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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.EP

The Non-Principal-Axis Rotation and Convex Shape Model of Earth Quasi-Satellite and the Target of China's Tianwen-2 Mission (469219) Kamo`oalewa

Xiaoyu Sun, Zhijun Song, Hanjie Tan, Bin Yang, Josef Ďurech, Nicholas Moskovitz, Audrey Thirouin, Samantha Hemmelgarn et al.

(469219) Kamo`oalewa is the most stable Earth quasi-satellite and the target of China's Tianwen-2 asteroid sample return mission. Due to its small size, fast rotation, and the limited observing geometry accessible from the ground, many physical properties of Kamo`oalewa remain poorly constrained, including the rotational status and shape. We obtained three epochs of high-cadence, high signal-to-noise photometric lightcurves of Kamo`oalewa with the Gemini North Telescope from 2026 April to May, s…

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astro-ph.IM

Facility integration of the NASA IRTF adaptive secondary mirror

Ellen Lee, Mark Chun, Michael Connelley, Ruihan Zhang, Olivier Lai, Tony Denault, John Rayner, Max Baeten et al.

IRTF-ASM-1 has been functioning well since its first light in 2024. This adaptive secondary mirror (ASM) was primarily developed to be an on-sky demonstration of the new hybrid variable reluctance actuator technology at the NASA Infrared Telescope Facility (IRTF). However, due to its physical robustness and our previous demonstrations of sensitivity enhancements with the ASM, we are interested in using it to optimize telescope image quality on a nightly basis. This will directly benefit science…

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astro-ph.EPastro-ph.IM

Physical Characterization of Moon Impactor 2025-010D

Tanner Campbell, Adam Battle, Bill Gray, Juan A. Sanchez, David Cantillo, Lucille LeCorre, Vishnu Reddy

Renewed interest in lunar exploration is creating a growing population of poorly tracked cislunar objects, some of which will ultimately impact the Moon$^{1}$. The ultimate fate of rocket upper stages or failed mission payloads is often unknown and unplanned. Determining the origin and physical properties of such objects will become increasingly important as sustained lunar exploration places humans and infrastructure on the surface$^{2;3;4;5}$. Here we present a ground-based physical and dynami…

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astro-ph.IMphysics.ins-det

Fundamental Noise Limits of Infrared Detectors in the Presence of Readout Glow

Michael Bottom, Gustav Pettersson, Pavaman Bilgi, Guillaume Huber, Charles-Antoine Claveau, Nathan Lourie, Robert Simcoe, Shane Jacobson et al.

Read noise in infrared sensor arrays remains a major obstacle for ground- and space-based astronomy. It has long been recognized that the upcoming extremely large telescopes cannot meet their full potential unless read noise is significantly improved, and it is also a prohibitive constraint on the Habitable Worlds Observatory, a space telescope with the goal of detection and characterization of nearby Earth-like exoplanets. The main strategy for lowering read noise is averaging through multiple…

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physics.space-phphysics.geo-ph

A Machine-Learning-Based Global Thermospheric Density Forecasting Model

Ruochen Wang, Xiaoli Bai

Thermospheric mass density governs aerodynamic drag in low Earth orbit and is a primary source of uncertainty in orbit prediction and conjunction assessment, particularly during geomagnetic disturbances. We present AETHER-P3 (Accelerometer-driven Estimation of THERmospheric density-A Physics-Informed Probabilistic Prediction Platform), a machine-learning-based global thermospheric density forecasting model that provides multi-step forecasts up to 6 hr ahead using a 3-hr input window, with predic…

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astro-ph.IMastro-ph.EP

Investigating the differential limb coupling effect for diffraction-limited spectrographs with PARVI

Andrea S. J. Lin, Ashley D. Baker, Samuel Halverson, Nemanja Jovanovic, Dimitri Mawet, Garreth Ruane, Gautam Vasisht

A promising new architecture for extreme-precision radial velocity (EPRV) spectrographs, hunting for small-amplitude stellar Doppler shifts induced by orbiting planets, is to build diffraction-limited instruments by using single-mode fibers fed by an adaptive optics system. However, the target stars are partially resolved when observing at the diffraction limit, and the resulting RVs are expected to be affected by differential limb coupling (DLC), an effect where the red- and blue-shifted sides…

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astro-ph.EPastro-ph.HEastro-ph.SR

The generation of spiral density waves by MRI in accretion discs

G. Mamatsashvili, D. Kobaidze, W. Mouhali, T. Lehner, L. Burdiladze

We investigate the linear dynamics of non-axisymmetric perturbations in Keplerian discs subject to a weak uniform vertical magnetic field in the shearing box approximation. Perturbations are decomposed into shearing waves and evolved by numerically integrating the linearized ideal MHD equations. The disc flow supports three basic perturbation modes: two incompressible modes - magnetic mode that undergoes magnetorotational instability (MRI) and inertia-magnetic waves - and compressible spiral den…

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astro-ph.HE

Fast Population Leakage in Astronomical Masers: Maser Amplification and Transient Superradiance

Vahid Anari, Toktam Rashidi, Fereshteh Rajabi

We use a $Λ$-type three-level Maxwell--Bloch model to test whether an inverted molecular transition in an astronomical maser source can produce maser amplification or superradiance when its upper level also decays through a second radiative pathway with a much larger spontaneous decay rate. Such shared-upper-level configurations occur in multilevel, radiatively pumped molecules, including Class II methanol masers and several OH maser transitions. The model follows the coupled evolution of level…

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astro-ph.IM

Design and Performance of 220 and 270 GHz Bandpass Filters for BICEP Array

A. Steiger, The BICEP/Keck Collaboration, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff et al.

The BICEP Array (BA) is the latest in the BICEP/ Keck series of experiments that aim to measure the polarization of the cosmic microwave background (CMB) with small aperture polarimeters located at the South Pole. To constrain the frequency response of these receivers, each detector is serially coupled to a band-pass filter (BPF). The electric circuits of these BPFs utilize series and shunt capacitors as well as series inductors, but critically do not include shunt inductors which simplifies fab…

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astro-ph.EPastro-ph.SR

Planetary atmospheric escape and disk formation around WDJ0914+1914

C. Villarreal D'Angelo, M. P. Ronco, M. R. Schreiber, O. Toloza, A. Esquivel, B. T. Gänsicke

The spectrum of the white dwarf WD J091405.30+191412.25 displays the absorption and double-peaked emission lines of the volatiles hydrogen, oxygen, and sulfur. This unique characteristic has been interpreted as evidence of this white dwarf accreting mass from a circumstellar disk that had formed from atmospheric material evaporating off a close-in Neptune-like or super-puff mass planet. Thus far, however, the orbital separation of the planet and its mass-loss rate have only been estimated using…

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astro-ph.HEastro-ph.GA

Polarization Angle Swings in Blazars Detected in the Millimeter-wave with the South Pole Telescope

A. Simpson, E. Anderes, A. J. Anderson, B. Ansarinejad, M. Archipley, L. Balkenhol, D. R. Barron, P. S. Barry et al.

We present the first systematic search for electric vector position angle (EVPA) swings in the millimeter-wave (mm-wave) emission of blazars, using five years of observations from the South Pole Telescope SPT-3G camera at 95 and 150 GHz, and investigate their connection to gamma-ray flares. Of the 168 bright sources in the ~1500 square degrees SPT-3G Main Field, eight have sufficient polarization signal-to-noise for reliable EVPA measurement, four of which have continuous Fermi LAT gamma-ray det…

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astro-ph.GA

A Review of How Supermassive Black Hole Binaries Can Be Detected and Characterized through Gravitational Lensing of Background Stars

Mu'allim Yakubu

Supermassive black hole binaries are an inevitable outcome of hierarchical galaxy mergers, but their sub-parsec evolutionary phase between the kpc separations resolvable by direct imaging and the millihertz gravitational-wave regime targeted by LISA remains observationally elusive. Gravitational lensing of background stars by SMBH binaries has emerged as a powerful complement to periodic variability searches, periodic Doppler-boost signals, and circumbinary accretion hydrodynamic models. Two dis…

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gr-qcastro-ph.HEastro-ph.IM

Can machine learning improve the detectability and disentanglement of the gravitational-wave background?

Hugo Einsle, Marie Anne Bizouard, Tania Regimbau, Mairi Sakellariadou, Jishnu Suresh

Gravitational waves from compact binary coalescences and from early Universe processes are expected to form a gravitational-wave background. We employ a custom deep learning multi-scale multi-headed autoencoder architecture to isolate gravitational-wave background from detector noise, followed by a Markov chain Monte Carlo inference stage to separate the astrophysical and cosmological components. Analyzing $108$-day mock datasets representative of the first period of the fourth LIGO-Virgo-KAGRA…

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astro-ph.GA

On an empirical method to build near-equilibrium axisymmetric and triaxial galaxy models

Pierfrancesco Di Cintio, Alessandro Alberto Trani, Valentina Cesare

We introduce a numerical technique to implement $N-$body realizations of axisymmetric and triaxial self-gravitating system starting from a spherical self-consistent models for which a phase-space distribution is known. The method is an improvement of the so-called adiabatic squeezing technique and allows one to have a better control of the effective ellipticities of the particle distribution and produces virialized systems that can be used as non-spherical initial conditions for $N-$body simulat…

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astro-ph.IMeess.SPeess.SY

A Comparative Systems-Engineering Framework for RFI Coexistence in Radio Astronomy and Aviation Safety Systems

Simthembile Dlamini

Radio astronomy and aviation safety systems occupy opposite ends of the signal-power spectrum, yet both depend on the same finite resource and are increasingly squeezed by commercial broadband wireless services. The two fields protect their receivers using separately derived, apparently incommensurable criteria: the ITU-R RA.769 detrimental-interference threshold for radio telescopes, and the radar-altimeter interference thresholds established by RTCA Special Committee 239 for the 5G C-band coex…

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astro-ph.IMastro-ph.HE

A Focal-plane X-ray Polarimeter with Spectral and Timing Capabilities for Future Missions

Hemanth Manikantan, Carlo Lefevre, Lorenzo Petrucci, Paolo Soffitta, Fabio Muleri, Enrico Costa, Alda Rubini, Vladislavs Plesanovs et al.

The NASA-ASI mission Imaging X-ray Polarimeter Explorer (IXPE) firmly established X-ray polarimetry as a core observation pillar of high-energy astrophysics, alongside imaging, timing, and spectroscopy. While IXPE made groundbreaking discoveries in the 2$-$8 keV range on both point and extended X-ray sources, the Gas Pixel Detectors onboard IXPE demand substantial improvements to be ready for the next generation of imaging X-ray polarimeters. Here, we present the development of a detector protot…

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astro-ph.SRastro-ph.HE

An extreme case of X-ray reflection in the symbiotic V648 Car

Jherssica Freitas, Raimundo Lopes de Oliveira, Koji Mukai

V648 Car is a $δ$-type symbiotic star known for its strong hard thermal X-ray emission, heavy local photoelectric absorption, and stochastic variability. We analyze NuSTAR observations, complemented by nearly contemporaneous Swift/XRT observations, to check for the expected presence and physical implications of Compton reflection in its X-ray spectrum. The spectra were fitted with X-ray models that accounted for thermal plasma components, different prescriptions to quantify the intrinsic absorpt…

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astro-ph.GA

Vortex State of Ultralight Dark Matter and the Fornax Timing Problem

V. Gorkavenko, O. Barabash, T. Gorkavenko, K. Korshynska, O. Teslyk, A. Zaporozhchenko, E. Gorbar

We investigate the impact of the vortex state of the ultralight dark matter (ULDM) on the dynamical friction acting on moving globular clusters. Comparing this force with that for the solitonic ground state, it is shown that the internal structure and rotation of the ULDM core strongly affect the orbital decay of globular clusters. In particular, co-directional rotation in a vortex state can lead to significant suppression of dynamic friction at certain distances where globular clusters and ULDM…

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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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