, we investigate the thermochemical kinetics of alkali species within a hot Jupiter atmosphere, thus allowing for the thermal ionisation fraction to depart from
equilibrium, and demonstrate that quenching of ions occurs between 1 and 10 mbar. This increase in ionisation fraction on the nightside and at mid-latitudes results in stronger
magnetic interaction, here modelled using the
magnetic drag approximation, further slowing the jet and altering the global circulation. We additionally show that while quenching occurs, large
magnetic resistivities resulting from low electron abundances continue to exist on the nightside between 10 and 100 mbar, in tension with magnetohydrodynamic models that assume horizontally uniform
magnetic resistivities to simplify the explicit integration of the induction equation. At lower pressures ($\sim$ 0.1 mbar) where the electrons have become horizontally homogenised, the
magnetic Reynolds number approaches or exceeds unity, signalling the breakdown of the
magnetic drag approximation. We thus stress that chemical kinetics represents a dynamically important component of modelling hot Jupiter atmospheres while at the same time further complicating the treatment of
magnetic effects.
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All authors D. A. Christie, T. M. Evans-Soma, N. J. Mayne, E. Hébrard, M. Zamyatina, J. E. Owen, K. Kohary
High Energy Astrophysical Phenomena
Inelastic scattering effects on polarization predictions for cold and warm atmospheres in the X-rays
J. Podgorný, L. Marra, M. Dovčiak et al. (+8 more)
X-ray polarization models of accreting compact objects often assume the so-called Chandrasekhar-Sobolev polarization prescription for elastic Thomson scattering in electron-scattering semi-infinite atmospheres. In this letter, we examine the effects of inelastic Compton scattering. We assume homogeneous slabs of cold and warm (up to 1 keV) electrons. We use a Monte Carlo approach. We discuss the polarization difference arising in the X-rays between the elastic and inelastic scattering assumptions for plane-parallel transmission and reflection, and the role it can play in the interpretation of X-ray polarimetric observations of accreting compact objects.
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All authors J. Podgorný, L. Marra, M. Dovčiak, R. Taverna, R. W. Goosmann, M. Gupta, F. Marin, G. Matt, J. Poutanen, A. Różańska, A. Veledina
Instrumentation and Methods for Astrophysics
Testing deep learning techniques for event reconstruction in pair-production gamma-ray telescopes
Mattia Maniscalco, Valentina Fioretti, Nicolò Parmiggiani et al. (+7 more)
In the development of next-generation tracking detectors for gamma-ray space observations, the integration of advanced deep learning techniques into event reconstruction
algorithms is a promising approach for improving the performance of the mission, reducing systematic uncertainties and maximizing the scientific output. In this study, we investigate the application of deep learning techniques such as Graph Neural Networks (GNNs) for the identification and reconstruction of particle tracks resulting from pair production events within the tracker of the AMEGO-X proposed concept. The goal is improving the angular resolution and the detection efficiency of the
telescope, especially in the soft energy range (below 100 MeV) where multiple Coulomb scattering significantly degrades track reconstruction and consequently limits the sensitivity in the so-called MeV gap. We use the Geant4-based MEGAlib framework and a Python-based dedicated read-out and data handler processor to format the input
datasets as close as possible to the real data. The simulated
datasets are then used to train and evaluate two graph neural network architectures, GraphSAGE and Interaction Networks, and to compare their performance in pair-production event reconstruction in terms of Point Spread Function 68% containment radius and effective area, also with that obtained using standard reconstruction techniques. The results of this study indicate that graph neural network-based reconstruction is a promising approach for pair-production event reconstruction below 100 MeV when compared with standard reconstruction methods, with significant potential for further optimization.
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All authors Mattia Maniscalco, Valentina Fioretti, Nicolò Parmiggiani, Andrea Bulgarelli, Carolyn A. Kierans, Adrien Laviron, Gabriele Panebianco, Alessio Aboudan, Luca Castaldini, Andreas Zoglauer
High Energy Astrophysical Phenomena
Dense Dump Codec: Error-Controlled, Random-Access Compression of GRMHD Time Series for Slow-Light Radiative Transfer
Zelin Zhang, Zhenyu Zhang and Bin Chen
Black-hole movies provide a unique venue to study the time
evolution of accreting
plasma. Modeling this
evolution with slow-light radiative transfer requires closely spaced simulation outputs, because the
plasma changes as light propagates through it. Saving these outputs in full is costly, whereas sparse sampling introduces time-interpolation errors. We present the Dense Dump Codec (DDC), a compression method for dense GRMHD time series. DDC stores exact anchor states and compactly represents the intermediate
evolution, while allowing direct access to selected times and variables. Applied to eight production sequences spanning SANE and MAD simulations at several black-hole
spins with 0.1M output, DDC archives are about 10 times smaller than the original dense data and even about 50% smaller than the original 0.5M output in aggregate. We further integrate a native DDC reader into polarized slow-light radiative transfer. Tests at 86, 230, and 345 GHz show that DDC may reduce aggregate Stokes-image errors by 54-79% relative to slow-light calculations using original 0.5M input. These results indicate that DDC enables high-cadence slow-light calculations without the prohibitive cost of saving every dense GRMHD state in its original form.
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