UchUchU

Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.HE

Radiation Pressure Instability-Driven Variability of Line-Driven Disk Winds in AGNs: Connection to Periodic Luminosity Variations and UFO Appearance

Yutaro Kuroda, Ken Ohsuga, Mariko Nomura, Kenya Watarai

We investigated the temporal variability of line-driven disk winds induced by radiation pressure instability in accretion disks surrounding supermassive black holes. This is the first study to self-consistently couple one-dimensional hydrodynamic simulations of accretion disks with two-dimensional radiation hydrodynamic simulations of line-driven winds and to analyze their time-dependent evolution. Our results show that periodic luminosity oscillations caused by radiation pressure instability le…

Read →
astro-ph.HEastro-ph.SRnucl-exnucl-th

Supernova nucleosynthesis: a review

Shuai Zha, Yudong Luo, Zhanwen Han

Supernovae are major drivers of cosmic chemical evolution. They synthesize heavy elements and disperse them into the interstellar medium via their explosion shocks. Light elements are converted into heavier ones during both presupernova evolution and the explosive event itself. Supernova explosions generate nucleosynthesis environments rich in neutrons, protons, and neutrinos under unique thermodynamic conditions, which can enable the production of heavy elements beyond iron. Modern numerical si…

Read →
astro-ph.EP

Multi-wavelength Constraints on Dust Dynamics and Size Evolution in Protoplanetary Disk Rings. II. Observational Implications

Linhan Yang, Ya-Ping Li, Ruobing Dong, Yinhao Wu, Hauyu Baobab Liu, Kiyoaki Doi, Anibal Sierra, Greta Guidi et al.

Spatially resolved dust rings in protoplanetary disks are widely used to infer disk and dust physics from multi-wavelength continuum observations. Their interpretation, however, often neglects grain growth and the evolution of the size distribution, limiting the connection between observed ring profiles and dust-evolution parameters. Building on a physical dust-ring model that includes coagulation and fragmentation, we develop a Bayesian inference framework that jointly incorporates radiative tr…

Read →
gr-qcastro-ph.COastro-ph.HEcond-mat.stat-mech

Bridging Between Statistical Mechanics and Black Hole Evolution: Theoretical Formalism

Suvodip Mukherjee

Black holes in the Universe span nearly ten orders of magnitude in mass over a large cosmic timescale, dating back to at least the Universe's early history, when it was only a few hundred million years old. The formation and evolution of these objects remain a mystery because no direct probe can trace each black hole across the full mass range and cosmic time. This work shows, for the first time, a statistical mechanical description of black hole evolution. I show that though each black hole and…

Read →
astro-ph.IM

Design of an atmospheric dispersion corrector and double scrambler for improved fiber coupling and illumination uniformity for the HET HRS

Devika K Divakar, Joseph Strubhar, Andrew Pinckney, Phillip MacQueen

The Hobby--Eberly Telescope High Resolution Spectrograph (HET--HRS) is undergoing a major instrument upgrade to improve its performance over the 360--1000 nm wavelength range. As part of this effort, a new fiber-feed system has been developed to increase throughput and enhance illumination stability. This paper presents the optical and opto-mechanical designs of the upgraded HRS Input Head Module Package and lens-based Double Scramblers. The Input Head incorporates a static Atmospheric Dispersio…

Read →
astro-ph.GA

The Study of Detailed Morphology of Milky Way Dwarf Galaxies: Draco and Boötes I

Kyosuke S. Sato, Masafumi Yagi, Sakurako Okamoto

We present a photometric study of the outer stellar structures of the Milky Way dwarf spheroidal galaxies (dSphs) Draco and Boötes I, using deep wide-field imaging data. The old main-sequence stars are used to trace their spatial distributions beyond their tidal radii. We derive global structural parameters and radial profiles of number density, ellipticity, and position angle from their stellar distributions. Draco and Boötes I show contrasting features. Draco shows no prominent extended stella…

Read →
astro-ph.SR

The Variation of Circumstellar Parameters through Early Stellar Evolution

Michael Connelley, Christian Flores, Bo Reipurth

We report on the evolution of extinction, mass accretion rate, and spectral index from analysis of SpeX observations and AllWISE spectral energy distributions, compared to stellar parameters (mass, age, and veiling) derived from analysis of previously reported and newly analyzed iSHELL observations of the same young stellar objects (YSOs). By using stellar gravity as an age indicator, we are able to infer age without any assumptions about the circumstellar environment. Our sample consists of 109…

Read →
gr-qcastro-ph.HE

Charging of rotating black holes: kinetic simulations of black hole magnetospheres

Martin Kološ, Farukh Abdulkhamidov, Arman Tursunov, Jorge A. Rueda, Benoît Cerutti

Whether a rotating black hole (BH) immersed in an external magnetic field charges up to the Wald value $Q_{\rm W}=2aMB$, where $M$ and $a$ are the BH mass and spin parameter, and $B$ is the strength of the external field, is a long-standing open question in BH electrodynamics, with consequences for charge separation, particle acceleration and the structure of BH magnetospheres. We address it with axisymmetric general-relativistic particle-in-cell simulations performed with GRZeltron, including s…

Read →
astro-ph.SR

Characterizing bright $δ$ Scuti pulsators using TESS light curves:II. Pulsation amplitude and energy distributions

Prasad Mani, Timothy Bedding, Simon Murphy, Daniel Hey, Tom Love

Pulsations in $δ$ Scuti stars exhibit a wide range of excited frequencies and amplitudes, but the underlying principles governing their amplitude distribution remain unclear. We revisit this problem using a global, energy-based perspective. For a complete sample of 3200 bright $δ$ Scuti stars observed by TESS, integrated power spectral density (PSD) of the Fourier spectrum allows us to measure the overall pulsation signal. From this, we derive a proxy for the total pulsation energy. We uncover a…

Read →
astro-ph.HEastro-ph.COhep-ph

Right Energy, Wrong Profile: Why the 43 GeV Cluster Line Is Unlikely to Be Dark Matter

Stefano Profumo

A narrow gamma-ray line would be a distinctive signature of dark matter, but its interpretation depends as much on its spatial distribution as on its energy. We reanalyze the reported 43 GeV feature in Fermi-LAT observations of Virgo, Fornax, and Ophiuchus. The excess is reproduced in the same public data and survives event-type partitions, a test using data withheld from the original selection, and detector-coordinate permutation tests. Realistic hadronic and inverse-Compton emission is too bro…

Read →
astro-ph.IM

RAMA: A new agile AO bench for the telescope FEELINGS

Matteo Pasinetti, Rodrigo Andres Munoz Gomez, Benjamin Andres Gonzalez Barraza, Francisco Oyarzun, Sylvain Cetre, Jean-François Sauvage, Axel Vincent-Randonnier, Julien Charton et al.

The ground-based observation of extended objects such as satellites suffer from severe atmospheric propagation constraints. Specifically, high tracking velocities and low-elevation lines of sight generate non-stationary turbulence alongside strong scintillation. Developing robust wavefront control strategies is therefore critical to maintain stable observations. In this context, we present RAMA, an adaptive optics (AO) testbench deployed on ONERA's 60\,cm FEELINGS telescope. Designed as a pathfi…

Read →
astro-ph.GA

CNN-Based Inference of Gaseous Halo Properties from Synthetic X-ray and 21-cm HI Observations

Kalvyn N. Poncelet Adams, Benjamin D. Oppenheimer, Naomi Gluck, Caleb Ogle, Matthew Ho, Daisuke Nagai

Quantifying the information content in multi-wavelength observations is critical for setting exposure times for upcoming X-ray and 21-cm HI radio surveys. We train convolutional neural networks (CNNs) on mock observations of halos from the IllustrisTNG100 and TNG300 simulations, combining data from soft X-ray channels from a CCD or a microcalorimeter with HI intensity, velocity, and dispersion maps, to infer halo mass, gas fractions, metallicity, and [O/Fe] abundance. Multi-band (X-ray and HI) c…

Read →
astro-ph.GA

SAMI and TNG-Cluster: tracing galaxy spin and environmental transformation across cluster phase-space and cosmic time

Gustavo F. Gonçalves, Ilaria Marini, A. Fraser-McKelvie, Natan de Isídio, Rubens E. G. Machado, Richards P. Albuquerque, Daudi T. Mazengo

The dense environment of galaxy clusters suppresses star formation and alters the kinematic properties of infalling satellites through gas stripping, tidal interactions, gravitational harassment and starvation. Projected phase-space diagrams connect the present-day distribution of cluster galaxies to their accretion histories. We combine SAMI Galaxy Survey integral field spectroscopy with the TNG-Cluster simulation to investigate how the stellar spin parameter ($λ_R$), $(g-i)$ colour, and sSFR v…

Read →
astro-ph.IM

Commissioning the AIP's ultrafast laser Inscription facility: defining the parameter space for type-I waveguide fabrication

Rima Islam, Aline N. Dinkelaker, Abani Shankar Nayak, Kalaga Madhav, Martin Roth

Astrophotonics offers a compact, stable alternative to bulk optics in traditional astronomical instrumentation, spanning high-precision spectroscopy to high-contrast interferometry. However, the strict requirements for throughput, accuracy, precision, and stability require tailored manufacturing processes that go beyond standard telecommunications technology. This work presents the iterative experimental and statistical methods used to determine the optimal laser-writing conditions for passive w…

Read →
astro-ph.IM

Optomechanical design of an ADC and image rotator for the HJST Coudé Spectrograph at McDonald Observatory

Devika K Divakar, Phillip MacQueen, Andrew Pinckney, Joseph Strubhar

High-resolution spectroscopic observations require stable slit illumination and mitigation of atmospheric refraction effects that degrade throughput and spectral fidelity. We present the optical and mechanical design of a Rotational Atmospheric Dispersion Corrector (RADC) for the coudé Tull Spectrograph on the Harlan J. Smith 2.7 m Telescope. Atmospheric dispersion introduces wavelength-dependent image displacement that increases with zenith distance and reaches approximately 4 arcsec across the…

Read →
astro-ph.HEastro-ph.SR

Properties of the circumstellar matter around the pair-instability supernova candidate SN 2018ibb revealed by its light curve

Takashi J. Moriya, Steve Schulze, Alexander Heger, Sergei I. Blinnikov, Marat Sh. Potashov

SN 2018ibb is one of the best pair-instability supernova (PISN) candidates identified to date. It, however, showed unexpected blue flux excess in late-phase spectra, likely originating from the interaction between supernova (SN) ejecta and dense circumstellar matter (CSM). We develop synthetic light-curve models of PISNe interacting with dense CSM and estimate the CSM properties of SN 2018ibb by comparing the synthetic and observed light curves. We found that the bolometric luminosity evolution…

Read →
astro-ph.GA

NOCTURNE. II. Extreme radio variability in the heart of early-stage active galactic nuclei

Emilia Järvelä, Patrizia Romano, Anne Lähteenmäki, Marco Berton

We report the discovery of extreme 37 GHz radio variability in early-stage active galactic nuclei (AGN). Most of these sources belong to the class of narrow-line Seyfert 1 (NLS1) galaxies, which harbour fast-growing, low-mass supermassive black holes that accrete at high Eddington ratios. At 37 GHz, these extraordinary AGN exhibit amplitude variability of three to four orders of magnitude over timescales of a few days. Notably, despite several attempts, we have not detected relativistic jets in…

Read →
astro-ph.SR

Using Gravity as an Age Indicator for Young Stars

Michael Connelley, Christian Flores, Bo Reipurth

The age of a young star is difficult to measure and yet is a fundamental property that is essential for understanding stellar evolution. Accurate age indicators across the early phases of low-mass stars are scarce and often rely on properties of the circumstellar environment. We investigate stellar surface gravity as a practical age estimator from the class I to the class III phases of low-mass stars. Gravity increases monotonically as young stars descend their Hayashi tracks. Gravity is a physi…

Read →
astro-ph.HE

Determination of the Angular Distributions of Dynamical and Emission Parameters of GRB Relativistic Outflows

A. Panaitescu

A previously-developed analytical treatment of the "Larger-Angle Emission" model for GRBs and afterglows is further developed to include the effect of a fixed magnetic field orientation. This model, has the uncanny ability to unify the prompt and delayed emissions and to account easily for the entire diversity of Swift X-ray light-curves. The LAE model is applied to seven GRBs (060526, 060614, 060714, 060729, 061007, 061121, 100902, 130427A) with well-sampled 0.3 keV/10 keV Swift/XRT and optical…

Read →
astro-ph.GA

Disentangling Stellar Mass and Environmental Effects on eROSITA AGN Activity using multi-wavelength data from GAMA, WISE, GALEX, and DESI Legacy Survey

Navya Saraswat, Shadab Alam, Subhabrata Majumdar

We use a stellar-mass complete sample of $\sim 36{,}000$ galaxies from GAMA/eFEDS to test whether AGN activity depends on environment independent of stellar mass. To isolate this effect, we introduce $δ_{\rm rank}$, a novel local overdensity metric defined within narrow stellar mass bins. Our main result is that X-ray-selected AGNs show a clear environmental trend, the AGN fraction rises from $\sim 4\%$ in low-density regions to $\sim 6\%$ in high-density regions, with a sharp transition at $δ_{…

Read →
astro-ph.HEhep-ph

Neutron Star Merger Universality Relations for a Quark--Hadron Crossover Equation of State

Wei Sun, Grant J. Mathews, Atul Kedia

A crossover transition from hadronic to quark matter during the merger of neutron stars can lead to interesting observational consequences in the emergent gravitational radiation. In particular, the increased pressure in the crossover density region ($2-5$ times the nuclear saturation density) can lead to an extended duration of high-frequency ($\sim 2-3.5$ kHz) gravitational wave emission during the post-merger epoch. We study the universality relations for a variety of equations of state with…

Read →
astro-ph.SR

The Post-Outburst Spectrum of L1415-IRS

Lynne A. Hillenbrand, Thomas P. Greene, Evan R. Portnoi, Bringfried Stecklum

We present near-infrared spectroscopic observations of L1415-IRS, a Class I type young stellar object that underwent a factor of $>$30 photometric outburst in the early 2000s. Ours is the first reported spectroscopy of this deeply embedded source. Both components of L1415-IRS present continuum plus $H_2$ emission. The southern component has additional weak HI Br$γ$ and $CO$ emission. Based upon our spectrum and evidence of a declining lightcurve, we hypothesize that either: the outburst was not…

Read →
astro-ph.HEastro-ph.GAastro-ph.SRgr-qc

Formation of Merging Black Hole Binaries Inside Massive AGN Stars

Sizheng Ma, Douglas N. C. Lin, David A. Velasco-Romero

Stars embedded in the disks of active galactic nuclei (AGN) can grow to hundreds of solar masses, and the same disks are expected to host a population of stellar-mass black holes. A star may therefore capture passing black holes, turning its interior into a potential factory for forming compact binary black hole systems and, ultimately, for the gravitational-wave events seen by our detectors. We test how readily this channel operates using three-dimensional hydrodynamic simulations of black hole…

Read →
astro-ph.GA

Cosmic Noon Galaxies in the Hubble Ultra Deep Field with MIRI Wide-Field Slitless Spectroscopy

S. Kendrew, G. Östlin, L. Colina, P. Rinaldi, J. Álvarez-Márquez, L. A. Boogaard, J. Melinder, J. P. Pye et al.

We present results from a survey of the Hubble Ultra-Deep Field using the Wide-Field Slitless Spectroscopic (WFSS) capability of the Mid-Infrared Instrument (MIRI) on JWST, demonstrating the capabilities of this new mode. We describe the data reduction and calibration methodology, and estimate calibration uncertainties. From our observations we obtain spectra of 47 galaxies with confirmed spectroscopic redshifts, with a maximum z_spec of 3.712. In the final sample we target in particular the 3.3…

Read →
gr-qcastro-ph.IM

Bridging the chirp-mass gap: searching for gravitational waves from inspiraling ultra-compact binaries using LIGO O4ab data

Andrew L. Miller

Gravitational-wave searches for subsolar-mass compact binaries have left a gap between the planetary-mass regime accessible to long-duration searches and the higher masses probed by conventional compact-binary analyses. We close this gap by searching for the inspiral of ultra-compact binaries with chirp masses $10^{-2}$--$10^{-1}\,M_\odot$ in LIGO O4ab data. Using the statistically robust BinaryGFH-v2 method, a time-frequency technique to search for rapidly evolving inspirals lasting minutes to…

Read →
gr-qcastro-ph.IM

Bridging the chirp-mass gap: searching for gravitational waves from inspiraling subsolar-mass ultra-compact binaries using LIGO O4ab data

Andrew L. Miller

Gravitational-wave searches for subsolar-mass compact binaries have left a gap between the planetary-mass regime accessible to long-duration searches and the higher masses probed by conventional compact-binary analyses. We close this gap by searching for the inspiral of ultra-compact binaries with chirp masses $10^{-2}$--$10^{-1}\,M_\odot$ in LIGO O4ab data. Using the statistically robust BinaryGFH-v2 method, a time-frequency technique to search for rapidly evolving inspirals lasting minutes to…

Read →
astro-ph.EP

What the Solar System Can Teach Us About Rocky Exoplanets

Paul K. Byrne, Claire Marie Guimond, Peter A. Cawood, Michael J. Way, Doris Breuer, Tilman Spohn, João C. Duarte, Diogo L. Lourenço et al.

The number of rocky extrasolar planets being discovered continues to increase, but so too does the apparent diversity of such worlds. As we work to understand the likely bulk properties and thermal, geological, and climatological attributes we might expect of rocky exoplanets, we can look to the Solar System for guidance. Here, we review the interior, surface, and atmospheric characteristics of modern Earth, and discuss how our homeworld has changed through Solar System history. We then visit in…

Read →
astro-ph.GAastro-ph.CO

Gravitational Wave Bias in IllustrisTNG300 from Machine-Learned Population-Synthesis Calibrated Merger Rates

Dorsa Sadat Hosseini, Taisiia Karasova, Nikshay Chugh, Alex Krolewski, Ghazal Geshnizjani

The large scale clustering of gravitational wave (GW) sources offers an independent probe of cosmology and compact-binary astrophysics. Interpreting future GW clustering measurements requires understanding how merger rates depend on host-galaxy properties and environment. We develop a simulation-based framework to model the clustering of binary black hole (BBH) mergers and estimate the corresponding GW bias. We populate IllustrisTNG300 with GW sources using a machine-learning emulator trained on…

Read →
astro-ph.GAphysics.plasm-ph

Filament Formation via Collision-induced Magnetic Reconnection -- Kinematic Features

Shuo Kong, Griselda Arroyo-Chávez, Volker Ossenkopf-Okada, Héctor G. Arce, Ralf S. Klessen, Duo Xu, Szu-Ting Chen

The Collision-induced Magnetic Reconnection (CMR) mechanism has recently been proposed as a filament formation model that emphasizes the active role of magnetic fields. To enable better observational tests with data from modern telescopes, we provide more specific observable predictions for filaments formed via CMR. Two types of CMR kinematics are revealed in position-velocity (PV) diagrams. First, due to the nature of CMR, the midplane contains a {\it converging motion} close to the filament an…

Read →
astro-ph.EPastro-ph.SR

Rescuing Kepler's False Positives: A Possible Habitable Zone Exoplanet in the Triple Star System KOI-1623

Rita Lanxuan Wang, Daniel Huber, Daniel Hey, Nathanael Burns-Watson, Alexander Larsen, Adam Kraus, Trent J. Dupuy, Steven Giacalone et al.

The Kepler mission has significantly advanced our understanding of exoplanet demographics. However, Kepler planet candidates showing centroid shifts are often classified as false-positives and thus excluded from demographic analyses. Some of these systems may be erroneous false positives, resulting from unresolved binary stars with planets orbiting one of the stars, thereby introducing biases into past exoplanet demographic studies. Here, we present updated Kepler centroid offset values derived…

Read →