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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.HE

Evolution of Main Sequence Stars Transferring Mass to a Supermassive Black Hole

Andrey Sandomirsky, Re'em Sari, Aleksandra Olejak, Selma E. de Mink

We consider main-sequence stars orbiting close to a supermassive black hole (SMBH), which are potential gravitational wave (GW) sources for LISA if their orbital periods are of the order of an hour. At such a short orbital period, mass transfer from the star to the SMBH occurs. The evolution of the semi-major axis and GW frequency depends on the evolution of the stellar mass and radius. We use MESA to study stars that transfer mass to SMBHs similar to Sagittarius A* starting on the zero-age main…

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astro-ph.SR

Cycle Variation in the Occurrence of Great Soft X-ray Solar Flares

V. N. Obridko, M. M. Katsova, D. D. Sokoloff

Powerful nonstationary processes such as flares and coronal mass ejections are detected mainly near the solar cycle maxima. However, the analysis of the great flares since 1975, when the GOES monitoring started, leads us to more precise conclusions. We have traced the latitudinal distribution of X-class flares and their dependence on the phase of the cycle throughout four cycles. Besides, we compared directly their positions with the magnetic field structure. It was found that the relatively wea…

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astro-ph.GAastro-ph.COastro-ph.IM

TDCOSMO XXX: Spatially resolved kinematics of the deflectors in time-delay lens systems B1608+656 and SDSSJ1206+4332 from JWST-NIRSpec observation

Pritom Mozumdar, Shawn Knabel, Anowar J. Shajib, Tommaso Treu, Michele Cappellari, Aymeric Galan

We present spatially resolved stellar kinematics of the deflector galaxies in two time-delay lens systems, B1608+656 and SDSS J1206+4332, measured from JWST NIRSpec integral field spectroscopy. B1608+656 is a quadruply imaged quasar lensed by a pair of tidally interacting galaxies, the primary deflector (G1) and a close companion (G2), for which we quantified G2's tidal influence on G1 and define a criterion identifying the region where this perturbation is negligible and standard Jeans-equation…

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astro-ph.EP

Beyond Pebble Isolation: Diverse Pathways to Giant Planet Formation Across Stellar and Orbital Scales

Lorenzo Peerani, Sho Shibata, Ravit Helled

Context. Giant planet formation requires reaching crossover mass, i.e., when the mass of the gaseous envelope becomes equal to the mass of the core, within the disc's lifetime. The formation process depends critically on the orbital distance and stellar mass. Aims. We simulate planet formation via pebble accretion up to crossover mass around stellar hosts with masses of 0.1-1.5 Msun, considering a range of formation locations, with and without Type I migration. Methods. We use a modified version…

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

The future of high-resolution UV spectroscopy: Science with a UV Échelle spectrograph on the Habitable Worlds Observatory, or a dedicated mission

Annalisa De Cia, David Cont, Kevin Heng, Boris Gänsicke, Frank Grupp, Ralf Bender, Helena Lamprecht, Frances H. Cashman et al.

High-resolution UV spectroscopy serves a diversity of science cases, from small bodies to planets, stars, and galaxies, but is currently limited to the Hubble Space Telescope and bright targets. Major advances require increasing sensitivity by at least one order of magnitude. Here we present the UV science cases for PEGASUS (Planets, Earths, Galaxies, And Stars UV Spectrograph), a UV Échelle high-resolution spectrograph concept, with $R = λ/δλ\sim 100\,000$ (full range 10 000-140 000) and coveri…

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astro-ph.SR

Chromospheric and Transition Region Responses of activities at the base of Coronal Plumes

Biswanath Malaker, Vishal Upendran, Durgesh Tripathi

We present the identification of the co-spatial and co-temporal small scale jets -- sometimes also named as jetlets -- at the base of the coronal hole plume associated with chromospheric and transition region (TR) flows. We identified 19 jets with coordinated observations recorded on March 19, 2016 using the Solar Dynamics Observatory (SDO) and the Interface Region Imaging Spectrograph (IRIS). Our analysis of \ion{Si}{4} 1393.7~Å line suggests blueshifts mostly in the range of 10 to 33~km~s$^{-1…

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astro-ph.HEastro-ph.IM

cuDART: a GPU-accelerated ray tracing code for generating synthetic observations of relativistic astrophysical sources

Henry Whitehead, Emma L. Elley, Christoper N. Everett

The generation of synthetic observations is required to compare simulations of astrophysical phenomena with real sources. We present a new open-source toolkit cuDART which allows meshed simulation data to be rapidly rendered into synthetic observations of optically thin emission, automatically accounting for a range of relativistic and geometric effects such as Doppler boosting. Unlike previous visualisation schemes which generally consider a single snapshot in time, cuDART is capable of account…

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astro-ph.EP

A Stellar-Type Dependence in the Rocky and Volatile Composition of Small Exoplanets

Ji Wang, Caroline Dorn, Komal Bali

We investigate the rocky and volatile composition of small exoplanets by modeling the population-level distribution of densities using a mixture framework that links interior structure models to observable quantities. We analyze three complementary samples spanning different stellar environments: the Luque \& Pallé M-dwarf sample, the DACE M-dwarf sample, and the DACE FGK sample. We consider a log-normal parameterization, which captures a characteristic core mass fraction (CMF) and the intrinsic…

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astro-ph.HEastro-ph.CO

Electromagnetic Emission and Orbital Evolution of Eccentric Supermassive Black Hole Binaries in Retrograde Disks

David ONeill, Mark J. Avara, Christopher Tiede, Daniel J. DOrazio, Zoltan Haiman, Andrew MacFadyen

Circumbinary disks around supermassive black hole binaries (SMBHBs) are expected to form across a broad range of inclinations, with retrograde configurations potentially a common occurrence. Here we present the first grid-based hydrodynamical simulations of retrograde circumbinary disks around eccentric SMBHBs, solving an energy equation that balances viscous and shock heating against blackbody radiative cooling. We investigate different initial disk Mach numbers $\mathcal{M}_a \in \{10, 20, 40\…

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astro-ph.HE

Free Neutron Decay in Kilonova Ejecta: X-ray/UV Flashes with Non-Thermal Effects

Daniel Brethauer, Daniel Kasen, Smaranika Banerjee, Raffaella Margutti, Ryan Chornock

Neutron star-bearing compact-object mergers can create a kilonova, a transient powered by the radioactive decay of material synthesized via rapid neutron capture ($r$-process). During the merger, a fraction of the ejecta is launched at high speeds ($\gtrsim$ 0.4c) that can lead to neutrons evading capture onto seed nuclei, resulting in free neutrons. The free neutrons then decay and inject additional energy that power early-time ($\lesssim$1 day) emission. Here, using \texttt{Sedona}, we present…

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astro-ph.COastro-ph.GAphysics.comp-ph

JZ-FMM: GPU-native differentiable N-body simulations with the Fast Multipole Method

Jens Stücker, Oskar Foldal

N-body simulations are an essential tool for modelling the evolution of gravitating systems. Differentiable N-body simulations allow solving complicated reconstruction problems by connecting observations of evolved systems to simple informative priors on their initial conditions. While so far most reconstruction efforts focus on mildly non-linear large scale dynamics, the internal dynamics of galaxies and clusters should exhibit rich information about their formation. The exploration of reconstr…

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astro-ph.GA

Little Dots: the ULX Analogy

Andrew King

I consider recent observations of the Little Dots (LDs) observed in high--redshift ($z\sim 7$) galaxies. I have suggested that the central black holes in these objects are probably fed mass at very super--Eddington (factors $\sim 50$) rates. In physical terms, this idea makes them supermassive analogues of the (stellar--mass) ultraluminous X--ray sources (ULXs), whose hard X--ray emission is strongly anisotropic (`beamed'). In this paper I argue that the recent discovery of extended rest--frame…

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astro-ph.GAastro-ph.CO

Exploring the AGN population in protoclusters: results from the TNG300 simulation and comparison with observations

A. Traina, F. Vito, A. Pillepich, A. Kapahtia, O. Cucciati, R. Gilli, F. Arrigoni-Battaia, C. Vignali et al.

In this work, we investigate the physical properties and cosmic evolution of galaxies and AGN in a sample of 280 protoclusters identified in the TNG300 simulation, selected to end up in $z = 0$ clusters with $M_{200, \rm c} > 10^{14} \, {\rm M_{\odot}}$. Our goal is to provide the first statistical view of AGN activity enhancement in a uniformly defined sample of overdense environments, and to identify the physical mechanisms driving it. We identify protoclusters as the progenitors of present-da…

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astro-ph.EPastro-ph.SR

The ALMA View of the Edge-on Gomez's Hamburger System: A Highly-Dynamic, Asymmetric Protoplanetary Disk Reveals the Earliest Phases of Giant Planet Formation

Charles J. Law, Jensen Lawrence, Richard Teague, Zhe-Yu Daniel Lin, Romane Le Gal, Kristina Monsch, Gordian Edenhofer, Hans Baehr et al.

Chemical tracers provide some of the strongest observational signatures of ongoing planet formation and localized dynamical perturbations in protoplanetary disks. In particular, sulfur-bearing molecules are predicted to be enhanced in regions of shock heating, ice sublimation, and gravitational instability. Here, we present high-angular-resolution ($\approx$0.$^{\prime\prime}$2) Atacama Large Millimeter/submillimeter Array observations of $^{12}$CO J=3-2, $^{13}$CO J=3-2, CS J=7-6, and SO J$_{\r…

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astro-ph.HE

Dispersion Measure Variability in Fast Radio Bursts from Photoionization

Brian D. Metzger

Magnetars became favored engines of fast radio bursts (FRBs) following the discovery of a luminous radio burst coincident with a hard X-ray flare from a Galactic magnetar. Several repeating FRB sources exhibit time-variable rotation measures and compact, spatially coincident persistent synchrotron radio emission, consistent with energetic-particle nebulae and confined by young supernova ejecta. Secular changes in the dispersion measure (DM) of repeating FRBs have also been observed, offering a c…

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astro-ph.HE

Dispersion Measure Variability in Fast Radio Bursts from Photoionization

Brian D. Metzger

Magnetars became favored engines of fast radio bursts (FRBs) following the discovery of a luminous radio burst coincident with a hard X-ray flare from a Galactic magnetar. Several repeating FRB sources exhibit time-variable rotation measures and compact, spatially coincident persistent radio emission, consistent with energetic-particle nebulae confined by young supernova ejecta. Secular changes in the dispersion measure (DM) of repeating FRBs have also been observed, offering a complementary pro…

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astro-ph.GA

Chasing Cosmic Reionization: An Extremely Faint Highly Magnified Source at $z=5.66$ with high $ξ_{\rm ion}$

Sofía Rojas-Ruiz, Matteo Messa, Eros Vanzella, Tommaso Treu, Pietro Bergamini, Giorgia Di Rosa, Marco Lombardi, Piero Rosati et al.

We present JWST NIRSpec IFU spectroscopic measurements of one of the faintest (M$_{UV}>-13.6$) known ionizing sources at $z=5.66$, dubbed Small And Lensed Source Arc, SALSA. This source is highly magnified ($μ>100$) by the lensing galaxy cluster Abell 2744, providing a unique opportunity to investigate the physical properties of faint sources in the Epoch of Reionization. We characterize SALSA's nebular emission using rest-frame UV and optical emission lines and investigate the relationship betw…

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gr-qcastro-ph.HEhep-ph

Ruling out matter-induced bumps in black-hole effective potentials

Matteo Della Rocca, Romeo Felice Rosato, Paolo Pani

Matter fields localized around black holes can produce small secondary bumps in the effective potentials governing black-hole perturbations, potentially leading to quasinormal-mode spectral instabilities and late-time echoes. Considering physically motivated models of anisotropic fluids surrounding a spherically symmetric black hole, we show that the appearance of such a secondary bump is accompanied by either singular matter profiles or divergent characteristic speeds in the fluid. These featur…

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astro-ph.GAastro-ph.HEnlin.CDphysics.class-ph

Deus Ex Statistica: A Statistical Solution to the binary-binary Outcome of the Chaotic, Non-Hierarchical Four-Body Problem

Yoav Zack, Hagai B. Perets, Yonadav Barry Ginat

We present an analytical, statistical solution to the binary-binary (2+2) outcome of the chaotic non-hierarchical four-body problem. The solution is based on the density-of-states formulation pioneered by J. J. Monaghan. The method skips the computationally expensive integration of the equations of motion, and instead samples the outcome from the chaotic phase-space, subject to conservation of energy, momentum, and angular momentum. From the joint distribution, we extract marginal distributions…

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astro-ph.EP

The GAPS programme at TNG LXXVIII. Phase-resolved detection of multiple atomic species in the atmosphere of KELT-20b/MASCARA-2b

F. Biassoni, F. Borsa, L. Fossati, M. C. D'Arpa, A. S. Bonomo, G. Guilluy, T. Zingales, D. Sicilia et al.

Among the different classes of exoplanets, ultra-hot Jupiters represent prime laboratories for atmospheric characterisation. With an equilibrium temperature of ~2300 K, KELT-20b/MASCARA-2b (HD 185603 b) is a well-studied ultra-hot Jupiter, for which several atomic species have already been detected in both transmission and emission spectroscopy. Nevertheless, important open questions remain regarding the completeness of the chemical inventory and the interpretation of spurious aliasing signals t…

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astro-ph.GAastro-ph.COastro-ph.HEastro-ph.SR

Overmassive No More: The Case for Little Red Dots Hosting Black Hole Seeds as Massive as Single Supermassive Stars

Wendy Q. Sun, Rohan P. Naidu, Hanpu Liu, Anna de Graaff, Jenny E. Greene, Jorryt Matthee, Chris Ashall, John Chisholm et al.

Little Red Dots (LRDs) display singular properties unlike any known class of AGN or galaxies, motivating novel mass estimators for their central engines. Inspired by their similarities to stellar phenomena, here we interpret the LRD continuum as being produced by a pseudo-photosphere. We fit tailored stellar atmosphere models to host-subtracted LRD central engines ("black hole stars," BH*s) represented by stacks of $117$ objects. Typical BH* continuum spectra are well fit by models in a narrow r…

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astro-ph.GAastro-ph.SR

The Ashes of Supermassive Stars: Globular Cluster-like Aluminum Enhancement in Little Red Dots

V. Kokorev, J. Chisholm, R. P. Naidu, M. Gieles, S. Finkelstein, D. Berg, H. Akins, A. Taylor et al.

The relative abundances of elements in galaxies serve as fossil records of the physical conditions and processes by which they were forged. While the Big Bang produced only the lightest elements, subsequent stellar nucleosynthesis imprinted characteristic abundance patterns onto the surrounding gas, set initially by the temperatures reached inside stars and subsequently shaped by how the processed material was mixed and released. Globular clusters - dense, ancient groups of stars - provide a str…

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astro-ph.GA

RIGEL: Ultra-faint dwarf galaxy diversity shaped by inhomogeneous cosmic reionization

Yunwei Deng, Hui Li, Ewald Puchwein, Boyuan Liu, Aaron Smith, Rahul Kannan, Federico Marinacci, Greg L. Bryan et al.

Ultra-faint dwarf galaxies (UFDs) are among the smallest and oldest galaxies in the Universe and are widely regarded as relics of cosmic reionization. To investigate how reionization quenches star formation and shapes the diversity of UFDs, we present a suite of eight cosmological zoom-in simulations of isolated UFDs with present-day halo masses of $\sim10^9\,{\rm M}_\odot$. The simulations are performed with the radiation-magnetohydrodynamic galaxy formation framework Realistic ISM modeling in…

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astro-ph.GAastro-ph.CO

A Spectral Framework for Testing the Quasi-Star Hypothesis in Little Red Dots I: Weighing LRDs by Their Super-Eddington Luminosity Ratios---No Signs of Overmassive Black Holes

Olivia Curtis, Nikko J. Cleri, Jakob M. Helton, Joel Leja, Jason T. Wright

We present a spectral test of the quasi-star hypothesis for Little Red Dots (LRDs) whereby a black hole grows inside a stellar-like envelope. We use \texttt{Prospector} to fit host galaxies and \texttt{TLUSTY} photospheres to four LRDs that show strong molecular or atomic absorption. We approximate each object's electron-scattered Eddington luminosity ratio, $φ\equiv κ_{\rm es}σT_{\rm eff}^{4}/(gc)$, and we use \texttt{MESA-QUEST} to simulate their envelopes. All four are super-Eddington at $φ=…

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astro-ph.GA

SHELLQs. Black Hole Mass and Eddington Ratio Distributions of Intermediate-Luminosity Quasars at 6<z<7

Masafusa Onoue, John D. Silverman, Yoshiki Matsuoka, Xuheng Ding, Camryn L. Phillips, Michael A. Strauss, Junya Arita, Takuma Izumi et al.

We present near-infrared spectroscopy of 21 quasars at 6.07 6 quasars identified in the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project. These quasars occupy the intermediate-luminosity regime between luminous quasars and the faint high-redshift AGNs uncovered by JWST. We detect broad Balmer emission lines and MgII 2798 with underlying continua from the NIRSpec and MOIRCS targets, respectively. The virial black hole masses of this sample span a wide range of 7.2 < log M_BH/…

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astro-ph.COastro-ph.GA

Sizing the Universe with DESI Galaxy Sizes: Plain Fundamentals of Fundamental-Plane Lensing

Kun Xu, Jiaqi Wang, Ravi K. Sheth, J. Aguilar, S. Ahlen, F. Beutler, D. Bianchi, D. Brooks et al.

Weak gravitational lensing provides a powerful way to map cosmic structure, but most current measurements rely on galaxy shape distortions from deep imaging surveys and are affected by systematics such as intrinsic alignments, photometric-redshift uncertainties and shape-measurement biases. Here we present a spectroscopic galaxy-galaxy lensing magnification measurement using Fundamental-Plane (FP) size residuals, $δ_r\equivΔ\log_{10}R_\mathrm{e}$, from 3.26 million DESI luminous red galaxy (LRG)…

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astro-ph.COastro-ph.IM

Differential Polarization Calibration: A Consistency Test for Cosmic Birefringence

Anto I. Lonappan, Brian Keating, Kam Arnold

The cosmic microwave background birefringence angle $β$ is exactly degenerate with a common instrumental polarization-angle offset. The Minami--Komatsu(MK) likelihood separates these quantities using Galactic foreground polarization, so its inferred detector angles merit a diagnostic that does not reuse the foreground-$EB$ model. We develop a birefringence-blind differential estimator from antisymmetric and symmetric cross-spectra and apply it for the first time as an explicit consistency test o…

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astro-ph.GA

The fading hierarchy of Galactic open clusters

Guimei Liu, João Alves, Yu Zhang, Emily L. Hunt, Ruqiu Lin, Josefa E. Großschedl, Efrem Maconi, Nora Wagner et al.

Galactic open clusters provide a record of both hierarchical star formation and the subsequent dynamical evolution of the Milky Way disk. We use the two-point correlation function to characterize the spatial and kinematic clustering of open clusters in the solar neighborhood, considering their three-dimensional (3D) distributions and their projections onto the Galactic plane, as well as subsamples divided by age, mass, and survey volume. We quantify the clustering through fractal dimensions and…

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astro-ph.COastro-ph.GA

TILING I: Field-level Bayesian reconstruction of cosmological initial conditions during the epoch of reionization

Nikolaos Triantafyllou, Andrei Mesinger, Steven Murray, Samuel Gagnon-Hartman

Reconstructing the initial conditions (ICs) of the matter field for an observed volume gives a complete picture of that region's temporal evolution. IC reconstruction is common at low redshifts but largely unexplored during the epoch of reionization (EoR; $z\gtrsim 5$), partly due to difficulties modeling inhomogeneous cosmic radiation fields. Yet the EoR spans half the observable Universe, offering unmatched potential for astrophysics and cosmology. Here we quantify how well upcoming galaxy and…

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gr-qcastro-ph.HEastro-ph.IM

NRHJSur3dq8: a spectral numerical-relativity surrogate family for non-eccentric aligned-spin binary-black-hole waveforms

Vaishak Prasad

We present NRHJSur3dq8, a family of numerical-relativity (NR) surrogates for non-eccentric aligned-spin binary-black-hole waveforms inspired by an action-angle parameterization. The model provides both the dynamics: the Hamiltonian values, azimuthal action $J_φ(Φ)$, the orbital clock $τ(Φ)$ as functions of its phasing, and the radiative pieces: the waveforms, their near-analytic derivatives, and modeling errors associated with each. The surrogated variables are conditioned into pieces that vary…

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