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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.SR

Three-dimensional magnetic reconnection in unipolar regions. A case study of coronal bright points in the Sun

D. Nóbrega-Siverio, F. Moreno-Insertis, A. S. H. To

Magnetic reconnection is a fundamental mechanism underlying the heating and a wide variety of eruptive phenomena in the solar atmosphere; however, characterizing its 3D aspects remains challenging. Our aim is to understand how 3D magnetic reconnection in unipolar regions drives localized heating and plasma ejections. To this end, we used a self-consistent 3D radiation-MHD simulation of a coronal bright point (CBP) performed with the Bifrost code. We focused on localized, intense heating events a…

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

Detection of knots in the supernova type Iax remnant Pa 30

Tim Cunningham, Ilaria Caiazzo, John C. Raymond, Scott J. Kenyon

We present deep, narrowband Gemini North/GMOS images of the Pa 30 nebula that reveal rich small-scale structure in the ejecta filaments. In [S II], the number of detected filaments increases by about an order of magnitude compared to previous studies. The imaging further reveals that the filaments are not smooth radial streaks, but instead are composed of cascades of knots or clumps. The images in [O III] yield the first confirmation that previously detected diffuse [O III] emission in fact orig…

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astro-ph.EP

Dynamics around non-spherical symmetric bodies - III. The case of a spherical body with a crater

P. V. S. Soares, G. Madeira, S. M. Giuliatti Winter, T. Ribeiro, O. C. Winter

Motivated by the peculiar features of the trans-Neptunian object (TNO) Máni and the discovery of ring systems around Centaurs and trans-Neptunian bodies, we investigate the stability of particles around a small irregular body hosting a deep equatorial crater. This study is the third contribution in a sequence devoted to the dynamics around non-spherically symmetric bodies. Using Máni as a reference model, whose crater depth exceeds 10% of its radius, we map the system stability through complemen…

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astro-ph.IM

Towards a GPU-Accelerated Real-Time Imaging Pipeline for SETI at the Allen Telescope Array

Karen I. Perez, Joe S. Bright, Vishal Gajjar, Luigi F. Cruz

Traditional technosignature and transient searches commonly operate on beamformed time--frequency products. Interferometric imaging adds spatial context and allows time-domain searches to be performed across many image pixels simultaneously. We report the development and testing of a GPU-accelerated interferometric imaging and image-domain dispersion-measure (DM) search pipeline for Allen Telescope Array (ATA) post-correlation UVH5 visibility data, integrated with the CyberEther streaming framew…

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astro-ph.GA

Tentative Detection of FeS toward Orion SrcI

Aitana Tasa-Chaveli, Holger S. P. Müller, Álvaro Sánchez-Monge, Asunción Fuente, Adam Ginsburg, Thomas Möller

Iron sulfide (FeS) is a key refractory compound in astrophysical environments. It is commonly found in meteorites and evidence of FeS has only been reported in solid form in a protoplanetary environment. Furthermore, FeS is of astrobiological interest since it acts as a precursor to the formation of pyrite (FeS$_2$), which plays a key role in anaerobic metabolism. We present millimeter-wave spectroscopic calculations for gaseous FeS and report its tentative detection toward the massive disk Orio…

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astro-ph.IMastro-ph.SR

Sub 35-ps Single-Photon Stellar Intensity Interferometry of Vega

Verena G. Leopold, Sebastian Karl, Stefan Richter, Jean-Pierre Rivet, Yury Prokazov, Evgeny Turbin, Gennady Sintotskiy, Iurii Datii et al.

SII enables measurements of stellar photospheres by correlating intensity fluctuations, offering a robust alternative to amplitude-based techniques. With the advent of modern single-photon counting detectors, this method has re-emerged as a powerful technique in stellar interferometry exploiting their ultra-high timing resolution. We determine the stellar diameter of Vega at 405 nm using spatial intensity correlations measured at the C2PU facility, part of the Observatoire de la Cote d'Azur. We…

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astro-ph.EP

Shadows cast by precessing annuli as evidence for an inclined planet in HD 139614

Katie L. Milsom, Tim J. Harries, Evan A. Rich, John D. Monnier, Anna S. E. Laws, Benjamin R. Setterholm

We analyse scattered-light images at multiple epochs of the protoplanetary disc HD139614 taken with GPI and SPHERE instruments. We show that the azimuthal distribution of the surface brightness of the inner bright ring ($13-21$au) varies with time (likely caused by a structure in the inner-disc at $\sim1$au) and constrain the timescale of this variation to be $<11$months. We show that inner arc ($31-44$au) is likely a spiral and tightly wound, measuring a pitch angle of $6.1\pm1.2^\circ$. Additi…

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astro-ph.HE

Continuous Gravitational Waves from Thermo-Elastic Mountains in Ultraluminous X-ray Pulsars

Hong-Bo Li, Ziming Wang, Lijing Shao, Ren-Xin Xu

Fast-spinning, nonaxisymmetrically deformed neutron stars (NSs) are promising targets for continuous gravitational-wave (CGW) searches with current and next-generation ground-based detectors. Ultraluminous X-ray pulsars (ULXPs), characterized by super-Eddington accretion and strong magnetic fields, provide extreme environments in which substantial nonaxisymmetric deformations may develop. In this Letter, we investigate thermo-elastic mountains generated by magnetically induced temperature asymme…

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astro-ph.IM

Design and development of the PRIMAger instrument for PRIMA

Anne Costille, Fabrice Madec, Johan Floriot, Tony Pamplona, Thomas Prouv{é}, Laure Ciesla, Marc Sauvage, Willem Jellema et al.

PRIMA (PRobe far-Infrared Mission for Astrophysics) is an infrared space observatory designed to operate over the next decade. Equipped with a 1.8 m telescope actively cooled to 4.5 K, the project is currently in the concept study phase as part of the NASA Probe Explorers program. PRIMA will carry two instruments: FIRESS and PRIMAger. PRIMAger will offer two observation modes: hyperspectral imaging and polarimetric imaging. Both channels will use ultra-sensitive kinetic inductance detector (KID)…

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astro-ph.GA

Water Abundance and Ortho-Para Ratio in the S140 Photon Dominated Region

Dariusz C. Lis, Sofia Lawsky, Emeric Bron, Franck Le Petit, Javier R. Goicoechea

We analyzed archival far-infrared to submillimeter Herschel PACS, SPIRE, and HIFI spectroscopic observations of the S140 photon dominated region (PDR) to constrain the water vapor abundance and ortho-para ratio in this region. Toward the high-mass protostar IRS1, 52 spectral lines, including 15 water lines, are detected with the PACS and SPIRE instruments. PDR modeling suggests a UV radiation field G0 ~ 1 x 10^3 Habing units, and a thermal gas pressure of 5 x 10^8 K cm^-3 in this region. The mod…

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eess.SYastro-ph.EPastro-ph.IM

Fast and Stable Nonlinear Emulation of TIEGCM Using an Autoregressive SINDy Framework

Daniele Sicoli, Sriram Narayanan, Piyush M. Mehta

The ever-growing number of satellites and resident space objects in low Earth orbit keeps increasing the risk of collision between these objects. To mitigate this risk, the development of new space situational awareness tools and a new generation of probabilistic emulators of the thermosphere is increasingly felt by the community of operators and scientists. We previously built a Reduced Order Probabilistic Emulator based on 3 steps: dimensionality reduction, dynamic modeling, and uncertainty qu…

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astro-ph.SR

Magnetohydrodynamic coronal modelling with high-fidelity magnetograms

Haopeng Wang, Stefaan Poedts, Wensi Wang, Rayan Dhib, Andrea Lani, Martina Condoluci, Tinatin Baratashvili, Quentin Noraz et al.

To resolve coronal structures in detail, it is essential to constrain the coronal model using high-fidelity magnetograms with minimal smoothing. In this paper, we improve the numerical stability of COCONUT to enable efficient coronal MHD simulations driven directly by photospheric magnetograms, including magnetic field strengths exceeding 1000 Gauss (G), and then use it to investigate the impact of small-scale magnetic field structures that are typically filtered out of photospheric magnetograms…

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gr-qcastro-ph.GAquant-ph

Black Hole Horizon Fluctuations from Unruh Quantum Noise

Kashif Ammar Yasir

The mean Hawking flux does not determine how quantum stress fluctuations perturb a black-hole geometry. That information resides in field correlations, including vacuum contributions absent from the outgoing luminosity. Here we connect the complete exterior Unruh Wightman function to a finite-band stochastic reconstruction of Schwarzschild geometry. We retain the incoming vacuum and both outgoing frequency branches, form the connected stress covariance before angular projection, and propagate it…

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astro-ph.GA

Broadband radio continuum and host galaxy properties of extremely inverted spectrum compact radio galaxies

Mukul Mhaskey, Barenya Dev, Aritra Basu, Helmut Meusinger, Surajit Paul, Matthias Hoeft

We present broadband radio continuum spectra spanning 0.15-8 GHz for a sample of ten Extremely Inverted Spectrum Extragalactic Radio Sources (EISERS), selected from narrowband, low-frequency surveys below 1.4 GHz. In these surveys, EISERS show unusually steep low-frequency spectral indices, approaching or exceeding the synchrotron self-absorption (SSA) limit of $α$= +2.5, expected for homogeneous synchrotron sources. We have performed follow-up quasi-simultaneous radio observations of these sour…

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astro-ph.COastro-ph.HEgr-qc

Gravitational-wave background from supermassive black holes without merger trees: Tidally regulated mergers and direct inference from the NANOGrav 15 yr data

Shin'ichiro Ando

We present a semi-analytic framework that computes the gravitational-wave background (GWB) from supermassive black hole (SMBH) binaries by direct integration of an $N$-body-recalibrated extended Press-Schechter accretion kernel, bypassing Monte Carlo merger trees entirely. The calculation is resolution-free and fast enough to be sampled directly against pulsar-timing data with no emulator or precomputed model bank. Between halo accretion and black-hole binary formation, we couple the satellite's…

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astro-ph.HE

Energy-independent X-Ray Polarization in 4U 1630-47 in the Intermediate State from Spectroscopy and Polarimetry

Elena Seifina, Lev Titarchuk, Paolo Soffitta, Lorenzo Marra, Fiamma Capitanio, Fabio Muleri, Anastasiia Emelianova

The IXPE mission enabled measurements of X-ray polarization in accreting binaries. The dependence of the X-ray polarization degree on the binary inclination and the optical depth of the emitting medium $τ_0$ are the new important tools in X-ray Astronomy. We analyzed the black hole X-ray binary 4U~1630--47 as an example of one of the enigmatic sources in our Galaxy. We consider spectral and polarimetric observations of outburst episodes from 4U~1630--47 observed with the IXPE and the NICER. We c…

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astro-ph.IM

Technological maturation of a Gigapixels Astrometry instrument for the Habitable World Observatory.

Florence Ardellier-Desages, Jer{ô}me Amiaux, J{é}r{ô}me Bobin, St{é}phane Chevobbe, Eric Doumayrou, Pierre-Antoine Frugier, Pierre-Olivier Lagage, Manon Lizzana et al.

This paper presents the development strategy for HWO-AGATE (Accurate Guiding and Astrometry Targeting Exoearths), a high-precision relative astrometry instrument concept designed for the future Habitable Worlds Observatory (HWO). The instrument is based on a gigapixel-class focal plane that incorporates the new generation of large-format GigaPyx CMOS sensors developed by Pyxalis. The proposed architecture relies on four 220-megapixel sensors assembled into a focal plane array and coupled with a…

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astro-ph.IM

Not just a phase: detecting nanohertz gravitational waves from phase alone

Kathrin Grunthal, Eric Thrane, Rutger van Haasteren, David J. Champion, Michael Kramer

Unambiguously detecting a gravitational-wave background (GWB) in pulsar-timing data requires a robust detection statistic. The pulsar timing community currently relies heavily on the cross-correlation-based "optimal statistic." Its design was motivated to avoid false-positive detections from unmodeled pulsar red noise. However, recent work by van Haasteren (2025) suggests that the optimal statistic is not, in fact, optimal. Moreover, the optimal statistic is still susceptible to false positives…

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astro-ph.GAastro-ph.SR

Linking simulations and observations of star-forming regions I. Masses and temperatures of ALMAGAL-like cores

Birka Zimmermann, Álvaro Sánchez-Monge, Stefanie Walch, Gary A. Fuller

Dense cores and clumps in massive star-forming regions are studied through (sub-)millimetre continuum observations, but inferred masses and temperatures can be biased by limited resolution, interferometric filtering, projection, and uncertain dust temperatures. We quantify how reliably core masses and temperatures can be inferred from ALMA-like continuum data using synthetic observations of such clumps. We post-processed radiation-hydrodynamic simulations of collapsing 1000 M$_\odot$ clumps with…

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astro-ph.EP

Spins and shapes of asteroids reconstructed from photometry from surveys

Josef Ďurech, Josef Hanuš

Modern asteroid surveys routinely acquire sparse photometric measurements for hundreds of thousands of asteroids. These data can be exploited to reconstruct asteroid spin states and shapes, providing statistical constraints on the rotational evolution of different dynamical populations.Our goal is to derive spin-state and shape models from publicly available survey photometry and use the enlarged sample to investigate the distributions of asteroid physical properties across the Solar System. We…

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astro-ph.EP

Giant impacts preferentially remove low-mass atmospheres: a generalised scaling law for impact-driven atmospheric loss

Matthew J. Roche, Simon J. Lock, Philip J. Carter, Zoë M. Leinhardt

Impact-driven atmospheric loss plays a key role in shaping the diversity of planetary atmospheres. However, existing prescriptions for calculating loss from a given impact neglect the critical role of atmospheric mass on loss, and thus often severely miscalculate the extent of loss. Using 3D smoothed particle hydrodynamics simulations, we quantify atmospheric loss during giant impacts onto planets with 1-20% mass fraction atmospheres and show that less massive (lower-pressure) atmospheres are si…

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physics.ins-detastro-ph.IM

Investigating Optical Coupling Material Candidates in NaI(Tl) Detectors for the SABRE-North Dark Matter Experiment

Chemseddine Ananna, Gabriella Cataldi, Davide D'Angelo, Giulia D'Imperio, Maria Luisa De Giorgi, Giuseppe Di Carlo, Attilio Di Giacinto, Marcella Diemoz et al.

Direct dark matter detection with NaI(Tl) scintillators requires ultra-low-background materials. Silicone optical pads can couple NaI(Tl) crystals to photomultiplier tubes (PMTs) if they provide adequate optical transmission and radiopurity. We characterize four candidate materials for the SABRE-North experiment: commercial EJ-560, used as a reference, and three materials produced at the University of Salento (SYLGARD 184, EGel 3002 A/B, and a hybrid formulation) using different catalyst ratios…

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astro-ph.GAastro-ph.CO

EMIR confirmation of the high-z Lyα blob SHARDS20018464

S. Zarattini, F. Garzón, C. Muñoz-Tuñón

A spectroscopic follow-up of the Ly$α$ blob SHARDS20018464 was performed using the infrared spectrograph EMIR (Espectrógrafo Multiobjeto Infra-Rojo) at the 10.4 m GTC telescope, equipped with its newly upgraded H2RG focal plane array detector. We observed the blob in the Ks band, which corresponds, at the photometric redshift of $z=3.49$ presented in the literature, to the rest-frame visible part of the spectrum. Thanks to the sensitivity of EMIR, we were able to identify the [OIII] emission dou…

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hep-phastro-ph.COastro-ph.IM

Lunar radio emission from dark photon dark matter

Ariel Arza

The dielectric surface of the Moon provides an efficient interface for the conversion of dark matter dark photons into radio waves. This work explores a novel detection strategy that aims to capture this radio emission using standard radio telescope antennas. Detailed sensitivity projections are presented that demonstrate the power of this technique. It is found that both current and future radio observatories, including large arrays such as the Atacama Large Millimeter/submillimeter Array (ALMA…

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astro-ph.SRastro-ph.HEphysics.plasm-ph

Coherent radio bursts, polarity reversal, and quiescent emission from the M4V dwarf WW PsA

Jackson Mitchell-Bolton, Laura Driessen, Tara Murphy, Joshua Pritchard, Barnali Das, Richard Dodson, Martin Meyer, Jonghwan Rhee et al.

Coherent radio emission from magnetically active M dwarfs is largely observed in two varieties: stochastic solar-like bursts and beamed, rotationally modulated emission including auroral pulses. Detailed monitoring of these stars is critical for probing the plasmas and magnetic fields driving the emission. We conducted a search for polarised radio emission from stars within 85 pc, covering $2.2\times10^4$ h of stellar dynamic spectra from the ASKAP Deep Investigation of Neutral Gas Origins (DING…

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astro-ph.EP

SPIRou near-infrared spectropolarimetry of the ultra-hot Jupiter KELT-9b: tentative detection of the planet magnetic field

Alexis Lavail, Florian Debras, David Rogé Royo, Arturo López Ariste, Nicholas W. Borsato, Jean-François Donati, Pascal Petit, Julian D. Alvarado Gómez et al.

Exoplanetary magnetic fields govern atmospheric escape and circulation but have eluded detection in close-in planets. In the ultra-hot Jupiter KELT-9b, atmospheric dynamo is predicted to generate atmospheric fields of 400--4000 G. We search for the circular polarization in atomic lines that a magnetic field would imprint, through the Zeeman effect, on the transmission spectrum of KELT-9b. We observed three transits with SPIRou at the CFHT, on 07 September 2025 and 03 and 06 July 2026, and applie…

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astro-ph.IM

A Technosignature Survey Of The Anti-Solar Point: The SETI Institute's Largest-Ever Campaign With The Allen Telescope Array

Isabel Gerrard, Sofia Z. Sheikh

The ATA-ASP campaign is a radio technosignature survey of the Anti-Solar Point as a "Schelling point", using the Allen Telescope Array (ATA) in the Search for Extraterrestrial Intelligence (SETI). We borrow from game theory the concept of Schelling points to hypothesize spacetime coordinates where both we and an extraterrestrial agent might send and search for a signal. From the perspective opposite the Sun, an extraterrestrial agent could detect Earth transiting within the habitable zone, thus…

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gr-qcastro-ph.HEhep-th

Gravitational-wave Echoes Beyond the Hubble Time from Quantum Black Holes

Che-Yu Chen, Naritaka Oshita, Yuki Yokokura

We investigate gravitational-wave echoes in a horizonless compact object model, a non-perturbative solution of the semi-classical Einstein equation that reproduces the entropy-area law from the bulk structure. By employing a model of anisotropic fluids in classical general relativity (GR), we show that odd-parity gravitational waves are not reflected at the object's surface but are trapped inside due to the exponentially strong redshift, and that the echo-delay time extremely exceeds the age of…

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astro-ph.GA

Cusps, cores, and one acceleration: dark-matter haloes versus modified dynamics across the full SPARC sample

Mikhael Da Silva

The rotation curves of the 175 disk galaxies in the SPARC database are confronted, one by one and under identical conditions, with the two mass models that have dominated the missing-mass debate for four decades: a cold dark-matter halo of Navarro-Frenk-White (NFW) form, and Milgromian dynamics (MOND) with the acceleration constant held at $a_0=1.2\times10^{-10}$ m s$^{-2}$. Stellar mass-to-light ratios, distances and inclinations are treated as nuisance parameters with priors set by the 3.6 $μ$…

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

From the Milky Way to the Early Universe: How Metallicity Shapes the Formation of Double Neutron Stars

Abhishek Chattaraj, Jeff J. Andrews, Monica Gallegos-Garcia, Max M. Briel, Michael Zevin, Tassos Fragos, Emmanouil Zapartas, David R. Aguilera-Dena et al.

Among the compact binaries detected through gravitational wave (GW) emission, double neutron stars (DNSs) hold the unique distinction of having well-characterized local analogs in the Milky Way. However, understanding their broader cosmological population remains challenging due to the complex metallicity-dependent evolution of their progenitors. Using the detailed binary population synthesis code POSYDON, we model DNS formation across a cosmological range of metallicities. We find that while DN…

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