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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.HEastro-ph.SR

Portraits of the young and old in X-ray: New millisecond pulsar detections and updated characterisation of young neutron stars

Wynn C. G. Ho, Patrick H. Wang, Sebastien Guillot

We present analyses of new and archival Chandra and NuSTAR data on two old millisecond pulsars, a young highly-energetic pulsar, and a young neutron star. PSR J1810-0623 is a recently-discovered 4.55 ms radio pulsar in a binary with a possible carbon-oxygen white dwarf companion. We tentatively detect the pulsar for the first time in X-ray using a new short Chandra HRC-I observation. Its faintness suggests a distance more in accord with the further (~1 kpc) of its dispersion measure-inferred dis…

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astro-ph.HEastro-ph.SR

Evidence for a luminosity-class dichotomy in the supergiant donors of persistent high-mass X-ray binaries and supergiant fast X-ray transients

Lara Sidoli, Vito Sguera

We have investigated the properties of the supergiant donors in two types of high-mass X-ray binaries (HMXBs, i.e. the so-called supergiant fast X-ray transients (SFXTs) and the classical X-ray sources), by collecting all available information from the literature. A prevalence of O-type versus B-type supergiant donors in SFXTs was previously suggested in the literature, possibly indicative of faster winds in SFXTs than in classical, persistent sources. Our aim is to investigate whether there is…

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astro-ph.HE

GRMHD Simulations of Accreting Proto-Magnetars I. Implications for Gamma-Ray Burst Jets and Energetic Explosions

Tejas Prasanna, Kyle Parfrey, Brian D. Metzger, Ore Gottlieb, Andrei Beloborodov, Koushik Chatterjee

Newly formed, rapidly rotating, strongly magnetized neutron stars ("millisecond proto-magnetars") are promising central engines for gamma-ray bursts (GRBs) and luminous supernovae. Although often modeled in isolation, they can be born surrounded by accretion disks in stellar collapse, neutron-star mergers, or accretion-induced collapse. We present axisymmetric GRMHD simulations of hyperaccretion onto such objects, including a physical equation of state and charged-current weak interactions. Hold…

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astro-ph.HEnucl-exnucl-th

Equation of state and neutron star properties with new mass-radius constraints from PSR~J1614--2230, PSR~J2124--3358, and 47~Tuc~X7

Melissa Mendes, Isak Svensson, Hannah Gottling, Kai Hebeler, Achim Schwenk, Nathan Rutherford, Lucien Mauviard, Christine Kazantsev et al.

We study the impact of new mass-radius information from PSR J1614-2230, PSR J2124-3358, and 47 Tuc X7 in a combined equation of state inference based on chiral effective field theory constraints at nuclear densities and using different high-density extensions, including perturbative QCD constraints. The largest impact stems from the heavy-mass PSR J1614-2230 star, which shifts heavy neutron stars to smaller radii by around 0.4 km. Moreover, the combined astrophysical NICER, LIGO/Virgo, and X-ray…

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astro-ph.HEnucl-th

A NICER view of PSR J1614$-$2230: a massive and compact millisecond pulsar

Lucien Mauviard, Sebastien Guillot, Lami Suleiman, Yves Kini, Denis González-Caniulef, Christine Kazantsev, Pierre Stammler, Devarshi Choudhury et al.

Using pulse profile modeling, we obtain the mass-radius measurement of a millisecond pulsar (MSP) with data from the Neutron Star Interior Composition ExploreR, XMM-Newton and the Chandra X-ray Observatory. We report here the radius of PSR J1614$-$2230, the second most massive MSP confirmed by radio timing. All of the data sets are well described by a simple model composed of two circular hot spots. The final result yields an equatorial radius of $R_{\rm eq}=10.06 ^{+1.25}_{-0.87}\,$km, and a gr…

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astro-ph.HE

Redshift Identifiability from Gamma-Ray Burst Prompt Emission

Shu-Xu Yi

We examine which prompt-emission observables of gamma-ray bursts (GRBs) carry identifiable redshift information in realistic structured-jet scenarios. By examining the photon-level Lorentz and cosmological transformations, we demonstrate any spectral observable reflecting the dominant-patch emission and any temporal observable reflecting the co-moving frame physics in the jet suffers from the same $z$-$θ_v$ degeneracy. The observable reflecting the absolute flux or count rate will also suffer fr…

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hep-phastro-ph.HEnucl-th

Magnetic field-induced enhancement and quenching of Urca emission in quark matter

William Gyory, Igor A. Shovkovy

Using first-principles field-theoretic methods, we investigate neutrino emission from strongly magnetized dense quark matter under conditions relevant to compact stars. We account for Landau-level quantization of both electron and quark states and show that it strongly modifies the kinematics of Urca processes. In particular, quark quantization restricts the available phase space in which both quark and electron energies can simultaneously lie near their respective Fermi surfaces. At moderately…

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astro-ph.COastro-ph.HE

Extended radio emission in and around the merging cluster A520 as seen by MeerKAT

S. Giacintucci, W. D. Cotton, M. Markevitch, T. Venturi, T. E. Clarke, H. Bourdin

We present results from a deep MeerKAT 1.28 GHz observation of Abell 520, a galaxy cluster in the middle of a merger and a treasure trove of merger-generated phenomena. MeerKAT's combination of high angular resolution and sensitivity to extended radio emission lets us uncover unprecedented detail of the cluster's giant halo and puzzling features beyond the halo. We find that the main radio halo is sharply bounded along the direction of the NE-SW merger axis by the two X-ray shock fronts. In the…

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astro-ph.GA

The Halo Gas of Local Spiral Galaxies and the Link to Gaseous Satellites

Yong Zheng, Jingyao Zhu, Ben Wertz, Yakov Faerman, Mary E. Putman

Gaseous satellites orbiting massive host galaxies experience gas stripping and may contribute additional gas to the hosts' circumgalactic medium (CGM). We identify a sample of 21 local spiral galaxies ($<$15 Mpc) and characterize their gaseous satellite populations from existing HI surveys to investigate the connection between host galaxy CGM and satellite gas content. Most of our spiral hosts have $\leq3$ gaseous satellites in their halos with $M_{\rm HI}\gtrsim10^{7}~M_\odot$. Using 26 HST/COS…

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astro-ph.IMastro-ph.GA

The promise of self-supervised and active learning for Strong Lens discovery: Astronomaly applied to KiDS

Margherita Grespan, Aprajita Verma, Michelle Lochner, Koketso Mohale, Verlon Etsebeth, Duncan Bowden

Strong gravitational lenses (SGLs) are rare systems whose discovery currently relies primarily on supervised machine learning methods trained on large simulated datasets. We present the first application of Astronomaly:PROTEGE to SGL discovery, demonstrating that a human-in-the-loop active learning framework can efficiently identify lenses in large imaging surveys without the need for simulated training data. We consider a sample of 3.7 million bright galaxies from the Kilo-Degree Survey (KiDS)…

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astro-ph.IMastro-ph.GA

The promise of self-supervised and active learning for Strong Lens discovery: Astronomaly applied to KiDS

Margherita Grespan, Aprajita Verma, Michelle Lochner, Koketso Mohale, Verlon Etsebeth, Duncan Bowden

Strong gravitational lenses (SGLs) are rare systems whose discovery currently relies primarily on supervised machine learning methods trained on large simulated datasets. We present the first application of Astronomaly:PROTEGE to SGL discovery, demonstrating that a human-in-the-loop active learning framework can efficiently identify lenses in large imaging surveys without the need for simulated training data. We consider a sample of 3.7 million bright galaxies from the Kilo-Degree Survey (KiDS)…

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astro-ph.EPastro-ph.IM

The Venus Benchmark: Resolving Degeneracies in Terrestrial Exoplanet Spectra with DAVINCI

Stephen R. Kane, David S. Alexander, Shahid Aslam, Giada N. Arney, James B. Garvin, Stephanie A. Getty, Amy E. Hofmann, Noam R. Izenberg et al.

The characterization of terrestrial exoplanets with thick, CO$_2$-dominated atmospheres via transmission and emission spectroscopy is limited by degeneracies between atmospheric composition, cloud structure, and surface conditions. These degeneracies are particularly acute for planets in or near the Venus Zone, where sulfuric acid aerosol layers and deep-atmosphere opacity render the lower atmosphere and surface spectroscopically inaccessible via many optical/IR wavelengths. Venus provides the o…

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astro-ph.EPastro-ph.SR

Self-induced edge rings in protoplanetary disks

Massimiliano Bolchini, Haochang Jiang, Jiaqing Bi

Observations with a high angular resolution by ALMA have revealed that substructures are ubiquitous in protoplanetary disks. Axisymmetric dust rings are the most common morphology. The profiles of some observed disks, including young disks, are smooth overall, with a localized dip or bump near the outer edge of the continuum disk that manifests as an edge ring. While embedded planets might contribute to these structures, their physical origin remains unclear. We investigated the possibility that…

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astro-ph.EP

Using Ringed Disks to Determine Fundamental Parameters of Planet Formation

Olivia Wu, Luca Camarra, Eve J. Lee

Two non-dimensional parameters, Stokes number (St) and turbulent $α$, critically control the early stage of planet formation. In spite of their importance, these two numbers are notoriously difficult to obtain and remain largely unconstrained, except in ringed disks. In particular, E. J. Lee (2024) showed that ringed disks can be uniquely leveraged to derive local St and $α$ through a simple model combining dust radial equation of motion with the measured distribution of dust masses in Class 0/I…

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astro-ph.SRastro-ph.EP

Conspicuous Gas, Cryptic Dust: Spectroscopy and Chromaticity of Complex Periodic Variables

Luke G. Bouma, Facundo Perez Paolino, Lynne A. Hillenbrand, Juliana Garcia-Mejia, Allyson Bieryla, Patrick Tamburo, David Charbonneau, John H. Livingston et al.

Complex periodic variables (CPVs) are young low-mass stars whose light curves show periodic dips indicative of transiting corotating material. The origin and composition of this material are unclear. Here we present new optical and near-infrared spectroscopy and photometry of four CPVs from Magellan, Keck, Hale, MuSCAT1, MuSCAT2, Tierras, KeplerCam, and TESS. The spectra imply that CPVs host magnetically bound circumstellar plasma clumps, on the basis of sinusoidal-in-time Balmer emission out of…

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astro-ph.GA

ACES VII. Compact Continuum Source Catalog of the Central Molecular Zone

Jennifer Wallace, Cara Battersby, Nazar Budaiev, H Perry Hatchfield, Ashley T. Barnes, Taehwa Yoo, Miriam G. Santa-Maria, Antonio Daley et al.

The Central Molecular Zone (CMZ) resides in the inner few hundred parsecs of our Galaxy, and despite being the largest reservoir of dense molecular gas in the Milky Way, it has a relatively low present-day star formation rate (SFR) of $\sim0.08~M_{\odot}~\text{yr}^{-1}$. Continuum and spectral line observations from the Atacama Large Millimeter/submillimeter Array (ALMA) CMZ Exploration Survey (ACES) provide the first full-coverage, high-resolution map of the inner 200 parsecs of the CMZ at 3 mm…

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astro-ph.SRastro-ph.GA

Modeling Rotation in the Old, Cold Domain: Implications on Gyrochronology and the Stellar Magnetic Wind

Amanda L. Ash, Yuxi, Lu, Marc H. Pinsonneault

Gyrochronology ties stellar rotation periods to ages. It is well studied in the young, open cluster age domain, but there are few constraints on gyrochronology in the old field star regime. In this work we use gyro-kinematic ages to explore the spin down of stars in this formerly inaccessible domain. Using forward modeling techniques which relax strict Rossby scaled assumptions, we find evidence for a departure from a standard spin down models. This departure can be explained with a mass-depende…

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hep-phastro-ph.HEgr-qchep-exhep-th

Dynamics and Frequency Conversion of Accreting Axion Clouds

Ximeng Li, Zhen Zhong, Yifan Chen, Yue Zhao, Hidetoshi Omiya, Vitor Cardoso

Axion fields can form exponentially growing gravitational clouds around compact objects through self-interaction-driven relaxation of ambient axion waves. As the field amplitude approaches the axion decay constant, nonlinear effects become important. We identify two distinct regimes of late-time evolution, determined by the gravitational fine-structure constant and the cloud growth rate: a Bosenova regime, characterized by collapse accompanied by explosive axion bursts, and a saturation regime,…

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astro-ph.SRastro-ph.HE

Exploring stellar evolution with Luminous Red Novae and Interacting Gap Transients

Nadejda Blagorodnova

Interacting gap transients encompass several families of astrophysical phenomena where eruptive mass loss and interaction play an important role in shaping the observational properties and energetics of the events. Composed of Luminous Red Novae (LRNe), Intermediate Luminosity Red Transients (ILRTs), Luminous Blue Variable (LBV) giant eruptions, and pre-supernova precursors, interacting gap transients offer crucial insights into unstable mass transfer, extreme stellar mass loss, and binary evolu…

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astro-ph.SR

Sinking and spreading of metal pollution in magnetic white dwarfs

Elad Shiftan, Sivan Ginzburg

Observations of magnetic polluted white dwarfs indicate that most of them have higher concentrations of metals near the poles compared to lower latitudes. Maintaining such abundance gradients requires gravitational sinking times $t_\downarrow$ below the convection zone that are shorter than the horizontal spreading time $t_\leftrightarrow$ across the surface by convective eddies. We show analytically that $t_\downarrow/t_\leftrightarrow\propto T^{8/3}$, where $T$ is the temperature at the base o…

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astro-ph.HE

Causal self-consistency of the Blandford--McKee self-similar solution

Gilad Sadeh, Tamar Faran, Doron Kushnir, Eli Waxman

The Blandford--McKee (BM) solution describes the ultra-relativistic self-similar flow behind a strong spherical blast wave propagating into an external density profile $\propto r^{-k}$, where $k<4$ and $r$ is the distance from the center, but it applies only to the hot shell adjacent to the shock, sufficiently deep behind it, the fluid leaves the BM regime. Since the similarity profiles are determined solely by the shock conditions, with no conditions imposed at the inner end, the validity of th…

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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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