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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.SRastro-ph.GA

SDSS-IV MaStar: Determination of Stellar Parameters Using Bayesian Averaging

Yan-Ping Chen, Renbin Yan, Szabolcs Mészáros, Claudia Maraston, Daniel Thomas, Daniel Lazarz, Guy S. Stringfellow, Lewis Hill et al.

We present the stellar parameters for 59,266 high-quality spectra of 24,130 unique stars from the MaNGA Stellar Library (MaStar) in the Sloan Digital Sky Survey (SDSS) Data Release 17 (DR17). The median signal-to noise ratio per pixel of the spectra is 96. We derive four stellar parameters, effective temperature (Teff), surface gravity (log g), metallicity ([M/H]), and {$α$}-enhancement ratio ($\rm [α/M]$), by comparing the data with BOSZ (ATLAS-9 based) and MARCS theoretical atmospheric models.…

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astro-ph.GA

Host Galaxy UV Emission and Dust Reddening in Little Red Dots

Emmanuel Durodola, Ryan C. Hickox, Jonathan Cohn, David M. Alexander

Little Red Dots (LRDs) have been the subject of extensive analysis to place them within the context of galaxy and black hole evolution. Despite several proposed scenarios for the nature of the rest optical emission in LRDs, our understanding of the UV emission remains a matter of debate. Here, we aim to study the origin of the UV emission in LRDs. We conduct emission-line and continuum fitting analysis of thirteen LRDs using a combination of NIRSpec PRISM and medium-resolution G235M and G395M sp…

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astro-ph.GA

Host Galaxy UV Emission and Dust Reddening in Little Red Dots

Emmanuel Durodola, Ryan C. Hickox, Jonathan Cohn, David M. Alexander

Little Red Dots (LRDs) have been the subject of extensive analysis to place them within the context of galaxy and black hole evolution. Despite several proposed scenarios for the nature of the rest optical emission in LRDs, our understanding of the UV emission remains a matter of debate. Here, we aim to study the origin of the UV emission in LRDs. We conduct emission-line and continuum fitting analysis of thirteen LRDs using a combination of NIRSpec PRISM and medium-resolution G235M and G395M sp…

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astro-ph.SRastro-ph.EP

Sinking Silicates I: Characterizing the benchmark system containing the T0 brown dwarf CWISE J210640.16+250729.0 using JWST

Austin Rothermich, Jacqueline K. Faherty, Ben Burningham, Catherine Manea, Emily Calamari, Genaro Suárez, Daniella C. Bardalez Gagliuffi, John M. Brewer et al.

In this study, we present the full (97.3\% complete) 0.8--12.5 $μ$m spectral energy distribution (SED) of an L/T transition object, CWISE J210640.16+250729.0 (CW2106), using the James Webb Space Telescope (JWST). We provide a full characterization of the host star's elemental abundances and age. We empirically derive the bolometric luminosity ($L_{\rm bol}\approx-4.825$ $\textup{L}_\odot$) of CW2106, and obtain estimates of its mass (M$\approx50-62$ M$_{\rm Jup}$), radius (R$\approx0.83-0.87$ R$…

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astro-ph.EPphysics.geo-ph

The core-mantle mode of gravitational oscillation

Mathieu Dumberry

We present the characteristics of a mode of axial oscillation between Earth's mantle, fluid core and solid inner core that has not been previously reported. The mode involves a quasi-rigid rotation of the fluid core outside the tangent cylinder (TC) exchanging its angular momentum with the mantle via a three step process. First, by a magnetic torque with the fluid inside the TC; second by a magnetic torque between the latter and the inner core; and finally by a gravitational torque between the i…

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astro-ph.GA

Mapping parameters of idealised hydrodynamic galaxy simulations to bar properties: a case study with the RAMSES code

Srikanth T. Nagesh, Benoit Famaey, Jonathan Freundlich, Yves Revaz, Giacomo Monari, Arnaud Siebert, Rodrigo Ibata

Cosmological simulations with high spatial resolution often struggle to reproduce the observed fraction of galactic bars across redshift and may produce bars that are too short. To investigate these issues from a purely Newtonian dynamical perspective, we run a grid of idealised hydrodynamic simulations of disc galaxies with stellar masses of $\sim10^{10},{\rm M}_\odot$ using {\tt RAMSES}. Without cooling, star formation, or feedback, we vary the resolution, gas mass, stellar velocity dispersion…

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astro-ph.HE

Gas absorption of soft X-rays strongly impacts the redshift distribution of dark Fast X-ray Transients

Javier Sánchez-Sierras, Peter G. Jonker, Jonathan Quirola-Vásquez, Agnes P. C. van Hoof, Andrew J. Levan, Maria E. Ravasio, Joyce N. D. van Dalen, Franz E. Bauer et al.

The progenitors of many Fast X-ray Transients (FXTs) and those of $γ$-ray bursts (GRBs) are strongly linked. Given that "dark" GRBs are typically found to be events suffering from enhanced extinction in the host galaxy, we investigate the nature of "dark" FXTs. However, unlike $γ$-rays, soft X-rays are strongly affected by absorption, implying that dark FXTs discovered by Einstein Probe's Wide-field X-ray Telescope (EP-WXT) have to be emitted at energies $>$2--3 keV restframe hence at a redshift…

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astro-ph.SR

Classical Cases of Non-solar Mixing Length in Low Mass Stars

Rebecca Woody, Charlie Conroy, Phillip A. Cargile, Aaron Dotter

The treatment of convection is one of the largest remaining uncertainties in models of low mass stars. The Mixing Length Theory (MLT) for super-adiabatic convection has come under particular scrutiny. Evidence is mounting that a single value of the mixing length parameter ($α_\mathrm{MLT}$) should not be applied universally across stellar model grids, although simulations and asteroseismic calibrations disagree on how it should vary with stellar parameters. A variable $α_\mathrm{MLT}$ causes cri…

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astro-ph.GAastro-ph.CO

The GMRT CAT$z$1-COSMOS Survey: HI 21 cm emission from star-forming galaxies at $z\approx1$ in the COSMOS field

Balpreet Kaur, Nissim Kanekar, Aditya Chowdhury, Jayaram N. Chengalur

We report a 216-hr upgraded Giant Metrewave Radio Telescope (GMRT) Band-4 $550-850$ MHz observation of the COSMOS field, using 7 GMRT pointings to cover an area of $2.4$ sq. deg., with on-source times of $67$ hrs in the central pointing, and $89$ hrs distributed across the other six pointings. We stacked, at a spatial resolution of 90 kpc, the HI 21 cm emission signals from 8,122 star-forming galaxies with accurate spectroscopic redshifts and lying within the FWHM of the GMRT primary beam at the…

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astro-ph.GAastro-ph.SR

Chemo-dynamical Analysis of a CNO-Enhanced Ultra Metal-poor Star ($\rm[Fe/H] < -4$): Insights into Early Enrichment by Faint Population III Supernova

Guilherme Limberg, Vinicius M. Placco, Alexander P. Ji, Yupeng Yao, Friedrich Anders, Wendy Q. Sun, Anna de Graaff, Rohan P. Naidu et al.

We report an independent identification of the ultra metal-poor (UMP) star ($\rm[Fe/H] =-4.06$) $Gaia$ DR3 $\texttt{source_id}$ 4795913112968206720 (GDR3_479591) in the $Gaia$ mission's Blue and Red Photometer 'XP' spectro-photometric catalog. We combine multi-band photometry, astrometry, and high-resolution spectroscopy to confirm GDR3_479591 as a red giant-branch (RGB) star located at ${\sim} 6\,{\rm kpc}$ from the Sun. Abundance analysis under local thermodynamic equilibrium reveals significa…

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astro-ph.HE

Spinning Between Models: Continuum and Reflection Constraints in the Intermediate States of GRS 1716-249 and GRS 1739-278

Tiffany Tausch, Paul A. Draghis, Erin Kara, Abderahmen Zoghbi, Laura Brenneman, Anna Ogorzalek, John A. Tomsick, Mark Reynolds et al.

Measurements of stellar-mass black hole spin probe accretion under strong gravity and constrain black hole formation and evolution. Intermediate states, in which thermal disk, coronal, and reflection emission all contribute significantly, are particularly complex environments for spin measurements and useful for probing spectral-modeling systematics. We investigate these effects using paired, non-simultaneous Swift/XRT and NuSTAR observations of GRS 1716-249 and GRS 1739-278. We jointly model th…

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astro-ph.GA

Reigniting the FUSE II: O VI Emission in Massive Elliptical Galaxies

Michael Reefe, Michael McDonald, Greg L. Bryan, Megan Donahue, Andrew C. Fabian, Massimo Gaspari, Eric Miller, Valeria Olivares et al.

This is the second paper in a series where we examine archival far-ultraviolet spectroscopy of 29 massive elliptical galaxies from the Far Ultraviolet Spectroscopic Explorer (FUSE) with modern methods. In the first paper, we performed SED modeling with aperture-matched photometry and analyzed the young and old stellar populations in these galaxies. In this paper, we report extinction-corrected O VI $λλ$1032,1038 $\mathring{\rm A}$ fluxes and upper limits for each galaxy, which we use to infer th…

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astro-ph.COastro-ph.HEgr-qc

The Loud Tail of the Supermassive Black Hole Binary Population: Multimessenger Candidates and Prospects for SKAO

Juhan Raidal, Ville Vaskonen, Juan Urrutia, Hardi Veermäe

We assess whether electromagnetically identified supermassive black hole (SMBH) binary candidates populate the rare, high-amplitude tail of the gravitational wave (GW) amplitude distribution. Using an SMBH binary population model fitted to the NANOGrav 15-year data, we find that 3C~66B and Mrk~501 are likely to stand out from the GW background, making them promising targets for individual-source searches. Furthermore, we show that individual detections can probe the binary hardening mechanism, a…

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astro-ph.EP

JWST/MIRI Imaging Search for Kinematically Detected Protoplanetary Candidates

G. Cugno, M. Benisty, R. Teague, A. Boccaletti, L. Pueyo, M. Perrin, M. Mâlin, J. Girard et al.

Kinematic perturbations observed with ALMA in CO line emission provide evidence for a population of embedded giant protoplanets shaping the structure of protoplanetary disks. We present JWST/MIRI F1140C ($λ= 11.3~μ$m) coronagraphic observations of five protoplanetary disks, HD163296, RXJ1615.3-3255, RXJ1842.9-3532, SY Cha, and LkCa 15, with the goal of directly detecting candidate protoplanets orbiting at $\gtrsim$ 70 au previously inferred from gas kinematics. The data were analyzed using a bes…

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astro-ph.GA

The Nature of Small-Scale Perturbation Modes in a Nonstationary Self-Gravitating Disk

K. T. Mirtadjieva, J. M. Ganiev, S. N. Nuritdinov

In this work, we investigate the nature of gravitational instability of small-scale perturbation modes during the early nonstationary stages of the evolution of disk-like galaxies. To this end, we study the gravitational instability of small-scale horizontal perturbation modes, such as $(m;N) = (12;20)$, $(14;20)$, $(16;20)$, and $(18;20)$, in the framework of a nonlinear nonstationary anisotropic model of a self-gravitating disk. The corresponding nonstationary analogues of the dispersion equat…

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astro-ph.IMastro-ph.EP

Spectro-polarimetry of HAbitable Planet Earth (SHAPE) on Chandrayaan-3: Instrument characteristics, calibration and onboard performance

Bhavesh Jaiswal, Swapnil Singh, Ravishankar B T, Anand Jain, Smrati Verma, Reenu Palawat, Brajpal Singh, Bijoy Raha et al.

The orbiter of the Chandrayaan-3 mission of the Indian Space Research Organisation (ISRO) carries an experimental payload called SHAPE (Spectro-polarimetry of HAbitable Planet Earth). This payload makes disc-integrated observations of Earth as an exoplanet, from the Moon as well as from the high altitude Earth orbit. The instrument consists of an Acousto-Optic Tunable Filter (AOTF) based near-infrared spectro-polarimeter making the measurements in the two orthogonally polarized directions using…

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astro-ph.EP

The atomic C/O ratio of KELT-9b

Stefan Pelletier, Nicholas W. Borsato, Jacob L. Bean, Andreas Seifahrt, David Kasper, Julian Stürmer, Ana Rita Costa Silva, David Ehrenreich et al.

The carbon-to-oxygen (C/O) ratio of a giant planet's atmosphere has long been theorised to hold compositional information that can be traced back to its formation history. Typically, the C/O ratio of an exoplanetary atmosphere is inferred from abundance measurements of major C- and O-bearing molecules such as CO, CO$_2$, H$_2$O, and OH. However, some exoplanets have such elevated temperatures that molecules can be nearly completely thermally dissociated at the pressure levels that observations p…

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astro-ph.GAastro-ph.COhep-ph

High-redshift supermassive black hole population from core-collapse in self-interacting dark matter halos

Sambo Sarkar, Ujjal Kumar Dey

Self-interactions between dark matter (DM) particles facilitate the inter-particle redistribution of energy within the central region of DM halos. Recent studies of dark matter spikes around massive black holes, and the diversity in rotation curves of dark matter rich low-mass galaxies motivate the exploration of self-interaction cross-section $\mathcal{O}(10)\,\rm cm^2/gm$. At such high scattering rates, DM can lead to the formation of supermassive black hole seeds, through the gravothermal col…

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astro-ph.HEgr-qc

An efficient approach to resistive GRMHD simulations of binary neutron star mergers

Miquel Miravet-Tenés, Ian Hawke, Rahime Matur, Alexander J. Wright

Astrophysical plasmas are often highly conducting, but finite resistivity can nevertheless influence the evolution of strongly magnetised systems. Capturing these effects in general relativistic magnetohydrodynamics is computationally challenging because high conductivity leads to stiff source terms in the evolution equations. Standard numerical approaches rely on implicit-explicit (IMEX) time integration to maintain stability, but this substantially increases the complexity and computational co…

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astro-ph.GAastro-ph.SR

Magnetized interstellar molecular clouds - III. Filament Collisions and Core Formation: Insights into Substructures and Evolution

Pak Shing Li, Christopher F. McKee, Richard I. Klein

We present the results of a driven, ideal magnetohydrodynamics simulation of a molecular cloud to study the formation of filamentary structures in molecular clouds and their fragmentation into dense cloud cores. Shock compression results in the formation of sub-parsec long filamentary structures. Large-scale supersonic flows push these small filaments together and form massive filamentary clouds. The main filament that forms stretches across the full 4.4 pc length of the simulation and has a med…

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gr-qcastro-ph.IM

\texttt{cWB-space}: A time-frequency transient-search pipeline for LISA

Shubhanshu Tiwari, Yumeng Xu, Giovanni A. Prodi

Gravitational-wave observations can reveal sources whose signals are not known in advance. Searches that do not require a predicted waveform are therefore an important complement to searches for specific source classes. For the Laser Interferometer Space Antenna (LISA), the challenge is to find such signals among overlapping astrophysical sources and disturbances in the instrument. We present \texttt{cWB-space}, which identifies candidate signals by following how their power is distributed in ti…

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astro-ph.SRastro-ph.GA

Late-Time Evolution of the Massive Stellar Merger M101 OT2015-1

Marco A. Gómez-Muñoz, Nadejda Blagorodnova, Tomasz Kamiński, Gerard Garcia-Moreno, Maxime Wavasseur, Hugo Tranin, Grace Katusiime, Jacob E. Jencson et al.

Luminous red novae (LRNe) are astronomical transients arising from unstable mass transfer and common envelope phases in close binary systems, culminating in stellar mergers. Their cold, expanding ejecta provide the ideal conditions for molecule and dust formation. We investigate the late-time dust and molecular evolution of the LRN M101 OT2015-1, a high-mass LRN progenitor ($18\pm 1$M$_\odot$), using multi-band near-infrared (NIR) and mid-infrared (MIR) observations spanning up to ~5 years post-…

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astro-ph.IMastro-ph.SR

XMST: An Extended Minimum Spanning Tree Framework with Objective Fracture-Scale Selection

Mark Gallaway

We present XMST, an extended minimum spanning tree framework for identifying spatially coherent stellar structures using an objective, data-driven fracture-scale criterion. XMST combines percolation analysis with Jenks Natural Breaks optimisation, restricting the MST edge-length distribution to the subcritical regime before determining the final fracture scale. The method was validated using 1000 controlled Monte Carlo realisations containing eight empirical stellar-association templates, includ…

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astro-ph.GA

The Infrared Glow of Galactic Outskirts: A New Window with NASIM

Elham Saremi, Ignacio Trujillo, Mohammad Akhlaghi, Zohreh Ghaffari, Johan H. Knapen, Manda Banerji, Helmut Dannerbauer, Sébastien Comerón et al.

The outskirts of galaxies retain fossil records of their assembly history and are dominated by old stellar populations shaped by tidal interactions, accretion events, and environmental processes. Observing these low-surface-brightness (LSB) regions in the near-infrared (NIR), particularly in the $K_s$ band, is crucial for tracing evolved stars and minimising the effects of dust. Yet, ground-based NIR studies of faint extended structures remain challenging because of the bright and variable sky b…

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astro-ph.HEastro-ph.SR

The influence of free-free absorption on the radio spectrum of Particle-Accelerating Colliding-Wind Binaries

Michaël De Becker, Agustina Belen Blanco, Mathilde Tasseroul, Anandmayee Tej, Anindya Saha, Paula Benaglia, Santiago del Palacio

The study of massive stars in binary and higher-multiplicity systems that participate in particle acceleration is a key topic at the crossroads of massive star physics, shock physics, and galactic cosmic ray astrophysics. From an observational perspective, radio measurements are our pri- mary tool for identifying these systems through their synchrotron radio emission. Out of the 54 such systems known to date, all but two have been discovered via their non-thermal radio emission. However, identif…

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hep-phastro-ph.HEgr-qc

Reconstructing the Dark Matter Equation of State with Compact Object Inspirals

Boris Betancourt Kamenetskaia, Qianhang Ding, Hui-Yu Zhu

We investigate the gravitational wave (GW) signatures of compact binaries embedded in extended dark matter (DM) configurations in hydrostatic equilibrium. If a neutron star is surrounded by a sufficiently massive and extended envelope, an inspiraling companion experiences dynamical friction (DF) in addition to the standard GW energy loss. We show that this environmental effect can be isolated through a GW observable, the $D$-function, which directly characterizes the additional dissipative power…

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gr-qcastro-ph.IM

The Wavelet Detection Filter: a real time unmodeled pipeline for gravitational wave transients, ranking coincidences with a graph neural network

Elena Cuoco

Accurate waveform models are unavailable for many potential sources of gravitational wave transients, motivating searches that do not assume a predefined template family. The Wavelet Detection Filter (WDF) is an unmodeled pipeline that identifies excess energy in the wavelet coefficients of whitened detector data. Here, we develop WDF into a low latency pipeline for both detection and reconstruction and this paper describes and validates that pipeline. We use a zero phase streaming autoregressiv…

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gr-qcastro-ph.HEhep-phhep-th

Intrinsic pressure anisotropy in spherical Proca stars

Ilídio Lopes

Pressure anisotropy in relativistic stars is commonly prescribed through a phenomenological closure, obscuring its microscopic origin and relation to stress-energy conservation. Here it is derived directly from the minimally coupled Einstein-complex-Proca theory. For spherical Proca stars, the principal-pressure difference admits an exact on-shell form whose sign is controlled solely by the local mass-shell threshold. The stress is radially dominated in the core, reverses on a surface of fixed g…

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astro-ph.EPastro-ph.GAastro-ph.IM

Limits on a Host Star around a Saturn-mass Free-floating Planet Candidate KMT-2024-BLG-0792/OGLE-2024-BLG-0516

Przemek Mróz, Klara Piotrowska, Antoine Mérand, Subo Dong, Zexuan Wu

Recent studies found a number of short-timescale microlensing events that are thought to be produced by free-floating or wide-orbit planets. The microlensing event KMT-2024-BLG-0792/OGLE-2024-BLG-0516 is currently the only free-floating planet candidate with a directly measured mass ($0.73^{+0.25}_{-0.15}$ Saturn masses), derived from joint ground-based and Gaia satellite observations. However, it remains unclear whether the lens is truly isolated or bound to a widely separated host star. Here,…

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physics.atom-phastro-ph.SR

Experimental Ni II Oscillator Strengths for Transitions from $3d^84d$ to $3d^84p$ Levels Measured Using High-resolution Fourier Transform Spectroscopy

Ruijie Chen, Christian P. Clear, Gillian Nave, Juliet C. Pickering

We present the first experimentally measured oscillator strengths for Ni II 3d$^8$4d - 3d$^8$4p transitions. High-resolution Fourier transform spectra were recorded of Ni-He hollow cathode lamps, and intensity calibrated using deuterium standard lamps to determine relative intensities of Ni II emission lines between 200 and 395 nm. Branching fractions were determined for observed lines from 35 3d$^8$4d upper levels in total, and account for at least 95% of the predicted transition probability fo…

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