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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.GAastro-ph.CO

Early Supermassive Black Holes and Little Red Dots Require Free-Fall Growth

Junehyoung Jeon, Volker Bromm, Michael Boylan-Kolchin, Julian B. Muñoz

Supermassive black holes/active galactic nuclei (SMBHs/AGN), forming only a few hundred million years after the Big Bang as observed with the James Webb Space Telescope (JWST), challenge theoretical understanding. How could they grow so massive $(M_{\rm BH} > 10^6 {\rm \,M}_\odot)$ so quickly after initial seeding? Is this rapid growth related to the numerous and enigmatic Little Red Dots (LRDs), compact sources with AGN-like characteristics, discovered by JWST? To address these mysteries, we co…

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astro-ph.GA

Skyfire: A Spectroscopic Census of Little Red Dots and Broad-Line AGN in the CEERS Field

Dale D. Kocevski, Anthony J. Taylor, Masafusa Onoue, Kohei Inayoshi, Steven L. Finkelstein, Guillermo Barro, Jingsong Guo, Pablo Arrabal Haro et al.

We present the Skyfire program, a 21-hour Cycle 3 JWST/NIRSpec survey with the G395M medium-resolution grating covering five pointings in the Extended Groth Strip. The survey is designed to carry out a systematic census of faint, broad-line AGN candidates with a range of rest-optical colors identified at z > 3 by the Cosmic Evolution Early Release Science (CEERS) Survey. Our primary targets include photometrically-selected Little Red Dots (LRDs), blue extreme emission line galaxies (EELGs), and…

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astro-ph.GAastro-ph.HE

Weighing Little Red Dots with Transient Events

Vinh Tran, Xuejian Shen, Oliver Zier, Anna de Graaff, Rohan P. Naidu, Mark Vogelsberger

Recent JWST observations have revealed a large population of compact red sources at $z \gtrsim 4$, known as Little Red Dots (LRDs), many of which show signatures of accreting massive black holes (BHs). The physical nature of these sources and their connection to host galaxies are under debate. We propose an independent avenue for constraining their nature through transient phenomena, such as tidal disruption events (TDEs) and quasi-periodic eruptions (QPEs), arising from interactions between a s…

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hep-phastro-ph.HEastro-ph.SR

Solar Spin-Dependent Dark Matter-Neutron Cross Section Constraints: The Lost Case

Thong T. Q. Nguyen, Carlos Blanco, Tim Linden

The Sun has long served as a natural dark matter detector, capturing halo particles that scatter with solar nuclei and electrons and subsequently produce indirect signals from dark matter annihilation that can be probed by either neutrino or $γ$-ray instruments. Previous efforts have computed cross-section constraints for dark matter scattering with electrons, as well as spin-independent and spin-dependent dark matter-proton scattering. However, the spin-dependent dark matter-neutron scattering…

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astro-ph.GA

Reconciling Galactic rotation curve constraints with stellar stream modeling

Mingyu Chang, Francois Hammer, Yanbin Yang

Recent Gaia-based measurements of the Milky Way rotation curve and stellar-stream modeling give significantly different estimates of the Galactic dynamical mass beyond Galactocentric radii of 15 kpc. The stream-based model predicts an outer halo five times more massive than that predicted by the Gaia rotation curve. We aim to test the impact of analytic assumptions used in stream modeling and to assess whether the currently available stream constraints can distinguish between low- and high-mass…

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astro-ph.GA

Reconciling Galactic rotation curve constraints with stellar stream modeling

Mingyu Chang, Francois Hammer, Yanbin Yang

Recent Gaia-based measurements of the Milky Way rotation curve and stellar-stream modeling give significantly different estimates of the Galactic dynamical mass beyond Galactocentric radii of 15 kpc. The stream-based model predicts an outer halo five times more massive than that predicted by the Gaia rotation curve. We aim to test the impact of analytic assumptions used in stream modeling and to assess whether the currently available stream constraints can distinguish between low- and high-mass…

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astro-ph.IMastro-ph.CO

Agentic research is oxymoronic

Natalie B. Hogg

The use of agentic large language models obviates human interpretation of scientific results, and will lead to substantial distrust in the literature.

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astro-ph.IMastro-ph.COastro-ph.HE

Ad Astra White Paper: A Pitch for the Next 25 Years of NASA's Physics of the Cosmos Program

Eric Burns, Ivan Agullo, Igor Andreoni, Catherine M. Deibel, Christopher L. Fryer, Natasha Latouf, M. Coleman Miller, Jillian C. Rastinejad et al.

Astrophysical observations of our universe have been key to our understanding of how the universe works. Shortly after the turn of the millennium, the National Research Council delivered \textit{Connecting Quarks with the Cosmos: Eleven Science Questions for the New Century}. In the subsequent quarter-century, we have made substantial progress in answering each question. These advancements have, in part, arisen because of the success of major US facilities across several domains of physics, guid…

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astro-ph.IMphysics.pop-ph

Slysh haloes: the waste heat of cold computing as a submillimetre technosignature

Michael Garrett

Searches for Dysonian waste heat have operated almost exclusively in the mid-infrared and are therefore sensitive primarily to technology radiating at 100-600K. We argue that mature, computation-dominated civilisations may instead dissipate much of their energy at far lower temperatures. The Landauer cost of irreversible computation scales linearly with temperature, while ambient temperatures at large circumstellar radii approach the 2.7K cosmic microwave background floor. Cold computation is th…

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astro-ph.IMastro-ph.HE

The Analysis, not the Aperture: End-to-End Transformer Reconstruction for Imaging Atmospheric Cherenkov Telescopes

Elli Jobst, Lea Heckmann, Lukas Heinrich, David Paneque

Imaging Atmospheric Cherenkov Telescopes (IACTs) detect very-high-energy gamma rays by imaging the nanosecond Cherenkov flash of the air shower they initiate in the Earth's atmosphere. For four decades the first steps of IACT event reconstruction have been essentially unchanged, relying on a heavy parameterisation and dimensionality reduction of the recorded images. This is reasonable when the image is bright, but discards important information when only a few tens of Cherenkov photons are recor…

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astro-ph.GA

The impact of hot mode accretion and angular momentum conservation on metallicity gradients of galactic discs

Jennifer K. S. Friske, Filippo Fraternali, Gabriele Pezzulli

The hot circumgalactic medium (CGM) of a galaxy inevitably rotates more slowly than the cold gas in the disc it surrounds, due to a higher pressure support against gravity. If it accretes vertically onto the disc, angular momentum conservation leads to radial flows, advection of metals inwards and the steepening of a metallicity gradient. The observed gradient hence carries information on the kinematics of the accreting gas. Previous models built on this premise parametrised the angular momentum…

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astro-ph.SRastro-ph.EPphysics.flu-dyn

Accretion Rates and Thermohaline Convection in Polluted White Dwarfs

J. R. Fuentes, Matias Castro-Tapia, Jim Fuller, Marcus King

Polluted white dwarfs provide a unique window into the composition of exoplanetary material, but interpreting their surface abundances requires a quantitative understanding of the mixing processes in their envelopes. Accretion of metal-rich debris onto hydrogen-rich white dwarfs drives thermohaline (fingering) convection in the underlying radiative zone. Previous studies have modeled this as enhanced diffusive transport, often inferring mass accretion rates, $\dot{M}_{\rm acc}$, that exceed cons…

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astro-ph.IMphysics.flu-dynphysics.space-ph

Feasibility of Capillary-Driven Orbital Liquid Mirror Telescopes

Janoad Dietrich, Álvaro Romero-Calvo

Space-based liquid mirror telescopes (LMTs) have been recently proposed to overcome the scaling limits of traditional rigid mirrors. In these new space architectures, capillary forces would shape a reflective liquid into a spherical optical surface in microgravity. However, the equilibrium, stability, and dynamic behavior of such liquid interfaces under orbital perturbations remain largely uncharacterized. This study investigates the feasibility of space LMTs by combining axisymmetric capillary…

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gr-qcastro-ph.HE

Bekenstein--Hod Bound: A $3.3σ$ Confirmation from GW250114

Hai-Tian Wang, Shao-Peng Tang, Yi-Zhong Fan

Black holes link gravity, thermodynamics and information via limits on the relaxation rate of a perturbed system. The Bekenstein-Hod bound imposes a minimum relaxation time at fixed temperature, but its observational test demands both black hole thermodynamic characterization and decay time measurement. Here we test this bound with GW250114, the loudest gravitational-wave signal yet observed from a binary black-hole merger. We infer the remnant temperature from pre-merger data truncated at least…

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astro-ph.IMastro-ph.HE

The Auger Radio Infill SKALA Extension (ARISE): Science Case and Instrumentation (ARENA 2026)

Frank G. Schröder for the Pierre Auger Collaboration

The Auger Radio Infill SKALA Extension (ARISE) at the Pierre Auger Observatory in Argentina was deployed in 2025 and measures cosmic-ray air showers in the energy region of the Galactic-to-extragalactic transition. ARISE is comprised of 18 SKALA-2 antennas featuring two polarization channels each, deployed within $100\,$m of a surface detector station in the enhancement area of the Pierre Auger Observatory. This area of the surface array features a denser spacing of $433\,$m between surface stat…

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astro-ph.GA

ALMA CO(2-1) Gas Dynamics in NGC 315: A Multi-Method Benchmark for Supermassive Black Hole Mass Measurement

Dieu D. Nguyen, Benjamin D. Boizelle, Hai N. Ngo, Elena Gallo, Tuan N. Le, Sabine Thater, Tien H. T. Ho, Tinh Q. T. Le et al.

We present ALMA Cycle~7 \cotwo\ observations of the circumnuclear disk in NGC~315 at an angular resolution of $0\farcs230\times0\farcs175$, improving on past measurements and resolving the sphere of influence (SOI) of the supermassive black hole (SMBH), whose mass has previously been estimated of $M_{\rm BH}= \left(2.08^{+0.33}_{-0.15}\right) \times 10^9$~M$_\odot$ The high spatial resolution and sensitivity enable robust full-cube forward modeling of the molecular gas kinematics and a direct co…

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gr-qcastro-ph.HE

Constraining equation of state of neutron star using neutron star-black hole mergers

Vasudev Dubey, Rahul Kashyap, Yugesh Bhoge

In this work, we study tidal effects that can be observed in gravitational wave transient from neutron star-black hole (NSBH) mergers. It has been well known that neutron star's tidal deformation has imprint of equation of state and hence composition of neutron star matter. Compared to binary neutron star mergers, where we observe a combined effect of two neutron stars by measuring the parameter known as lambda tilde. In neutron star black hole mergers, we measure the tidal deformability of the…

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astro-ph.HEastro-ph.IM

The First Array-Wide Diffuse Flux Search for UHE Neutrinos with the Askaryan Radio Array

Alan Salcedo-Gomez, Marco Stein Muzio, for the ARA Collaboration

The Askaryan Radio Array (ARA) is an ultrahigh energy (UHE) neutrino detector at the South Pole that searches for impulsive broadband radio signals from neutrino-induced particle showers in glacial ice. ARA consists of five autonomous stations with receiving antennas deployed up to 200 m deep and has accumulated the largest livetime of any in-ice radio array. We present the first array-wide diffuse UHE neutrino search using data collected from January 2013 to December 2023, incorporating improve…

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astro-ph.IM

METIS high-contrast imaging simulations: From instrument modelling to science readiness

Gilles Orban de Xivry, Olivier Absil, Iain Hammond, Thomas Bertram, Roy van Boekel, André Boné, Gaël Chauvin, Valentin Christiaens et al.

The Mid-infrared Extremely Large Telescope (ELT) Imager and Spectrograph (METIS) instrument, expected to see first light in early 2030, aims to detect and characterise exoplanets and circumstellar disks through high- contrast imaging (HCI) and spectroscopy. The High-contrast End-to-End Performance Simulator (HEEPS), initially developed to support the design of the METIS HCI modes, has evolved into a crucial tool for the METIS science team to prepare and optimize observations. HEEPS is an open-so…

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astro-ph.EP

Öpik-type collision frequency for Kozai-driven projectiles: Target bodies on eccentric and inclined orbits

Youpeng Liang, Xiaodong Liu

For high-inclination projectiles undergoing Lidov--Kozai secular evolution, coupled variations in eccentricity and inclination complicate estimates of long-term collision frequencies with a target body. Previous collision-frequency studies for Kozai-driven projectiles have considered target-body orbits that are either circular or confined to the reference plane. The present study considers the general case in which the target body's orbit has both non-zero eccentricity and non-zero inclination.…

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astro-ph.SRastro-ph.GA

From spectroscopic abundances to evolutionary [$α$/Fe] in stellar models

Pedro Diaz Reeve, Aldo Serenelli

Large-scale, high-resolution spectroscopic surveys map detailed chemical abundance patterns for millions of stars. However, libraries of stellar evolution models and isochrones still rely on a simplified description of chemical abundances, generally assuming either solar-scaled compositions or a constant enrichment for all $α$-elements. Moreover, the definition of $α$-enrichment is survey-dependent and is not necessarily the most relevant quantity for stellar structure and evolution. In the era…

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astro-ph.HEastro-ph.COastro-ph.IM

The DSA/Chronoscope fast radio burst survey: forecasts and science overview

Liam Connor, Kaitlyn Shin, Vikram Ravi, Stella Koch Ocker, Casey J. Law, Kritti Sharma, Samuel McCarty, Gregg Hallinan et al.

Fast radio bursts (FRBs) are bright extragalactic transients with several mysteries surrounding their origins. Large FRB samples enable accurate measurements of the cosmic matter distribution, in particular on scales $\lesssim 10$ Mpc. These measurements will impact cosmological inference and our understanding of astrophysical feedback, from the circumgalactic medium to cluster scales. Here we forecast the expected yields, redshifts, and host galaxies of FRBs as observed by the Deep Synoptic Arr…

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astro-ph.IM

Beyond $X_\mathrm{max}$ : Reconstructing Air Shower Profiles with Information Field Theory with SKA-Low

Keito Watanabe, Tim Huege, Torsten Enßlin, Vincent Eberle, Sjoerd Bouma, Justin Bray, Stijn Buitink, Arthur Corstanje et al.

While radio measurements of extensive air showers have shown to achieve a high precision of $X_\mathrm{max}$ sensitivity, it has been shown that parameters beyond $X_\mathrm{max}$ can also be reconstructed. These shape parameters contain additional sensitivity to the hadronic physics in the shower as well as its mass composition. In this work, we showcase a reconstruction framework to recover the full longitudinal profile from realistic radio measurements. The framework is based on Information F…

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astro-ph.SRastro-ph.IMstat.AP

Extremes of solar spectral irradiance in the SORCE/XPS record

Enzo Brasil, Cira E. G. Otiniano, Carolyne Brito, Beatriz Albernaz, Fidel Morales

Extreme and rare changes in space mission solar irradiance records are scientifically relevant but difficult to quantify because these records are finite, instrument dependent, and affected by observational gaps and time varying measurement quality. We evaluated extreme daily logarithmic changes in the band integrated 0.1-7.0 nm irradiance measured by photodiode 7 of the Solar Radiation and Climate Experiment/X-Ray Photometer System (SORCE/XPS) from 2005 to 2019. After constructing a regular dai…

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astro-ph.IMgr-qc

Detectability-Aware Screening of Post-Merger Gravitational-Wave Damping Anomalies in Real Detector Noise: A Graph-Spectral Approach with Empirical Null Calibration

Ruslan Alaskarov

A two-stage methodological proof of concept for screening simplified post-merger gravitational-wave damping anomalies in real LIGO Livingston noise is presented. The injected signal is a controlled damped-sinusoid proxy rather than a physically complete binary-neutron-star post-merger waveform; it is used to test statistical detectability and damping-time scoring under real-noise calibration. Stage 1 constructs a local time-frequency graph from Constant-Q representations of whitened candidate wi…

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astro-ph.SR

Study of Butterfly-Shaped Coronal Hole Evolution Across the Solar Disk

Bhairab Ale, Khagendra Katuwal, Shiv Narayan Yadav

We studied the evolution of a butterfly-shaped coronal hole (CH) observed from 2025 September 8 to 14 using SDO/AIA 193~Å images and SDO/HMI line-of-sight magnetograms. The CH boundary was identified using a fixed 100~DN intensity threshold, and its area, mean EUV intensity, and total unsigned magnetic flux were tracked across the solar disk. As the CH approached the central meridian, its area increased from approximately $7.70\times10^{16}$ to $1.63\times10^{17}$~m$^{2}$ and its unsigned magnet…

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astro-ph.GA

Stellar streams around dwarf galaxies are observationally rare in the local Universe

Joanna D. Sakowska, David Martíınez-Delgado, Sarah Pearson, Francisco J. Riquel-Castilla, Tjitske K. Starkenburg, Giuseppe Donatiello, Alis Deason, Denis Erkal et al.

The frequency and properties of stellar streams around dwarf galaxies remain observationally under-explored. Building a statistically significant sample is challenging because dwarf galaxies are smaller, fainter, and far more numerous than massive galaxies. We present the first results from a systematic survey for stellar streams around dwarf galaxies. We first introduce a classification metric for satellite accretion features (streams, shells, and asymmetric stellar haloes) using DECam imaging…

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astro-ph.IMastro-ph.HE

Radio measurements of air showers with the IceCube-Gen2 surface prototype station at the Pierre Auger Observatory

Stef Verpoest, or the IceCube-Gen2 Collaboration, for the Pierre Auger Collaboration

The design of the IceCube-Gen2 observatory, proposed as a next-generation extension of IceCube, includes a surface array consisting of scintillators and radio antennas. In addition to several such detectors already deployed at IceCube's surface array at the South Pole, a complete prototype station including three SKALA antennas has been operating at the Pierre Auger Observatory for several years. This setup has been used to successfully observe radio signals from air showers, demonstrated throug…

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astro-ph.IMastro-ph.HE

Radio measurements of air showers with the IceCube-Gen2 surface prototype station at the Pierre Auger Observatory

Stef Verpoest, for the IceCube-Gen2 Collaboration, for the Pierre Auger Collaboration

The design of the IceCube-Gen2 observatory, proposed as a next-generation extension of IceCube, includes a surface array consisting of scintillators and radio antennas. In addition to several such detectors already deployed at IceCube's surface array at the South Pole, a complete prototype station including three SKALA antennas has been operating at the Pierre Auger Observatory for several years. This setup has been used to successfully observe radio signals from air showers, demonstrated throug…

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astro-ph.GAastro-ph.SRphysics.plasm-ph

Magnetohydrodynamics of charged interstellar dust. Multifluid models and study of the linear modes

Gabriel Verrier, Patrick Hennebelle, Ugo Lebreuilly, Valentin Vallucci-Goy

Interstellar grains play key roles in star and planet formation, including the coupling of the gas to the magnetic field during the protostellar collapse. These roles depend on the local grain size distribution, which requires a multifluid treatment of charged dust. We aim to understand the fundamental physics of the dynamics of a dust distribution in interaction with the gas and the magnetic field. In particular, the purpose is to characterize the (de)coupling conditions of these different comp…

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