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Research Trends

Latest preprints in space engineering and astrophysics.

physics.space-phastro-ph.SR

Adaptive Hybrid Modeling of Collisionless Plasma Shocks and Ion Acceleration

Yuri A. Omelchenko, Igor V. Sokolov, Lulu Zhao, Keheng Zhu

We present a novel efficient technique for hybrid (kinetic ions, quasi-neutral fluid electrons) simulations of non-relativistic magnetized collisionless plasma shocks, frequently observed near the Sun, in the solar system, and beyond. This Adaptive Frame-Of-Reference Algorithm (AFORA) enables multi-dimensional simulations of plasma shocks along with concomitant ion acceleration in the shock frame, where shock evolution remains quasi-steady. Compared to moving shocks, this technique allows us to…

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physics.space-ph

Shrinking the Haystack: One-Class Machine Learning Detection of Magnetosheath Current Sheets in MMS Burst Data

Deep Ghuge, Daniel J. Gershman, Vadim Uritsky, Julia E. Stawarz

We present a morphology-first framework for narrowing the search for magnetic-reconnection candidates in Magnetospheric Multiscale (MMS) burst-mode data. The target is the small, short, and frequently electron-only reconnecting current sheets that occur in turbulent magnetosheath plasma. The pipeline operates in two stages. A local frame-quality gate based on minimum-variance analysis first retains only windows whose current-sheet coordinates are well defined. A one-class Deep Support Vector Dat…

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astro-ph.IMgr-qc

Directional Anisotropic Sensitivity Curves for Pulsar Timing Arrays

Daniel J. Oliver, Jeffrey S. Hazboun, Martine Maggi, Jeremy G. Baier, Kyle E. Gourlie

After two decades of observations, pulsar timing array collaborations have reported strong evidence for a stochastic gravitational wave background, most likely sourced by an inspiraling population of supermassive black hole binaries. Because that population is finite, anisotropy in the background is inevitable, producing hotspots on the sky that track the loudest binaries. Building on the Fisher formalism for anisotropic backgrounds, we recast the directional Fisher information as effective sens…

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astro-ph.GAastro-ph.HEastro-ph.SR

Stellar mergers and chemical element mixing: implications for the metamorphic stellar evolution in AGN disks

Yanlong Shi, Xiaoshan Huang, Douglas N. C. Lin, Norman Murray

Chemical mixing during stellar mergers can significantly influence the subsequent evolution of the merger remnant. We perform a suite of three-dimensional hydrodynamical simulations of stellar mergers, each evolved for $\sim100$ stellar dynamical times until the remnant reaches a quasi-hydrostatic equilibrium. The simulations incorporate subgrid-scale diffusion models to capture the turbulent mixing of chemical elements. Starting with an idealized polytropic equation of state (EOS), we first ide…

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astro-ph.IM

Calibration of MEMS DM actuator gains using a Zernike wavefront sensor on the HiCAT testbed and implications for Habitable Worlds Observatory operations

Sarah Steiger, Raphaël Pourcelot, Rémi Soummer, Emiel H. Por, Laurent Pueyo, Iva Laginja, Nathan Scott

Deformable mirrors (DMs) are a key component of coronagraph instruments performing adaptive optics on the ground, and for future space observatories such as HWO and Roman CGI. Here, they will be used as part of the wavefront sensing and control system to "dig a dark zone'' - remove residual stellar light to create a high-contrast region in the focal plane where faint companions can be detected. To reach the deep contrasts needed to directly image cool or reflected light planets (<1e-8) accurate…

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astro-ph.IM

WST instrument Exposure Time Calculator: full simulation of multi-mode spectrograph performance from source to detector

Matteo Ferro, Matteo Genoni, Henri M. J. Boffin, Jose Schiappacasse-Ulloa, Sofia Randich, Roland Bacon, Vincenzo Mainieri, Alessio Mucciarelli et al.

We present a comprehensive Exposure Time Calculator (ETC) developed for the Wide-field Spectroscopic Telescope (WST) concept. The WST, currently in its conceptual phase, is designed as a next-generation large spectroscopic survey facility featuring three complementary observing modes: an Integral Field Spectrograph (IFS) covering 370-930 nm at R of about 4800; a high-resolution Multi-Object Spectrograph (MOS-HR) with four bands at R of about 40000; and a low-resolution Multi-Object Spectrograph…

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astro-ph.IM

An upgraded frequency-selectable laser source (FLS) calibrator for CMB bandpass characterization

Lauren J. Saunders, Sara M. Simon, Shreya Sutariya, Elisa Russier, Sanah Bhimani, Erin Healy, Jeffrey McMahon

One of the biggest challenges for Cosmic Microwave Background (CMB) experiments comes from the uncertainty in instrument bandpass calibration. Uncertainties in bandpass can limit foreground removal and spectral fitting, which are critical for inflationary and galaxy cluster measurements. CMB experiments currently use Fourier Transform Spectrometers (FTSes) to measure instrument bandpasses. However, FTS systems are currently systematics-limited, so significant improvements in bandpass measurement…

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astro-ph.SRastro-ph.GAastro-ph.HE

On Bimodality in the Eccentricity Distribution of Galactic Double Neutron Stars

Aldana Grichener, Paul Disberg, Ryosuke Hirai, Ilya Mandel

The detection of Galactic double neutron stars (DNSs) through pulsar timing offers a unique opportunity to probe massive stellar and binary evolution. The observed DNS population exhibits an apparently bimodal eccentricity distribution, with an absence of systems at measured intermediate eccentricities, $0.4 \lesssim e_{\rm m} \lesssim 0.58$, whose origin remains unclear. We propose that this possible gap can arise naturally if the relationship between the progenitor masses and neutron star (NS)…

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astro-ph.EPastro-ph.SR

The Dynamics of Planetary Ejection

Malena Rice, William DeRocco, Sean N. Raymond

The ubiquity of free-floating planets inferred from microlensing and direct imaging surveys suggests that planetary ejection---a process in which planets initially born encircling a stellar host become gravitationally unbound---is common. Four overarching mechanisms have been proposed to induce planetary ejection: close approaches of neighboring planets, instabilities in binary or multi-star systems, stellar and planetary flybys, and post-main-sequence stellar evolution. Here we review the mecha…

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astro-ph.COastro-ph.GA

Evidence for a thermal pressure deficit in galaxy groups from the tSZ effect and weak lensing

Jared Siegel, Alexandra Amon, Jenny E. Greene, Ian G. McCarthy, Eliot Quataert, William Coulton

Measurements of the thermal Sunyaev-Zel'dovich (tSZ) effect have yet to form a consistent picture of the thermodynamic state of the gas in the intracluster medium: their interpretation is complicated by foreground contamination and uncertain halo masses. We present new measurements of the tSZ effect around the Dark Energy Spectroscopic Instrument (DESI) Luminous Red Galaxy (LRG) sample, together with galaxy-galaxy lensing (GGL) measurements that enable a like-with-like comparison to state-of-the…

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hep-phastro-ph.COastro-ph.GA

Ubiquitous Corotation of Dark Matter Halos: Implications for Direct Detection

Dylan Folsom, Carlos Blanco, Mariangela Lisanti, Mark Vogelsberger

Cosmological simulations have recently begun to quantify the halo-to-halo variance in the phase-space distribution of dark matter around the Sun. We use a sample of nearly one hundred Milky Way-like galaxies from the TNG50 simulation to determine what aspects of this variance control the predictions for dark matter direct detection. Contrary to the isotropy assumed in the standard halo model, we find the dark matter median azimuthal velocity is nonzero and preferentially corotating, i.e., in the…

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hep-phastro-ph.COastro-ph.HE

Dark Photons from Perturbative Decay of a Misaligned Higgs Field

James M. Cline, Gonzalo Herrera, Jean-Samuel Roux

We reconsider the production of dark photons $A'$ as dark matter, from the perturbative decay of a dark Higgs field $h$, that is stochastically misaligned from the minimum of its potential during inflation. This is a simple and predictive framework for generating the $A'$ relic abundance. It is constrained by structure formation, since the $A'$ are initially boosted, and inflationary isocurvature fluctuations, which require small quartic couplings $λh^4$. We identify $A'$ masses between 100 eV a…

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astro-ph.SRastro-ph.GA

The IACOB project XIX. Revisiting massive-star evolution with empirical TAMS constraints: updated models, overshoot calibration, and the population of blue supergiants

Luca Sciarini, Abel de Burgos, Sophie Rosu, Sylvia Ekström, Sergio Simón-Díaz, Cyril Georgy

Massive stars play a fundamental role in the evolution of the Universe. Yet, several physical processes governing their evolution remain poorly constrained. Notably, the main-sequence width is sensitive to the convective boundary mixing efficiency; it becomes necessary to account for binary interactions to explain some observed properties of massive-star populations. We constrain single-star models using recent observations of massive Galactic stars from the IACOB database. We use the latest pro…

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astro-ph.EPastro-ph.IM

Critical Sizes of Satellite Constellations

Hugh G. Lewis

The precipitous growth of commercial space activity, largely from the development of satellite constellations, threatens to produce a runaway orbital debris population. National regulators are attempting to limit these risks through orbital debris mitigation requirements, but these fail to address the large scale and long lifetimes of satellite constellations. Instead, evaluations are based on the risks from single satellites, and the aggregate risks across constellations are neglected. This sit…

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astro-ph.SR

On the use of field RR Lyrae as Galactic probes:. IX. Radial velocities

K. Baeza-Villagra, V. F. Braga, M. Fabrizio, G. Bono, V. D'Orazi, Z. Prudil, F. Berrilli, G. Böcek Topcu et al.

We present the largest and most homogeneous catalog of radial velocity (RV) measurements for field RR Lyrae (RRL) variables, based on both proprietary and publicly available spectroscopic data. The sample includes 17,563 RRLs pulsating in the fundamental mode (12,353 RRab), in the first overtone (5,011 RRc), and in double-mode (199 RRd). The RV curve (RVC) templates for metallic and Balmer lines were used to derive RV amplitudes and $V_γ$ velocities, defined as the RV of the stellar barycenter w…

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astro-ph.GA

A Massive Galaxy at the Edge of Feedback-Free Efficiency

K. Aditya, Kartick C. Sarkar

The efficiency with which galaxies convert their available baryonic reservoir into stars sets a fundamental ceiling on stellar mass assembly in the early Universe and encodes the cumulative effect of stellar feedback. in this paper, we report the measurement of star-formation efficiency (SFE) of a photometrically and spectroscopically vetted reference sample at $z=9-10$, out of which 31 are spectroscopically confirmed. Among them, we highlight a spectroscopically confirmed galaxy, \texttt{UNCOVE…

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astro-ph.SR

Asteroseismic models of the magnetic binary HD 156424

C. C. Lovekin, S. Davis, V. Khalack

HD 156424 is a hot magnetic star in the Sco OB4 association and has previously been identified as part of a binary system. Spectropolarimetric results show that the companion star is also strongly magnetic, and thus this is a rare example of a doubly magnetic hot binary. In this work, we aim to present a more detailed analysis of Transiting Exoplanet Survey Satellite data including phase variation. We find short-term phase variation consistent with an oblique magnetic rotator, as well as long-te…

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astro-ph.IMastro-ph.EPastro-ph.SR

The Tartu Observatory Fiber-fed Echelle Spectrograph (TOFES) Data Reduction Pipeline

Sandipan P. D. Borthakur, Tõnis Eenmäe, Nikolai Piskunov, Luca Fossati, Mihkel Kama, Thomas Marquart, Anni Kasikov, Heleri Ramler et al.

We introduce the data reduction pipeline for the Tartu Observatory Fiber-fed Echelle Spectrograph (TOFES). TOFES is installed in the Coudé room and will be connected to the 1.5 m Tartu Observatory AZT-12 telescope through a four-channel instrument adapter to be mounted at the Cassegrain focus of the telescope. The spectrograph has an average spectral resolution of 30,000 and covers the 390 to 900 nm wavelength band in a single exposure. The data reduction pipeline, based on the PyReduce package,…

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astro-ph.EP

Warm Sub-Saturns Orbiting Single Stars Are Spin-Orbit Aligned

Xian-Yu Wang, Songhu Wang

In this work, we show that warm sub-Saturns orbiting single stars are predominantly aligned, in contrast to hot sub-Saturns, which are frequently misaligned, with the two populations differing at the 3.2$σ$ level. Because both populations are observed around cool stars, they are free from the ambiguity introduced by the $T_{\rm eff}$-$λ$ dependence. Together with the established alignment of warm Jupiters, this demonstrates, among single-star systems, that spin-orbit misalignment arises specific…

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astro-ph.EPastro-ph.IM

Towards Autodifferentiable Point Spread Function Modelling for the VLT/ERIS Vortex Coronagraph

P. Van de Walle Suarez, G. Orban De Xivry, O. Absil, M. J. Bonse, R. J. De Rosa, V. Christiaens

High-contrast imaging of exoplanets is limited by the presence of quasi-static speckles and existing post-processing methods remain above the theoretical noise limit. We investigate a novel framework that incorporates adaptive optics (AO) wavefront sensor telemetry into post-processing using a differentiable optical model of the ERIS vortex coronagraph. As a first proof of concept, we inject AO telemetry into an ERIS forward model and assess its ability to reproduce the on-sky point spread funct…

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astro-ph.GA

The TOP-SCOPE Survey of Planck Galactic Cold Clumps: Molecular gas properties

Yuebin Yang, Jarken Esimbek, Tie Liu, Willem Baan, Xunchuan Liu, Kee-Tae Kim, Gang Wu, Xindi Tang et al.

We surveyed 2008 Planck Galactic Cold Clumps (PGCCs) in $^{12}\mathrm{CO}$ and $^{13}\mathrm{CO}$ $J=1$--0 lines using the Taeduk Radio Astronomy Observatory (TRAO) 14 m telescope's multi-beam receiver. We detected 2784 ($^{12}\mathrm{CO}$) and 2291 ($^{13}\mathrm{CO}$) velocity components, their closely correlated centroid velocities suggest that $^{12}$CO and $^{13}$CO generally trace kinematically associated gas. PGCCs have low excitation temperatures (mean $\sim$10 K), mean $^{13}\mathrm{CO}…

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astro-ph.GA

ROLLIN': Rotating globular cluster simulations II. The complex morphology of globular clusters driven by multi-scale dynamics

Arn Marklund, Paolo Bianchini, Anna Lisa Varri, Katarina Kraljic, Giulia Pagnini

Globular clusters (GCs) are inherently non-spherical systems that in many cases show internal rotation. Typically, rotation is considered the main driver of GC morphology; however, the relationship between ellipticity and rotational support is not a simple one-to-one mapping, and other multi-scale dynamical processes may contribute. We investigate how morphology evolves in realistic models of rotating GCs, and how it correlates with key physical ingredients, including mass loss, stellar evolutio…

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astro-ph.SR

Spectroscopic Analysis of the 2025 Eclipse of the Symbiotic Binary V1413 Aquilae

David Boyd, James Foster, Forrest Sims, David Cejudo, Robin Leadbeater, Pavol Dubovsky, Xavier Dupont, Keith Shank et al.

We report on a coordinated campaign by amateur astronomers using a combination of high and low resolution spectroscopy to observe the 2025 eclipse of the symbiotic binary V1413 Aql shortly after a probable Z And-type symbiotic outburst. We measured the eclipse time of minimum and computed an updated eclipse ephemeris. Our spectra were calibrated in absolute flux and multi-Gaussian fits were used to resolve and quantify components of the Hα emission line. We measured the radial velocity curve of…

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astro-ph.HE

Gamma-ray emission from particle illumination and shock-cloud interaction in the W51 Complex

Alan Sunny, Martina Cardillo

In the current era of very-high-energy (VHE) and ultra-high-energy (UHE) $γ$-ray astronomy, understanding Galactic PeVatrons and their acceleration mechanisms remains a primary objective. Recent LHAASO observations of the W51 Complex make it an ideal laboratory for investigating the origin of UHE emission, particularly due to the presence of massive and dense molecular environment surrounding multiple potential particle accelerators. In this work, we study two hadronic scenarios for the W51 Comp…

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astro-ph.EPastro-ph.IM

Twin Impact Lunar Telescope network: Lunar Impact Flash observations of the 2025 Geminids

Daniel Sheward, Marco Delbo, Chrysa Avdellidou, Philippe Lognonné, Jeremie Vaubaillon, Pierre-Yves Froissart, Christelle Saliby, Paul Girard et al.

Meteoroid impacts on the Moon, observed from Earth as flashes typically lasting a few tens of milliseconds, have been monitored for three decades for determining meteoroids' size and mass frequency distribution in the cm to dm range. Studies link these observed impact events to fresh craters advancing our understanding of energy partitioning during an impact. Currently we are transitioning to a new era where lunar impact flashes (LIFs) can be used to supplement upcoming lunar seismology to study…

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astro-ph.SRastro-ph.EPastro-ph.IM

The Fe I 4377 Å Line as a Solar Faculae Indicator: Insights from Spectral Ratio Analysis

Katlyn L. Hobbs, Christopher A. Watson, Jean C. Costes, Yvonne Unruh, Dana Clarice Yaptangco, Krishnamurthy Sowmya, Mitchell E. Young, Ernst J. W. de Mooij et al.

Faculae are a dominant source of stellar activity noise in radial velocity measurements, yet their low contrast and broad surface distribution make them difficult to track in disc-integrated observations. We apply Spectral Ratio Analysis (SRA) to HARPS-N Sun-as-a-star observations to isolate and characterize the spectral imprint of facular regions over rotational timescales. The resulting SRA spectra show coherent, line-dependent variability sensitive to surface magnetic activity, with the Fe I…

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astro-ph.HEastro-ph.GA

Rates of tidal disruption events from constrained cosmological simulations of the local Universe: population properties and implications for transient surveys

Julian S. Sommer, Ildar Khabibullin, Klaus Dolag, Luca Sala, Benjamin Seidel, Jenny G. Sorce, Alice Damiano

(abridged) Motivated by upcoming surveys like LSST, we estimate tidal disruption event (TDE) rates using the constrained cosmological Simulation of the LOcal Web (SLOW) to test the limitations of traditional 2D analytical extrapolations within a fully 3D framework. We aim to provide reliable TDE budgets extracted from the simulated zoom-in volumes of the digital counterparts of the Coma, Hercules, Shapley, Virgo, and Perseus supercluster environments, and the Fornax galaxy cluster. From the zoom…

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astro-ph.IM

Charge migration characterization in the METIS H2RG detectors

Danny Gasman, Benoît Serra, Roy van Boekel, Ioannis Argyriou, Daniel Dicken, Vianak Naranjo, Peter Bizenberger

The Mid-infrared ELT Imager and Spectrograph (METIS) is one of the first-light instruments of the Extremely Large Telescope (ELT). For the L and M band, the instrument makes use of Teledyne's H2RG detectors, known to be affected by charge migration, also known as the brighter-fatter effect (BFE). In the H2RG detectors this manifests as photo-electrons moving from a central bright pixel to neighboring pixels as the depletion region of the central pixel shrinks with accumulated charge. Due to its…

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astro-ph.GA

CatBoost versus Spectral Energy Distribution-Fitting: Estimating Galaxy Properties under Controlled Photometric Incompleteness

Vahid Asadi, Hosein Haghi, Akram Hasani Zonoozi

Estimating galaxy physical parameters from photometric data is fundamentally challenged by missing measurements that are endemic to astronomical surveys. Using a mock catalog from the Horizon-AGN hydrodynamical simulation that provides the true physical parameters, we evaluate CatBoost, a gradient-boosting algorithm that natively handles missing data, under a deliberately adversarial scenario: we train it on 12 photometric bands with increasing levels of injected missingness (10%, 20%, 30% missi…

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astro-ph.IMphysics.ins-det

Persistence characteristics of H4RG-15 detectors for ESO instruments

Elizabeth M. George, Domingo Alvarez Mendez, Nagaraja Naidu Bezawada, Derek J. Ives, Mark Neeser, Benoit Serra

As a part of the ESO Instrumentation Program, we already ordered 23 H4RG-15 (2.5 um cut-off) detectors for the instruments MOONS, MICADO, and HARMONI, with more of these detectors planned for future instruments on the ELT as well as possibly other ESO telescopes. As part of our comprehensive detector testing program, we characterize detector persistence at different temperatures between 40 and 85 K, allowing the best-informed choice of operating temperature for the science focal planes. We repor…

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