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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.GA

Examining the stellar-merger origin of the blue main sequence in the open cluster NGC\,3532 with N-body simulations

Khushboo K. Rao, Sambaran Banerjee

Extended main-sequence turnoffs, extended main sequences, and split main sequences observed in the colour-magnitude diagrams of young and intermediate-age star clusters are now widely interpreted as the consequence of a distribution of stellar rotation rates among their intermediate-mass (1.5-1.8~M$_\odot$) members. However, the origin of the slowly rotating population that occupies the blue main sequence (bMS) remains uncertain, and stellar mergers have been proposed as one possible pathway. We…

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astro-ph.GA

Morphology-spin connection in the SAMI Galaxy Survey

Youngmin Baek, Sree Oh, Sukyoung K. Yi, Scott M. Croom, Matthew Colless, Jesse van de Sande, Stefania Barsanti, Sam P. Vaughan et al.

The spin parameter $λ_{\rm{R_e}}$ is a proxy for the specific stellar angular momentum of galaxies and is a useful metric for classifying kinematic morphology. This study aims to quantify the relative importance of galaxy properties in explaining $λ_{\rm{R_e}}$, using data from the Sydney-AAO Multi-object Integral-field spectrograph (SAMI) Galaxy Survey. We apply partial correlation analysis and partial least squares regression to assess the relative contributions of different parameters in expl…

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astro-ph.HEhep-ph

Time-Domain Axion Searches with Magnetic White Dwarfs

Hong-Yi Zhang, Heng Bian, Zhao-Yu Zuo

Magnetic white dwarfs can convert photons into axions in their strong magnetic fields, with the conversion probability modulating the light curve as the star rotates. However, this observable is degenerate with intrinsic stellar variability if the background is modeled too simplistically. We develop a controlled background-degeneracy framework that computes the axion-induced modulation from reconstructed stellar magnetic fields while fitting it simultaneously with a flexible Fourier model of the…

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astro-ph.SRastro-ph.HE

A multiwavelength light curve analysis of the very fast nova V1723 Sco

Izumi Hachisu, Mariko Kato

We have analyzed multiwavelength light curves of the very fast nova V1723 Sco, based on our fully self-consistent nova explosion models. The time-stretching method gives the distance modulus in the $V$ band of $(m-M)_V = 15.3\pm 0.2$. Then the absolute $V$ magnitude reaches $M_{V,\rm max}= m_{V, \rm max} - (m-M)_V= 6.77 - 15.3\pm 0.2 = -8.5\pm 0.2$. Using our fully self-consistent nova outburst model combined with the optically thick winds on a $1.25 ~M_\odot$ white dwarf accreted by a mass accr…

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astro-ph.SR

Stream-Driven Ignition of a Realistic Undisturbed Helium Shell on a White Dwarf

Nethra Rajavel, Dean M. Townsley, Ken J. Shen

The dynamically driven double degenerate double detonation (D$^6$) model has emerged as a promising progenitor scenario for Type Ia supernovae. In this model, a carbon-oxygen white dwarf (WD) in a close double WD binary undergoes a double-detonation triggered by dynamical mass transfer from its companion. The mass transfer stream directly impacts the surface of the primary WD, potentially igniting a helium detonation in the surface layer. The resulting shock converges in the core, triggering a c…

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

Capture of interstellar objects during stellar encounters

Sean N. Raymond, Nathan A. Kaib, Matthew J. Hopkins

As they orbit within the Galaxy, stars swim through a vast population of interstellar objects (ISOs). In this paper, we use N-body simulations to show that a fraction of ISOs within $\sim$1 pc of the Sun (its tidal radius) may be captured during the flyby of another star -- a mechanism that requires no planets. Capture is most efficient when the impulse imparted by the flyby is comparable to the escape speed at the widest stable orbit, which is roughly 0.1 km/s for the Sun. ISO capture is domina…

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astro-ph.EP

Chondrite Parent Bodies as Escaped Satellites of Proto-Planetary Embryos

Harold F. Levison, Rogerio Deienno, Kevin J. Walsh, Brandon C. Johnson, Harold C. Connolly, Shigeru Wakita, Robert E. Grimm

Chondrites are composed of formerly partially molten material, known as chondrules, surrounded by fine-grained matrix. They date from the earliest times in Solar System history. However, their role in the formation of the planets is uncertain because, in part, it is not clear how they were produced. Here, we show a robust pathway for forming meteorite-producing asteroids that contain chondrules through embryo-embryo collisions during the late stages of terrestrial planet formation. Melted materi…

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astro-ph.GA

Vz-GAL Dusty Star-Forming Galaxies: Revisiting the CO-H2 Conversion Factor Tension

Prachi Prajapati, Axel Weiss, Dominik Riechers, Tom J. L. C. Bakx, Leindert A. Boogaard, Diana Ismail, Pierre Cox, Andrew J. Baker et al.

The CO luminosity-to-H$_2$ mass conversion factor ($α_{CO}$) remains a debated uncertainty in determining molecular gas masses of high-redshift dusty star-forming galaxies (DSFGs). Dynamical mass constraints have often favored $α_{CO}=0.8$~$M_{\odot}~{(K~km~{s}^{-1}~{pc}^{2})}^{-1}$, whereas dust- and radiative-transfer-based methods imply higher values. We revisit this ``tension" using the largest homogeneous sample of 21 unlensed $z\sim1-4$ DSFGs, with securely measured \coonezero luminosities…

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astro-ph.GA

Clarifying Dead Quasars and Downsizing through the Evolution of Star-Forming Galaxies and Active Galactic Nuclei

Shingo Sumie

From the catalogs of visible emission lines of galaxies measured by the Subaru Fiber Multi-Object Spectrograph (Subaru-FMOS) and the KECK Multi-Object Spectrograph For InfraRed Exploration (KECK-MOSFIRE), galaxies were classified into Star-Forming Galaxies (SFGs) and Active Galactic Nuclei (AGNs) based on the Baldwin-Phillips-Terlevich (BPT) diagram. In the redshift (z) range 0.8 <= z <= 2.6, z dependence of their number densities was examined, and it was found that SFGs dominate at lower redshi…

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astro-ph.HE

Can We Find the Emission Mechanism Behind the Extremely Bright GRB 230812B?

Utkarsh Pathak, Sameer K. Patil, Hitesh Tanenia, Yashowardhan Rai, Viswajeet Swain, Anuraag Arya, Gaurav Waratkar, Anirudh Salgundi et al.

GRB 230812B is a bright long-duration GRB with a luminous, long-lived afterglow and an AstroSat/CZTI polarization measurement during the prompt phase, enabling a joint study of its prompt spectral evolution, polarization, and broadband afterglow. Time-resolved spectroscopy of the prompt emission shows that during the rising phase, the low-energy Band-function index exceeds the synchrotron line of death, favoring the presence of an additional thermal component. At later times, from $T_0+2$ s to $…

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astro-ph.IM

First results for second generation SiSeRO CCD devices

Abigail Y. Pan, Declan O'Neill, Kevan Donlon, Peter Orel, Sven Herrmann, Steven Allen, Marshall W. Bautz, Tanmoy Chattopadhyay et al.

The Astro2020 Decadal recommended the development of a suite of next generation astronomical observatories spanning the X-ray to near-IR spectrum. These programs require fast, extremely low noise detectors to fulfill their science goals. To address this technology gap, Stanford X-ray Astronomy and Observational Cosmology (XOC) group, MIT Lincoln Laboratory (MIT-LL), and MIT Kavli Institute (MKI) are advancing Single electron Sensitive Read Out (SiSeRO), a multiband detector technology capable of…

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

Nancy Grace Roman Space Telescope Wide Field Instrument: Bright Point Source Saturation Response and Persistence Properties from Thermal-Vacuum Testing

Dana R. Louie, Robert F. Wilson, Thomas Barclay, Joshua E. Schlieder, Nicholas Bond, Evan Bray, Mario Cabrera, Stephanie Cheung et al.

The Nancy Grace Roman Space Telescope's Wide Field Instrument (WFI) will observe hundreds of thousands of bright stars across its Core Community Surveys, particularly in the dense stellar fields of the Galactic Bulge Time Domain Survey (GBTDS). Sources brighter than ~17th magnitude will saturate WFI detector pixels in typical survey exposures, with the brightest stars deeply saturating large pixel regions and potentially producing persistence signals that may impact subsequent observations. Prio…

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astro-ph.GA

The Next Generation Virgo Cluster Survey (NGVS). II. A Catalog of Galaxies in the Virgo Cluster

Laura Ferrarese, Patrick Cote, Lauren A. MacArthur, Joel C. Roediger, John P. Blakeslee, Michele Cantiello, Jean-Charles Cuillandre, Puragra Guhathakurta et al.

The Next Generation Virgo Cluster Survey (NGVS) is a deep, high resolution imaging campaign that used the 1 deg$^2$ MegaCam instrument on the Canada-France-Hawaii Telescope to carry out a comprehensive optical survey of the Virgo cluster, from its core to its virial radius. The NGVS covers a contiguous area of 104 deg$^2$ (8.63 Mpc$^2$ at the 16.5 Mpc distance of Virgo) in the $u^*$-,$g$-,$i$-, and $z$-band, with additional limited coverage in $r$. In this paper, we present the final catalog of…

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astro-ph.EPastro-ph.IM

Precise Determination of the Metallicity and C/O of WASP-39~b From a Single JWST Instrument Mode with Phase-Resolved Cross-Correlation Retrievals

Arjun B. Savel, Eliza M. -R. Kempton, Erin M. May, Matthew C. Nixon, Jegug Ih, Katherine A. Bennett, Joost P. Wardenier

Measuring atmospheric metallicities and C/O ratios is a key goal of JWST exoplanet science, given their proposed link to planet formation. Achieving this goal has previously been shown to require broad wavelength coverage ($\sim$1--5 $μ$m), typically demanding multiple instrument modes to complete the molecular inventory. Here, we show that the multi-instrument requirement can be circumvented using phase-resolved cross-correlation retrievals at native pixel resolution -- an approach more typical…

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astro-ph.EPastro-ph.GA

Characterizing Microlensing Planetary System OGLE-2014-BLG-0676L with High-Resolution Image Constrained Light Curve Modeling

Asahi Idei, Naoki Koshimoto, Daisuke Suzuki, Kansuke Nunota, David P. Bennett, Ian A. Bond, Jean-Philippe Beaulieu, Takahiro Sumi et al.

We present an analysis that incorporates high-resolution Keck adaptive optics (AO) imaging into microlensing light-curve modeling for the planetary microlensing event OGLE-2014-BLG-0676. Using Keck AO observations obtained 6.3 years after the event, we directly resolved the lens and source. The Keck images reveal a tension, in that the $K$-band source flux is $0.52 \pm 0.22$ magnitudes brighter than predicted by previously reported light-curve models. By incorporating the Keck imaging constraint…

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astro-ph.GA

Star formation powers optical line emission from the CGM

Huanian Zhang, Lizhi Xie, Zhijie Qu, Dennis Zaritsky, Luis C. Ho, Min Bao, Fabio Fontanot, Michaela Hirschmann et al.

Using integral field spectroscopy, we explore the disk-halo interface, or the inner circumgalactic medium (CGM), of individual galaxies by constructing and analyzing emission-line maps for a large sample (72) of normal, low-redshift galaxies spanning three orders of magnitude in stellar mass and four orders in star formation rate (SFR). We find a steep turnover occurring at $(1-2) R_e$ in the H$α$, [O {\small II}], and [O {\small III}] line emission radial profiles. Beyond this radius, the slope…

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astro-ph.EP

Late-infall-induced formation of giant planets, multi-generational planetesimals, and disk substructures

Haichen Zhao, Tommy Chi Ho Lau, Joanna Drążkowska, Tilman Birnstiel, Sebastian M. Stammler

Late infall can replenish the building materials of planets in protoplanetary disks and dramatically alter their structural evolution. The resulting pressure bumps effectively accumulate dust, facilitate grain coagulation, and trigger planetesimal formation via the streaming instability. In this work, we investigate the potential for planetesimal and planet formation, as well as the emergence of observable substructures, in disks undergoing late-stage infall. We utilize a comprehensive modeling…

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astro-ph.GAastro-ph.SR

Discovery of an Unbound Flyby Companion of UBC 63: In the Immediate Aftermath of a Close Encounter

Samrat Biswas, Biman J Medhi, Sergio Messina, Zhanpeng Zhu, Songmei Qin, Sukanta Deb, A. H. Sheikh, H. S Das et al.

We re-investigate the open cluster UBC 63 using the Gaia DR3 data and show that, rather than being a single cluster as previously classified, it is a compelling candidate for a double cluster undergoing an unbound flyby interaction. A GMM decomposition performed in the 5D astrometric space reveals the two statistically distinct components, namely UBC 63A (98 members, Age = 21 $\pm$ 4 Myr) and UBC 63B (148 members, Age = 562 $\pm$ 43 Myr). A significant age difference of $Δ\mathrm{Age} = 541 \pm…

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gr-qcastro-ph.HE

Search for continuous gravitational waves from the pulsar J0435+3233

Brian McGloughlin, Jing Ming, Maria Alessandra Papa, Kartikey Sharma, Reinhard Prix, Benjamin Steltner, Heinz-Bernd Eggenstein, Na Wang et al.

We perform a search for continuous gravitational waves from J0435+3233 using LIGO O4a public data. J0435+3233 is unique among millisecond pulsars as it exhibits an exceptionally large spin-down and marks the first pulsar observed to date with a spin-down larger than $10^{-12}$ Hz/s in the sub $10$ ms spin period range, making it a potentially strong source of continuous gravitational waves. We target signals at exactly twice the rotation frequency, a narrow band around this frequency, and also s…

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astro-ph.EP

A Self-Consistent 3D Hydrodynamic Model for Helium Transit Signatures in Evaporating Hot Jupiters

Anselmo Falorca, Aline Vidotto

The HeI triplet line (1083 nm), together with hydrodynamic models, can be used to characterize atmospheric escape of exoplanets. However, most of the available models cannot capture the three dimensional (3D) physics of escaping atmospheres, such as tidal forces and the interaction with stellar winds. To investigate how 3D effects affect the helium transit signature, we update our 3D atmospheric evaporation model to self-consistently solve the hydrodynamic equations together with the atomic hydr…

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astro-ph.IMphysics.flu-dyn

Per Astronomix ad Astra: High-Order Differentiable (Magneto)hydrodynamics with Energy-Conserving Self-Gravity

Leonard Storcks, Nils Thuerey, Tobias Buck

We present astronomix, a performant differentiable (magneto)hydrodynamics simulator written in Python/JAX. We demonstrate how automatic differentiation, validated against hand-derived analytical functional derivatives and finite differences, enables inverse modeling over millions of parameters and allows for sensitivity and stability analysis as well as correct eigenmode initialization. The differentiability of astronomix furthermore enables training machine-learning models inside the simulator.…

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gr-qcastro-ph.IM

Post-Newtonian Global Conservation Laws in the Presence of Sensitive Bodies

Timothy Clifton, Asta Heinesen, Oliver Pitt

The parameterized post-Newtonian (PPN) approach is the state of the art formalism for performing theory independent tests of weak-field gravity, and for constraining possible deviations from Einstein's theory. Within this framework, global conservation laws are useful for the calculation of dynamics and for giving meaning to parameters. In this paper we extend the concept of semi-conservative and fully-conservative theories of gravity to include situations in which compact astrophysical bodies a…

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astro-ph.IMgr-qc

An Unsupervised Search for Novel Instrumental Glitches in LIGO O4a: Multi-Scale Sensitization, Empirical Physical Vetoes, and Rate Upper Limits

Luca Cirfeta

The fourth observing run (O4) of Advanced LIGO, Virgo, and KAGRA presents unparalleled sensitivity, rendering unsupervised pipelines highly vulnerable to the non-stationary domain shift of the detectors' noise manifolds. We present DANTE V3, concluding a longitudinal investigation into unmodeled anomalies during early O4a. By expanding to a multi-scale geometric framework (0.5 s to 4.0 s), we amplify morphological sensitivity, extracting 10,372 unique candidates. To mitigate domain-shift artifac…

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astro-ph.HEastro-ph.GAastro-ph.SRnucl-exnucl-th

Quantifying the Information Gain from Future High-Precision Radius Measurements for Identifying Twin Neutron Stars

Bao-An Li, Xavier Grundler

Twin neutron stars (NSs), characterized by identical gravitational masses but different radii, are among the most promising astrophysical signatures of a strong first-order hadron--quark phase transition in supradense matter. We investigate how increasingly precise NS radius measurements improve the Bayesian inference of twin-star observability using mock radius data for a canonical $1.4\,M_\odot$ NS. Radius uncertainties are varied from the current level of about $0.9$ km to the $\approx 0.1$ k…

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

The science of the cycle of matter in our Galaxy with the SKA

Marc Audard, Ke Wang

Exploring how matter cycles through the Galaxy, from the birth of stars in dense interstellar clouds to the ejection of matter and energy during a star's final stages-requires a multi-faceted approach. Radio observations are essential to reveal the intricate interactions at play. By studying our Galaxy in detail, we can use it as a model to better understand these processes in galaxies as well. The Square Kilometre Array offers unique capabilities in wide-field, high-sensitivity, high-resolution…

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astro-ph.IMastro-ph.HEcs.CV

Co-addition and Subtraction of Undersampled Images

Matan Schlanger, Barak Zackay

In astronomical imaging surveys, repeated observations of the same sky patches are taken in order to obtain deeper images and detect new sources. This is the case in the search for many transient phenomena, such as supernovae, gravitational wave (GW) optical counterparts and other cataclysmic variables. In many such surveys some of the images are undersampled, meaning that the pixel size is too large, and the image suffers from aliasing. For undersampled images, both co-addition of the images an…

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astro-ph.GA

Comparing the Near-infrared Spectral Energy Distributions from Different Stellar Population Synthesis Models with SPHEREx Observations

Jeong Hwan Lee, Minjin Kim, Woong-Seob Jeong, Yujin Yang, Daniel C. Masters, Kyuseok Oh, Bomee Lee, Zhaoyu Huai et al.

While stellar population synthesis (SPS) models have been widely used for spectral analysis in optical wavelengths, their characteristics remain uncertain in the near-infrared (NIR) due to a relative lack of observed NIR spectra. The spectrophotometric data from SPHEREx are well-suited for investigating the performance of SPS models in the NIR, thanks to its wide wavelength coverage over $0.7-5.0~{\rm μm}$. In this work, we compare the observed SPHEREx data of SDSS compact galaxies, including 2,…

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astro-ph.GA

Ergodicity of FIRE: star formation variations within and between simulated galaxies

Fraser M. Smith, Robert J. Thacker

We investigate the ergodicity of star formation in simulated galaxies from the FIRE-2 (Feedback In Realistic Environments) project. We restrict ergodicity considerations to being related to deviations from the star-forming main sequence (SFMS), and in turn whether ensemble averages across populations match time-averaged star formation histories (SFHs) based on simulated observable properties. We find that in these high-resolution simulations the deviations of individual galaxies from the SFMS te…

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astro-ph.SR

Evidence for elemental diffusion in the eclipsing binary star AI Phoenicis

Pierre F. L. Maxted, Nicholas Storm, Andreas J. Korn, Marília Carlos, Matthew R. Gent, Sviatoslav B. Borisov, Paula Jofré, Maria Bergemann et al.

AI Phe is an eclipsing binary star with an orbital period of 24.6 days for which the surface gravity and effective temperature are known from direct measurements to very high precision and accuracy. We have obtained high-quality spectroscopy of the K0IV star during the total eclipse of the F7V companion, and also obtained spectra with a very high signal-to-noise ratio for this star and its F7V companion using the spectral disentangling technique. We have used these spectra to measure the abundan…

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astro-ph.HE

The Complete Catalog of Gamma-Ray Transients Observed by GRBAlpha & VZLUSAT-2 CubeSat Missions

Marianna Dafcikova, Jakub Ripa, Andras Pal, Norbert Werner, Michaela Duriskova, Yasushi Fukazawa, Martin Kolar, Laszlo Meszaros et al.

We present the largest sample of gamma-ray transients observed by any CubeSat mission so far. Observations were acquired by a 1U CubeSat GRBAlpha, the smallest astrophysical space observatory, and a 3U CubeSat VZLUSAT-2. Both missions were technological pathfinders and carried a novel CsI scintillator-based detector read-out by silicon photomultipliers. They operated on Sun-synchronous low Earth orbits below 550 km for about four years; GRBAlpha between March 2021 and June 2025 while VZLUSAT-2 b…

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