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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.GAastro-ph.IM

The MICADO first light imager for the ELT: Simulated Observations of Star Forming Clumps at Cosmic Noon

Matteo Simioni, Carmelo Arcidiacono, Andrea Grazian, Marco Gullieuszik, Elisa Portaluri, Alvio Renzini, Benedetta Vulcani, Anita Zanella et al.

Galaxies at redshift z$\sim$2-6 exhibit prominent star-forming regions (clumps). Characterisation of these galactic structures requires both high sensitivity and spatial resolution of $\sim$100 pc or less. Currently, these spatial scales are achievable only with the aid of strong gravitational lensing. However, lensing introduces model-dependent uncertainties and limits the sample to galaxies behind massive clusters. The upcoming 40m-class telescopes, such as the ESO Extremely Large Telescope (E…

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astro-ph.EP

Sea Ice as an Origin of Life Location for Hycean and Ocean Worlds

Edouard F. L. Barrier, Nikku Madhusudhan, Frances E. Rigby

Water worlds with potential deep oceans are at the forefront of currently observable exoplanetary habitability. The standard requirements for habitability are the presence of an energy source, a source of nutrients, and a solvent, all of which can be met in exoplanets with deep liquid water oceans. Such planets may be numerous, ranging from hycean worlds and ocean worlds to terrestrial-size planets with enhanced water content. However, abiogenesis requires additional conditions, namely a mechani…

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astro-ph.HEphysics.plasm-ph

Two-Phase Structure of Synchrotron-Cooling-Unstable Relativistic Plasma

Agnieszka Wierzchucka, Pablo J. Bilbao, Robert J. Ewart, Dmitri A. Uzdensky, Alexander A. Schekochihin

Using analytic theory, radiative particle-in-cell (PIC) simulations, and fluid simulations, we show that relativistic, synchrotron-cooling, collisionless, high-$β$ pair plasmas filament into a two-phase medium. This process occurs through the interplay of the synchrotron cooling instability (SCI) with the synchrotron firehose instability (SFHI). One phase has high plasma~$β$ and is infested with small-scale firehose fluctuations, which scatter particles and pin the pressure anisotropy to the fir…

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astro-ph.IMastro-ph.HEgr-qc

Search for Long-Transient Gravitational Waves from Supernova SN2023ixf using GFH-v2 Pipeline

Sandhya Sajith Menon, Lorenzo Pierini, Pia Astone, Cristiano Palomba, Francesco Safai Tehrani, Lorenzo Silvestri, Ornella Juliana Piccinni, Simone Dall'Osso et al.

We present a directed search for long-transient gravitational waves from the possible newborn magnetar remnant of SN2023ixf, a nearby Type II core-collapse supernova in the M101 galaxy. The analysis uses LIGO Hanford and Livingston data from Engineering Run 15, using coincident data lying within the on-source window associated with the supernova. We target signals from a rapidly rotating, non-axisymmetric neutron star whose spin-down is dominated by gravitational-wave emission, producing a power…

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astro-ph.HEgr-qc

Bridging the Population Synthesis of Supermassive Binary Black Holes and the Gravitational Wave Background

Kanyuni Iemoto, Boris Goncharov, Gabriela Sato-Polito, Xiaoming Bi

Pulsar Timing Arrays (PTAs) constrain population properties of supermassive binary black holes (SMBHBs) through the observation of the gravitational wave background (GWB). Unlike other approaches that interpolate population-synthesis libraries or only consider the mean of the strain spectrum, here we capture its full strain probability density directly from semi-analytic population models. We apply our new method to the semi-analytic SMBHB population model, independently reproducing the paramete…

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astro-ph.GAgr-qc

Improving constraints on the Yukawa correction at the Galactic Center with multiple stellar orbits

GRAVITY+ Collaboration, :, A. Foschi, K. Abd El Dayem, N. Aimar, A. Berdeu, J. -P. Berger, G. Bourdarot et al.

We investigate the presence of a Yukawa-like correction ($\propto \, αe^{- r/λ}$) to Newtonian gravity at the Galactic Center, using a multi-star fitting code, including the newly discovered star S$301$, to improve the constraints obtained using S$2$ orbit alone. We perform a Markov Chain Monte Carlo analysis using the astrometric and spectroscopic data of stars S$2$, S$55$, S$29$, S$38$ and S$301$ collected by GRAVITY, GRAVITY$^+$, NACO and SINFONI instruments, covering the period from $1992$ t…

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astro-ph.IMastro-ph.GAastro-ph.HE

Approximating the statistics of a gravitational wave background

Mikel Falxa

The astrophysical origin of the gravitational wave background (GWB) reported by pulsar timing array (PTA) collaborations has yet to be confirmed. A GWB signal made of the sum of individual gravitational wave (GW) from the population of supermassive black hole binaries (SMBHB) would show the imprint of a discrete Poissonian statistics in its spectral properties. In this work, we propose a tool based on the saddlepoint approximation method to estimate the distribution of characteristic strain for…

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astro-ph.SRphysics.atom-phphysics.plasm-ph

R-matrix calculations for opacities: V. Temperature-density dependence of photoabsorption cross sections and opacity spectra of oxygen ions O VI and O VII

Divya Chari, Sultana N Nahar, Anil K Pradhan

We present R-matrix photoabsorption cross sections for Li-like oxygen O VI and He-like oxygen O VII and examine how plasma broadening modifies them as a function of temperature and density in astrophysical and laboratory high-energy-density (HED) plasma sources. All atomic systems are subject to plasma environment effects, and the propagation of radiation depends on photoabsorption via bound-bound transitions as spectral lines and autoionizing resonances in bound-free photoionization cross secti…

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astro-ph.HE

Interior Magnetic Fields in Magnetars and Radio Pulsars

Raj Kishor Joshi, Brynmor Haskell, William Cook, Sebastiano Bernuzzi

Magnetic fields are fundamental for neutron star physics and play a central role in powering the extreme phenomenology of magnetars, including Soft Gamma Repeaters and Anomalous X-ray Pulsars. However, the structure and stability of their internal magnetic fields remain largely unconstrained, as they cannot be directly probed by electromagnetic observations. Using 3D general-relativistic magnetohydrodynamics simulations across a range of rotation rates and magnetic field strengths, we identify t…

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astro-ph.SRphysics.space-ph

Amplification of active region equatorial dipole

Ismo Tähtinen

The effect of active region parameters on the evolution of solar axial dipole is well understood. However, their effect on the solar equatorial dipole has not been studied in detail. Understanding the development of the equatorial dipole is important as it drives the interplanetary magnetic field on intracyclic timescales (~ 1yr). We study how the latitude, tilt angle, and the polarity separation affect the evolution of solar equatorial dipole. We use dipole flux transport (DFT), a matrix implem…

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astro-ph.GA

A new clump-based star formation model for galaxy simulations: implications for high-redshift compact star clusters

Shu Horie, Hidenobu Yajima

We develop a new star formation model for galaxy simulations in which star-forming gas clumps are identified on-the-fly and converted into stars with an efficiency $ε_{\rm SF}$ set by the clump surface density $Σ_{\rm c}$, calibrated against radiation hydrodynamics simulations of star cluster formation. Applying this model to isolated disc galaxies embedded in haloes of $M_{\rm h}=10^{9}$, $10^{10}$ and $10^{11}\,\mathrm{M_\odot}$, with disc compactness corresponding to redshift $z=0$--$10$, we…

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astro-ph.HEastro-ph.IM

A cosmic-ray database update: CRDB v4.2

Davud Maurin

The cosmic-ray database, CRDB, has provided data and meta-data to the community since 2013. We present a new release, CRDB v4.2, which includes data and time series published in the last three years (from AMS-02, CALET, DAMPE, LHAASO, etc.), datasets missed in previous releases, and all peer-reviewed ultra-high energy cosmic-ray data (both historical and recent datasets). These data and meta-data are available from the web interface or from the CRDB pip-installable Python library. This release i…

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astro-ph.IMphysics.space-ph

Optical Flashes from Beam-Driven Light Sails with the Roman, Rubin and Euclid Observatories

James Guillochon, Abraham Loeb

The primary challenge of rocket propulsion is the burden of accelerating the spacecraft's own fuel. Light sails leave the propellant at home, with the achievable speed set by the sail area, the thermal tolerance of its material, and the power of the driving array. In GL15 we showed that leakage from a microwave array driving such a sail between habitable worlds produces Jansky-level radio transients lasting tens of seconds at $100$~pc. We take that leak to optical and near-infrared, where Fresne…

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astro-ph.HEastro-ph.IM

Mining the time axis with TRON - III. Discovery of a nulling pulsar towards the SMC with MeerKAT

T. Blecher, M. Geyer, O. M. Smirnov, A. Coelen, I. Heywood, I. Pelisoli, A. K. Hughes, J. S. Bright et al.

We report on the discovery of a nulling pulsar, PSR J0052$-$7551, in archival MeerKAT L-band observations of the Small Magellanic Cloud (SMC). The discovery was made using the image-plane transient detection pipeline, TRON, which creates a residual image for each time sample and uses a heuristic pruning strategy to identify promising candidates in the resulting temporal image cube. The TRON pipeline triggered on the approximately minute timescale variability associated with the nulling behaviour…

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astro-ph.GA

ALMA Reveals an Explosive Outflow Candidate in IRAS 16119--5048

Yongquan Luo, Jianjun Zhou, Tie Liu, Jarken Esimbek, Siju Zhang, Xindi Tang, Sami Dib, Prasanta Gorai et al.

We present a multiwavelength study of the massive star formation region IRAS 16119-5048 (I16119) using ALMA ATOMS Band 3 and QUARKS Band 6 observations, complemented by archival ATCA radio continuum and Spitzer mid-infrared data. The CO (2-1) emission reveals a system of high-velocity streamer-like structures around the central region. Using dendrogram analysis of velocity-channel maps followed by linking in position-position-velocity space, we identify 16 approximately radially distributed stre…

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astro-ph.GA

Irreducible-Mass Balance for Magnetized Null Horizons with an Internal Current Sheet

Remo Ruffini, Giorgio Sonnino

We begin with a general question: how does the irreducible mass of a magnetized black hole change when the horizon is not stationary? The null Raychaudhuri equation gives an exact area balance for any smooth null horizon, without assuming stationarity or axisymmetry. When the horizon is axisymmetric and admits an integrable quasilocal Hamiltonian, this geometrical identity becomes an energy balance. The equation keeps area growth, rotational and electromagnetic work, nonstationary focusing, cano…

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astro-ph.HE

Oblique Collision of a Relativistic Cold Shell with an Ideal Reflecting Wall

Jonathan Granot, Prasanta Bera, Michael Rabinovich, Paz Beniamini

Relativistic flows are common in astrophysics and often form shocks when different parts of the flow collide at relativistic relative velocities. Such collisions are often oblique, forming two shocks whose shocked fluids are separated by a contact discontinuity, which is treated here as an ideal reflecting ``wall'' where the flow on either side is modeled separately. The latter is modeled in the lab frame $S$ as a uniform cold planar shell propagating into vacuum at velocity $v_1=β_1c$ normal to…

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astro-ph.HEgr-qc

Timing Gravity with Pulsars in the Strong Field

Riccardo Della Monica, Ivan de Martino

We propose a novel approach for the timing of pulsars orbiting a supermassive black hole, which implements the fully relativistic calculations of the photon travel time into a robust timing model. We generate realistic mock catalogues of pulsar times-of-arrival for several putative pulsars on tight orbits around the Galactic Center supermassive black hole, Sagittarius A* (Sgr A*). Then, we perform a proof-of-concept sensitivity analysis to forecast the accuracy that future observational faciliti…

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astro-ph.EP

Long-baseline ATLAS photometry of the seven main-belt asteroid targets of the Emirates Mission to the Asteroid Belt

Nicolas Erasmus, Josef Ďurech, David E. Trilling, Larry Denneau, John L. Tonry, Henry Weiland, Ken W. Smith, Javier Licandro et al.

The Emirates Mission to the Asteroid Belt (EMA) will use the MBR Explorer spacecraft to fly past six main-belt asteroids -- (10253) Westerwald, (623) Chimaera, (13294) Rockox, (88055) Ghaf, (23871) Ousha and (59980) Moza -- before rendezvousing with, and deploying a lander onto, the extremely red (269) Justitia. We present a homogeneous analysis of a decade of sparse photometry of all seven targets from the Asteroid Terrestrial-impact Last Alert System (ATLAS). For each object we derive absolute…

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physics.opticsphysics.app-phphysics.space-phquant-ph

Mechanical quality factor estimation from a nonlinear optical cavity response

Zohran Ali, Davide Tomasella, Daniel Allepuz Requena, Alexander Huck, Ulrik Lund Andersen

Intrinsic damping rate and quality factor ($Q$) are key parameters in optomechanical systems. However, in high-Q devices, their measurement is often challenging because probe-induced dynamical backaction (DBA) and the need to resolve and accurately track the mechanical resonance limit the performance of state-of-the-art techniques. Here, we introduce an all-optical ringdown method in the unresolved-sideband regime that exploits the nonlinear, time-averaged optical response induced by strong mech…

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astro-ph.SRastro-ph.GA

An Eccentric Massive Protobinary Assembled via a Core-merger Parabolic Encounter

Yao Wang, Yichen Zhang, Rubén Fedriani, Kei E. I. Tanaka, Viviana Rosero, Kai Yang, Morten Andersen, Maria T. Beltrán et al.

Most massive stars form in binary systems, which profoundly influence their subsequent evolution. However, how such systems form remains poorly understood, with several competing scenarios proposed, including disk fragmentation, core fragmentation and capture. Determining the orbital architectures of massive binaries, particularly during their earliest embedded phases, is therefore crucial for distinguishing among these formation pathways, but direct measurements of their three-dimensional motio…

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astro-ph.HE

Correlation between X-ray and gamma data of Swift measurements

Istvan I. Racz, Lajos G. Balazs, Istvan Horvath, Sandor Pinter

Several studies over the last two decades have used canonical correlation analysis (CCA) to study the relationships between main γ-ray (e.g. fluence, peak flux, and duration) and main X-ray (flux, decay and spectral index, and hydrogen column density) data from gamma-ray bursts (GRBs). In this paper, we revisit this approach using a much larger dataset to identify potential new insights into these relationships. We used CCA to investigate the interrelationship of the aforementioned gamma-ray and…

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astro-ph.EP

A semi-analytical Ring-Arc model for Plutino perturbations

Yue Chen, Jian Li

Neptune's 2:3 mean motion resonance induces an asymmetric spatial distribution of Plutinos. We previously proposed a 9000-point-mass arc model that successfully captures the resulting influence on planetary ephemerides. However, integrating thousands of point masses involves significant computational cost. In this paper, to more efficiently simulate the total perturbation of Plutinos, we develop a semi-analytical Ring-Arc model described by gravitational potentials. This model consists of an out…

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gr-qcastro-ph.HEhep-th

Exact Cancellation of Horizon Modes in Kerr Ringdown

Kei-ichiro Kubota, Yusuke Manita, Hayato Motohashi, Daiki Watarai

Ringdown gravitational waves probe black hole spacetimes via quasinormal modes (QNMs). Recent studies have reported oscillatory features in QNM-filtered waveforms, and have led to conflicting interpretations as to whether they represent a near-horizon "direct wave". Reexamining a particle plunging into a Kerr black hole, we show that the saddle-point approximation underlying the proposed interpretation fails near the horizon. Our exact analysis reveals that every source-induced horizon-mode pole…

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astro-ph.EPastro-ph.IM

That's no moon: Exomoon survival and detection limitations

Alicia Pérez-Rodrigo, Isabel Rebollido

While moons are ubiquitous in the Solar System, exomoons have not yet been unambiguously confirmed despite the discov- ery of over 5,600 exoplanets. We investigated the reasons for this lack of detections by reviewing high-impact literature searches, assessing dynamical stability and detectability constraints, and comparing these with the moon population in the Solar System. We compiled a homogeneous catalogue of 24 proposed exomoon candidates, including stellar, planetary, and inferred lunar pa…

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astro-ph.SR

Statistical structure and physical interpretation of the fillout factor distribution in contact binary stars

A. Poro, K. Li, E. Paki, F. Alicavus, N. Alan

Contact binary systems exhibit complex evolutionary behavior governed by mass transfer, angular momentum loss (AML), and Roche geometry. The fillout factor ($f$) is widely used as a descriptor of the degree of overcontact, yet its physical and statistical role remains nonuniformly defined across the literature. We used a compiled observational sample of W UMa-type contact binaries to construct a data-driven classification framework based on $f$ and its relation to fundamental system parameters.…

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astro-ph.EP

The effect of the atmospheric C/O ratio on interiors of hot Jupiters

Esther van Dijk, Yamila Miguel, Paul Mollière

The atmosphere is the outer boundary of a gas giant exoplanet's interior. Therefore, compositional changes in the atmosphere can affect interior inferences. Typically, only metallicity is considered in atmospheric boundary conditions, while other elemental ratios, in particular the C/O ratio, are assumed to be solar. In light of the observational constraints now achievable with JWST, this assumption might no longer be justified. In this work, we investigate the effect of the C/O ratio on atmosph…

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astro-ph.IM

One Merger, Three Bands: Multiband Detection Rates and Parameter Estimation of Stellar-mass Binary Black Hole Coalescences from Millihertz to Kilohertz

Anson Chen, Jun Zhang

Stellar-mass binary black holes sweep through the millihertz, decihertz, and kilohertz gravitational-wave bands before merger, making them prime targets for multiband observations. We forecast their detection rates and parameter-estimation precision for networks combining the millihertz observatories LISA, Taiji, and TianQin; the decihertz concepts LGWA, AMIGO, and AMIGO-5; and the ground-based LVK and Cosmic Explorer. Using the binary-black-hole mass and redshift distributions inferred from GWT…

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astro-ph.HE

LOFAR follow-up of sources in the First LHAASO Catalogue

Maria Arias, Timothy Shimwell, Martin Hardcastle, Roland Timmerman

The First LHAASO Catalogue lists 90 sources of very-high-energy gamma-ray emission, many without an established counterpart at other frequencies, reopening the question of which Galactic accelerators produce the highest-energy cosmic rays. We search for low-frequency radio counterparts to the 55 1LHAASO sources that fall within the Galactic fields of the LOFAR Two-metre Sky Survey Data Release Three (LoTSS-DR3), using 144~MHz continuum maps at $6''$ and $20''$ resolution, complemented with archi…

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astro-ph.IMcs.AI

AstroSpecLM: A Spectrum-Language Model for Evidence-Grounded Astronomical Spectral Analysis

Jinghang Shi, Yanxia Zhang, Ali Luo, Changhua Li, Xiao Kong

Astronomical spectra encode rich physical information, but drawing scientific conclusions from spectral features typically requires expert interpretation. This paper presents AstroSpecLM, a spectrum-language model that connects one-dimensional DESI spectra with Qwen3-4B to answer questions and provide explanations grounded in spectral evidence. Instead of generating question-answer pairs directly from templates or raw catalog fields, we first distill each spectrum into a compact set of catalog-…

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