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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.HEastro-ph.GA

Evidence for a bursty $γ$-ray QPO in the neutrino-associated FSRQ PKS 1424$-$418 using Fast Template Periodograms and Machine Learning

Aaron A. Maldonado, Alberto Domínguez, Adithiya Dinesh, Alba Rico, Pablo Peñil, Sara Buson, Marco Ajello

Standard frequency-domain searches for quasi-periodic oscillations (QPOs) in active galactic nuclei generally assume sinusoidal variability. However, $γ$-ray blazar emission often shows asymmetric flares and localized bursts, causing spectral leakage that can reduce the sensitivity of conventional methods to non-sinusoidal periodic signals. We analyze a blind sample of 100 high-cadence (7-day binned) Fermi-LAT blazar light curves. After baseline detrending with Singular Spectrum Analysis, we app…

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astro-ph.GA

Formation of extragalactic Star Clusters

Gerhard Hensler, Yannick Hein, Alessandro Boselli, the VESTIGE consortium

The outskirts of galaxies show their beauty by an assembly of Globular Clusters and satellite galaxies, but also by interactions with their environment. Galaxies in clusters experience dynamical effects by mutual encounters and by the intra-cluster gas. This latter exerts a drag to remove gas from the outskirts. These stripped clouds are capable to form stars and open fundamental questions on astrophysical processes, as e.g. the survival of intergalactic clouds, the star-formation process, the e…

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astro-ph.HEastro-ph.GA

Metal sign of a large-scale AGN feedback in cool-core cluster MACS J1931.8-2634

Qinnan Zhu, Junjie Mao, Ping Zhou, Yuanyuan Su, Dan Hu

The spatial distribution of metals in the intracluster medium (ICM) is a sensitive tracer of the chemical and dynamical history of galaxy clusters. While most cool-core (CC) clusters exhibit a centrally peaked Fe abundance profile, several outliers show an anomalous central Fe drop, potentially associated with the AGN activities. We revisit the reported large-scale (sim 100 kpc) central Fe drop in the massive CC cluster MACS J1931.8-2634 using new XMM-Newton observations. We aim to verify this f…

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astro-ph.SR

Three-dimensional Magnetic Structures of Ellerman Bombs revealed by SUNRISE III/SCIP

Yusuke Kawabata, Yukio Katsukawa, Masahito Kubo, Takayoshi Oba, Takuma Matsumoto, Ryohtaroh T. Ishikawa, Yoshihiro Naito, Hirohisa Hara et al.

Ellerman bombs (EBs) are widely recognized as photospheric and chromospheric signatures of magnetic reconnection. However, the three-dimensional (3D) magnetic topology has remained elusive due to the lack of seamless height coverage in observations. Here, we present initial results from the SUNRISE III/SCIP (Sunrise Chromospheric Infrared spectroPolarimeter) observations of an emerging flux region. Exploiting the seeing-free, high-spatial-resolution observations provided by the 1-meter balloon-b…

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astro-ph.HEhep-ph

Gamma Rays from ALP-Photon Conversion and Inverse Compton Reprocessing in Neutron Star Magnetospheres

Federica Giacchino, Conrado A. Torres, Giorgio Galanti, Bradley J. Kavanagh, Maria A. Pérez-García, Jose M. Diego

Exploring axion-like particle (ALP) signatures from neutron stars (NSs) in the \emph{Fermi}-LAT energy range remains largely unexplored. Neutron stars with exceptionally strong magnetic fields, such as magnetars and pulsars with magnetar-like magnetic fields, provide particularly promising environments for ALP--photon conversion. Magnetars are characterized by surface magnetic fields as large as $B_0\sim(10^{14}$--$10^{15})\,\mathrm{G}$; however, despite their extreme magnetic fields, no steady…

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gr-qcastro-ph.HEhep-th

Evading Cauchy Horizon Excision in Scalarized Regular Black Holes

Ernesto Contreras, Pedro Bargueño, Arthur G. Suvorov

Spontaneous scalarization provides a dynamical mechanism to evade the no-hair paradigm, but it has been argued to generically eliminate the Cauchy horizon in charged black holes. We show that this obstruction is not universal, but instead follows from the sign-definite structure of the Einstein-Maxwell source term. Within the $P$-dual formulation of nonlinear electrodynamics, we derive a general condition under which the effective scalar source changes sign between the horizons, allowing the int…

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astro-ph.IM

Pollux: high-resolution precision spectroscopy and polarimetry for the Habitable Worlds Observatory

David Le Mignant, Coralie Neiner, Jean-Claude Bouret, Luca Fossati, Eduard Muslimov, Kjetil Dohlen, Anne Bonnefoi, Jean-Michel Reess et al.

Pollux is a high-resolution spectrograph and spectropolarimeter (R from 65000 to 100000) covering a spectral range from 100 nm to 1750 nm, proposed by a European consortium to equip NASA s Habitable Worlds Observatory (HWO). This instrument aims to revolutionize the study of stellar and (exo)planetary systems, as well as cosmic ecosystems, by combining high spectral resolution, broad and simultaneous spectral coverage, temporal stability, and unique UV spectropolarimetric capabilities, thus open…

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astro-ph.EPastro-ph.IM

Using High-Resolution Spectroscopy to Study the Composition, Temperature, and Dynamics of Exoplanet Atmospheres

Mu'allim Yakubu

High-resolution spectroscopy, typically operating at resolving powers R greater or equal to 25,000, has matured into one of the primary techniques for characterising the atmospheres of extrasolar planets. The ability of HRS to resolve individual rotational-vibrational lines of molecular bands, combined with the large Doppler shifts experienced by close-in planets during their orbits, allows planetary signals to be separated from quasi-stationary telluric and stellar contamination. Since the pion…

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astro-ph.IM

Development and Evaluation of a CNN-Based Charged-Particle Event Rejection Algorithm for Soft X-ray Detection in a pnCCD-Based Satellite System

Hsien-Chieh Shen, Ryuji Kondo, Makoto Arimoto, Tatsuro Kanenaga, Hiro Otsuka, Shutaro Ueda, Junko Hiraga, Daisuke Yonetoku et al.

All-sky surveys in the soft X-ray band are essential for detecting transient objects such as high-redshift gamma-ray bursts (GRBs), which provide key insights into the early universe. HiZ-GUNDAM is a future satellite mission designed to detect and localize high-redshift GRBs. Its wide-field X-ray monitor, EAGLE, combines Lobster Eye Optics with a pnCCD imaging detector operating in the 0.4-4 keV band. Because of limited satellite telemetry, full-frame pnCCD images cannot be downlinked, requiring…

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astro-ph.GA

Hub-filament systems and the growth of massive stars: episodic accretion, clustered environments, and projection effects

Dana Makarova, Dana Alina, Paolo Padoan, Baurzhan Kumarioldanov, Mika Juvela, Dilda Berdikhan, Naval Bhadari

The processes controlling the early mass growth of future massive stars remain poorly understood, particularly the connection of this growth to star clustering and hub-filament systems (HFSs). This connection is difficult to establish observationally, because projection effects and line-of-sight confusion in position-position-velocity (PPV) data can distort the information about the intrinsic filamentary structure. To investigate this connection, we used a three-dimensional magnetohydrodynamic (…

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astro-ph.SR

Solar Orbiter SEP Dropout during a Magnetic Cloud with Evidence for Strong Connectivity Gradients

Radoslav Bucik, Raul Gomez-Herrero, Samuel T. Hart, Maher A. Dayeh, Nariaki V. Nitta

We analyze an impulsive solar energetic particle (SEP) event observed by Solar Orbiter at 0.93 au on 2022 December 24 that exhibits a pronounced intensity dropout between approximately 07:15 and 10:00 UT. Pitch-angle distributions show a near-field-aligned beam before the dropout, which disappears abruptly at the dropout onset. At the same time, a weak 100--200 keV component appears at pitch angles of about 90--180 degrees; no comparable enhancement over this pitch-angle range is present at MeV…

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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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