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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.HEgr-qc

Controlling artificial surface heating in neutron star simulations: Application to hybrid equations of state

Georgios Doulis

The treatment of the stellar surface in binary neutron star simulations is crucial for the accuracy of the numerical evolution and the physical reliability of the predicted observables. Numerical artifacts associated with the treatment of steep gradients near the stellar surface can produce spurious heating during the inspiral, leading to an artificial increase of the internal energy and an unphysical expansion of the neutron star. In this work, we investigate the effectiveness of the entropy-ba…

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astro-ph.HEgr-qc

Controlling artificial surface heating in neutron star simulations: Application to hybrid equations of state

Georgios Doulis

The treatment of the stellar surface in binary neutron star simulations is crucial for the accuracy of the numerical evolution and the physical reliability of the predicted observables. Numerical artifacts associated with the treatment of steep gradients near the stellar surface can produce spurious heating during the inspiral, leading to an artificial increase of the internal energy and an unphysical expansion of the neutron star. In this work, we investigate the effectiveness of the entropy-ba…

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hep-phastro-ph.HE

Blazar Boosted Dark Matter in IceCube

Alberto M. Gago, Jaime Hoefken Zink, Joel Jones-Pérez, Gabriel D. Zapata

We study the sensitivity of IceCube to blazar-boosted dark matter in a fermionic dark matter model with a massive vector mediator coupling to quarks. To this aim, we compute the diffuse flux arising from a sample of 324 blazars with proton spectra inferred from multiwavelength observations, adopting conservative dark matter spike profiles around the central supermassive black holes and consistently accounting for attenuation effects during propagation through the Earth. The dark matter-nucleon s…

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astro-ph.HE

Cosmic Ray Diffusion and the Origin of Very High Energy Gamma-Ray Emission in Young Massive Stellar Clusters

Lucas Barreto-Mota, Elisabete M. de Gouveia Dal Pino, Gaetano Di Marco, Rafael Alves Batista, Stela Adduci Faria

The search for Galactic sources capable of accelerating cosmic rays (CRs) to PeV energies has advanced significantly in recent years. High-energy observatories such as LHAASO have detected extended gamma-ray halos around several sources, suggesting that CRs escape their acceleration sites through anomalously slow diffusion. Theoretical studies propose that magnetic mirror diffusion combined with pitch-angle scattering in turbulent flow can naturally suppress CR transport. Here, we first show how…

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astro-ph.GA

ATLAS. IV. A JWST+MUSE Demographic Study of Ly$α$ Profiles in Little Red Dots

Yuta Kageura, Masami Ouchi, Hiroto Yanagisawa, Makoto Ando, Yuichi Harikane, Tomokazu Kiyota, Minami Nakane, Yoshiaki Ono et al.

We present an initial demographic study of Ly$α$ profiles in little red dots (LRDs) at $z=3$--9 using $R\sim1000$--4000 spectroscopy. Our sample consists of 8 LRDs observed in the VLT/MUSE Deep and Wide surveys and 23 LRDs observed with JWST/NIRSpec grating spectroscopy from JADES, CANUCS, and GO programs including SPURS. We identify Ly$α$ emission in 5 MUSE LRDs and 9 JWST LRDs. Only two of them exhibit broad Ly$α$ emission (FWHM $>1000\ \mathrm{km\ s^{-1}}$), both reported previously. The othe…

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astro-ph.EP

Hydrogen Engulfment into Sub-Neptune Cores through Magma Ocean Convective Surface Renewal

Edward D. Young

A convective surface renewal explanation for ingassing of hydrogen from H2-rich envelopes into molten cores of growing planets is presented, with particular application to sub-Neptunes. The ingassing of hydrogen occurs at a moving front comprising the upper boundary of the magma ocean that engulfs hydrogen from the envelope above as it moves. The mechanism of engulfment is surface renewal as the upper diffusive boundary layer is diluted by convection. Surface renewal results in ingassing even wh…

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astro-ph.GA

The deepest color-magnitude diagrams for the benchmark open cluster NGC 2437 from Gaia and VVVX

Tali Palma, Matías Gómez, Dante Minniti, Alan Montecinos, Nicholas J. G. Cross, Javier Alonso-García, Daniel Majaess, Bruno Dias et al.

Deep photometry of Galactic star clusters provides one of the most powerful tools for determining their physical properties. In particular, in low Galactic latitude regions that suffer from heavy extinction and crowding. NGC2437 is the most extended star cluster in the near-IR footprint of the VVV Extended Survey (VVVX), covering more than one degree on the sky. We aim to characterize its physical properties using Gaia DR3 in the optical and the VVVX in the near-IR. We use Gaia DR3 proper motion…

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astro-ph.GA

OH Line Detections in Southern Galaxies of the IRAS Revised Bright Galaxy Sample

Han Zhao, Zhongzu Wu, Bo Zhang, Timur Mufakharov, Yongjun Chen, Zhiqiang Shen, Yulia Sotnikova

We present a systematic study of OH main-line emission and absorption in 186 southern galaxies from the IRAS Revised Bright Galaxy Sample, using archival MeerKAT snapshot data. OH features are detected in 38 galaxies, including eight with OH maser emission (three new) and 30 showing OH absorption, mostly unreported previously. Four absorption systems exhibit weak OH emission superposed on strong absorption. OH-emitting regions are generally more compact than the associated radio continuum. Most…

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astro-ph.HEastro-ph.GA

XRISM reveals sloshing-driven gas motions in the core of Abell 2029

Yuusuke Uchida, Yuna Saito, Naomi Ota, Erwin T. Lau, Eric D. Miller, Tommaso Bartalesi, Stefano Ettori, Kotaro Fukushima et al.

We investigate the velocity structure of the intracluster medium (ICM) in the core of the relaxed cool-core cluster Abell 2029 using XRISM Resolve spectroscopy. We analyze combined XRISM Resolve observations and divide the central region into several subregions. To account for photon mixing caused by the XRISM point spread function, we perform a spatial-spectral mixing analysis. We detect an ordered line-of-sight bulk-velocity gradient across the cluster core: the northern regions are blueshifte…

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astro-ph.HEastro-ph.GA

XRISM reveals sloshing-driven gas motions in the core of Abell 2029

Yuusuke Uchida, Yuna Saito, Naomi Ota, Erwin T. Lau, Ming Sun, Eric D. Miller, Tommaso Bartalesi, Stefano Ettori et al.

We investigate the velocity structure of the intracluster medium (ICM) in the core of the relaxed cool-core cluster Abell 2029 using XRISM Resolve spectroscopy. We analyze combined XRISM Resolve observations and divide the central region into several subregions. To account for photon mixing caused by the XRISM point spread function, we perform a spatial-spectral mixing analysis. We detect an ordered line-of-sight bulk-velocity gradient across the cluster core: the northern regions are blueshifte…

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astro-ph.HE

Optical Spectroscopy of TeV-emitting BL Lac Candidates

Cassidy Metzger, Ryan C. Hickox, John R. Thorstensen

TeV-emitting BL Lacertae (BL Lac) blazars have important implications for the study of jet phenomenology, particle acceleration, and ultra high-energy cosmic ray production. They also allow for indirect studies of the extragalactic background light, cosmic magnetic fields, and axion-like particles. The upcoming Cherenkov Telescope Array (CTA), a ground-based gamma-ray observatory, will expand the observed TeV-emitting BL Lac population and enhance the aforementioned fields of study. However, rel…

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astro-ph.GAastro-ph.SR

The Galactic Centre G+0.633-0.0604 Molecular Cloud: A New Gold Mine for Astrochemistry

D. San Andrés, L. Colzi, V. M. Rivilla, M. Sanz-Novo, S. Martín, I. Jiménez-Serra, S. Zeng

Astrochemistry is living a golden age, with more than a quarter of the ~350 molecules in the current interstellar census having been detected over the last three years. One of the sources driving this progress is the G+0.693-0.027 cloud, located in the northern part of the Galactic Centre Sgr B2 complex. In this contribution, we present the astrochemical characterisation of G+0.633-0.0604, a newly discovered chemically rich molecular cloud at the southern edge of Sgr B2. With an inventory of >12…

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astro-ph.GAastro-ph.SR

The Galactic Centre G+0.633-0.0604 Molecular Cloud: A New Gold Mine for Astrochemistry

D. San Andrés, V. M. Rivilla, L. Colzi, M. Sanz-Novo, S. Martín, I. Jiménez-Serra, S. Zeng

Astrochemistry is living a golden age, with more than a quarter of the ~350 molecules in the current interstellar census having been detected over the last three years. One of the sources driving this progress is the G+0.693-0.027 cloud, located in the northern part of the Galactic Centre Sgr B2 complex. In this contribution, we present the astrochemical characterisation of G+0.633-0.0604, a newly discovered chemically rich molecular cloud at the southern edge of Sgr B2. With an inventory of >12…

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astro-ph.HEastro-ph.IM

The Evolution of the ACIS Contamination Layer on the Chandra X-ray Observatory from 2010 to 2026

Paul P. Plucinsky, Peter W. Ratzlaff, Akos Bogdan, Herman L. Marshall

The Chandra X-ray Observatory (CXO) was launched over 27 years ago and has been delivering spectacular science over the course of its mission. The Advanced CCD Imaging Spectrometer (ACIS) is the prime instrument on the satellite, conducting over 90% of the observations. The CCDs operate at a temperature of $-$120$^\circ$C and the optical blocking filter (OBF) in front of the CCDs is at a temperature of approximately $-$60$^\circ$C. The surface of the OBF has accumulated a layer of contamination…

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astro-ph.HE

Launching Jets in Tidal Disruption Events: Magnetic Flux Advection and Plasma Loading

Rin Oikawa, Yuri Sato

A tidal disruption event (TDE) occurs when a star approaches a black hole (BH) and is disrupted by its tidal forces. Although several hundred TDEs have been identified to date, only a small fraction are accompanied by relativistic jets. These jets are thought to be Poynting-flux-dominated outflows powered by the Blandford--Znajek (BZ) mechanism. However, the origin of the magnetic flux and plasma needed to power BZ jets remain unclear. In this Letter, we propose a scenario in which magnetic flux…

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astro-ph.SRastro-ph.GA

Magnetoacoustic Portals in Quiet-Sun Fluxtubes Revealed by Chromospheric Spectropolarimetry with SUNRISE III/SCIP

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

Acoustic waves propagate into the chromosphere, contributing to energy transport and their dynamics. Their upward propagation is restricted to frequencies above the acoustic cutoff frequency. The magnetic field configuration plays a key role in determining whether acoustic waves can propagate upward because the cutoff frequency is reduced in regions where the field is inclined with respect to gravity, forming so-called magnetoacoustic portals. Previous studies linked magnetic fields and oscillat…

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physics.plasm-phastro-ph.SR

Physics of Circular Polarized Ion-Scale Waves in Hybrid Simulations of Alfvénic Fluctuations

Hai Yang Harry Qian, Trevor A. Bowen, Carlos A. Gonzalez, Nikos Sioulas, Alfred Mallet, Kristopher G. Klein, Daniel Verscharen, Stuart D. Bale et al.

Ion cyclotron waves (ICW) and fast magnetosonic/whistler waves (FMW) are fundamental electromagnetic modes at ion kinetic scales, yet their generation mechanisms and roles in plasma evolution remain poorly understood. We analyze a 2.5D hybrid simulation of broadband Alfvénic fluctuations, where the proton velocity distribution is modeled as a sum of two bi-Maxwellian components: a thermal core and a drifting beam. Using wavelet-based wave identification, bi-Maxwellian VDF fitting, and the PLUME…

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astro-ph.GA

A Reproducible Two-Boundary Kinematic Correction for Baryonic Rotation-Curve Reconstruction in an 84-Galaxy SPARC Benchmark

David C. Flynn

We present a reproducible computational validation and failure analysis of the empirical omega kinematic correction introduced by Flynn and Cannaliato (2025). The algorithm is deliberately minimal: one coefficient per galaxy is calculated from the innermost and outermost measured rotation-curve points and applied to the full observed radial profile before comparison with a baryonic reconstruction assembled from SPARC gas, disk, and bulge components. We preserve the predecessor's frozen 84-galaxy…

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astro-ph.SR

The B-Index as a Diagnostic of Cool Stars: Assessing Metallicity Dependence of TiO Absorption in the Visible Spectrum

Fatemeh Azizi, Mohammad Taghi Mirtorabi, Zahra Mohammadian

Molecular absorption features constitute essential diagnostics of late-type stellar atmospheres, with titanium oxide (TiO) bands serving as sensitive tracers of effective temperature and magnetic activity. While near-infrared TiO indices are well established, visible-band diagnostics provide complementary constraints for stellar classification and parameter estimation. This study investigates the metallicity dependence of the B-index, a TiO absorption measure centered at 567 nm, through syntheti…

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astro-ph.IM

Aether.jl : A High-Performance 3D MHD and Multifluid Dust Code Written in a Dynamic Language with an Interactive Human-AI Development Framework

Ka Wai Ho

We present Aether.jl, a new finite-volume code for compressible hydrodynamics and magnetohydrodynamics, written in Julia and primarily designed for GPU systems. The code solves the MHD equations with constrained transport in Cartesian, cylindrical, and spherical-polar coordinates, using standard high-order Godunov methods. An arbitrary number of dust fluids can be coupled to the gas through stiff mutual drag. It was developed from scratch with interactive Human-coding agent workflow; the paper d…

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astro-ph.IM

$\texttt{Aether.jl}$ : A High-Performance 3D MHD and Multifluid Dust Code Written in a Dynamic Language with an Interactive Human-AI Development Framework

Ka Wai Ho

We present $\texttt{Aether.jl}$, a new finite-volume code for compressible hydrodynamics and magnetohydrodynamics, written in Julia and primarily designed for GPU systems. The code solves the MHD equations with constrained transport in Cartesian, cylindrical, and spherical-polar coordinates, using standard high-order Godunov methods. An arbitrary number of dust fluids can be coupled to the gas through stiff mutual drag. It was developed from scratch with interactive Human-coding agent workflow;…

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astro-ph.IM

$\texttt{Aether.jl}$ : A High-Performance 3D MHD and Multifluid Dust Code Written in a Dynamic Language with an Interactive Human-AI Development Framework

Ka Wai Ho

We present $\texttt{Aether}$, a new finite-volume code for compressible hydrodynamics and magnetohydrodynamics, written in Julia and primarily designed for GPU systems. The code solves the MHD equations with constrained transport in Cartesian, cylindrical, and spherical-polar coordinates, using standard high-order Godunov methods. An arbitrary number of dust fluids can be coupled to the gas through stiff mutual drag. It was developed from scratch with interactive Human-coding agent workflow; the…

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astro-ph.SR

High-order Paschen emission from the quiet-Sun off-limb chromosphere

Haocheng Yu, Yukio Katsukawa, Mingde Ding, Takuma Matsumoto, Sami K. Solanki, Julian Blanco Rodríguez, David Orozco Suárez, Masahito Kubo et al.

We report the detection of high-order hydrogen Paschen emission lines (Pa~15, Pa~16, and Pa~17) in the quiet-Sun chromosphere off the solar limb using the Chromospheric Infrared SpectroPolarimeter (SCIP) on board the {\sc Sunrise~iii} balloon telescope. These lines reveal thread-like structures resembling spicules and exhibit systematically smaller Doppler velocities than Ca~II~854.2~nm, suggesting that they are optically thinner and more affected by line-of-sight averaging, especially near the…

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astro-ph.GA

The galaxies' energy balance problem solved

C. J. Inman, C. C. Popescu, D. Murphy

We attempt to resolve the long-standing energy balance problem encountered by Radiative Transfer (RT) models, particularly in edge-on galaxies by incorporating a treatment for the clumpy structure of the Interstellar Medium (ISM). A subgrid approach is adopted, treating the quiescent dust clouds as pseudo-dust grains, with equivalent optical and thermal emission properties. Deriving key quantities such as the absorption, scattering and extinction cross-sections enables the virtualisation of the…

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astro-ph.GA

The SAMI Galaxy Survey: Linking Tidal Features and Orbit Populations Using Schwarzschild Modelling

T. H. Rutherford, J. van de Sande, S. M. Croom, A. Fraser-McKelvie, G. Santucci, G. van de Ven, S. M. Sweet, S. Brough et al.

The evolution of angular momentum in galaxies is shaped by a combination of internal secular processes and external mechanisms such as mergers. Orbit-superposition based dynamical modelling provides a powerful means of linking the intrinsic orbital structures of galaxies to their global properties and merger histories. We construct Schwarzschild orbit-superposition models of massive ($\log(M/M_{\odot})>10$) SAMI galaxies using the DYNAMITE code, utilising deep KiDS photometry to accurately repro…

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astro-ph.HE

Detection of possible burst oscillation in the neutron star low-mass X-ray binary 4U 1323-62

Manoj Mandal, Sachindra Naik

Burst oscillations observed during thermonuclear X-ray bursts arise from asymmetric brightness patterns on the neutron star surface and provide a direct probe of the neutron star spin frequency. We present a detailed timing analysis of the neutron star low-mass X-ray binary 4U 1323-62 using 2024 observations with XMM-Newton and NuSTAR observatories. We identify nine thermonuclear X-ray bursts in the XMM-Newton/EPIC-pn data, along with eclipsing dips in the light curve. One of the XMM-Newton burs…

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astro-ph.HEastro-ph.SR

X-ray Activity of the RS CVn-type Star σ Gem with the First-Year Observations of Einstein Probe

Xuan Mao, Giuseppina Micela, Fabio Favata, Weimin Yuan, He-yang Liu, Huaqing Cheng

Context. Stellar flares are energetic events driven by the sudden release of magnetic energy in the stellar atmosphere. Studying these flares is crucial for understanding their impact on exoplanets, the circumstellar environment, and stellar evolution itself. The launch of the Einstein Probe (EP) offers a unique opportunity to systematically detect such events. Aims. We present a systematic analysis of the flaring activity of the active RS CVn-type binary σ Gem, utilizing the first-year monitori…

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astro-ph.GA

How mergers shape galaxy morphology in the IllustrisTNG simulation

Guangquan Zeng, Lan Wang, Liang Gao

How galaxy mergers drive morphological evolution remains an open question. Traditional views hold that major mergers produce elliptical galaxies, while minor mergers form dispersion-dominated components such as galactic bulges. However, more recent work has challenged this simple picture, suggesting a more complex evolutionary scenario. In this study, we use the IllustrisTNG cosmological simulation to investigate how mergers shape galaxy morphology, across a broad range of galaxy masses and merg…

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astro-ph.IMastro-ph.HE

On the Acceleration of Pulsar Timing computations using Normalising Flows and Parallelisation

Churchil Dwivedi, Hiya Shah, Hemanga Tahbildar

Single-Pulsar Noise Analysis (SPNA) and Gravitational Wave (GW) searches done on Pulsar Timing Array (PTA) datasets have everlastingly suffered from the computational bottleneck arising due to high dimensionality and multi-modality of the PTA likelihood landscape, along with strong correlations amongst various single-pulsar noises and ensemble-level common noise processes. We addressed this outstanding issue by employing a Normalising Flow-based Preconditioned Monte-Carlo sampling technique impl…

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astro-ph.SR

Evidence for Dynamical Filtering: High Binary Fraction, Hard-binary Excess, and Unresolved Triples in the Surviving Core of NGC 6791

Huanbin Chi, Zhi Li, Feng Wang, Xuefen Tian, Linfeng Chang, Hongbo Liu, Yiqin Liu

We present a deep photometric analysis of the main-sequence (MS) population in the old, metal-rich open cluster (OC) NGC 6791 using Gaia Data Release 3 data. After correcting for differential reddening, we use the Bayesian model comparison to test whether stellar rotation can account for the observed MS broadening and find that a rotation-dominated interpretation is strongly disfavored. We therefore infer that unresolved multiplicity is the primary contributor to the photometric offsets. We deri…

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