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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.EPastro-ph.IM

The Role of Extended-Source Geometry and Diurnal Cycles on Exoplanetary Thermal Baselines: Reconciling the Brightness Temperature of 55 Cancri e

Mradumay Sadh

This study augments the geometry-based InstellCa code that calculates accurate irradiance values to InstellCa-2.0, which computes the longitude averaged instellation over a given latitude on the planet along with its thermal profile. The estimation of instellation is performed considering the planet as a 3D body that rotates with respect to the star with a varying zenith angle of the star across the diurnal cycle. We focus on the implications of irradiation geometry on a specific class of ultra-…

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astro-ph.IM

Optimizing Wavefront-Deformation Sensor Placement for Active Radio-Telescope Surfaces

Stefan Thoms, Martin Timpe, Matthias Reichert

Next-generation high-frequency radio telescopes require primary-surface accuracies that passive structures alone cannot reliably achieve. The Atacama Large Aperture Submillimeter Telescope (AtLAST), a 50 m single-dish concept operating up to $\approx$ 1 THz, imposes a $\approx$ 20 $μ$m rms surface-accuracy requirement across its full aperture. This is practically unattainable for a purely passive reflector subject to gravitational, thermal, and wind-induced deformation. Closed-loop active collim…

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nucl-thastro-ph.HEgr-qc

Hadron-quark phase transitions along proto-neutron-star evolution

P. Laskos-Patkos, P. S. Koliogiannis, Ch. C. Moustakidis

The new era of multi-messenger astronomy requires the accurate and self-consistent derivation of the nuclear equation of state at high temperature. In the present work, we focused on the calculation of hot hybrid equations of state, studying the different evolution stages of a proto-neutron star with a quark matter core (proto-hybrid star). For the hadronic matter we used two distinct Skyrme effective interactions, while for quark matter the well-known vector MIT bag model was employed. To model…

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astro-ph.GAastro-ph.HE

Statistical inference of fast radio burst environments using galaxy number density

Vignesh V. V. Rao, Tetsuya Hashimoto, Tomotsugu Goto, Shotaro Yamasaki, Mohanraj Madheshwaran, Sridhar Gajendran, Tomoki Wada, Simon C. -C. Ho et al.

Fast radio bursts (FRBs) are bright, millisecond-duration radio transients of unknown origin. They are categorized as repeaters and non-repeaters, possibly indicating distinct progenitor types. However, validating this distinction is difficult because of the limited number of localized FRBs. Large-scale galactic environments can provide insight into the nature of the host galaxies of FRBs and their progenitors. High-number-density regions are typically associated with old galaxies, whereas low-n…

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gr-qcastro-ph.GA

A Dynamical-Photometric Phase Space for Spiral Galaxies: Probing the Local Coupling Between Light and Gravity

Aritra Sanyal, Farook Rahaman

The interplay between luminous matter distribution and the local gravitational field within disc galaxies encodes physical information beyond that captured by global scaling relations. We introduce a \emph{dynamical--photometric phase space} defined by the kinematic variable $X(R)=V(R)/R$ and the photometric variable $Y(R)=\mathrm{d}\ln I/\mathrm{d}\ln R$, placing the local gravitational scale and the logarithmic surface brightness gradient into direct pointwise correspondence at each galactocen…

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astro-ph.IMastro-ph.CO

Foreground Subtraction with a Tensor-Based Oriented Singular Value Decomposition Method for HI Experiments

Shifan Zuo, Xuelei Chen, Yi Mao

We introduce a native tensor-based framework for foreground mitigation in 21\,cm intensity mapping (IM), utilizing the Oriented Singular Value Decomposition (O-SVD) algorithm. While 21\,cm IM is a powerful probe of the large-scale structure of the Universe, its efficacy is severely limited by astrophysical foregrounds that are orders of magnitude brighter than the cosmological signal. Traditional mitigation strategies often necessitate flattening multidimensional data cubes into two-dimensional…

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astro-ph.COastro-ph.GA

Multi-tracer mass bias in matched cosmic voids from SDSS DR7 and the ELUCID constrained simulation

Youcai Zhang, Xiaohu Yang, Hong Guo, Peng Wang

Cosmic voids provide a unique environment for studying the relationship between galaxies, subhaloes, and dark matter in the underdense Universe. Using the SDSS galaxy catalogue and the ELUCID constrained simulation, we establish an observationally anchored framework for measuring multi-tracer mass bias within matched cosmic voids. A sample of 102 matched void pairs is constructed to directly compare galaxy, subhalo, and dark matter mass distributions within an observationally constrained realisa…

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astro-ph.GA

Unveiling Metal Mixing in a Grand-Design Spiral: A UV-optical multiphase spatially resolved study of M83

Adarsh Ranjan, Bethan L. James, Svea Hernandez, R. Rickards Vaught, Nimisha Kumari, Alessandra Aloisi, Peter Zeidler

We present a spatially resolved, multiphase study of chemical enrichment around young star clusters (YSCs) in the nearby grand-design spiral M83 by combining far-ultraviolet(UV) absorption-line spectroscopy from HST/COS with cospatial optical spectroscopy from VLT/MUSE and LBT/MODS. Our sample includes 18 YSCs spanning spectroscopic ages of ~1-6 Myr and galactocentric radii out to R/R_{25}=0.56. Neutral (H I) abundances were derived from UV absorption-line spectroscopy and compared with ionised…

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astro-ph.HEastro-ph.CO

Locating the missing baryons in the warm-hot intergalactic medium with fast radio bursts and the Sunyaev-Zel'dovich effect

Dao-Hong Zhai, F. Y. Wang, Zi-Gao Dai, Renyue Cen

Traditional astronomical censuses in the late-time Universe can only account for a fraction of the baryonic matter budget. Hydrodynamical simulations predict that the missing baryons reside in the vast filamentary structures of the cosmic web as a highly diffuse, warm-hot intergalactic medium (WHIM). Observing the WHIM directly has remained a long-standing challenge due to its typical temperature. In this study, we report the first detection of spatial cross-correlations between the dispersion m…

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astro-ph.GA

An Identifiability Audit of One-Parameter Structural Corrections to the Radial Acceleration Relation in SPARC

Lukas A. Sosna

We ask whether any one-parameter structural correction to the radial acceleration relation (RAR) can be uniquely recovered from SPARC rotation curves, and answer with an identifiability audit: each candidate is benchmarked against per-galaxy nuisance freedom, with predictive scoring against mass-only and data-quality baselines. In the full sample (N = 126) the answer is no: a hybrid compactness term improves the fit, but zero-point freedom absorbs the gain, and in cross-validation the model fail…

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eess.SYastro-ph.IMmath.OC

Horizon-Dependent Tube MPC for Spacecraft Rendezvous on Elliptical Orbits with Conditional Robust Constraint Satisfaction

Omer Burak Iskender

Spacecraft rendezvous on elliptical orbits must hold a safety corridor under navigation noise, unmodelled perturbations, and thrust errors driven by propellant mass uncertainty. This paper develops a tube-based model predictive controller for the Yamanaka-Ankersen linear time-varying dynamics, carrying constraint-tightening tube methods from circular to elliptical orbits. A horizon-dependent, element-wise error bound propagates the actual closed-loop matrices along the prediction window, so earl…

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astro-ph.EP

Atmospheric Diversity of Giant Planet Analogs from 3-5um with SPHEREx

Rocio Kiman, Brendan P. Bowler, Jerry W. Xuan, Narisara Mayer, Claire Finley

The emergent spectra of giant planets peak at thermal infrared wavelengths (3-5um) and possess atmospheric features in this regime that trace carbon chemistry, vertical mixing, clouds, and composition. However, this spectral region is challenging to access from the ground, and with JWST generally requires an independent pointing for each target. SPHEREx is providing all-sky spectra of millions of sources from 0.75-5um, enabling both individual and population-level studies of isolated and widely…

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astro-ph.SRastro-ph.EP

Gas Flows and Mass Accretion Rates in Eight Dippers: HD 142666, HD 143006, HD 145718, V935 Sco, DoAr 25, EPIC 204638512, EPIC 205151387, and EPIC 203850058

Michael L. Sitko, Ray W. Russell, Korash D. Assani, Lucia Villanueva, Jesus Hernandez

One of the scenarios used to explain the dipper phenomenon in stars is having the innermost disk regions being close to the line of sight to the star - inclined greater than 60 degrees - regardless of the inclination of the outermost disk ("mis-aligned" or "broken" disks). If the dust and gas in these disks sample the same material, edge-on disks will be viewed through larger column densities of gas and dust than the average disk. We have examined inter-night variability of eight Kepler-discover…

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cs.CReess.SPphysics.space-ph

Treating Statewide CORS Networks as Spatially Distributed Sensors for GNSS Integrity Monitoring under Unintentional and Deliberate Threats

Minhaj Uddin Ahmad, Sagar Dasgupta, Muhammad Sami Irfan, Mizanur Rahman, Mashrur Chowdhury, Thejesh Bandi

State departments of transportation (DOTs) in the United States increasingly rely on statewide continuously operating reference station (CORS) networks to support high-precision Global Navigation Satellite System (GNSS)-based positioning and timing for intelligent transportation systems. These networks also provide continuous observations that can support regional GNSS integrity monitoring. This study develops and demonstrates a framework that treats a statewide CORS network as a spatially distr…

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astro-ph.SR

Synthetic Fe XIII 1074.7 nm Observations of Torsional Alfvén Waves in Coronal Waveguides

Samuel Skirvin, Richard Morton, Thomas Schad

Torsional Alfvén waves are a promising mechanism for transporting energy through the solar atmosphere, with implications for coronal heating and solar wind acceleration. Recently, signatures of torsional Alfvén waves have been observed with the Daniel K. Inouye Solar Telescope. We aim to investigate the effects of line of sight integration and plasma conditions on the observable properties of the torsional mode. Here we present three-dimensional magnetohydrodynamic simulations of multiple corona…

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astro-ph.IM

A Hybrid R-Theta Fiber Positioning Robot Using a Piezoelectric Bender for Radial Motion

Michael Schubnell, Tim Fanning, Andrew Hope, Joseph Silber, Greg Tarlé, Nicholas Wenner

Future massively multiplexed spectroscopic surveys require focal planes with increasingly dense arrays of robotic fiber positioners. The DESI (Dark Energy Spectroscopic Instrument) fiber positioners, based on a two-axis Theta-Phi motorized architecture, have demonstrated excellent reliability and performance during operations and provide the benchmark for evaluating new concepts. However, proposed next-generation instruments such as Spec-S5 require a substantially smaller positioner pitch than D…

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astro-ph.HE

Timing and statistical analysis of single-pulse search pulsar discoveries from the PALFA survey

Graham M. Doskoch, Maura A. McLaughlin, B. Allen, A. Brazier, F. Camilo, F. Cardoso, S. Chatterjee, J. M. Cordes et al.

Almost two decades after their discovery, pulsars discoverable only through their single, dispersed radio pulses, known as rotating radio transients (RRATS), remain a poorly-understood class of objects. Compared to the overall pulsar population, few have timing solutions, limiting our ability to understand the mechanisms underlying their sporadic emission. Here, we present a single-pulse analysis of twelve sources from the PALFA survey, consisting of eleven objects initially identified as RRATs…

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astro-ph.HE

Simulation-based inference for AGN jet population modelling: Towards more robust comparisons of black hole jet speeds

Clara Lilje, James H. Matthews, Rob Fender

We present the most complete modelling of the MOJAVE 1.5 Jansky Quarter Century active galactic nuclei (AGN) jet population, using likelihood-free simulation-based inference. Due to the complex impact of a flux-limit on observed AGN data sets, careful modelling of the parent population is required. In particular, when observing and fitting to multiple data distributions likelihoods become non-intuitive. Parameter degeneracies further complicate the problem and make it suitable for likelihood-fre…

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astro-ph.IM

The James Webb Space Telescope Absolute Flux Calibration. VI. Near-Infrared Camera Imaging and Coronagraphy

Martha L. Boyer, Benjamin Sunnquist, Bryan Hilbert, Dan Coe, Varun Bajaj, Paul Bennet, Julien Girard

We present an updated flux calibration for all imaging modes of the Near-Infrared Camera on JWST that converts instrumental units to physical surface brightness units of MJy sr^-1. This calibration includes observations of 19 flux standard stars spanning 3.5 years, with a mix of A dwarfs, solar analogs, and hot stars. All 5 coronagraphic setups, all 29 filters, and both weak lenses are calibrated. This is the first on-sky calibration for the weak lenses used in Time Series observations and for s…

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astro-ph.IMastro-ph.CO

QUIJOTE scientific results - XX. Commissioning and First Results from the Thirty and Forty Gigahertz Instrument (TFGI)

M. Fernández-Torreiro, J. A. Rubiño-Martín, R. T. Génova-Santos, G. Pascual-Cisneros, A. Fasano, F. J. Casas, R. J. Hoyland, M. W. Peel et al.

We present the commissioning and first results of the Thirty and Forty Gigahertz Instrument (TFGI), which observes the sky at 31 and 41 GHz with angular resolutions of 21' and 18' from the second QUIJOTE telescope at the Teide Observatory. Its primary goal is to conduct a deep cosmological survey in selected regions of the Northern sky with high-sensitivity polarization measurements. The commissioning phase covered Nov2021-Oct2022, during which the instrument operated with a configuration of 7 r…

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astro-ph.SR

Sun-to-Earth Coronal Mass Ejection Simulations From a Vector Magnetogram

Yifu An, Gábor Tóth, Beatrice Popescu Braileanu

We implement a novel approach to performing Sun-to-Earth coronal mass ejection (CME) simulations and test it on three geo-effective space weather events. Using a vector magnetogram observed prior to the CME as the boundary condition, we reconstruct non-linear force free field (NLFFF) solutions in solar active regions with an established magneto-frictional method. We find a pre-eruption solar corona containing the NLFFF in the AWSoM model, which then spontaneously erupts. We apply STITCH, a photo…

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astro-ph.GAastro-ph.IMastro-ph.SR

Exploration of UV-bright sources in Globular cluster NGC 3201 using UVIT observations

Manasi Kulkarni, Sonika Piridi, Ranjan Kumar, Ananta C. Pradhan

We present a comprehensive study of the ultraviolet (UV)-bright stellar population in the globular cluster NGC 3201 using the Ultraviolet Imaging Telescope (UVIT) onboard AstroSat. By combining far-UV photometry of the UVIT F148W and F169M filters with Gaia and ground-based telescope optical data, we construct UV$-$optical color-magnitude diagrams (CMDs) to identify UV-bright stellar evolutionary phases. Physical parameters of all detected sources are derived by fitting stellar atmosphere models…

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astro-ph.SR

Coronal Rain Driven by Low-Frequency Impulsive Heating: Dependence of Dynamics and Morphology on Coronal Heating and Magnetic Field

Takero Yoshihisa, Takaaki Yokoyama

We performed numerical simulations to investigate how coronal heating and magnetic field strength regulate the dynamics and morphology of coronal rain in the solar corona. Coronal rain is widely interpreted as a manifestation of thermal non-equilibrium and thermal instability. Many previous studies have investigated condensation under (quasi-)steady heating scenarios, but such heating models do not fully explain the observed properties, including multiple clumps and symmetric drainage toward bot…

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astro-ph.HE

Slow Cosmic-Ray Diffusion in Supersonic and Super-Alfvénic Turbulence

Yue Hu

Extended TeV-PeV gamma-ray halo observations imply cosmic-ray (CR) diffusion that is both substantially slower than the Galactic mean and only weakly anisotropic, despite the presence of a large-scale Galactic magnetic field. We investigate whether such transport can arise in partially ionized source environments, where ion-neutral damping removes the small-scale fluctuations responsible for gyroresonant scattering. Using two-fluid magnetohydrodynamic turbulence simulations with relativistic tes…

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astro-ph.HEphysics.plasm-ph

Plasmoid-Mediated 2D Magnetic Reconnection in Partially Ionized Plasmas

Yue Hu, Siyao Xu, Grzegorz Kowal, James M. Stone, Alex Lazarian, Hui Li

Magnetic reconnection in partially ionized plasmas is an important channel for energy release. While the plasmoid instability is well characterized in 2D fully ionized plasmas, its behavior in the presence of neutral-dominated plasma remains poorly understood in the nonlinear, high-Lundquist-number ($S = 10^5$) regime. We present high-resolution ($16384 \times 4096$ cells) two-dimensional two-fluid (ion $+$ neutral) simulations of Harris-sheet reconnection with upstream plasma beta $β= 2$, compa…

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astro-ph.SRastro-ph.IMphysics.comp-ph

FORTVSH: A Fortran Module For Vector Spherical Harmonics Computations

Justin G. Elfritz

The vector spherical harmonics (VSH) are crucial ingredients for representation of arbitrary vector fields in curvilinear coordinate systems throughout mathematical physics. Performant, efficient computations of the VSH are essential to high-performance computing applications that utilize spectral analysis, including magnetohydrodynamics (MHD) simulations for geophysics and astrophysics. The open-source FORTVSH package provides a catalog of numerical routines for evaluating various VSH forms and…

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astro-ph.HE

Three-Dimensional Expansion of Iron Ejecta in Cassiopeia A with Chandra and XRISM

Aya Bamba, Tomoki Kadoya, Kouichi Hagino, Jacco Vink, Manan Agarwal, Masahiro Ichihashi, Paul Plucinsky

Measurement of the expansion structure of ejecta in supernova remnants (SNRs) provides important information about their explosion mechanism. We combine Chandra proper-motion measurements with XRISM Doppler measurements to derive an approximate, region-averaged three-dimensional velocity map of the Fe-K-emitting ejecta in Cassiopeia A (Cas A), one of the youngest Galactic core-collapse SNRs. Proper motions were measured using the optical flow method. We find that the Fe-K-emitting ejecta expand…

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astro-ph.GAastro-ph.IM

A Catalog of Giant Radio Source Candidates from TGSS ADR1 Using a Deep Learning--based Pipeline

Baoqiang Lao, Binghua Liang, Shaoguang Guo, Junxiu Liu, Xiaolong Yang, Rushuang Zhao, Yang Kun

We present a catalog of 5,595 giant radio source (GRS) candidates, defined by a largest (projected) linear size (LLS) exceeding 0.7 Mpc. Of these, 4,566 would be new discoveries if confirmed. These candidates were identified through a systematic and automated search of the first Alternative Data Release of the TIFR GMRT Sky Survey (TGSS ADR1) using a deep learning--based pipeline that incorporates a radio sources detection model and the likelihood ratio method. Across the full sample, the LLS re…

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cs.AIastro-ph.IM

Estimating Uncertainty in Galaxy Morphology Classification

Kai Cheng, Ruoqi Wang, Qiong Luo

Astronomers classify galaxy morphology to investigate cosmic evolution. While deep foundation models are increasingly utilized in Galaxy Morphology Classification (GMC), little work has been done on evaluating the uncertainty of GMC results. Uncertainty evaluation is important because astronomical data are inherently noisy due to instrumental and environmental limitations. Also, the continuous evolution of galaxies creates intrinsic morphological ambiguity. However, current foundation models ope…

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astro-ph.GA

Constructing a Hydrogen Line Library for Lyα Emitters at Low Redshifts (z < 0.4): Estimating Dust Extinction and Assessing Paschen line Detectability with SPHEREx

Junho Song, Hyunmi Song, Hyunjin Shim

Hydrogen recombination lines, one of the strongest emission lines from star-forming galaxies, are used to probe the early Universe as indicators of star formation rates and ionizing photon production rates. Ratios between different recombination lines provide clues to estimate dust attenuation, in addition to the H II region physical diagnostics. To prepare for future near-infrared spectral surveys and optical narrow-band imaging surveys aiming for hydrogen lines in different redshifts, we const…

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