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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.SRcond-mat.stat-mechnlin.CDphysics.space-ph

Tracking nonlinear solar-wind dynamics over three solar cycles using Wind observations

Dario Javier Zamora, Facundo Maximo Abaca

The solar wind is a turbulent, weakly collisional plasma characterized by non-Gaussian fluctuations, long-range correlations, and multifractal dynamics. We investigate the long-term evolution of these properties using hourly proton density measurements obtained directly by the Wind spacecraft over 1995--2025. The use of a single-spacecraft dataset provides an independent test of previous results derived from the multi-spacecraft OMNI database. The three components of the nonextensive $q$-triplet…

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physics.comp-phastro-ph.IMcs.PLnlin.CD

Validating direct solvers for Newton's gravitational N-body problem, and the systematic comparison between IEEE floating point and Posits

Simon Portegies Zwart

We present a systematic comparison between arbitrary precise arithmetic and integration, IEEE-754 compliant floating point arithmetic (fp16, bfp16, fp32, double precision fp64, and quadruple precision fp128), and two implementations of Posits (type III unum) for solving Newton's chaotic N-body problem. Each implementation is benchmarked with arbitrary precise calculations to objectively evaluate their performance in precision as well as speed. We rely on hardware and compiler implementations for…

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astro-ph.EPastro-ph.SR

Understanding the Energy Input Required for Methane Emission on CWISEP J193518.59-154620.3: A Comprehensive Analysis

Kayla J. Smith, Mark S. Marley, Tommi T. Koskinen, James Mang

The Y dwarf WISE 1935 exhibits a thermal inversion in its radiative atmosphere, producing methane emission features in its JWST spectrum, but the physical mechanism responsible for this inversion remains unknown. Using the open-source radiative--convective equilibrium code PICASO, we model atmospheric heating with Chapman energy deposition profiles to reproduce the observed thermal inversion and methane emission feature. Our models require heating rates of approximately 10^5-10^6 erg cm^-2 s^-1.…

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astro-ph.GA

Measuring Simulated Circumgalactic Medium Turbulence with Emission-Weighted Projected Velocity Structure Functions in FOGGIE

Helena Bouchereau, Cassandra Lochhaas, Jake S. Bennett, Mandy C. Chen

The spatially-resolved kinematics of line emission from the circumgalactic medium (CGM) of a galaxy can contain information about the CGM turbulence, which may play an important role in galaxy evolution. Due to the region's diffuse nature, there have been limited observations of low-redshift CGM emission until recent efforts that use spatially-resolved emission line kinematics to probe CGM turbulence. We use velocity structure functions (VSFs) as a measure for the properties of turbulence using…

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astro-ph.GA

The VariableTNG project: Unveiling the physical drivers of galaxy quenching

Ignacio G. Alfaro, Antonio D. Montero-Dorta, Hong Guo, Catalina Riveros-Jara, Kexin Liu, Yikai Liu, Luis C. Ho

Understanding the physical processes that regulate galaxy quenching is a key challenge in galaxy formation and evolution. The VariableTNG (VTNG) project provides a laboratory to investigate these processes, as it systematically varies eight parameters of galaxy formation while keeping the initial conditions fixed, allowing the effects of individual feedback prescriptions to be isolated. We use interpretable machine-learning techniques as a tool to identify the parameters that most strongly regul…

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astro-ph.IMastro-ph.CO

A novel technique for reflection coefficient measurement in precision cosmology

Adarsh Kumar Dash, Yash Agrawal, Somashekar R., Jayadev Ashok T., Keerthipriya S., Vishwapriya Gautam, Saurabh Singh, Mayuri Sathyanarayana Rao et al.

The detection of the global 21-cm signal from the Cosmic Dawn and Epoch of Reionisation remains a challenge to experiments worldwide. Emitted at a rest-frame frequency of 1420.405~MHz, this signal from the early Universe is redshifted to 40-200~MHz with a maximum brightness temperature of a few 100~mK. Efforts to detect this sky-averaged signal include experiments such as the Shaped Antenna measurement of the background RAdio Spectrum (SARAS) and Probing ReionizATion of the Universe using Signal…

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astro-ph.EPastro-ph.IMastro-ph.SR

SCExAO/CHARIS High-Contrast Pre-Launch Vetting of Roman Coronagraph Technology Demonstration PSF Reference Stars

Thayne Currie, Jie Li, Mona El Morsy, Olivier Guyon, Julien Lozi, Erica Dykes, Danielle Bovie, Sebastien Vievard et al.

We present deep, SCExAO/CHARIS high-contrast integral field spectroscopy and archival imaging of four candidate Roman Coronagraph PSF reference stars within/near the Roman Continuous Viewing Zone and potentially suitable for the Coronagraph's key technology demonstration targets HIP 71618 and HIP 54515. For CHARIS data, we achieve 5-$σ$ contrasts down to $\sim$1.4$\times$10$^{-5}$, $\sim$6$\times$10$^{-6}$, and 10$^{-6}$ to 4$\times$10$^{-7}$ at 0\farcs{}16, 0\farcs{}25, and 0\farcs{}5 to 1\arcs…

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astro-ph.EP

A Statistical Mechanics Model for Stable Rings Outside the Roche Limit

Jack T. Dinsmore

Stellar occultations have revealed two rings around the dwarf planet Quaoar outside the Roche limit. Simulations suggest that the rings are sustained by large velocity dispersions. We present the first analytical, first-principles theory that extends the Roche limit to describe planetary rings with large velocity dispersion. The underlying principle is an analogy between a liquid/gas phase transition and the moon/ring transition: just as high temperatures can boil a liquid under pressure, high v…

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astro-ph.HEgr-qc

Extreme-Mass-Ratio Inspirals in Gaseous Disks

Alexander J. Dittmann, Abhishek Hegade K. R., Callum W. Fairbairn

Gravitational waves from extreme mass ratio inspirals (EMRIs) are precise probes of the environment of the supermassive black holes (SMBHs) they orbit. If an SMBH is actively accreting, the surrounding gaseous disk can impart hydrodynamic torques on and assist the formation of EMRIs within it. Such disk-EMRI interactions could leave measurable imprints on future observations by the Laser Interferometer Space Antenna (LISA), and potentially provide a route to constrain disk properties using gravi…

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astro-ph.SRastro-ph.GA

Sr and Ba yields of the First Generation(s) of stars: Constraints from metal-poor stars

Sarah Hughes, Anna Frebel, Xiaowei Ou, Alexander Yelland, Felicia Xiao, Jorian Benke, Kali Kraus, Reidyn Wingate et al.

We present our chemical abundance analysis of ten new extremely metal-poor stars with $-4.05\leq\mbox{[Fe/H]}\leq-2.33$, based on high-resolution (R $\sim28,000$) Magellan/MIKE spectra. Eight of our stars have low heavy-element abundances of $\mbox{[Sr/H]}<-4.5$ and $\mbox{[Ba/H]}<-4.0$, making them Small Accreted Stellar System (SASS) stars. Four are hyper neutron-capture-element poor with $\mbox{[Sr/H]}<-5.0$, including Gaia DR3 5729400267359655680, which sets a new record for the lowest detec…

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astro-ph.HE

Broadband emission of microquasar remnants

Leandro Abaroa, Gustavo E. Romero, Valentí Bosch-Ramon

Microquasar remnants (MQRs), the long-lived cocoons inflated by extinct microquasar jets, have recently been proposed as hidden Galactic PeVatrons capable of producing ultra-high-energy gamma rays without an active central engine. While hadronic interactions can account for bright gamma-ray emission from nearby clouds, the direct detection of MQRs remains challenging because their intrinsic emission is expected to be extended and of low surface brightness. In this work, we explore the broadband…

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astro-ph.GA

Diverse ionized gas conditions in a dynamically hot, interacting galaxy at $z = 9.31$ revealed by JWST/NIRSpec IFU

Ryota Ikeda, Takahiro Morishita, Massimo Stiavelli, Antonello Calabrò

We present a spatially and spectrally resolved study of an interacting galaxy, Gz9p3 at $z=9.31$, using the James Webb Space Telescope NIRSpec/G395H IFU observation with high-spectral resolution ($R\approx 2700$) mode. Gz9p3 consists of two sub-regions (`core' and `tail'), which show stark contrast in their physical properties. The HII regions in the core are characterized by high electron density ($n_{e}\gtrsim2900$ cm$^{-3}$), low gas-phase metallicity ($0.25$ dex below the mass-metallicity re…

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astro-ph.GAastro-ph.HE

Interacting stellar winds feeding Sgr A*: from the system of mass-losing stars to the binary IRS 16SW

Diego Calderón, Jorge Cuadra, Christopher M. P. Russell, Andreas Burkert, Stephan Rosswog, Mayura Balakrishnan

The discovery of cold structures around Sgr A* has challenged our understanding of the gas dynamics and thermodynamic state of the plasma in its vicinity. This work aims to constrain the conditions for the formation of such structures, namely the cold disc-like structure and the recently discovered G-1-2-3 complex. We conduct hydrodynamic simulations of the observed Wolf-Rayet stars feeding Sgr A*. Our simulations show that the plasma chemical composition is crucial for determining the medium pr…

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astro-ph.HE

The Gamma-ray Burst Jet Energy Distribution Suggests A Quasi-universal, Weakly Magnetized Jet Evolving Over Cosmic Time

Nicole M. Lloyd-Ronning, Fabio De Colle, Gal Birenbaum, Omer Bromberg, Jarrett Johnson

We present distributions of gamma-ray burst observed and inferred properties for those GRBs with redshifts. We show that the isotropic energy distribution, which spans over four orders of magnitude, can be reproduced reasonably well under a simplistic assumption that every observed GRB originates from a quasi-universal jet with roughly the same decreasing power-law profile of energy as a function of angle, with a power-law index of $ 3 \lesssim ζ\lesssim 4$. The spread in the observed distributi…

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astro-ph.EP

GEMS JWST: Hold on to your HATS(-6 b), a sub-solar metallicity giant planet with water, methane and ammonia in its atmosphere

Giannina Guzmán Caloca, Caleb I. Cañas, Nicole L. Wallack, Erin M. May, Shang-Min Tsai, Simon Müller, Ravit Helled, Shubham Kanodia et al.

HATS-6 b is one of several recently discovered Giant Exoplanets orbiting M-dwarf Stars (GEMS) and is part of a JWST survey that aims to compare bulk and atmospheric properties of these rare planets against their FGK star counterparts. HATS-6 b is a warm ($\mathrm{T_{eq}}\sim700$ K), Saturn-mass ($M_p\sim0.3~\mathrm{M_J}$), Jupiter-radius ($R_p\sim1~\mathrm{R_J}$) planet that transits its star every $\sim$ 3 days. In this study, we present the transmission spectrum of HATS-6 b obtained with two t…

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astro-ph.GAastro-ph.SR

A comprehensive cluster census of Orion. An application of the Significance Mode Analysis (SigMA) algorithm

Alena Rottensteiner, Sebastian Ratzenböck, João Alves, Stefan Meingast, Sebastian Hutschenreuter

Precise astrometric surveys and modern clustering algorithms are working in step to transform our view of star-forming regions. By revealing a much richer substructure than previously accessible, they pave the way for reconstructing star formation histories by accurately resolving and age-dating individual sub-populations. The Orion star-forming complex is the best-studied stellar nursery in the solar neighborhood and the nearest one currently forming massive stars. Even so, a comprehensive char…

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astro-ph.EP

Causes of Hot Jupiter Inflation from Causal Discovery

Zehao Jin, Mohamad Ali-Dib, Yujia Zheng, Mario Pasquato, Benjamin L. Davis, Andrea V. Maccio

Hot Jupiters often have radii larger than predicted by standard cooling--contraction models, but it remains unclear which process supplies or preserves the extra internal heat. We analyze 328 short-period giant planets with measured $M_p$, $R_p$, $P_{\rm orb}$, and host-star $T_{\rm eff}$ using causal discovery, a statistical framework that asks which observed properties remain directly connected to planet radius after the others are accounted for. As a check, the same pipeline recovers the expe…

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astro-ph.HE

General relativistic hydrodynamics of stellar tidal disruptions in Kerr spacetime: methods, validation, and first applications

Diego Calderón, Stephan Rosswog

The disruption of a star by the tidal field of a super-massive black hole may provide insights into dormant and otherwise hard-to-study galactic nuclei. State-of-the-art numerical tools have not converged on the importance of the strong relativistic effects in the disruption of stars by potentially spinning black holes. We present a specialised numerical tool to perform global hydrodynamic simulations of stellar tidal disruptions in curved spacetimes. We quantify the role of impact strength and…

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astro-ph.HEastro-ph.IM

Resolving Nearby Supermassive Black Holes with the Black Hole Explorer

Yuto Akiyama, Kazunori Akiyama, Dominic W. Pesce, Daniel C. M. Palumbo, Angelo Ricarte, Paul Tiede, Marvin N. Martinez, Hikaru Yoshida et al.

Recent Event Horizon Telescope results have demonstrated unique and transformative science in gravitational physics and black hole astrophysics enabled by event-horizon-scale imaging of supermassive black holes (SMBHs). Nevertheless, the angular resolution of current ground-based very long baseline interferometry (VLBI) arrays limits such studies to only two sources, precluding systematic investigations of horizon-scale emission across a nearby SMBH population. The proposed Black Hole Explorer (…

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astro-ph.HEastro-ph.GA

Probing the $γ$-ray emission region and the connection to jet ejections in NRAO 150 with VLBI

L. C. Debbrecht, G. F. Paraschos, E. Ros, I. Agudo, T. P. Krichbaum, H. Müller, S. G. Jorstad, A. P. Marscher et al.

Relativistic jets launched by active galactic nuclei are fundamental for understanding the physics of accreting supermassive black holes and their immediate environments, yet the origin of these jets remains an open question. NRAO 150 is a blazar with a complex relativistic jet morphology that evolves on short timescales due to strong projection effects, enabling detailed kinematic analysis. In this study, we utilise data by the Very Long Baseline Array and the European VLBI Network from 2010 un…

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astro-ph.HE

A JWST/MIRI Study of Dust in a Sample of Normal Type IIP Core Collapse Supernovae

Bhagya M. Subrayan, David J. Sand, Olivia Culbert, Jennifer E. Andrews, Jeniveve Pearson, Griffin Hosseinzadeh, Saurabh W. Jha, Stefano Valenti et al.

Core collapse supernovae (CCSNe) are invoked as major dust producers in the early Universe, yet the amount of dust they form, the timescale over which it grows, and the physical conditions that regulate the yield remain uncertain. We present a detailed JWST/MIRI mid-infrared (MIR) imaging census of 11 nearby Type IIP CCSNe spanning $\sim$1-7 yr after explosion, investigating dust emission across the different phases of their evolution. The spectral energy distributions show a coherent evolution…

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astro-ph.HE

The first comprehensive spectral and timing study of the ultra-compact X-ray binary 4U 1812-12 with NICER and NuSTAR

Swarnendu Jana, Aditya S. Mondal, Aru Beri, Gulab C. Dewangan

The source 4U 1812-12 is a persistent, weakly variable low-mass X-ray binary containing a neutron star. The source was observed by NICER between 2019 and 2021 and, more recently, by NuSTAR in 2025. During the NICER and NuSTAR observations, the source was detected in a hard spectral state with a bolometric luminosity of $\sim 1.90\times 10^{36}$ ergs s$^{-1}$. Its $3-70$ keV NuSTAR spectrum is characterized by a soft thermal emission from the disc, a hard Comptonized emission from the corona, and…

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astro-ph.GA

Identifying AGNs from X-ray detections$-$II: Metallicity calibrations for the $\rm N_2O_2$ and $\rm N_2S_2$ diagnostics

Mark Armah, O. L. Dors, Rogério Riffel, M. V. Cardaci, G. F. Hägele, Rogemar A. Riffel, J. M. Vílchez

Emission-line ratios from ions with nearly identical ionization potentials offer a robust solution to the degeneracies inherent to traditional active galactic nuclei (AGNs) metallicity diagnostics. We introduce new semi-empirical metallicity calibrations for the $\rm N_2O_2$ and $\rm N_2S_2$ diagnostics, explicitly designed to isolate the chemical abundance from the incident radiation field. By coupling an extensive grid of CLOUDY photoionization simulations directly to the intrinsic 2$-$10 keV…

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astro-ph.SRastro-ph.GA

Eta Carinae's historical light curve: evidence for cyclic Roche lobe overflow from the primary star

Augusto Damineli, Leonardo A. Almeida, Francisco J. Jablonski, Eduardo Fernández-Lajús, Felipe Navarete, Eder Martioli, Gerd Weigelt, Rodrigo Capobiango et al.

The large amount of ground-based photometric measurements of $η$ Carinae obtained since 1940 have remained problematic for quantitative modeling due to the blending of flux from the stellar core and the surrounding circumstellar nebula. In the era of the Hubble Space Telescope, spatially resolved imaging & spectrophotometry have enabled disentanglement of these components, allowing recovery of the stellar core $V$-band brightness from ground-based observations. We isolate the $V$-band fluxes of…

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astro-ph.EP

Eclipse Timing of the Eccentric Planet HD 80606b with JWST: Constraints on a Second Planet and other Dynamical Effects

Charles Beichman, Billy Quarles, B. J. Fulton, Nikole Lewis, Ryan Challener, Julien de Wit, Malena Rice, Julie Inglis et al.

A variety of effects can perturb the orbital properties of single planets in close orbits around their host stars. HD80606 b is a highly eccentric ($ε$=0.93) exoplanet orbiting its host G5V star, HD80606. HD80606 b became a compelling target for exoplanet research after (Laughlin et al 2009) discovered that the 4.16 MJup planet transits and is eclipsed by HD80606, thereby enabling photometric and spectroscopic observations to yield a wealth of information about the object. The exquisite precisio…

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astro-ph.GA

JWST Whirlpool Galaxy Treasury: Mid-Infrared Emission in M51 and its Relation to Gas Column and Star Formation

Mansi Padave, Karin M. Sandstrom, Daniel A. Dale, Adam K. Leroy, Eric W. Koch, Tony D. Weinbeck, Angela Adamo, Jessica Sutter et al.

Using JWST/MIRI imaging of M51 in eight broadband filters, we investigate correlations of mid-infrared emission from polycyclic aromatic hydrocarbons (PAHs) and dust continuum with molecular, atomic, and ionized gas traced by CO(1-0), HI, and Pa-alpha, respectively. In molecular gas-dominated regions, PAH-dominated filters (F560W, F770W, F1130W, F1280W) exhibit near-linear correlations with CO(1-0) at 40 pc scale, indicating that PAHs are well-mixed with gas and experience relatively constant ra…

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astro-ph.GA

A Critical Eddington Ratio for X-Shaped Radio Galaxies

David Garofalo

We derive a quantitative condition for the formation of X-shaped radio galaxies by evaluating the competition between black hole spin evolution and the radiative fading of relic plasma within our previously proposed framework. The simultaneous visibility of two jet axes requires that the timescale for spin evolution across zero, t_trans, be shorter than the fading timescale of relic radio emission, t_fade. We estimate the transition timescale as t_trans about 5 million /lambda yr, where lambda i…

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astro-ph.HEastro-ph.GAastro-ph.IM

A Cross-Band (X-ray $\times$ Optical) Periodicity Search for Supermassive Black Hole Binaries: A Null Result and the First Completeness-Corrected Constraint

Karan Akbari

We present the first sample-level search for supermassive black hole binaries (SMBHBs) requiring coherent quasi-periodicity at a common period in the X-ray and optical bands, over 1194 Swift-BAT hard X-ray AGN (Stage 1) and 175 4XMM-DR14 AGN (Stage 2). No source is a co-periodic candidate. Each light curve is modelled as a damped random walk (DRW) and searched with a Lomb-Scargle periodogram and a look-elsewhere-corrected Monte-Carlo significance. Because DRW red noise is largely independent bet…

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astro-ph.HEastro-ph.GAastro-ph.IM

A Cross-Band (X-ray $\times$ Optical) Periodicity Search for Supermassive Black Hole Binaries: A Null Result and the First Completeness-Corrected Constraint

Karan Akbari

We present the first sample-level search for supermassive black hole binaries (SMBHBs) requiring coherent quasi-periodicity at a common period in the X-ray and optical bands, over 1194 Swift-BAT hard X-ray AGN (Stage 1) and 175 4XMM-DR14 AGN (Stage 2). No source is a co-periodic candidate. Each light curve is modelled as a damped random walk (DRW) and searched with a Lomb-Scargle periodogram and a look-elsewhere-corrected Monte-Carlo significance. Because DRW red noise is largely independent bet…

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astro-ph.HEastro-ph.GAgr-qc

Inclination Diffusion in Relativistic Loss Cones

Wenkang Xin

Relativistic capture and tidal disruption around a spinning black hole depend on both the magnitude and direction of the star's angular momentum, yet loss-cone models often assume fixed orbital inclinations by ignoring the associated diffusion. We show that this is not justified: for isotropic two-body relaxation near a small loss threshold, angular-momentum magnitude $L$ and inclination $x = L_{z}/L$ diffuse on comparable timescales, $t_{E} \gg t_{L} \sim t_{x}$. For Kerr capture, retaining inc…

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