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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.SR

Rotation in the Lagoon Nebula with K2

L. M. Rebull, A. M. Cody, L. Venuti, S. Thanvantri, A. Thanvantri

A low-mass star's rotation rate drives its magnetic field, and in the case of young stars, also affects accretion and planetary formation. Observations of the rotation rates of young stars help constrain models of star and planet formation. We present rotation rates from K2 observations of stars in the ~1-2 Myr Lagoon Nebula, one of the youngest clusters with space-based rotation rates available. From 414 light curves we obtain reliable rotation periods for 325 stars; 124 of them are disk-bearin…

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astro-ph.GA

The H IX galaxy survey IV: What does the molecular gas reveal in HI eXtreme galaxies

V. A. Capa, H. Dénes, K. A. Lutz, T. H. Brown

Galaxies with extreme amounts of neutral atomic hydrogen (HI), known as HI-eXtreme (HIX) galaxies, paradoxically exhibit normal or low star formation rates. To investigate the bottleneck in their star formation, we present ALMA CO(1-0) observations for five HIX survey galaxies: ESO208-G026, ESO378-G003, ESO381-G005, ESO417-G018, and ESO055-G013. While these systems possess massive, extended HI discs, their molecular gas discs are compact with normal H$_{2}$ masses relative to their stellar mass.…

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astro-ph.SR

Direct Injection of Chemically-Enhanced Plasma into a Solar Flare Arcade

Jeffrey W. Reep, Andy S. H. To

The magnetic reconnection event that drives "standard" solar flares ejects material from the reconnection site, loading mass directly onto the newly-reconnected flare arcade. To et al (2024) suggested that this model can explain observations of the distribution of elemental abundances measured in post-flare loops: the reconnection exhaust directly injects plasma with coronal abundances onto the arcade, flowing from the apex downwards. We test this idea directly by modeling the spatiotemporal var…

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astro-ph.HE

Interpreting the $γ$-ray emission from Westerlund 1: hadronic or leptonic?

Ben Li, Pasquale Blasi, Elena Amato

High-energy $γ$-ray emission has been detected from several star clusters, indicating that these sources are sites of cosmic-ray acceleration. However, it is still unclear whether the $γ$-ray emission is of hadronic or leptonic origin. We present a comprehensive study of the $γ$-ray emission from Westerlund 1, under the assumption that high-energy particles are accelerated at the cluster WTS. We investigate both the hadronic and leptonic scenarios by fitting simultaneously the spectrum and morph…

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physics.space-phphysics.optics

Optimized Bragg Grating Liquid Crystal Solar Sail

Sai Keshav Sasanapuri, Xiulian, Shan, Grover A. Swartzlander

We have designed a thin 3-layer sun-facing diffractive Bragg reflector comprised of a chiral polymeric liquid crystal film. Using Rigorous Coupled-Wave Analysis (RCWA), the stack was optimized to maximize the transverse radiation pressure force across the wavelength band 0.47 - 1.67 micrometers. The optimized structure operates on a single polarization state of light. A two structure stack, each operating on a different state of polarization, is predicted to provide a transverse momentum transfe…

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astro-ph.HE

X-ray Comptonization in an Accreting Kerr Black Hole System with a Tilted Disc and Thermal Corona: A General-Relativistic Monte Carlo Simulation. II. Polarization Signatures

Mainak Chatterjee, Dipankar Bhattacharya

Relativistic precession of the inner accretion flow is widely invoked to explain low-frequency QPOs, and the Relativistic Precession Model (RPM) predicts phase-dependent X-ray polarization. However, IXPE observations challenge simple precession and Comptonization models; for example: SwiftJ1727.8-1613 shows weak or undetected QPO-phase polarization modulation, while IGRJ17091-3624 shows a hard-state polarization degree (DOP) of ~9%, versus ~4% in other hard-state black hole binaries. In Paper I,…

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stat.APastro-ph.IM

Dual-Phase Flow Matching for Probabilistic Source Detection and Measurement in Astronomical Images

Yicun Duan, Jeffrey Regier

Using the largest digital camera ever built, the NSF-DOE Vera C. Rubin Observatory's 10-year Legacy Survey of Space and Time (LSST) will image over half the night sky. Most astronomical analyses of LSST data operate not on images but on catalogs derived from them: tables of light sources detailing their positions, fluxes (colors and brightnesses), and types (e.g., star, galaxy). At LSST's imaging depths, light sources often overlap visually, so the configuration of sources in each image is itsel…

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astro-ph.GAastro-ph.IM

KROME-X: a GPU-ready library for chemistry and microphysics in astrophysical simulations

Alessandro Lupi, Tommaso Grassi, Stefano Bovino

KROME is a Python pre-processor that writes a complete Fortran solver of chemistry and microphysics for each chemical network, widely used in astrophysical simulations. We introduce here KROME-X, a complete rewrite of KROME in modern C++, which incorporates updated physics. A code generator translates a declarative network description into a compact core (rates, right-hand side, analytic Jacobian, thermal terms, and tables), which a fixed, header-only runtime integrates with a C++ port of the `b…

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astro-ph.EPastro-ph.SR

White dwarf pollution in wide binaries I: the effects of stellar evolution

Constanza Norambuena, Carolina Charalambous, Claudia Aguilera-Gómez

Context. Atmospheric pollution in white dwarfs is interpreted as evidence for the accretion of rocky material from remnant planetary systems. Wide binary companions can influence the delivery of planetary material onto white dwarfs, making it essential to understand the interplay between stellar evolution and binary perturbations. Aims. We investigate how uncertainties in stellar mass-loss histories affect the dynamical evolution of remnant planetary systems in wide binaries, and assess their re…

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astro-ph.COastro-ph.GA

Not so Fast: Revised Calibration of SIDM Core Collapse

Frank C. van den Bosch, Yarone M. Tokayer

Self-interacting dark matter (SIDM) haloes undergo gravothermal evolution whose late-time behaviour is central to predictions for dense substructure and black-hole seed formation. We revisit the calibration of this evolution using a new spherical Direct Simulation Monte Carlo code, SphDSMC, which follows spherically symmetric SIDM systems without force softening and to substantially higher central densities than standard N-body simulations. We compare SphDSMC calculations with conventional N-bod…

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astro-ph.HE

Probing the QPO and spectro-temporal evolution of MAXI J1750-327 with XPoSat during its first detected outburst : Constraints on black-hole mass and spin

Meghamani Haldar, Biki Ram, Shubhrangshu Ghosh, Kishor Chaudhury, Rajat K. Dey, Tamal Sarkar

We present a comprehensive timing and broadband spectral study of the newly discovered black hole low-mass X-ray binary candidate MAXI J1750-327 during its August 2026 outburst, using 11 continuous observations obtained with the XSPECT instrument onboard XPoSat. During epochs 1-2, we detect prominent type C QPO exhibiting a systematic upward frequency drift, accompanied by a prominent low-frequency noise component, with a clear transition from type-C to type-B, with subsequent disappearance of Q…

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astro-ph.EPastro-ph.GAastro-ph.SR

FAUST XXXII. Chemically layered structures and ionisation in the disk and envelope of NGC 1333 IRAS 4C

Shota Notsu, Nami Sakai, Yichen Zhang, Ana Lopez-Sepulcre, Claire J. Chandler, Ziwei E. Zhang, Cecilia Ceccarelli, Claudio Codella et al.

Recent molecular line observations with high spatial resolutions have revealed vertical chemical stratification in Class I/II disks (i.e. chemical composition changing with height in the vertical direction of the disk), as well as a radial variation of ionisation rates. However, such chemical layered structures in Class 0 disk and envelope systems have been investigated only for limited objects, such as L1527. In the context of the ALMA Large Program FAUST, we report the results of molecular lin…

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astro-ph.HE

A Comprehensive X-ray Characterization of the Pulsar Wind Nebula CTB 87: Evidence for Reverse-Shock Interaction from Its X-ray and Broadband Emissions

Jaegeun Park, Jason Alford, Hongjun An, Joseph D. Gelfand, Chanho Kim, Kaya Mori, Samar Safi-Harb

We present a comprehensive X-ray study of the pulsar wind nebula (PWN) CTB 87, utilizing new NuSTAR observations and archival Chandra and XMM-Newton data. Our joint analysis reveals that the PWN's X-ray spectrum exhibits significant curvature, well described by a broken or cutoff power law. The broken power-law fit yields photon indices $Γ_{1}=1.89\pm 0.05$ and $Γ_{2}=2.73 \pm 0.10$ below and above a break energy of $E_{\rm b}=5.12 \pm 0.26$ keV, respectively, while the cutoff power-law fit give…

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astro-ph.HEastro-ph.COgr-qc

Can we constrain the binary neutron star merger time from kilonova light curves?

Noah Jamsin, Marion Pillas, Marko Ristić, Laurence E. H. Datrier, Daniel Brethauer, Stefano Ascenzi, Mattia Bulla, Barbara Patricelli et al.

The joint observation of gravitational waves (GWs) from a binary neutron star (BNS) merger (GW170817), together with a short Gamma-Ray Burst (GRB 170817A) and a kilonova (KN, AT2017gfo), marked the birth of multimessenger astronomy with GWs, and demonstrated the informative power of multimessenger observations. More BNS merger and KN detections are expected , thanks to the increasing sensitivity of GW detectors and the advent of new electromagnetic facilities such as the Vera C. Rubin Observator…

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astro-ph.COastro-ph.GA

Constraints on Reionization from Planck Low-$\ell$ EE Polarization and the Lyman-Series Forests

Garett Lopez, Anson D'Aloisio, Christopher Cain

CMB measurements tightly constrain the Thomson scattering optical depth ($τ_{\rm es}$), but they still permit a broad range of degenerate reionization histories. Incorporating Lyman-series forest constraints on the end of reionization can alleviate the degeneracy and narrow the range of allowed histories. We explore this effect using forest measurements combined with full Planck likelihoods. We apply upper limits on the neutral fraction at $4.9\lesssim z\lesssim6.9$ derived from the dark pixel f…

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astro-ph.GAastro-ph.COastro-ph.IMhep-ph

PIANISTpy: A JAX-based Python package for velocity-anisotropic astrophysical equilibrium models

Barry T. Chiang, Frank C. van den Bosch, Hsi-Yu Schive

The hierarchical assembly of dark matter haloes and galaxies via mergers and anisotropic mass accretion naturally imprints non-trivial velocity anisotropy onto haloes and galaxies, an empirical fact emerging from cosmological simulations. However, dynamical studies based on idealised numerical simulations typically assume isotropic velocity distributions for the systems studied. This is mainly because no tools exist to construct anisotropic initial conditions with fully self-consistent (i.e., ph…

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astro-ph.GA

The MIni-Halos in MIni-Clusters (MIMIC) project: New insights into the origin of mini-halos from a LOFAR, uGMRT, and MeerKAT study of diffuse radio emission in Abell 496 and ZwCl 235

F. Ubertosi, S. Giacintucci, A. Botteon, A. Bonafede, T. Pasini, M. Balboni, N. Biava, G. Brunetti et al.

We aim at investigating the presence of diffuse radio emission in low-mass (M$_{500}\leq3\times10^{14}$ M$_{\odot}$), relaxed galaxy clusters. We present a pilot study for the MIMIC (MIni-halos in MIni-Clusters) project, focusing on Abell 496 and ZwCl 235, using LOFAR (54, 144 MHz), uGMRT (400, 650 MHz), and MeerKAT (1.28 GHz) data, as well as Chandra X-ray data. We detect diffuse radio emission in the central 100 kpc of both Abell 496 and ZwCl 235, spatially confined within sloshing-induced col…

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astro-ph.EPastro-ph.IM

Systematic Uncertainties in Rocky Exoplanet Reflected Light from Incomplete Laboratory BRDF Measurements

Leonardos Gkouvelis, Michael K. Shepard, Paul Helfenstein, Francisco J. Pozuelos, Renyu Hu

The first observations of short-period rocky exoplanets have initiated the era of terrestrial exoplanet characterization. The interpretation of these observations relies on forward models used in atmospheric and surface retrieval frameworks. While atmospheric modeling is supported by extensive laboratory datasets of molecular opacities, the experimental basis for rocky surface characterization remains limited. Most reflectance libraries of planetary analog materials provide spectra measured at a…

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astro-ph.GA

Link between the properties of circumgalactic outflows and the recent star formation history of their host galaxies

Ismael Pessa, Lutz Wisotzki, Constanza Muñoz López, Tanya Urrutia, Ramona Augustin, Thierry Contini, Yucheng Guo, Daria Kozlova et al.

Galactic outflows play a key role in galaxy evolution, yet their connection to the star formation history of their host galaxies remains poorly constrained. Building on previous work modeling extended Mg II emission of galaxies observed with VLT/MUSE to infer outflow properties, we investigate how these properties depend on the recent SFH. We derive non-parametric SFHs by fitting spectroscopic and photometric data with linear combinations of single stellar population models, and compute star for…

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astro-ph.HE

A new view of the cosmic-ray knee after LHAASO

Carmelo Evoli

Recent LHAASO measurements offer a new view of the cosmic-ray knee by combining the all-particle spectrum and mean logarithmic mass with proton and light-component spectra across the PeV region. This contribution reviews these results and their implications for Galactic acceleration and transport. Approximately charge-ordered proton and helium knees coexist with different spectral evolution, while their turnover shapes constrain source populations and escape mechanisms. These measurements anchor…

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astro-ph.GAastro-ph.SR

Ammonia Fitting of Multiple Velocity Components in High-Mass Star-Forming Regions

T. Withers, S. Sadavoy, M. Chen, J. Di Francesco, R. Friesen, J. Keown, E. Rosolowsky, H. Kirk et al.

We perform a multiple velocity component analysis of ammonia (NH$_3$) gas from KEYSTONE, a Green Bank Telescope survey covering 11 giant molecular clouds (GMCs) at distances from 0.7 to 2.7 kpc. We extend existing codes to enable simultaneous fitting of up to three velocity components in NH$_3$ (1,1) with radiative transfer. Using our multiple component fitting technique, we produce the best maps of the centroid velocity and velocity dispersion in these clouds to date. Over the entire survey, mu…

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hep-phastro-ph.HE

The renormalization-group running of neutrino mixing is undetectable

Gabriela Barenboim, Mauricio Bustamante, Qinrui Liu

Quantum corrections make the parameters of a theory depend on an arbitrary renormalization scale, $μ$. The renormalization-group (RG) running of neutrino masses and mixing is a standard tool to relate models defined at a high mass scale to measured values. A growing body of work holds that the running is also directly observable: a neutrino produced or detected at momentum transfer $Q$ would carry the mixing matrix evaluated at $μ= Q$. Proposed signatures include flavor change at zero distance f…

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astro-ph.GA

Unveiling the correlation between the UV 2175 Å dust attenuation bump, PAH emission, and gas-phase metallicity at cosmic noon

L. Arriscado, I. Shivaei, L. A. Boogaard, A. Mizener, D. Calzetti, P. G. Pérez-González, F. Rodríguez Montero, G. H. Rieke et al.

The UV 2175 Å attenuation bump is one of the most prominent yet poorly understood features of galaxy attenuation curves. Its main candidate carrier is polycyclic aromatic hydrocarbon (PAH) molecules, which are more prevalent in high-metallicity environments. We present the first systematic study of the relationship between PAH abundance and the UV bump in 49 galaxies at cosmic noon (1.5 < z < 2.7), examining its dependence on stellar mass, star formation rate (SFR), and V-band optical depth. For…

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astro-ph.HEastro-ph.SRgr-qc

Exploring PSR J0901-4046 as an ultra-slowly rotating neutron star versus a white dwarf

Banibrata Mukhopadhyay, Nirupam Roy, Zenia Zuraiq, Chandrachur Chakraborty, A R Rao

The source PSR J0901-4046 shows a very long rotational period, of $\approx 75.88$ s. In fact, its long period suggests that it could be a white dwarf. We examine the properties of the source and compare the outcomes under the hypotheses of the source being a highly magnetized white dwarf (B-WD) and neutron star. We find that assuming it to be a B-WD with a surface field $\sim 10^{10}$ G explains many properties, including its storage/rotational energy, explaining luminosity. On the contrary, the…

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astro-ph.HEastro-ph.COastro-ph.IMgr-qc

Prior volume effect inflates the gravitational-wave background in pulsar timing arrays

Biwei Dai, Matias Zaldarriaga, Yacine Ali-Haïmoud

Pulsar timing arrays (PTAs) have found evidence for a nanohertz gravitational-wave background (GWB) whose amplitude exceeds most predictions based on supermassive black hole binaries (SMBHBs). Using NANOGrav 15-year data, we show that a substantial part of this excess arises from a prior volume effect. The GWB amplitude is constrained mainly by the pulsars' auto-correlations, where the GWB is degenerate with each pulsar's intrinsic red noise. By decomposing the GWB posterior, we find that margin…

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astro-ph.HE

A Hybrid Neural Network Emulator for M1 Neutrino Reaction Rates in Binary Neutron Star Merger Simulations

Yi Qiu, David Radice, Raffaele Ferrari, Albino Perego

We present a neural network emulator for the bns_nurates library, which computes neutrino reaction rates used in binary neutron star merger simulations. Following a hybrid strategy, we emulate only the computationally dominant two-dimensional reactions---pair processes, bremsstrahlung, and inelastic neutrino-electron scattering---while evaluating the inexpensive one-dimensional processes still with bns_nurates. We find that the emulator reproduces the opacities to within a few percent across the…

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astro-ph.GAastro-ph.SR

A combined HST and JWST analysis of the stellar population in Draco II

Axelle C. Raffin, Giacomo Cordoni, Helmut Jerjen, Gary S. Da Costa, Maria V. Legnardi, Anna F. Marino, Antonino P. Milone, Fabrizio Muratore et al.

Draco II (Dra II) is one of the faintest and most metal-poor Milky Way satellites known, yet its nature as either an ultra-faint dwarf galaxy or an extended globular cluster remains debated. We perform a photometric analysis of the stellar population of Dra II reducing deep multi-band observations from the Hubble Space Telescope (HST) and the James Webb Space Telescope (JWST). We select Dra II member stars based on their proper motions and photometric quality criteria. For the first time, optica…

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astro-ph.GA

Discovery of a Broad-Line Active Galactic Nucleus at $z = 9.98$

Xingyao Cai, Akio K. Inoue, Masafusa Onoue, Suzuka Arai, Yoshinobu Fudamoto, Rohan P. Naidu, Pascal A. Oesch, Jenny E. Greene et al.

The James Webb Space Telescope (JWST) has uncovered a previously unexplored population of faint active galactic nuclei (AGNs) in the early Universe. We present MoM-BL-z10 at $z=9.9837\pm0.0009$, identified through a systematic search for broad-line AGNs at $z\geq6$ using public JWST/NIRSpec PRISM spectra from the DAWN JWST Archive. The PRISM spectrum exhibits a broad component in H$β$ at 5.35 microns. A narrow+broad Gaussian fit yields a broad H$β$ detection at S/N = 3.87, with FWHM = $3480^{+20…

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astro-ph.EPastro-ph.SR

Saturation Level of the Streaming Instability

Yanqin Wu, Xuqi Chen, Joshua Bromley

In proto-planetary disks, gas turbulence can cluster dust grains and catalyze the formation of planetesimals. This process depends on the strength of the turbulence. Here, we evaluate the turbulence strength that is induced by the streaming instability. Based on the amount of free energy available, we estimate the viscous parameter to be alpha ~ St Pi^2 f(epsilon), where St (< 1) is the Stokes number of the streaming grains, Pi is the dimensionless pressure gradient, and f (epsilon) is an explic…

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astro-ph.HE

The (missing) gamma-ray counterparts to EP events

Maria Edvige Ravasio, Ansh Chopra, Peter G. Jonker, Qinyu Wu, Eric Burns, Biswajit Banerjee, Gor Oganesyan, Stefano Ascenzi et al.

While the connection of Fast X-ray Transients (FXTs) detected by Einstein Probe (EP) with Gamma-ray Bursts (GRBs) is increasingly compelling, most lack gamma-ray counterparts, leaving their relation to GRBs unclear. We performed a systematic search for gamma-ray counterparts to the 72 transients detected by EP in its first year, using targeted searches in Fermi/GBM and Fermi/LAT data, complemented by SVOM/GRM, SVOM/ECLAIRs, Swift/BAT and Konus-Wind. For the visible events without a gamma-ray cou…

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