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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.GAastro-ph.CO

Cool Embeddings: Predicting Galaxy Cluster Cooling Times in IllustrisTNG and TNG-Cluster with AstroCLIP

Rawan Karam, Carter Lee Rhea, Julie Hlavacek-Larrondo, Laurence Perreault-Levasseur, Marine Prunier, Adam Alexandre, Hyunseop Choi

Foundation models trained on optical astronomical data have not previously been applied to X-ray cluster thermodynamics. We show that embeddings from AstroCLIP, a contrastive vision-language model trained on optical galaxy images and spectra, retain physically meaningful structure when applied to mock Chandra X-ray images of simulated galaxy clusters - a significant shift in observational modality and physical scale. We target the central cooling time ($t_{\mathrm{cool},0}$) of the intracluster…

astro-ph.EPastro-ph.IM

Application and Evaluation of the Material Point Method for Low-Velocity Asteroid Collisions Involving Large Deformations

Haru Fukuta, Tomoaki Ishiyama, Shu-ichiro Inutsuka

The collisional lifetimes of asteroids larger than $\sim 10$ km in the present-day main belt are estimated to exceed the age of the solar system, suggesting that their shapes may preserve memories of the collisional environment in the primordial solar system. Recent studies performed systematic simulations of equal-mass and low-velocity ($50$--$400\,\mathrm{ms}^{-1}$) collisions between 50-km-radius asteroids using Smoothed Particle Hydrodynamics (SPH), identifying the impact conditions that pro…

astro-ph.COastro-ph.HE

AGN hosting jets. II: Deriving fundamental information from semi-analytical models and the LoTSS sample

Pau Beltrán-Palau, Manel Perucho, José-María Martí, Xavier López-López

Galactic activity has been shown to play a fundamental role in galaxy and cluster evolution throughout the history of the Universe. In the last decades, a number of works have tackled the determination of radio luminosity functions and their evolution, with the aim to understand and quantify this role. In this work we propose a different approach, based on the application of a semi-analytical model to produce mock populations of radio loud active galaxies throughout several orders of magnitude i…

astro-ph.SR

Multiple regular frequency spacings in $δ$ Scuti stars from automated analysis of TESS oscillation spectra

Shravan M. Hanasoge, Shashwat Chamoli, Subrata Kumar Panda, Daniel R. Reese

The oscillation spectra of rapidly rotating $δ$ Scuti stars are difficult to interpret because rotation modifies both the frequencies and spatial structure of the modes. Although theoretical studies predict that acoustic modes should organize into approximately equally spaced frequency sequences, systematic searches for such patterns have been limited by the absence of scalable, statistically robust detection methods. We present an automated statistical framework for identifying approximately eq…

astro-ph.IMcs.DC

GPUPHOT: A Python Framework for High-Performance GPU-Accelerated Photometry and Distributed Astronomical Data Reduction

Samuel Lemes-Perera, Miguel R. Alarcon, Miquel Serra-Ricart, Pino Caballero-Gil

We present GPUPHOT, an open-source Python framework for GPU-accelerated real-time photometry and astrometry of astronomical CCD and scientific CMOS images. Four of its seven stages run entirely on the GPU through CuPy (background estimation, source detection, PSF modeling and aperture photometry); the catalog crossmatch selects a CPU or GPU backend by problem size, and the zero-point and astrometric calibrations run on the CPU, within a containerized distributed system. Checkpoint-based GPU memo…

astro-ph.HE

15-Year X-ray Study Links Variable Mass Accretion to Changing Look Behavior in AGN NGC 7582

Santanu Mondal, V. Jithesh, Neeraj Kumari, Tek P. Adhikari

Changing Look Active Galactic Nuclei (CLAGN) are a subclass of AGN that exhibit spectral state transitions in both optical/UV and X-ray bands on timescales of days to years. In this work, we studied fifteen years of X-ray data of the CLAGN NGC 7582 taken from {\it Suzaku}, {\it XMM-Newton}, and {\it NuSTAR} to understand the origin of the CL behavior. Our study reveals that the obscuration (Hydrogen column density, $N_H$) along the line of sight is associated with the failed wind scenario. The v…

astro-ph.HEastro-ph.GA

Constraints on Supermassive Black Hole Binaries from the Lack of Resolvable Sources in the NANOGrav 15-yr Dataset

Emiko C. Gardiner, Kayhan Gültekin, Philippe Turgeon, Bence Bécsy, Laura Blecha, Nikita Agarwal, Gabriella Agazie, Akash Anumarlapudi et al.

Pulsar timing arrays (PTAs) have found evidence of a gravitational wave background (GWB) consistent with a population of supermassive black hole binaries (SMBHBs), but have not yet resolved a continuous wave (CW) from an individual binary. We present the first SMBHB population constraints incorporating PTA upper limits on CWs, based on the NANOGrav 15-year (NG15) data. Using semi-analytic models to generate simulated populations, we calculate each sample's GWB likelihood by free spectral compari…

astro-ph.GAastro-ph.CO

The Physical Origins of Scatter in the Dust Attenuation Scaling Relation of Star-Forming Galaxies: Star--Dust Geometry

Zongfei Lyu, Xian Zhong Zheng, Zhizheng Pan, Antonios Katsianis, Stijn Wuyts, Haiguang Xu, Pedro Cataldi, Wenhao Liu et al.

Characterising the physical drivers of dust attenuation in star-forming galaxies (SFGs) is essential for interpreting their spectral energy distributions and star formation histories. The infrared excess (IRX$\equiv$$L_{\rm IR}/L_{\rm UV}$) follows a universal scaling relation with metallicity, star formation rate, galaxy size, and inclination. However, the origin of the scatter around this relation remains poorly understood. We revisit this relation using $\sim$32,000 local SFGs from SDSS, GALE…

astro-ph.SR

Successfully Reproducing Solar Orbiter Polar Field Observations with a Surface Flux Transport Model

Ruihui Wang, Jie Jiang, Yukun Luo, D. Calchetti, S. K. Solanki

The solar polar field plays a fundamental role in predicting solar-cycle strength and determines the large-scale structure of the heliospheric magnetic field. The High Resolution Telescope of the Polarimetric and Helioseismic Imager aboard Solar Orbiter (SO/PHI-HRT) provides unprecedented observations of the solar polar regions, as Solar Orbiter currently reaches heliographic latitudes of up to $\pm17^\circ$, about $10^\circ$ higher than those accessible from near-ecliptic observations. Using th…

astro-ph.HEgr-qc

Spin wandering of an accreting neutron star near torque balance: implications for gravitational wave searches

Andrew Melatos

Torque balance between gravitational radiation reaction and magnetocentrifugal accretion is one reason why accreting neutron stars rotate slower than centrifugal break-up. Random processes in the accretion disk, such as Rayleigh-Taylor instabilities and flicker noise, drive the spin frequency $f_\ast$ and gravitational wave frequency $f_{\rm gw}\propto f_\ast$ to wander stochastically around their torque balance values. Here it is shown theoretically, in terms of an idealized Ornstein-Uhlenbeck…

astro-ph.GA

H-alpha Star Formation Rates of the SHIELD Dwarf Galaxies

Madeline Shepley, David G. Gormanous, John J. Salzer, Nathalie Haurberg, Steven Janowiecki, John M. Cannon, Elizabeth A. K. Adams, Martha P. Haynes et al.

The Survey of HI in Extremely Low-mass Dwarfs (SHIELD) galaxy sample is an HI-selected catalog of galaxies that occupy the extreme low-mass end of the HI mass function. Our team is carrying out a comprehensive multi-wavelength observational program targeting these gas-rich, star-forming dwarf galaxies. The current paper presents H-alpha narrowband observations of the full SHIELD sample. We detect 55 of the 82 galaxies (67%) with nebular H-alpha emission, and infer sensitive upper limits to the H…

astro-ph.SR

Self-constrained Magnetic Reconnection of a Solar Flare Co-spatial with a Non-ejected Filament

Ye Qiu, Changxue Chen, Anqin Chen, Chuan Li, Yang Guo, Linggao Kong, Feng Lu, Xiaohu Zhang et al.

For flares associated with eruptive filaments, the filament normally rises above the post-flare loops. Here, we report an unusual event in which the post-flare loops instead overlie a filament that remains non-ejected throughout the flare. This event was simultaneously captured by the Chinese H$α$ Solar Explorer (CHASE), the Solar Extreme-UltraViolet Imager (SUVI) onboard Fengyun-4C, the Hard X-ray Imager (HXI) onboard the Advanced Space-based Solar Observatory (ASO-S) and the Solar Dynamics Obs…

astro-ph.GA

Tracing Winds through the Fog: A Comprehensive Survey of LMC's Galactic Outflows with ULLYSES

Suraj Poudel, April Horton, Kathleen A. Barger, Frances H. Cashman, Jo Vazquez, Andrew J. Fox, Nicolas Lehner, J. Christopher Howk et al.

We investigate nearside stellar-driven outflows from the Large Magellanic Cloud (LMC) using UV absorption-line spectroscopy of 170 OB stars, complemented by HI 21-cm emission and H$_α$ emission. Using Voigt-profile fitting and AOD analysis of SiII, OI, and SII transitions, we map the velocity-dependent structure of foreground gas. The SiII column densities for the Voigt-fitted components decline smoothly from the LMC disk and reach a minimum at $v_{\rm LMCSR} \approx -100$ to $-200~{km~s^{-1}}$,…

astro-ph.HEgr-qc

Polarization Signatures of Sgr A* with Tilted Hybrid Magnetic Fields

Yushu Feng, Hao Yin, Songbai Chen, Jiliang Jing

The magnetic field geometry in the near-horizon region is very important in shaping polarimetric signatures of black hole images. With a hybrid magnetic field consisting of an axisymmetric split-monopole field and a tilted uniform external field, we investigate the effects of external magnetic field inclination on the polarimetric signatures of Sgr A* by employing a stationary semi-analytical radiatively inefficient accretion flow (RIAF) model and general relativistic polarized radiative transfe…

physics.ins-detastro-ph.IM

Enhancing Conversion Gain in HEB Mixers using Negative Differential Resistance

Boris S. Karasik, Changyun Yoo

This work investigates how negative differential resistance (NDR) can be utilized to enhance conversion gain in superconducting niobium nitride (NbN) hot-electron bolometer (HEB) mixers. Conventional HEB operation avoids NDR regions due to parasitic oscillations caused by interactions between thermal inertia and bias-line reactance. Recent experimental results show that reducing the bias-T inductance suppresses these oscillations and enables stable biasing within the NDR regime, thereby increasi…

astro-ph.EP

COSINE (Cometary Object Study Investigating their Nature and Evolution) II: Colors and Sizes of Comet Nuclei

Yuna G. Kwon, Dar W. Dahlen, Joseph R. Masiero, Yanga R. Fernández, Adeline Gicquel, James M. Bauer, Yoonyoung Kim, Frank Masci et al.

Comet nuclei preserve a record of planetesimal formation, but their sizes are difficult to measure because the nucleus is usually blended with its coma. We present a catalog of nucleus sizes for 523 comets (235 long-period and 288 short-period comets; LPCs and SPCs) from the 14.5-year WISE/NEOWISE archive, supplemented by Spitzer photometry. A coma-nucleus decomposition of the radial profiles yields conservative upper limits for all 523 comets and diameters with uncertainties for 301 (107 LPCs a…

astro-ph.EPastro-ph.SR

The NEID Earth Twin Survey. VI. Discovery of a Low-Mass Planet Orbiting HD 126053 and RV Signals Near the Rotation Periods of HD 168009 and HD 10780

Arvind F. Gupta, Sarah E. Logsdon, Jacob K. Luhn, Evan Fitzmaurice, Suvrath Mahadevan, Paul Robertson, Eric B. Ford, Chad F. Bender et al.

Extreme precision radial velocity (EPRV) spectrographs are making strides in extending the limits of radial velocity exoplanet detection. Perhaps the best evidence for this is how readily EPRV instruments are facilitating the discovery and detailed characterization of small-amplitude planetary signals around stars that have already been intensively monitored for decades with less stable instruments. In this paper, we use data from the ongoing NEID Earth Twin Survey (NETS) to detect and confirm t…

astro-ph.GA

The AURORA Survey: Determining the Production Mechanism for OI $\mathbf{λ8449}$ Emission in Star-forming Galaxies at Cosmic Noon

Leonardo Clarke, Alice E. Shapley, Zhiwei Shao, Massimo Pascale, Ryan L. Sanders, Naveen A. Reddy, Tucker Jones, Harley Katz et al.

We analyze deep JWST/NIRSpec observations of 58 star-forming galaxies at $1.3< z <4.8$ in the AURORA survey to investigate the origin of the permitted OI $λ8449$ emission feature. Based on the detection of OI $λ8449$ in a stack of objects with non-detections, we infer that this feature is ubiquitous among star-forming galaxies at $\sim$0.5% the strength of H$α$. We additionally compare our results with measurements of this line in local HII regions from the CHAOS survey and star-forming galaxies…

astro-ph.EP

Investigating potential causes for high inferred intrinsic temperatures of warm transiting Neptune and Sub-Neptune planets

Saugata Barat, Jean-Michel Désert, Allona Vazan, Ritika Sethi, Sagnick Mukherjee, Sarah Millholland, Jonathan J. Fortney, William Misener et al.

Atmospheric characterization of a warm 10-30 Myr old sub-Neptune progenitor (V1298 Tau b) and a $\sim$3.4 Gyr old warm super-Neptune (WASP-107b) using JWST have revealed extremely low methane abundance. Atmospheric forward models find higher than expected inferred intrinsic temperatures (450~K and 500~K) --- inconsistent with theoretical planet formation and core-envelope evolution predictions (70K and 150K respectively) assuming a convective interior. We explore three hypotheses to reconcile th…

astro-ph.COastro-ph.IM

CMB Data Analysis in the example of the POLARBEAR experiment and the LiteBIRD experiment

Kolen Cheung

In this dissertation, I briefly go through my subject areas -- from Astrophysics, Cosmology, to Cosmic Microwave Background (CMB) radiation; and Data Science & High-Performance Computing. I go through the beginning of the Universe briefly in Part I and introduce the Physics of the CMB in Part II. Then I move on to how it can be observed experimentally, mathematically, and computationally in Part III. In Parts IV, V and VI, I write about 2 specific CMB experiments -- POLARBEAR & LiteBIRD, togethe…

astro-ph.IM

An Analytic Error-Budget Model for the Habitable Worlds Observatory Coronagraph: From Optical Disturbances to Flux-Ratio Noise

Slava G. Turyshev

A coronagraph stability allocation must protect a planet measurement, not merely satisfy a contrast target. Residual starlight both generates photon noise and interferes with small field perturbations, coupling optical stability to detection reliability. We develop a modular analytic model for the Habitable Worlds Observatory (HWO), using a reduced two-roll angular-differential-imaging realization of its OS-1 scenario. Complex-field sensitivities, wavefront sensing/control, finite observing wind…

astro-ph.IMastro-ph.HE

A Delayed Rejection Reversible Jump Markov Chain Monte Carlo Method for Multi-Resolution Maps of the Stochastic Gravitational Wave Background with Pulsar Timing Array Data

Taha T. Moursy, Nihan S. Pol

Pulsar timing array anisotropy analyses often use a naive counting argument to set resolutions of inferred maps of the stochastic gravitational wave background (GWB). We present a data-driven method in the form of a delayed rejection reversible jump sampler tailored to multi-resolution pixel decompositions of the angular power density of the GWB. We also consider a rapid, frequentist alternative based on information criteria statistics. We verify our methods with a series of injection-and-recove…

astro-ph.EP

The First Hubble Detection of a Secondary Eclipse from a Rocky Exoplanet: the 5.4-hour planet TOI-2431 b

Sebastian Zieba, Billy Edwards, Samuel N. Quinn, Leoni J. Janssen, Nicolas B. Cowan, Laura Kreidberg, Mercedes Lopez-Morales, Lisa Dang et al.

We present an HST/WFC3 G141 phase-curve observation of the ultra-short-period rocky planet TOI-2431 b and detect its secondary eclipse in the near infrared. Combined with the TESS optical eclipse, these measurements constrain the planet's dayside brightness temperature, reflected light contribution, albedo, and heat redistribution. We detect the eclipse in the optical and near infrared wavelengths of TESS and HST/WFC3 G141, with a planet-to-star flux ratio of 37+/-10 ppm and 69(+14/-13) ppm, res…

astro-ph.COastro-ph.GA

SLICE: Unveiling the Multi-Component Merging Core of SPT-CLJ1150-2805 Through Strong-Lensing Mass Modelling

James R. Betts, Benjamin Beauchesne, Mathilde Jauzac, David Lagattuta, Guillaume Mahler, Jean-Paul Kneib, Gavin Leroy, Marceau Limousin et al.

We present a new strong-lensing and X-ray mass model of the merging galaxy cluster SPT-CLJ1150-2805 ($z=0.383$), combining JWST NIRCam, HST, Chandra, and VLT/MUSE data to robustly decompose its collisionless and collisional components. Exploiting JWST, we expand the multiple-image catalogue with 66 new images (30 comprising 6 new systems). Our baseline model uses 118 spectroscopically confirmed images from 20 systems, achieving an image-plane root-mean-square offset of $0.56''$. An expanded mode…

astro-ph.SRphysics.flu-dynphysics.plasm-ph

Transport of Magnetic Fields by Thermohaline Convection in Crystallizing White Dwarfs

Nicolas Frazao Fernandes, J. R. Fuentes, Jim Fuller

The origins of strong magnetic fields observed in many white dwarfs are uncertain. Recent observations show that such fields are more common for white dwarfs with crystallized cores. Crystallization creates a destabilizing composition gradient that drives thermohaline convection in the star's fluid envelope, which may play an important role in magnetic field emergence. We perform 3D magnetohydrodynamical simulations of thermohaline convection with magnetic fields of various strengths and orienta…

astro-ph.GA

Dynamical Evolution of The Open Clusters Collinder 110 and NGC 2477

Zahra Al, Yüksel Karataş, Forough Rajaei

Using Gaia DR3 photometric and astrometric data, we identified the likely members of the open clusters Collinder 110 and NGC 2477, and derived their astrophysical and dynamical parameters. We obtained reddening values of $E(B-V) = 0.43 \pm 0.05$ and $0.33 \pm 0.04$, and ages of $1.82 \pm 0.10$ Gyr and $1.05 \pm 0.10$ Gyr for Collinder 110 and NGC 2477, respectively. Within the uncertainties, the distances derived from the color-magnitude diagrams ($2.09 \pm 0.06$ and $1.38 \pm 0.04$ kpc) are con…

astro-ph.EP

JWST Reveals the Kuiper Belt-like Compositions of the Uranian Rings and Small Moons

Matthew Belyakov, M. Ryleigh Davis, Zachariah Milby, Ian Wong, Michael E. Brown

We present the JWST NIRSpec 1--5 micron spectra of the Uranian rings and four ringmoons: Puck, Perdita, Portia, and Juliet. We find that the compositions of the rings and moons strongly resemble water-type Kuiper belt objects, showing deep 3.0 micron O--H and water ice features as well as the CO$_2$ band at 4.27 micron. The volatiles show a radial trend of decreasing volatile abundance at closer radial distance to the planet, consistent with recent estimates of the densities of the innermost moo…

astro-ph.SR

Spectroscopic Signatures of Nonuniform Lateral Expansion of a Coronal Mass Ejection in the Low Corona with ADITYA-L1/VELC

Saurabh Tripathi, Tanmoy Samanta, Jayant Joshi

Coronal mass ejections (CMEs) undergo rapid evolution in the low corona ($<2R_\odot$), yet their three-dimensional kinematics remain poorly constrained. We present a spectroscopic and imaging analysis of a CME observed on 2024 August 5 using the Visible Emission Line Coronagraph (VELC) on board ADITYA-L1 and Atmospheric Imaging Assembly (AIA)/Solar Dynamics Observator (SDO). The VELC Fe XIV 5303 Å spectra captured the erupting CME as it crossed the western slit. Space-time maps from single-Gauss…

astro-ph.SRastro-ph.EPphysics.plasm-phphysics.space-ph

Negative and Positive Cascade Rates of Slow Alfvénic Turbulence in Switchback and Non-switchback Intervals: \emph{Wind} Observations

Sofiane Bourouaine

We estimate the turbulent cascade rate in imbalanced Alfvénic turbulence in the slow solar wind using a Politano--Pouquet-based approach that does not require an isotropic assumption. We analyze selected 8-hour intervals provided by \emph{Wind} spacecraft. These intervals are characterized by near-homogeneity, weak velocity shear, and imbalanced Alfvénic fluctuations, and are classified as switchback or non-switchback depending on the angular spread of the magnetic field relative to the mean fie…

astro-ph.HEgr-qc

Not all spins of black-hole binaries formed in clusters are isotropic and not all spins of black-hole binaries formed in isolation are aligned

Sofia Dossena, Davide Gerosa, Tristan Bruel

Spin directions are promising observables for distinguishing between the formation channels of merging stellar-mass binary black holes with gravitational-wave observations. In this work, we challenge the standard expectation that binaries formed via dynamical interactions in stellar clusters have isotropically distributed spins and that binaries formed in isolation have spins aligned with the orbital angular momentum. For dynamically formed binaries, we account for observational findings suggest…