Instrumentation and Methods for Astrophysics · Cross-listed from physics.space-ph
First Multi-Constellation Observations of Navigation Satellite Signals in the Lunar Domain by Post-Processing L1/L5 IQ Snapshots
Lorenzo Sciacca, Alex Minetto, Andrea Nardin et al. (+5 more)
The use of Global
Navigation Satellite Systems (GNSS) to increase spacecraft autonomy for orbit determination has gained renewed momentum following the Lunar GNSS Receiver Experiment (LuGRE), which demonstrated feasible onboard GPS and Galileo signal reception and tracking at lunar distances. This work processes in-phase and quadrature (IQ) snapshots collected by the LuGRE receiver in cis-lunar space and on the lunar surface to assess multi-frequency, multi-constellation signal availability. Signals from additional systems beyond GPS and Galileo, including RNSS and SBAS constellations, are observable and successfully acquired exclusively in the recorded IQ snapshots. These observations provide the first experimental evidence that signals from multiple constellations, including systems not supported by LuGRE realtime operations, are detectable at unprecedented distances from Earth. Useful observables can be extracted from the IQ snapshots, despite minimal sampling rates, 4-bit quantization, and short durations (200 ms-2 s), through a hybrid coherent/non-coherent acquisition stage compensating for code Doppler. These observations are exploited to tune simulation tools and to perform extended simulation campaigns, showing that the inclusion of additional constellations significantly improves availability; for a 26 dB-Hz acquisition threshold, the fraction of epochs with at least four visible satellites increases from 11% to 46% of the total epoch count. These findings indicate that BeiDou, RNSS, and SBAS signals can substantially enhance GNSS-based autonomy for lunar and cislunar missions.
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All authors Lorenzo Sciacca, Alex Minetto, Andrea Nardin, Fabio Dovis, Luca Canzian, Mario Musmeci, Claudia Facchinetti, Giancarlo Varacalli
Solar and Stellar Astrophysics
3D Radiative MHD Modeling of Particle Beam Heating of the Solar Atmosphere
Samuel Granovsky, Alexander G. Kosovichev, Irina N. Kitiashvili et al. (+1 more)
While
solar flares are primarily associated with enhanced ultraviolet and X-ray emission, a subset of
flares exhibit significant continuum brightening in visible light and are classified as white-light
flares (WLFs). Despite extensive observational and modeling efforts, the physical mechanisms responsible for the compact, short-lived photospheric brightenings in WLF kernels observed during the impulsive phase of
solar flares remain uncertain. Thick-target electron-beam models typically deposit energy in the upper chromosphere, and their ability to reproduce the magnitude and spatial localization of photospheric continuum enhancements observed in white-light
flare kernels remains an open question. To investigate the role of self-consistent atmospheric structuring and multidimensional hydrodynamic transport in
flare energy deposition, we perform three-dimensional radiative MHD simulations of electron-beam heating using the StellarBox code for a beam energy flux density of $10^{12}$ erg\,s$^{-1}$\,cm$^{-2}$ and low-energy cutoffs of 10–25\,keV. We then compute Fe\,I 6173\,Å~Stokes profiles using the RH 1.5D radiative transfer code for direct comparison with Helioseismic and
Magnetic Imager (HMI) observations. The simulations produce strong upper-chromospheric heating, multiple shock fronts, and continuum enhancements up to a factor of 2.5 relative to pre-
flare levels, comparable to continuum enhancements observed during strong X-class white-light
flares. Comparison with one-dimensional RADYN simulations highlights the influence of fine-scale structuring on
flare dynamics and continuum emission that arises in three-dimensional geometry.
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All authors Samuel Granovsky, Alexander G. Kosovichev, Irina N. Kitiashvili, Alan A. Wray
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Higgs-like inflation in scalar-torsion $f(T,\phi)$ gravity in light of ACT-SPT-DESI constraints
Nitesh Kumar, Giovanni Otalora, Rodrigo Reyes et al. (+3 more)
We study
Higgs-like inflation in the framework of scalar-torsion
gravity, focusing on the general class of $f(T,\phi)$ theories in which gravitation is mediated by torsion rather than
curvature. Motivated by the increasing precision of
cosmic microwave background and large-scale-structure observations, we examine whether
Higgs-like inflation remains compatible with current data in this extended gravitational setting. Working within the slow-roll approximation, we analyze the inflationary dynamics both analytically and numerically. In the dominant-coupling regime we derive closed-form expressions for the scalar spectral index and the tensor-to-scalar ratio as functions of the number of e-folds, and we subsequently relax this assumption by numerically solving the slow-roll equations. Confrontation with the latest constraints from Planck 2018, ACT DR6, DESI DR1, and BICEP/Keck shows that
Higgs-like inflation in $f(T,\phi)$
gravity is fully consistent with current bounds, naturally accommodating the preferred shift in the scalar spectral index and leading to distinctive tensor-sector signatures.
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All authors Nitesh Kumar, Giovanni Otalora, Rodrigo Reyes, Bastian Espinoza, Manuel Gonzalez-Espinoza, Emmanuel N. Saridakis
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Memories of Prof. George Lazarides
C. Pallis
I present some
memories of my Ph.D supervisor and, later, collaborator but always encouraging supporter Prof. G. Lazarides. Some of his contributions to our common and related scientific activities on the phenomenology of MSSM and inflation are also summarized.
Instrumentation and Methods for Astrophysics
Understanding Solar Flares and Energetic Events: Open questions, observational requirements, and instrumental needs over the coming decade
Malcolm K. Druett, Graham S. Kerr, Joel C. Allred et al. (+15 more)
Solar flares are the largest energy-release events in the
Solar System, allowing us to study fundamental physical phenomena under extreme conditions. Those include
magnetic reconnection, particle acceleration, radiation transport, and various
plasma physics processes, all of which occur throughout the heliosphere and rest of the Universe.
Flares and eruptive events are also components of geo-effective space weather. Their impacts from a space weather perspective are numerous, such as harm to satellites, disruption to GPS, communications and power systems, and impacts on passenger air travel. A comprehensive understanding of
solar flares is therefore not just a compelling science problem, but also important for national security and infrastructure. This white paper (WP) addresses critical open science questions related to
solar flares. Key observations and capabilities required to make significant advancements over the coming decade are identified. The UK has a robust and vibrant
solar flare community. We are key partners in international collaborations, and also provide instrumentation for existing and upcoming ESA/NASA/JAXA space missions. Continuing this effort over the coming decade is vital to maintain UK leadership in this field, achieve
Solar System Advisory Panel roadmap goals, and to work under the UK Space Agency's National Space Strategy Pillars. Several complementary WPs have been submitted that discuss instruments or concepts that would directly address the observational requirements we describe (including: SPARK,
solar optimised IFUs,
Solar-C/EUVST, and OSIRIS), as well as required numerical modelling efforts and infrastructure.
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All authors Malcolm K. Druett, Graham S. Kerr, Joel C. Allred, Philippa K. Browning, Giulio Del Zanna, Jaroslav Dudík, Robertus Erdélyi, Andrzej Fludra, David R. Graham, Hamish A. S. Reid, Laura A. Hayes, Sarah A. Matthews, James A. McLaughlin, Christopher M. J. Osborne, Alex G. M. Pietrow, Vanessa Polito, Alex J. B. Russell, Peter F. Wyper
Instrumentation and Methods for Astrophysics
Nine years of UVIT: assessing sensitivity variation
Akanksha Dagore, Prajwel Joseph, S. N. Tandon et al. (+3 more)
The Ultra-Violet Imaging
Telescope (UVIT) is one of the five payloads onboard the first Indian multiwavelength astronomical observatory, AstroSat, launched by the Indian Space Research Organisation on 28 September 2015. UVIT, designed for simultaneous imaging in the far-ultraviolet (FUV; 1300-1800 Å) and near-ultraviolet (NUV; 2000-3000 Å) channels, has completed nine years in orbit in 2024 despite the failure of the NUV channel in 2018. As the FUV optics is subject to possible reduction in sensitivity due to microscopic amounts of contaminants, we used the FUV data acquired by UVIT over the past nine years on the open cluster NGC 188 and the white
dwarf HZ 4 to study sensitivity variations in the UVIT FUV channel. Our findings indicate no significant reduction in the sensitivity of the FUV channel over the last nine years, with no significant episodic variations due to unknown causes.
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All authors Akanksha Dagore, Prajwel Joseph, S. N. Tandon, Annapurni Subramaniam, S. K. Ghosh, C. S. Stalin
Instrumentation and Methods for Astrophysics
Picture an Astronomer: Best Practices for Retaining Talent in Astrophysics
Ava Polzin, Katherine E. Whitaker, C. Megan Urry et al. (+85 more)
Women are consistently underrepresented in astrophysics yet are simultaneously subject to disproportionate attrition at every career stage. This disparity between demonstrated efficacy in job performance and ultimate career outcome was the primary motivation for the Picture an Astronomer series, which included both targeted public outreach to increase representation of women in astrophysics and high-level, solution-oriented discussions among professional astronomers. In March 2025, more than 200 astronomers came together in a hybrid-format symposium focused on the state of the field for female scientists, combining scientific exchange with discussions of policies and practices to strengthen retention of talent in the field. This white paper is the result of those discussions, offering a wide range of recommendations developed in the context of gendered attrition in astrophysics but which ultimately support a healthier
climate for all scientists alike.
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All authors Ava Polzin, Katherine E. Whitaker, C. Megan Urry, Henna Abunemeh, Sanyukta Agarwal, Aadya Agrawal, Nathaniel Alden, Ann-Marsha Alexis, Sydney Andersen, Melanie Archipley, Yasmeen Asali, Katie Auchettl, Bradford Benson, Binod Bhattarai, Sarah Biddle, Madison Brady, Katelyn Breivik, Disha Chakraborty, Mikel Charles, Hsiao-Wen Chen, Josephine Chishala, Anirudh Chiti, Panagiota Eleftheria Christopoulou, Mi Dai, Flaminia Fortuni, Shanika Galaudage, Daniel Glazer, Anika Goel, Andrea Gokus, Jenny E. Greene, Ryn Grutkoski, Yiqing Guo, Joseph Guzman, Renée Hložek, Lindsay R. House, Lillian N. Joseph, Molly Beth Jourdan, Tanvi Karwal, Zuzanna Kocjan, Emily Koivu, Varun Kore, Andrey Kravtsov, Keerthi Kunnumkai, Shalini Kurinchi-Vendhan, Johannes U. Lange, Sarah R. Loebman, Kira Lund, Julie Malewicz, Olivia McAuley, Rebecca McClain, Stephen McKay, Emily McPike, Cassidy Metzger, Lamiya A. Mowla, Katherine Myers, Erica Nelson, Aline Novais, Camilla Nyhagen, Micah Oeur, Lou Baya Ould Rouis, Paarmita Pandey, Raagini Patki, Sonu Tabitha Paulson, Haile M. L. Perkins, Ashi Poorey, Izabella Pozo, Heather L. Preston, Pazit Rabinowitz, Alexandra S. Rahlin, Janiris Rodriguez-Bueno, Francisco Rodríguez Montero, Huei Sears, Álvaro Segovia Otero, Uliana Solovieva, Rachel Somerville, Jessica Speedie, Tjitske Starkenburg, Laura Stiles-Clarke, Chin Yi Tan, Yu-Hsuan Teng, Tanya Urrutia, Padmavathi Venkatraman, Margaret E. Verrico, Amanda Wasserman, Claire E. Williams, Tony Wong, Shirin Gul Zaidi, Chantene Zichterman
Astrophysics of Galaxies
A Convolutional Neural Network for the Recovery of Transfer Functions From Velocity-Resolved Reverberation Mapping Data
Kirk Long, Keith Horne, Jason Dexter et al. (+1 more)
One of the hallmarks of active
galactic nuclei are that they are highly variable with time. In watching the spectra vary it has been observed that the emission-lines often appear to "reverberate" – that is they vary in response to continuum variations assumed to originate close to the black hole. This critical observation underlies the reverberation mapping technique, an elegant physics experiment that has allowed us to characterize the environment around many supermassive black holes in nearby active
galactic nuclei. Recent observations are of such quality that the response can be measured as a function of velocity across the emission-line, and in doing so we can construct velocity-delay maps that show the structure and physics of the gas in the broad-line region better than any other measurement to date. Unfortunately constructing such maps requires a deconvolution, and given that the data are often noisy and with gaps such deconvolutions are non-trivial. Here we present a novel deconvolution method for the recovery of velocity-delay maps using a custom convolutional neural network architecture, showcasing that such methods have great promise for the deconvolution of reverberation mapping data products. While we have designed this new method with the BLR in mind, in principle this technique could be applied to any reverberation deconvolution problem, including in the
accretion disk and
torus.
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All authors Kirk Long, Keith Horne, Jason Dexter, Benoit Tremblay
Solar and Stellar Astrophysics
Turbulence-Driven Corrugation of Collisionless Fast-Magnetosonic Shocks
Immanuel Christopher Jebaraj, Mikhail Malkov, Nicolas Wijsen et al. (+4 more)
Collisionless fast-magnetosonic shocks are often treated as smooth, planar boundaries, yet observations point to organized corrugation of the shock surface. A plausible driver is upstream
turbulence. Broadband fluctuations arriving at the front can continually wrinkle it, changing the local shock geometry and, in turn, conditions for particle injection and radiation. We develop a linear-MHD formulation that treats the shock as a moving interface rather than a fixed boundary. In this approach the shock response can be summarized by an effective impedance determined by the Rankine-Hugoniot base state and the shock geometry, while the upstream
turbulence enters only through its statistics. This provides a practical mapping from an assumed incident spectrum to the corrugation amplitude, its drift along the surface, and a coherence scale set by weak damping or leakage. The response is largest when the transmitted downstream fast mode propagates nearly parallel to the shock in the shock frame, which produces a Lorentzian-type enhancement controlled by the downstream normal group speed. We examine how compression,
plasma $\beta$, and obliquity affect these corrugation properties and discuss implications for fine structure in heliospheric and
supernova-remnant shock emission.
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All authors Immanuel Christopher Jebaraj, Mikhail Malkov, Nicolas Wijsen, Jens Pomoell, Vladimir Krasnoselskikh, Nina Dresing, Rami Vainio
Cosmology and Nongalactic Astrophysics
OmniCosmos: Transferring Particle Physics Knowledge Across the Cosmos
Vinicius Mikuni, Ibrahim Elsharkawy and Benjamin Nachman
Foundation models build an effective representations of data that can be deployed on diverse downstream tasks. Previous research developed the OmniLearned foundation model for
collider physics and showed that it could significantly advance discovery potential across
collider experiments. In this paper we go beyond
collider physics and show that Foundation Models trained on
collider data can help improve the prediction of cosmological parameters and to predict
halo and
galaxy velocities in different
datasets from CosmoBench. This is the first time a
collider physics model is shown to generalize across scientific fields.
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Solar and Stellar Astrophysics
A closer look at the young stellar group around Sh 2-295
João Victor Corrêa-Rodrigues and Jane Gregorio-Hetem
Star formation is governed by multiple physical processes, making it inherently complicated. One excellent example is the Canis Major OB1/R1 Association, whose complex history of
star formation is related to different episodes. Three
supernova (SN) events potentially altered the environment and impacted
star formation and
stellar evolution. Prior investigations revealed two
stellar groups of different ages associated with GU CMa and Z CMa. This work focusses on identifying the low-mass young
stellar population near FZ CMa, located between these two groups and spatially related to the H II region Sh 2-295. Our main goal is to verify whether this group is age-mixed and characterise its physical properties. We analysed multi-object spectroscopic data acquired with Gemini/GMOS to search for typical features of T Tauri
stars (TTs) and to determine their spectral types. Lithium absorption line ($\lambda$ 6708 $\mathring{A}$) was used as a youth indicator, while H$\alpha$ emission was investigated to probe
accretion activity. We also derived ages based on optical photometry from
Gaia DR3 and compared the projected spatial distribution to diffuse infrared (IR) emission. We identified 29 TTs, including six new members of the association and three Classical TTs (CTTs). The equivalent width of the Li I absorption line suggests an age of $8.1^{+2.1}_{-3.8}$ Myr, while optical photometric data indicate
stellar ages ranging from $\sim$1 to 14 Myr. Younger
stars are concentrated around Sh 2-295, whereas the older ones are more widely dispersed. We increased the number of known TTs related to the CMa association. Our results support a scenario of multiple
star-formation episodes, including a younger group that may have been triggered by the expansion of Sh 2-295. The influence of SN events appears limited in this context.
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Solar and Stellar Astrophysics
A millimeter methanol maser ring tracing the deceleration of the heat wave powered by the massive protostellar accretion outburst in G358.93-0.03 MM1
T. R. Hunter, C. L. Brogan, G. C. MacLeod et al. (+3 more)
We present multi-epoch, multi-band ALMA imaging of the new Class II millimeter methanol masers excited during the
accretion outburst of the massive protostar G358.93-0.03 MM1. The highest angular resolution image (24 mas $\approx$ 160 au) reveals a nearly complete, circular ring of strong maser spots in the 217.2992 GHz ($v_t$=1) maser line that closely circumscribes the
dust continuum emission from MM1. Weaker maser emission lies inside the eastern and southern halves of the maser ring, generally coincident with the centimeter masers excited during the outburst, but avoiding the densest parts of the hot core gas traced by high excitation lines of CH$_3$CN. Using a variety of fitting techniques on the image cubes of the two strongest maser lines, each observed over 3-4 epochs, we find the diameter of the ring increased by $\gtrsim$60% (from $\approx$1100 to $\approx$1800 au in the 217 GHz line) over 200 days, consistent with an average radial propagation rate of $\approx$0.01c, while the maser intensity declined exponentially. Fitting the angular extent of the millimeter masers versus time yields a power law of index 0.39$\pm$0.06, which also reproduces the observed extent of the 6.7 GHz masers in the first VLBI epoch of R. A. Burns et al. (2020). This exponent is consistent with the prediction of radius vs. time in the Taylor-von Neumann-Sedov self-similar solution for an intense spherical explosion from a point source ($R \propto t^{2/5}$). These results demonstrate the explosive nature of
accretion outbursts in massive protostars and their ability to generate subluminal heat waves traceable by centimeter and millimeter masers for several months as the energy traverses the surrounding molecular material.
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All authors T. R. Hunter, C. L. Brogan, G. C. MacLeod, C. J. Cyganowski, R. A. Burns, B. A. McGuire
Cosmology and Nongalactic Astrophysics
Integrated Sachs-Wolfe maps from the Gower Street $w$CDM simulations
Mina Ghodsi Yengejeh, András Kovács, István Szapudi et al. (+1 more)
The late-time linear Integrated Sachs-Wolfe (ISW) effect directly probes the dynamics of
cosmic acceleration and the nature of dark energy. Detecting these weak, secondary temperature anisotropy signals of the CMB requires accurate theoretical predictions of their amplitude across cosmological models. By extending the pyGenISW package, previously limited to $\Lambda$CDM, we aim to generate full-sky ISW maps for a suite of 791 $w$CDM cosmologies using the Gower Street N-body simulations, thereby enabling ISW analyses across a broader dark-energy parameter space. We make our code and ISW data publicly available. We compute the ISW signals by tracing the time
evolution of the gravitational potential across large-volume simulations that span dark energy equation of state parameters from phantom to quintessence, $-1.79 \lesssim w \lesssim -0.34$. These data are projected onto the sphere using HEALPix to obtain full-sky temperature maps. We validate our pipeline by comparing the measured ISW angular power spectra and ISW-density cross-correlations against linear theory expectations ($2 \leq \ell \leq 200$) computed with
benchmarks from the pyCCL library. The agreement is excellent across the multipole range where the ISW contribution is expected to dominate, confirming the reliability of our modelling of gravitational-potential
evolution. With additional tests of the ISW signal's strength in density extrema, as well as comparing all models to a reference $\Lambda$CDM cosmology, we found that quintessence-like models ($w > -1$) show higher ISW amplitudes than phantom models ($w < -1$), consistent with enhanced late-time decay of gravitational potentials. The consistency of our $w$CDM ISW maps and their agreement with theory predictions confirm the robustness of our methodology, establishing it as a reliable tool for theoretical and observational ISW-LSS analyses.
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All authors Mina Ghodsi Yengejeh, András Kovács, István Szapudi, István Csabai
High Energy Astrophysical Phenomena · Cross-listed from physics.acc-ph
The sun as colliding beam, betatron cosmic ray factory
Richard M. Talman
A theory of
cosmic ray production within the
solar system (not extra-
galactic) is presented. The sun's time variable
magnetic flux linkage makes the sun (as well, perhaps, as Jupiter) a natural, all-purpose, betatron storage ring, with semi-infinite acceptance aperture, capable of storing and accelerating counter-circulating, opposite-sign, colliding beams. The puzzle of how positrons and anti-
protons can be well represented at all energies, is explained, initially, by the low energy capture of particles of either sign by the sun's
magnetic dipole field. Later, as the
magnetic field bending has become negligible compared to the gravitational bending, both positive and negative beams will have survived the gradual transition from predominantly
magnetic to predominantly gravitational bending. Later, anti-particles produced in QED beam-beam collisions of sufficiently high energy, are also accelerated. The high quality of
cosmic ray data collected over recent decades, at steadily increasing energies, especially by the International Space Station (ISS), make the study of
cosmic ray production mechanisms both timely and essential. The paper describes how longitudinal electric fields, explained by the Parker
solar wind theory can enable the sun to serve as a “booster” accelerator of
cosmic rays, increasing the maximum
cosmic ray energies enough to produce the observed 13 orders of magnitude maximum particle energy and the energy flux needed to maintain the observed
cosmic ray atmosphere
equilibrium within the
solar system. A steady state mechanism is described, based on semi-quantitative discussion of a relativistic Hamilton-Jacobi formalism, according to which the highest energy
cosmic rays observed can have been produced by the Parker longitudinal electric field component, during fractionally brief, but periodic, circular or semi-circular turns centered on the sun.
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Cosmology and Nongalactic Astrophysics · Cross-listed from nucl-ex
Big Bang Nucleosynthesis results refined via the Trojan Horse Method
Roberta Spartà, Rosario Gianluca Pizzone, Livio Lamia et al. (+13 more)
This work presents the Trojan Horse Method (THM) as a powerful technique for measuring
nuclear reaction cross sections at astrophysical energies. We then explore the impact of THM-derived reaction rates on the predictions of Standard Big Bang Nucleosynthesis (SBBN) using the PRIMAT code.
Primordial abundances are shown for the single rate impact and, for the first time, also for all the THM rates together. The result shows significant differences with the use of THM rates, which in some cases goes in the direction of improving the agreement with the observations with respect to the use of only reaction rates from direct data, especially for the $^7$Li and deuterium abundances, which are still open issues for SBBN.
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All authors Roberta Spartà, Rosario Gianluca Pizzone, Livio Lamia, Alessandro Alberto Oliva, Marco La Cognata, Alessia Di Pietro, Pierpaolo Figuera, Giovanni Luca Guardo, Marco La Commara, Dario Lattuada, Marco Mazzocco, Sara Palmerini, Giuseppe Gabriele Rapisarda, Stefano Romano, Maria Letizia Sergi, Aurora Tumino
Cosmology and Nongalactic Astrophysics
Self-Gravitating Scalar Field Configurations, Ultra Light Dark Matter and Galactic Scale Observations
Bihag Dave
In this thesis, we investigate the possibility that dark matter consists of ultra light
spin-zero particles with mass $m \sim 10^{-22}\ \text{eV}$. We focus on the role of self-interactions, assuming all other non-gravitational couplings to Standard Model particles are negligible. Such ultra light dark matter (ULDM) is expected to form stable self-gravitating scalar field configurations (
solitons), whose properties depend on the particle mass and self-coupling $\lambda$. Using solutions of the Gross-Pitaevskii-Poisson equations, we explore how
galactic-scale observations can constrain $m$ and $\lambda$. We show that observational upper limits on the mass enclosed in central
galactic regions can probe both attractive and repulsive self-interactions with strengths $\lambda \sim \pm 10^{-96} - 10^{-95}$. We further demonstrate that self-interactions can allow ULDM to describe observed rotation curves as well as satisfy an empirical
soliton-
halo mass relation in low surface brightness
galaxies for $m \sim 10^{-22}\ \text{eV}$ and $\lambda \gtrsim 10^{-90}$. We also study
tidal effects in satellite
dwarf galaxies and find that attractive self-interactions can extend their lifetimes over cosmological timescales, allowing ULDM to evade recent constraints derived for the non-interacting case. Finally, we explore machine learning based inference of dark matter and baryonic parameters from
galaxy rotation curves, showing that neural networks can recover parameters consistent with observations.
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Solar and Stellar Astrophysics
The Likelihood of Hosting Undetected Brown Dwarfs in the Solar Vicinity
Diana Bakirova and Oleg Malkov
Based on the spatial distribution of objects in the
solar neighbourhood with a radius of 20 parsecs, and after correcting for the incompleteness of observational data, an expression was obtained for estimating the probability of finding an object at a given distance from the Sun. According to these estimates, with a probability of about 0.5, there exists a brown
dwarf in the immediate
solar vicinity (< 1.2 pc). The possible multiplicity of this hypothetical object is discussed, as well as the reasons why it has not yet been detected.
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Cosmology and Nongalactic Astrophysics
$S_8-H_0$ tension in a SI-ULDM scenario
Jessica N. López-Sánchez
We study the cosmological impact of a transient self-interaction phase in Ultra-Light Dark Matter (ULDM), focusing on its simultaneous effects on the sound horizon and the late-time growth of structure. In the presence of a quartic self-interaction, the scalar field undergoes a short-lived radiation-like phase before evolving into matter-like behaviour, inducing a localized modification of the expansion history at early times. We develop a perturbative and model-independent framework in which the self-interaction energy density is parametrized as a localized contribution to the total energy budget. Within this approach, the responses of the sound horizon and the linear growth factor can be expressed as weighted integrals over
cosmic time, with distinct kernels encoding the temporal sensitivity of each observable. This structure leads to a simple analytic relation linking the corresponding early- and late-time responses, and naturally predicts correlated shifts in $H_0$ and $S_8$ whose sign and magnitude depend on the timing of the self-interaction episode. Our results show that a single transient modification of the expansion history can interpolate between early-time effects on the sound horizon and late-time suppression of structure growth within a unified physical framework, providing an analytical understanding of their joint response.
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Instrumentation and Methods for Astrophysics
From Nbody1 to Nbody7: the Growth of Sverres Industry
Rainer Spurzem
From NBODY1 to NBODY6 : The Growth of an Industry is the title of a 1999 invited review by Sverre Aarseth, for Publications of the Astronomical Society of the Pacific (PASP). I took this as an inspiration for the title of this paper; it describes how Sverres NBODY Industry has further grown since 90s of the previous century, and how it is further flourishing and hopefully developing, in his spirit, even after the sad news of his passing away reached us. My contact and friendship with Sverre started a few decades ago being sent to Cambridge to learn NBODY5, counting input parameters, and learning about the fact that even a sophisticated code (which had already at that time quite a history) requires permanent maintenance and bug fixes. Managed by Sverre, who relentlessly ran his code and responded to the widely spread crowd of customer colleagues. There has been a phase of massive and fast development and improvements due to vectorization, parallelization, GRAPE and GPU acceleration, and Sverre has been always on top of it if not ahead, but also fully adopting ideas of collaborators, once they tested well. NBODY6++GPU and NBODY7 entered the scene, and also recent new competitors, such as PETAR or BIFROST . We all have learnt a lot from Sverre, and strive to continue in his open-minded spirit, for open source and exchange. A striking evidence for the further growth of the industry is the number of papers here (and two of them follow in this session, but also in other sessions) using and further developing the aforementioned codes, as well as the occurrence of new and competing codes, which keep the field alive.
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High Energy Astrophysical Phenomena
Improved lanthanide constraints for the kilonova AT 2017gfo
J. H. Gillanders, A. Flors and R. Ferreira da Silva
Spectroscopic observations of the kilonova AT 2017gfo provide a unique opportunity to identify signatures from individual heavy elements freshly synthesised via the r-process, the nucleosynthetic channel responsible for producing $\sim$half of all trans-iron-group elements. Limitations in the available atomic data have historically hampered comprehensive line identification studies; however, renewed interest has led to the generation of improved (more complete and accurately calibrated) line lists for r-process species. Here we demonstrate the utility of such data, by exploiting newly generated line lists for the lanthanides to model the photospheric-phase 3.4d X-shooter spectrum of AT 2017gfo with the radiative transfer tool TARDIS. We find the data can only be reproduced by invoking a substantially diminished lanthanide mass fraction ($X_{\textsc{ln}}$) than that proposed by previous studies. Specifically, our model necessitates $X_{\textsc{ln}} \approx 2.5 \times 10^{-3}$ in the line-forming region, a value $20 \times$ lower than previously claimed. This substantial reduction in $X_{\textsc{ln}}$ is driven by our inclusion of much more complete lanthanide line information that enables better estimation of their total contribution to the observations. We encourage future modelling works to exploit all atomic data advances, and also encourage continued efforts to generate the necessary data for the remaining r-process species of interest.
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High Energy Astrophysical Phenomena
H.E.S.S. detection and multi-wavelength study of the $z \sim$ 1 blazar PKS 0346$-$27
H.E.S.S. collaboration
PKS 0346-27 is a Low Synchrotron Peaked (LSP) blazar at
redshift 0.991. The very-high-energy (VHE, E > 100 GeV) spectra of blazars are always affected by $\gamma\gamma$ absorption by the Extragalactic Background Light (EBL) and subsequently, no blazars have been detected in VHE $\gamma$-rays at
redshifts exceeding 1. Extending the
redshift range of VHE-detected blazars to $z \gtrsim 1$ will yield insights into the cosmological
evolution of both the VHE blazar population and the EBL. This is the goal of a target-of-opportunity (ToO) programme by H.E.S.S. to observe flaring high-
redshift ($z \gtrsim 1$) blazars. We report on H.E.S.S. ToO and multi-wavelength observations of the blazar PKS\,0346$-$27. Along with H.E.S.S., simultaneous data from
Fermi-LAT, Swift (XRT and UVOT), and ATOM have been analysed and modelled using single-zone leptonic and hadronic models. PKS~0346-27 has been detected by H.E.S.S at a significance of 6.3$\sigma$ during one night, on 3 November 2021, while for other nights before and after this day, upper limits on the VHE flux are determined. No evidence for intra-night $\gamma$-ray variability has been found. A
flare in high-energy (HE, $E > 100$~MeV) $\gamma$-rays detected by
Fermi-LAT preceded the H.E.S.S. detection by 2 days. A fit with a single-zone emission model to the contemporaneous spectral energy distribution during the detection night was possible with a
proton-synchrotron-dominated hadronic model, requiring a
proton-kinetic-energy-dominated jet power temporarily exceeding the source's Eddington limit, although alternative (e.g. multi-zone) models can not be ruled out. A one-zone leptonic model is, in principle, also able to fit the
flare-state SED, however, requiring implausible parameter choices, in particular, extreme Doppler and bulk Lorentz factors of $\gtrsim 80$.
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High Energy Astrophysical Phenomena
Abundance Stratification in Type Iax SN 2020rea with TARDIS
Sohini Kayal, P. Gayatri, Mridweeka Singh et al. (+1 more)
Using the 1D Monte Carlo-based radiative transfer code TARDIS, we investigate the spectral
evolution of the Type Iax
supernova (SN) 2020rea from -7 days before to +21 days after maximum light. Our best-fit models indicate stratified, velocity-dependent abundances at early times, successfully reproducing most observed spectral features. As the SN evolves, the ejecta transition from a layered to a more homogeneous composition, posing an alternative to pure deflagration models that predict fully mixed ejecta. These results highlight the need for further investigation, as current pure deflagration models cannot fully explain the origin or spectral properties of Type Iax SNe like SN 2020rea.
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All authors Sohini Kayal, P. Gayatri, Mridweeka Singh, Kuntal Misra
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
A. C. Khunt, K. Yavuz Ekşi and P. C. Vinodkumar
We investigate the impact of pressure anisotropy on the structural and
geometric properties of
neutron stars within general relativity, focusing primarily on the phenomenological Bowers-Liang (BL) model, and comparing selected results with a quasi-local prescription. Using the SLy equation of state, we explore how anisotropic stresses modify global observables such as the mass-radius relation, moment of inertia, compactness, and
tidal deformability over a broad range of anisotropy parameters. We find that moderate positive anisotropy can increase the maximum supported mass up to approximately $2.4\;M_\odot$ and enhance
stellar compactness by up to $20\%$ relative to isotropic configurations, while remaining broadly consistent with current NICER and gravitational-wave constraints. To probe the internal gravitational field, we compute
curvature invariants including the
Ricci scalar, the
Ricci tensor contraction, the Kretschmann scalar, and the Weyl scalar. We show that
curvature measures directly tied to the matter distribution exhibit a strong sensitivity to anisotropy, whereas the Weyl
curvature remains comparatively insensitive, reflecting its role as a measure of the free gravitational field. Within the phenomenological BL framework, the maximum compactness increases with anisotropy and reaches values as high as $\mathcal{C}_{\max}\approx 0.25$-$0.38$ for $\lambda_{\rm BL}\in[-4,+4]$, although the physical realizability of such highly compact configurations depends sensitively on the underlying anisotropy mechanism. A comparison with the quasi-local model highlights the strong model dependence of anisotropic effects, underscoring both the potential significance and the limitations of phenomenological anisotropy prescriptions in modeling strong-field
neutron-
star interiors.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Sommerfeld Enhancement from Background Force and the Galactic Center GeV Excess
Yu Cheng and Shuailiang Ge
We study the impact of background-induced forces on dark matter (DM) annihilation and their implications for indirect detection. In the presence of a finite number density of background particles, loop-level interactions can generate an effective force that is significantly enhanced relative to the
vacuum case. We construct a two-component DM model in which the dominant component is a fermionic particle $\chi$ and the subdominant component is an ultralight pseudoscalar particle $\phi$. The annihilation of $\chi$ proceeds through the p-wave channel and produces gamma-ray emission. The finite density of $\phi$ particles induces a background-enhanced force between $\chi$ particles, leading to a sizable Sommerfeld enhancement of the annihilation. We show that a viable region of parameter space in this model can account for the gamma-ray excess observed in the
Galactic Center using
Fermi-LAT data. The background-induced force substantially amplifies the Sommerfeld enhancement and thus enlarges the parameter space capable of explaining the excess, highlighting the importance of background effects in astrophysical environments.
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Instrumentation and Methods for Astrophysics
Connecting disc-corona physics and ionised outflows in AGN in the 2040s
Susanna Bisogni, Giustina Vietri, Andrea Travascio et al. (+3 more)
We outline a science case for next-generation wide-field spectroscopic surveys aimed at connecting the physics of the
accretion disc and X-ray corona in active
galactic nuclei (AGN) with the properties of their nebular regions and circumgalactic medium (CGM). We focus on the non-linear Lx-Luv relation and on deviations from this canonical coupling encoded in $\Delta \alpha_{OX}$, the offset of the optical-to-X-ray index from the mean relation, and propose to use broad and narrow line emission and CGM nebulae as calorimeters of the ionising SED to trace different
accretion "states". We propose an observational strategy based on rest-frame UV/optical spectroscopy of $\sim 10^{4}-10^{5}$ AGN, a time-domain reverberation-mapping tier for a well-defined subsample, coordinated X-ray coverage, and wide-field IFU mapping of CGM emission (including H$\alpha$ and Ly$\alpha$). From these goals we derive requirements for a future ESO facility in the 2040s: a dedicated, wide-field, high-multiplex optical-NIR spectroscopic
telescope with time-domain flexibility and arcmin-scale IFU capability.
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All authors Susanna Bisogni, Giustina Vietri, Andrea Travascio, Adriana Gargiulo, Chiara Mancini, Swayamtrupta Panda
Solar and Stellar Astrophysics
Tidally Trapped Two-pole Pulsations Discovered in a Close Binary with a Massive $\beta$ Cephei Star
Ping Li, Wen-Ping Liao, Sheng-Bang Qian et al. (+4 more)
Tidally tilted pulsators (TTPs), whose pulsation axis aligns with the binary's semi-major axis, represent a newly established class of oscillators in binary systems. While all previously known TTPs are either $\delta$ Scuti or subdwarf B-type
stars, their existence has remained unidentified in more massive $\beta$ Cephei variables. Here, we report the discovery of tidally trapped pulsations in the massive ellipsoidal variable HD~329379, based on photometry from the Transiting
Exoplanet Survey Satellite (TESS). Our analysis reveals a $\beta$ Cephei pulsator in a 2.25-day orbit whose pulsation mode amplitude is strongly modulated with the orbital frequency. Based on our analysis, we concluded that this modulation can be explained by pulsations with significantly larger amplitude near the
star's two
tidal poles (apsides). We interpret this as a tidally distorted quadrupole pulsation chariacteristiced by trapped two-pole pulsations, with a pulsation axis aligned with the
tidal axis. This represents the first identification of such a pulsation mode in a $\beta$ Cephei
star, which differs from single-sided pulsations observed in previous works, marking a rare and important discovery. Our work extends the family of TTPs beyond $\delta$ Scuti and subdwarf B-type
stars to include more massive $\beta$ Cephei variables. In particular, the two-pole pulsator HD~329379 stands out as the prototype of a new class of TTPs in massive
stars. These results not only provide a new insight to probe the interior structure and evolutionary state for massive
stars but also offer a unique opportunity to study the interaction between pulsations and strong
tidal distortions.
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All authors Ping Li, Wen-Ping Liao, Sheng-Bang Qian, Li-Ying Zhu, Jia Zhang, Qi-Bin Sun, Fang-Bin Meng
High Energy Astrophysical Phenomena
A Seyfert galaxy as a hidden counterpart to a neutrino-associated blazar
Emma Kun, Santiago del Palacio, Imre Bartos et al. (+5 more)
The origin and production mechanisms of high-energy astrophysical
neutrinos remain open questions in multimessenger astronomy. Previous studies have hinted at a possible linear correlation between the hard X-ray and high-energy
neutrino emission in active
galactic nuclei. New NuSTAR observations, first presented here, reveal that blazar PKS 1424+240, located within a prominent IceCube
neutrino hotspot, is far fainter in hard X-rays than expected from this trend. Motivated by this apparent ambiguity, we identify the nearby Seyfert
galaxy NGC 5610, also coincident with the hotspot, whose unabsorbed hard X-ray flux exceeds that of PKS 1424+240 by about an order of magnitude. When the local IceCube
neutrino flux is apportioned between the two AGN in proportion to their hard X-ray emission, both align with the previously suggested X-ray-
neutrino correlation. This suggests that certain IceCube hotspots may be unresolved blends of multiple AGN, and supports a multimessenger scenario in which high-energy
neutrinos and hard X-rays originate from the same hadronic interactions, with the X-ray emission produced through cascade reprocessing.
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All authors Emma Kun, Santiago del Palacio, Imre Bartos, Francis Halzen, Julia Becker Tjus, Peter L. Biermann, Anna Franckowiak, Claudio Ricci
High Energy Astrophysical Phenomena
Evolution of Accretion Properties in Mrk 1040 using long-term X-ray Observations
Prantik Nandi, Narendranath Layek, Sandip K Chakrabarti et al. (+2 more)
We present a comprehensive long-term, multi-epoch spectral and timing study of the Seyfert 1 Active
Galactic Nucleus (AGN) Mrk~1040, utilizing X-ray observations spanning from 2009 to 2024 ($\sim$15 years). The source exhibits pronounced spectral and temporal variability, indicative of transitions between different
accretion regimes in the vicinity of the central supermassive black hole. The earlier reported soft excess is re-examined within a uniform, physically motivated multi-epoch framework. We confirm the presence of this soft excess in the 2009 observation, where it is well described by a warm, extended Comptonizing corona with $kT_{\rm e,warm} \sim 0.26$~keV and a radial extent of $R_{\rm warm} \sim 30~r_g$. In subsequent epochs, the soft excess is not statistically significant, possibly due to a combination of enhanced ionized absorption, intrinsic weakening of the warm Comptonizing region, or partial truncation of the inner disc. A strong correlation between the soft and hard X-ray fluxes suggests a common physical origin for both components, likely within a multi-layered Comptonizing structure that evolved into a compact and thermally stable corona after 2013. The observed spectral variability, together with changes in the Fe~K$\alpha$ line strength, reflects the evolving coronal geometry and
accretion flow dynamics. Variations in the intrinsic column density ($N_H$) further indicate that Mrk~1040 is embedded within a clumpy, dynamically variable absorber responding to changes in the
accretion rate. Using the TCAF model, we estimate the black hole mass as $M_{\rm BH} = (4.50 \pm 1.62) \times 10^7~M_\odot$, consistent with previous estimates.
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All authors Prantik Nandi, Narendranath Layek, Sandip K Chakrabarti, Sachindra Naik, Priyadarshee P. Dash