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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.SR

Velocity-field estimation techniques for on-disk solar coronal bright fronts (CBFs) and shock-wave propagation

Oleg Stepanyuk, Kamen Kozarev

Coronal mass ejections (CMEs) are large expulsions of plasma and magnetic fields from the solar corona into the heliosphere. Coronal shock waves are driven by CMEs, and accurate Solar Energetic Particles (SEP) forecasting requires knowing when and where shocks form, how fast they propagate, and how they interact with the coronal magnetic field. By measuring the speed, geometry and temporal evolution of coronal bright fronts (CBFs), one can create more realistic predictions of SEP onset and inten…

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astro-ph.GAastro-ph.CO

The connection between massive galaxies and their dark matter haloes from $z=0.25$ to $z \sim 4$ from the combined COSMOS, XMM-LSS and ECDF-S fields

Natalia Stylianou, Matt J. Jarvis, Rohan G. Varadaraj, Peter W. Hatfield, Joel Hamlett, Catherine L. Hale, Tariq Yasin

Understanding how galaxies populate and grow within dark matter haloes is essential for linking the observed evolution of galaxies to the hierarchical growth of structure. We present a galaxy clustering analysis using optical and near-infrared data from the UltraVISTA and VIDEO surveys covering $9.3$ deg$^2$ across the COSMOS, XMM-LSS and ECDF-S fields, $\sim 5\times$ larger than previous comparable studies, providing sufficient volume to determine the halo occupation of the most massive galaxie…

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astro-ph.SR

SPICY 30021: an embedded bona fide FUor with a mid-infrared precursor

Zhen Guo, Calum Morris, Vitor Fermiano, Carolina Lizana-Vidal, Aldo Aliaga, Javier Osses, Felipe Navarete, Philip Lucas et al.

Unstable mass accretion in young stellar objects (YSOs) often leads to observable outbursts, which play a key role in stellar mass assembly during pre-main-sequence evolution. The highest-amplitude, longest-duration events are classified as FUors. Until recently, only 50 FUor events had been confirmed. Many occur in embedded protostars, which are difficult to monitor in optical surveys. We present photometric and spectroscopic observations of SPICY 30021, an eruptive young star discovered in the…

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astro-ph.SR

First L-type substellar object discovered in the vicinity of the embedded cluster NGC 2023

Styliani Tsilia, Carlos Dominguez-Tagle, Maruša Žerjal, Eduardo L. Martín, Hervé Bouy, Nafise Sedighi, Sara Muñoz Torres, Nikola Vitas et al.

We present the first substellar object in a star-forming region spectroscopically confirmed with Euclid, namely J054158.70-021031.4. This young and faint source is located close to the embedded open cluster NGC 2023. It has a spectral type of L3, a reddening of Av = 3 mag, proper motion consistent with the nearby cluster NGC 2024, and a magnitude of $\sim24.5$ in the Euclid optical band. At the distance of 403 pc, its inferred mass lies close to the planetary-mass boundary. We discovered the obj…

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gr-qcastro-ph.HE

The WDM time-frequency transform in gravitational-wave data analysis II: Evolutionary spectrum and noise covariance

Aaron D. Johnson, Katerina Chatziioannou, Robert Rosati

Noise cannot be treated as stationary over the timescales required for upcoming gravitational-wave detectors, minutes for ground-based and months for space-based detectors. Nonstationarity leads to a non-diagonal frequency-domain noise covariance matrix, thus motivating a shift to the time-frequency domain. We introduce \emph{evolutionary power spectra} for describing nonstationary noise in the Wilson-Daubechies-Meyer time-frequency basis. Under the framework of oscillatory processes, we show th…

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astro-ph.IMastro-ph.CO

jax-SNANA: A GPU-accelerated Supernova Framework for the SBI Era

Matthew Grayling

We present jax-SNANA, a JAX reimplementation of the supernova analysis framework SNANA. jax-SNANA enables GPU-accelerated transient simulations and light curve fitting, supernova standardisation and cosmological inference. Running in single precision on an NVIDIA A100 GPU, jax-SNANA simulates more than 100,000 LSST-observed supernovae per second and fits 5,000 light curves per second after JIT compilation, a two orders-of-magnitude increase over current tools, essential for analysing samples at…

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astro-ph.GA

The convective-transition gap in 47 Tucanae with JWST

M. Scalco, L. R. Bedin, M. Libralato, M. Griggio, E. Vesperini, R. Gerasimov

We report the detection of the convective-transition gap along the lower main sequence (MS) of the Galactic globular cluster (GC) 47 Tucanae using deep James Webb Space Telescope (JWST) observations. We analyse the stellar luminosity function (LF) in the vicinity of the gap location using two independent colour-magnitude diagrams (CMDs). In both cases, the LF is characterised by a narrow gap followed by a discontinuous increase in the stellar number counts, and presents an overall morphology qua…

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astro-ph.SRastro-ph.GA

The mass functions of multiple stellar populations in 47 Tucanae

M. Scalco, J. Bruce, E. Vesperini, L. R. Bedin

We used a combination of James Webb Space Telescope (JWST) and Hubble Space Telescope (HST) observations to investigate the mass functions (MFs) of the different stellar populations in the globular cluster (GC) 47 Tucanae (NGC 104) over a wide stellar-mass interval. We identified the multiple populations along the lower main sequence using only JWST photometry and, in particular, colour combinations sensitive to variations in oxygen abundance. We derived the MFs of the first- and second-populati…

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astro-ph.SRastro-ph.GA

JWST observations of 47 Tucanae: I. The low-mass main sequence down to the hydrogen-burning limit

M. Scalco, R. Gerasimov, L. R. Bedin, E. Vesperini, M. Griggio, D. Nardiello, J. Anderson

We present the first results of a series of studies based on JWST observations of the globular cluster 47 Tucanae (47 Tuc, or NGC 104) obtained with NIRCam. By combining new data with earlier JWST observations, we derive high-precision proper motions (PMs) over a multi-year baseline (of ~3 years) and construct a clean sample of cluster members extending to very faint magnitudes (F444W~24.25 mag, corresponding to ~0.077 solar masses, slightly above the estimated hydrogen-burning limit of 47 Tuc,…

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gr-qcastro-ph.HE

Black Hole Fine Structure

Adrian Ka-Wai Chung, Richard Dyer, Tomasz Kinowski, Christopher J. Moore

In General Relativity, axial and polar black-hole perturbations share identical quasinormal-mode spectra, a property known as isospectrality. New physics can break this degeneracy, producing a spectral splitting analogous to atomic fine structure. We perform a theory-agnostic search for such splitting in gravitational-wave observations. We find no evidence for isospectrality breaking and place a combined $90\%$ upper limit of $<28.5\%$ on the relative frequency splitting. We map these constraint…

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astro-ph.GA

Substructure-enhanced Collisional Relaxation in Stellar Systems

Jian-Yu Gu, Xiao-Bo Dong, Run-Yu Meng

Two-body collisional relaxation in stellar systems is conventionally estimated using the classical Chandrasekhar theory, in which a subject star is assumed to be embedded in a homogeneous medium of field stars and their velocity distribution taken to be isotropic and Gaussian. Real stellar systems, however, can exhibit pronounced spatial and kinematic substructures. We investigate how such substructures -- particularly the non-classical spatial inhomogeneity -- modify the two-body diffusion coef…

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astro-ph.EPastro-ph.SR

Thermodynamically consistent equation of state tables for use in giant planet and brown dwarf interior modeling

Emily Sandford, Yamila Miguel

Equation of state (EOS) tables used in giant planet modeling exhibit regions of strong thermodynamic inconsistency, or disobedience to the first law of thermodynamics. These generally result from smooth interpolation over physical discontinuities or between thermodynamic sub-domains governed by different physical models. The effect of thermodynamic inconsistency on structure models of planets evolved with these EOS has never been studied in detail, although it is understood to introduce spurious…

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astro-ph.COastro-ph.IM

Forecasting a Cosmological 21 cm Stacking Detection with Early HIRAX Data

Pascal Hitz, Devin Crichton, Alexandre Refregier

Post-reionization 21 cm intensity mapping provides a powerful technique for efficiently mapping the Universe on large scales. The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a compact and highly redundant radio interferometer designed to exploit this technique. We present a forward modelling pipeline for forecasting a statistical detection of the cosmological 21 cm signal with HIRAX through cross-correlation with an external source catalogue. We simulate the cosmological sign…

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gr-qcastro-ph.HE

Strong-Field Gravitational-Wave Lensing from Ray-Traced Arrival-Time Surfaces

Luka Vujeva, João S. Santos, Brian C. Seymour

The diffraction integral formalism has been greatly successful in describing gravitational wave lensing effects in scenarios where the wavelength of the signal is comparable to the characteristic length scale of the lens, known as the wave optics regime. However, the assumptions required to construct its integrand break down as the source approaches the strong gravity region of a black hole lens. In particular, we are interested in the lensed signal from a binary (the source) near a massive blac…

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astro-ph.GA

GroArnold: A Framework for Constructing Action-based Models for Triaxial Galaxies and Dark Matter Halos

Jian-Yu Gu, Xiao-Bo Dong, Shi-Yan Zhong, Run-Yu Meng

Action-based distribution functions $f(\mathbf{J})$ provide a powerful description of stellar systems. Consequently, the construction of physically accurate and dynamically stable $f(\mathbf{J})$ for galactic components has emerged as a key challenge in the field. In this study, we present GroArnold, a computational framework designed to construct analytical $f(\mathbf{J})$ expressions for axisymmetric and triaxial galaxies and dark matter halos. The framework integrates modules for $N$-body ini…

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astro-ph.GA

A Nonlinear General Implicit Runge-Kutta Integrator for Multifluid Charged Dust and Gas

Mengxuan Chen, Hui Li, Chong-Chong He, Benjamin D. Wibking, Mark R. Krumholz, Xue-Ning Bai

Charged dust in magnetized gas is subject to aerodynamic drag and the Lorentz force, both of which can be difficult to model numerically in a fluid simulation where their characteristic timescales are shorter than the timestep set by the Courant condition. We present a two-stage general implicit Runge-Kutta (GIRK) source integrator for multifluid charged dust coupled to an ideal magnetohydrodynamic (MHD) gas, implemented in the open source GPU-accelerated quokka code. Drag and Lorentz forces are…

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gr-qcastro-ph.HE

Spinformation: do gravitational-wave events carry information beyond effective spins?

Cailin Plunkett, Jack Heinzel, Noah E. Wolfe, Davide Gerosa, Salvatore Vitale

While the spin vectors of binary black holes offer insight into the astrophysical formation channels of these systems, individual spins are less precisely measured through gravitational-wave observations than the effective inspiral spin $χ_\mathrm{eff}$ and the effective precession spin $χ_\mathrm{p}$. Reducing to effective parameters discards information in the data, but how much information is lost has yet to be demonstrated. Here we show how to quantify whether individual mergers carry inform…

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astro-ph.HE

The Second Catalog of Low-Energy Fermi-LAT Sources

The Fermi-LAT Collaboration

We used 14 years of Fermi-Large Area Telescope (LAT) data to derive a catalog of sources detected between 20 MeV and 200 MeV. For each source we provide localization, spectral, and association information. The Second Catalog of Low-Energy Fermi-LAT sources (2FLE) contains 450 sources detected at $TS>25$, with median energy flux of $F_{20-200 \, \text{MeV}} = 1.9\times10^{-11}$ erg cm$^{-2}$ s$^{-1}$. Using a Bayesian and likelihood-ratio method, we associate 377 2FLE sources with a known counter…

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astro-ph.GA

Wave Cold Dark Matter Can Reproduce the Radial Acceleration Relation in X-ray Elliptical Galaxies

Runyu Meng, Xiaobo Dong

Wave cold dark matter (wave CDM) is a well-motivated variant within the collisionless CDM paradigm, in which the de~Broglie wavelengths of ultralight bosons become relevant on galactic scales. While many of the previous tests of wave CDM have focused on small-scale tensions involving solitonic cores and certain soliton--halo relations in galaxies, the radial acceleration relation (RAR) provides a complementary test: for a given baryonic mass distribution, it probes whether the DM halo can reprod…

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astro-ph.SRastro-ph.IM

Any colour you like: The diverse chromaticities of white dwarfs

Mark A. Hollands, Boris T. Gaensicke, Pier-Emmanuel Tremblay, Detlev Koester

Main sequence stars have perceived colours ranging from orange to white to blue with increasing effective temperature. This is because their atmospheric opacities cause only minor deviations from blackbody colours when integrated over the broadband sensitivity curves of the human visual system. White dwarfs can have much denser atmospheres, reaching ~ 1 g/cm3 for the coolest known objects. If metals such as carbon, calcium, or sodium are present in these ultra-dense atmospheres, extreme broadeni…

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astro-ph.GAastro-ph.COastro-ph.HE

The Dance of the Little Red Dots: Spectroscopy of Two Blue Companions at z = 3.9 and 5.5 Reveals Young, Metal-Poor Starbursts Merging with Their LRDs within a Few Hundred Myr

Fabio Pacucci, Pierluigi Rinaldi

The Little Red Dots (LRDs) are compact, red sources, abundant at $4 \lesssim z \lesssim 9$ and likely powered by massive black holes. Photometric studies have found blue companions around them, but none has yet been confirmed spectroscopically. This Letter presents the only two LRD-companion pairs with spectroscopy of both members in the literature: "Waltz" at $z = 3.9$ and "Tango" at $z = 5.5$, with projected separations of $3.6$ and $2.5$ kpc. Both companions lie at the redshift of their LRD,…

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astro-ph.HEastro-ph.COgr-qc

Identity Crisis: Untangling Mass-Ordering Artifacts from Compact-Object Pairing in Gravitational-Wave Populations

Soumendra Kishore Roy, Asad Hussain, L. A. C. van Son, Maya Fishbach, Carl L. Rodriguez, Will M. Farr

Mass distributions of binary black hole mergers inferred from gravitational-wave observations offer clues to how binaries form. These distributions conventionally label the heavier component as the primary, with mass $m_1$, and the lighter as the secondary, with mass $m_2$, such that $m_1 \geq m_2$. This ordering folds the physically labeled mass distribution along the equal-mass line, potentially reshaping the underlying population structure. In this Letter, we determine which population featur…

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astro-ph.GAastro-ph.HEgr-qc

EMRIs in Kerr Spacetime: The Role of Inclination Diffusion

Yael Alush, Nicholas C. Stone, Scott A. Hughes

Extreme mass ratio inspirals (EMRIs) are expected to be a major source of gravitational waves (GWs) for the future {\it Laser Interferometer Space Antenna} ({\it LISA}). An EMRI occurs when a compact object, driven by the emission of gravitational radiation, slowly inspirals into a massive black hole (MBH). The classical formation channel involves repeated two-body interactions within dense nuclear star clusters. However, both EMRI event rates and the expected distribution of their orbital param…

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astro-ph.GA

How JWST is Revolutionizing Our View of Early Galaxy Formation

Rychard Bouwens

The James Webb Space Telescope (JWST) has been revolutionizing our understanding of early galaxy formation over its first four years of science operations. With un- precedented sensitivity, spatial resolution, and wavelength coverage from the near- to mid-infrared, JWST has enabled astronomers to identify hundreds of star-forming galaxies at redshifts z>~8 (within ~650 million years of the Big Bang) through strong spectral breaks and characterize these galaxies through sensitive spectroscopy. Th…

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gr-qcastro-ph.HEastro-ph.SR

Nonlinear Perturbations of Relativistic Stars

K. J. Kwon, Abhishek Hegade K. R., Tejaswi Venumadhav, Hang Yu, Nicolás Yunes

We extend the general relativistic Lagrangian perturbation formalism of Friedman and Schutz [Astrophys. J. 200, 204 (1975)] beyond linear order, retaining full time dependence of the perturbations. We provide general formulae to relate the Lagrangian and Eulerian perturbations to any general perturbative order. As a proof of principle, we apply the framework to tidally perturbed relativistic stars in Regge-Wheeler gauge and reduce the second-order field and conservation equations to master equat…

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astro-ph.COastro-ph.GA

TNGC-SIDM I: Evolution of massive cluster mergers under the self-interacting dark matter paradigm

Wonki Lee, Dylan Nelson, Myungkook J. Jee, Giulia Despali, Mark Vogelsberger, Annalisa Pillepich, Cian Roche, Kyle Finner et al.

Merging galaxy clusters provide an ideal laboratory for testing the self-interacting nature of dark matter. In this paper, we present a pilot study of magnetohydrodynamical cosmological zoom-in simulations of two cluster mergers selected from TNG-Cluster, with $M_{\rm 200c} \sim 9\times10^{14}~M_\odot$ and $M_{\rm 200c}\sim 2\times10^{14}~M_\odot$. The simulations are performed with both standard collisionless cold dark matter (CDM) and self-interacting dark matter (SIDM), assuming an isotropic,…

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astro-ph.EPphysics.ao-ph

Simulations of the Evolving Ozone Layer: Implications for the Early Earth, Exoplanets, and the Search For Life

Akhil Kumar, Gregory J. Cooke

Over 4 billion years, Earth's atmosphere has been transformed from a composition devoid of molecular oxygen (O$_2$) to one where O$_2$ is now 21% of our modern atmosphere by volume. With high quantities of O$_2$, an ozone (O$_3$) layer can form and partially shield the surface from biologically harmful ultraviolet radiation (UV). The evolution of the O$_3$ layer has previously been simulated under the modern Sun by independent groups with separate models. Here, we present simulations of Earth's…

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astro-ph.HE

Seeing Double: The Theory Defying Twin Flares of TDE 2022dbl

Xinze Guo, Ryan Chornock, Raffaella Margutti, Yuhan Yao, Erica Hammerstein, Natalie LeBaron, S. Bradley Cenko, Matthew J. Graham et al.

Partial tidal disruption events, in which a star survives a close passage by a supermassive black hole and may be disrupted again on a subsequent encounter, provide a unique probe of supermassive black hole properties and accretion physics. We examine TDE 2022dbl, a partial tidal disruption event candidate that exhibits two separate UV/optical flares, using 11 new optical spectra, updated UV/optical photometry, and a Keck-II/ESI host-galaxy spectrum. We trace the evolution of the prominent blend…

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astro-ph.EPastro-ph.SR

Peering into the Midplane of the DM Tau Disk using N2H+ and DCO+

Amina Diop, Kevin Flaherty, Chunhua Qi, Ilse Cleeves, A. Meredith Hughes, Agnes Kospal, Sean Andrews, David J. Wilner et al.

Planets form in the midplanes of protoplanetary disks, thus investigating the properties of the midplane region can shed light on the physical and chemical processes governing the evolution of planetary systems. In this work, we study the conditions near the midplane of the disk around DM Tau using 0."3 (~43 au) ALMA observations of N2H+ (J = 3 - 2) and DCO+ (J = 4 - 3). The radial profiles reveal that DCO+ is centrally peaked, with a depression near 120 au, while N2H+ exhibits a central depress…

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astro-ph.SR

Differential Luminosity Response of Balmer-Line Profiles in Galactic B/A Luminous Stars

N. L. Vaidman, S. A. Khokhlov, Sh. T. Nurmakhametova, N. A. Litvinov, A. T. Agishev, D. A. Alimbetova

We investigate the differential luminosity response of the optical Balmer series from H8 to H-alpha in Galactic B5-A5 luminous stars using homogeneous measurements of central depth, FWHM, and equivalent width at a resolving power of approximately 12,000. Direct line-to-line comparisons show a systematic change in the central-depth response toward the lower-order transitions. For the primary 72-star luminosity sample, the fitted luminosity coefficients show an overall positive trend with upper-le…

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