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Research Trends

Latest preprints in space engineering and astrophysics.

astro-ph.GA

Testing Covarying Coupling Constants (CCC) against the full SPARC rotation-curve sample: a like-for-like comparison with MOND and NFW

Rajendra P. Gupta, Nikolaos Samaras

The Covarying Coupling Constants (CCC) framework, developed to account for high-redshift JWST observations, contains a mechanism -- a covarying-constant effective mass field keyed to local density -- that modifies galactic dynamics without particle dark matter. We test it against the full Spitzer Photometry and Accurate Rotation Curves (SPARC) sample of 175 disc galaxies, extending an earlier study of a few objects. Working in an inverse formulation, in which each model predicts the baryonic rot…

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astro-ph.SR

A Helium-shell Burning Blue Horizontal Branch Star Produced from Common Envelope Evolution

Jiao Li, Changqing Luo, Hai-Liang Chen, Zhicun Liu, Bo Zhang, Shi Jia, Hongwei Ge, Tao Wu et al.

Observationally, blue horizontal branch (BHB) stars are defined as hot stars occupying a characteristic region between the extreme blue horizontal branch and RR Lyrae variables in the Hertzsprung-Russell diagram. Most of them are interpreted as stripped core-helium-burning stars, but the role of binary interaction in their formation remains unclear. Here, we report the discovery of a metal-rich BHB star in a 0.82628-day binary system (\Feige 64) comprising a $0.35\pm0.03\,M_{\odot}$ BHB star and…

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astro-ph.SR

A Helium-shell Burning Blue Horizontal Branch Star Produced from Common Envelope Evolution

Jiao Li, Changqing Luo, Hai-Liang Chen, Zhicun Liu, Bo Zhang, Shi Jia, Hongwei Ge, Tao Wu et al.

Observationally, blue horizontal branch (BHB) stars are defined as hot stars occupying a characteristic region between the extreme blue horizontal branch and RR Lyrae variables in the Hertzsprung-Russell diagram. Most of them are interpreted as stripped core-helium-burning stars, but the role of binary interaction in their formation remains unclear. Here, we report the discovery of a metal-rich BHB star in a 0.82628-day binary system (Feige 64) comprising a $0.35\pm0.03\,M_{\odot}$ BHB star and…

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astro-ph.GA

Chemistry here and there: Comparison between the CMZ of the Milky Way and NGC 253

Sergio Martín, Álvaro López-Gallifa, David San Andrés, Victor Rivilla, ALCHEMI Collaboration

For decades, chemical studies in external galaxies have been limited by sensitivity, resolution, bandwidth or a combination of them. A decade of ALMA operations, made the detailed study of the molecular abundances in nearby galaxies a routine job. We can finally bridge the ISM chemistry from Galactic to extragalactic environments, through one to one comparison, albeit probing significantly different scales. The ALMA large program ALCHEMI imaged the chemistry of the starburst galaxy NGC 253 at an…

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astro-ph.SRastro-ph.GA

Numerous bow shocks in the outer Helix Nebula

Pieter van Dokkum, Roberto Abraham, William P. Bowman, Seery Chen, Steven R. Janssens, Deborah M. Lokhorst, Imad Pasha, Carter Rhea et al.

Near the end of their lives, low- and intermediate-mass stars expel metal-enriched material in winds and outflows, ultimately producing planetary nebulae (PNe). The ejected material is expected to fragment and mix into the interstellar medium (ISM), but this final assimilation step has been difficult to observe directly. Here we report evidence for this process in the form of twenty-two bow shocks in the eastern outskirts of the Helix Nebula, detected in H$α$ emission with the partially complete…

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astro-ph.SRastro-ph.EPastro-ph.IM

Diameters and Temperatures VII: High-angular resolution measurements of Solar-type stars with the CHARA Array

Tabetha S. Boyajian, Ashley A. Elliott, Emelly D. Tiburcio, Kaspar von Braun, Gail Schaefer, Timothy R. White, Daniel Huber, Michael Ireland et al.

We present interferometric measurements of angular diameters for 27 nearby solar-type stars obtained with the Precision Astronomical Visible Observations (PAVO) beam combiner at the CHARA Array. The sample spans a broad range of metallicities, includes several known exoplanet hosts, and covers evolutionary stages from the zero-age main sequence to mildly evolved subgiants. Uniform-disk and limb-darkened angular diameters were measured for each target and combined with bolometric fluxes and Gaia…

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astro-ph.SRphysics.space-ph

Solar-Cycle Modulation and Photospheric Magnetic Control of Turbulence in the Young Solar Wind

Yanwen Wang, Rohit Chhiber, Arcadi V. Usmanov, Marc Swisdak, William H. Matthaeus

The solar wind is an outflow of solar plasma that expands from the corona to fill the heliosphere. Its turbulence provides a pathway for non-adiabatic heating and acceleration, and is therefore central to understanding the thermodynamic and magnetohydrodynamic (MHD) evolution of the young solar wind. However, the variation of its turbulence properties over the solar activity cycle and the connection of these properties to solar source regions remains incompletely understood. Here we analyze obse…

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astro-ph.GAastro-ph.CO

Magnetic fields in extreme primordial halos: turbulent collapse and implications for early quasar formation

V. B. Díaz, D. R. G. Schleicher, M. A. Latif, R. Banerjee

It is sometimes suggested that the most massive quasars at high redshift may have formed from rare high-sigma peaks in the cosmic density field. We explore here the evolution in a massive primordial halo corresponding to one of these rare sigma peaks, employing cosmological high-resolution magneto-hydrodynamical zoom-in simulations with initial field strength of $10^{-14}-10^{-8}$ G. The dark matter halo forms at the intersection of strongly convergent flows, leading to the formation of highly s…

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astro-ph.HEgr-qc

Long-duration GW Searches for Sub-solar NSs and Superkilonovae using CoCoA

Abby Tejera, Divyajyoti, Alessandra Corsi, Yossef Zenati, Robert Coyne, Logan Cote

On 2025 August 18, the LIGO-Virgo-KAGRA collaboration reported a sub-threshold gravitational-wave (GW) candidate, S250818k, consistent with a binary neutron star (NS) merger potentially involving a sub-solar-mass compact object. Follow-up electromagnetic (EM) observations identified a Type IIb supernova, SN 2025ulz within the broad localization area of the GW signal. This potential link between a sub-solar GW event candidate and a Type IIb SN, while not confirmed given the low statistical signif…

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astro-ph.GA

From blue to red spirals: Slow galaxy transformation via ram pressure stripping in TNG-50

V. Lora, J. I. Gonzalez-Carbajal, A. Pasquali, A. Marasco, J. Fritz, E. K. Grebel, J. P. Ortiz-Jimenez, S. Estrada-Dorado et al.

Late-type galaxies lose gas through ram-pressure stripping (RPS) after falling into a massive halo. Because this mechanism primarily removes the gaseous component while leaving the stellar disk largely undisturbed, it provides a pathway for quenching star formation without immediate morphological transformation. While RPS is well established in galaxy clusters, galaxy evolution in low-mass groups is often attributed to mergers, leaving open the question of whether RPS alone can drive the transit…

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astro-ph.EP

Spectral Energy Distribution Analysis for Habitable Worlds Observatory Target Stars

Stephen R. Kane, Kaspar von Braun, Tara Fetherolf, Natalie R. Hinkel

The Habitable Worlds Observatory (HWO) will directly image and characterize planets potentially similar to Earth orbiting nearby stars. Accurate stellar properties, particularly effective temperatures ($T_\mathrm{eff}$), angular diameters ($θ_\star$), and bolometric fluxes ($F_\mathrm{bol}$), are essential for reliable Habitable Zone (HZ) calculations, exoplanet yield predictions, and coronagraph design trade studies. We present a spectral energy distribution (SED) analysis for the 164 stars fro…

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astro-ph.EP

A Pair of Warm Saturn-mass Planets near the 2:1 Mean Motion Resonance around TOI-3850

Sean Collins, Michelle Kunimoto, Nicolas B. Cowan, Keivan G. Stassun, Jack J. Lissauer, Ze'ev Vladimir, Teo Močnik, Ernesto Elenter et al.

Warm Jupiters, with orbital periods of $10$--$200~\rm{days}$ and radii exceeding $8~R_{\oplus}$, are a relatively understudied class of exoplanets occupying the parameter space between hot Jupiters and more widely separated, colder Jupiter analogs. In this work, we report the detection of a multi-planet warm Jupiter system around TOI-3850 (TIC-143008050), a moderately active, near-solar metallicity G0 dwarf star observed by TESS in Sectors 15, 21, 41, 48 and 75. Initially, a single candidate pla…

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astro-ph.HE

XRISM Spectroscopy of Variable Accretion-driven Disk Winds in NGC 4151: When, Where, and How Fast Outflows are Launched

Xin Xiang, Jon Miller, Missagh Mehdipour, Ehud Behar, W. Niel Brandt, Laura Brenneman, Luigi Gallo, Elias Kammoun et al.

X-ray observations probe the inner accretion flow within active galactic nuclei, revealing the highest gas column densities and fastest winds. The most diverse winds yet revealed with the Resolve calorimeter spectrometer aboard XRISM are found in NGC~4151, a nearby Seyfert-1 AGN that may qualify as a ``changing-look'' source (CLAGN). Herein, we report on wind variability in 14 XRISM observations of NGC~4151, summing to 0.9~Ms of exposure over a period of 395 days. We examined the dependence of k…

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astro-ph.EP

Formation of multiple dust rings and gaps in protoplanetary discs by a single migrating planet. A parameter study in locally isothermal discs

Sören C. Meiners, Kim M. Weiskopf, Thomas Rometsch, Cornelis P. Dullemond

ALMA observations show that large protoplanetary discs usually contain multiple concentric dust rings separated by dark gaps. A natural explanation is dust-trapping at the edges of gaps opened by newly formed planets. However, planets typically migrate inward on timescales shorter than disc lifetimes, seemingly at odds with rings at large radii. We aim to investigate the conditions under which migrating planets can form long-lived, multi-ringed structures out to $r\sim 150$ au to constrain the p…

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astro-ph.EP

Formation of multiple dust rings and gaps in protoplanetary discs by a single migrating planet. A parameter study in locally isothermal discs

Sören C. Meiners, Kim M. Weiskopf, Thomas Rometsch, Cornelis P. Dullemond

ALMA observations show that large protoplanetary discs usually contain multiple concentric dust rings separated by dark gaps. A natural explanation is dust-trapping at the edges of gaps opened by newly formed planets. However, planets typically migrate inward on timescales shorter than disc lifetimes, seemingly at odds with rings at large radii. We aim to investigate the conditions under which migrating planets can form long-lived, multi-ringed structures out to $r\sim 150$ au to constrain the p…

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astro-ph.HEastro-ph.SRgr-qc

A Diverse Distribution of Black Hole Spins from Stable Mass Transfer

Linhao Ma, Jakub Klencki, Eliot Quataert, Lieke van Son

Gravitational wave observations have found over 300 merging binary black holes, yet their origins remain uncertain. Recent work showed that many may come from isolated stellar binaries whose orbits shrink through stable mass transfer. If true, their spins may help to distinguish this channel from other formation pathways. We investigate the tidal spin up of black hole progenitor stars with detailed modeling of binaries undergoing stable mass transfer. We calculate the tidal torques by solving ti…

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astro-ph.HE

ATLAS22kjn (AT 2022fpx): A Coronal Line Emitter with an Early Light Curve Bump and Mid-Infrared Dust Echo

Athena C. Engholm, Jason T. Hinkle, Benjamin J. Shappee, Katie Auchettl, Dhvanil D. Desai, Willem B. Hoogendam, Christopher S. Kochanek, Nicholas Earl et al.

We present an analysis of ATLAS22kjn (AT 2022fpx), whose high-ionisation coronal lines (CLs) and pre-peak light curve bump provide distinctive opportunities to investigate the physical mechanisms powering tidal disruption events (TDEs). In addition to CLs, the optical spectra show common TDE features, including a strong, blue continuum and broad Balmer and He II lines. The CLs appear before UV/optical light curve peak, preceding the detection of X-rays by $\sim 300$ days and persisting after X-r…

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

Early Exploration of the Scientific Discovery Space for the Habitable Worlds Observatory

Courtney D. Dressing, Danica Adams, Evelyne Alecian, Gagandeep Anand, Giada Arney, Sarah Gomes Aroucha Barbosa, Martin Barstow, Joanna K. Barstow et al.

The Habitable Worlds Observatory (HWO) is a future NASA flagship mission concept identified by the Astro2020 Decadal Survey as the highest priority for large space missions. HWO should conduct "transformative astrophysics" and search for biosignatures in the atmospheres of approximately 25 potentially Earth-like planets. To further the early-stage development of HWO, NASA formed the Science, Technology, Architecture Review Team (START). In turn, START invited the scientific community to join wor…

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astro-ph.IMastro-ph.SR

Eclipses by Artificial Satellites to Measure the Angular Sizes of Stars

Leo W. H. Fung, Albert Wai Kit Lau, Richard Massey, George F. Smoot

Direct measurements of the angular sizes of stars (other than our Sun) are inherently limited by telescopes' optical diffraction limit. The spatial diffraction limit can be overcome by using time-domain information when stars are `eclipsed' by anything moving in the foreground: artificial satellites or the Moon (known as `lunar occultation imaging'). Here we analyse the angular resolution achievable by high-speed photon counting devices, when stars are eclipsed for several microseconds by one of…

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gr-qcastro-ph.HEastro-ph.IM

All You Need is not $Ω_\mathrm{gw}$: Beyond the Mean of the Cross-Correlation Estimator when Searching for an Astrophysical Gravitational-Wave Background

Haowen Zhong, Francesco Iacovelli, Vuk Mandic, Emanuele Berti

Searches for the stochastic gravitational-wave background (SGWB) using ground-based detectors rely heavily on the cross-correlation estimator $\bar C_f$, whose statistical properties determine the theoretical foundation for inference frameworks built on it. Past analyses usually assume Gaussianity of $\bar C_f$, but this assumption has not been systematically tested for a background of astrophysical origin like the one produced by compact binary coalescences. In this work, we decompose $\bar C_f…

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astro-ph.IM

High-temperature photovoltaics for solar-electric Oberth maneuvers: ton-class payload feasibility for interstellar-precursor missions

Nadim Maraqten, Willem van Lynden, Carlos Gómez de Olea Ballester, Andreas M. Hein

In-situ exploration beyond the giant planets remains rare because timely Solar System escape demands very high specific orbital energy, which existing concepts typically achieve only with small payloads, super-heavy launchers, or nuclear-powered propulsion. Motivated by laboratory demonstrations of high-intensity, high-temperature (HIHT) solar cells operating near $400\,^{\circ}\mathrm{C}$, we assess a solar-electric Oberth maneuver that concentrates thrust near a $0.3\,\mathrm{AU}$ perihelion.…

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astro-ph.SRastro-ph.EP

Intense but Harmless: Exo-Space Weather Around an M Dwarf with a Single-Hemisphere Dynamo

Zheng Sun, Julián D. Alvarado-Gómez, Hui Tian, Ofer Cohen, Jeremy J. Drake, Katja Poppenhäger, Yue-Hong Chen

M dwarfs are among the most promising host stars in the search for habitable exoplanets. However, their active atmospheres drive intense magnetic activity, including energetic flares and possibly coronal mass ejections (CMEs), which may pose serious threats to planetary habitability. In this study, we perform three-dimensional magnetohydrodynamic (MHD) simulations of CMEs on a fully convective M dwarf with a rotation period of 30 days, corresponding to the moderate-rotation regime. The magnetic…

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astro-ph.EP

Opposition effect of comet 28P/Neujmin observed with Subaru Hyper Suprime-Cam

Takafumi Ootsubo, Hideyo Kawakita, Tadafumi Takata, Junko Furusawa, Hisanori Furusawa, Tsuyoshi Terai, Toshihiro Kasuga, Akira Keida et al.

We present an observational study of the nucleus of comet 28P/Neujmin at a heliocentric distance exceeding 10 au, where coma contamination is effectively minimized. Observations were conducted in the $g$, $r$, and $y$ bands with the Hyper Suprime-Cam (HSC) on the 8.2-m Subaru Telescope. The measured colors, $g - r = 0.67\pm0.17$ and $r - y = 0.41\pm0.19$, yield a spectral index of $S' = 8.8\pm4.2\%/100$ nm, comparable to that of D-type asteroids. By incorporating new observational data at a phas…

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astro-ph.SR

Gravity modes and potential evidence for Rossby Waves in late O-type supergiants

Lydia S. Cidale, Alejandra Christen, Aldana Alberici Adam, Suryani Guha, Alex Lobel, Gunther F. Avila Marin, Michaela Kraus, Alejandro H. Corsico et al.

The properties of O-type supergiant stars remain largely unexplored. By analysing their light variations, we can unravel underlying physical phenomena, such as binarity, stellar pulsations, and rotation modes. This study aims to analyse the TESS light curves of 3 O-type supergiants to identify periodic signatures and gain deeper insights into their internal dynamics and structure. Our primary goal is to search for the presence of rotational modulation and possible evidence of Rossby waves. A per…

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astro-ph.SR

Gravity modes and potential evidence for Rossby Waves in late O-type supergiants

Lydia S. Cidale, Alejandra Christen, Aldana Alberici Adam, Suryani Guha, Alex Lobel, Gunther F. Avila Marin, Michaela Kraus, Alejandro H. Corsico et al.

The properties of O-type supergiant stars remain largely unexplored. By analysing their light variations, we can unravel underlying physical phenomena, such as binarity, stellar pulsations, and rotation modes. This study aims to analyse the TESS light curves of 3 O-type supergiants to identify periodic signatures and gain deeper insights into their internal dynamics and structure. Our primary goal is to search for the presence of rotational modulation and possible evidence of Rossby waves. A per…

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astro-ph.COastro-ph.HE

Fitting trends in quasar emission and absorption line redshifts

Netra K Subramanian, Prasad Subramanian, Nimisha G Kantharia

The spectrum of a quasar consists of a few emission lines whose wavelengths are shifted by similar redshifts and numerous absorption lines whose wavelengths are shifted by different redshifts. Hence each quasar is characterised by an emission line redshift and the absorption lines redshifts are all less than the emission line redshift. The distribution of observed absorption line redshifts ($z_{abs}$) with respect to emission line redshift ($z_{em}$) for a large sample of quasars shows a systema…

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astro-ph.COastro-ph.HE

Fitting trends in quasar emission and absorption line redshifts

Netra K Subramanian, Prasad Subramanian, Nimisha G Kantharia

The spectrum of a quasar consists of a few emission lines whose wavelengths are shifted by similar redshifts and numerous absorption lines whose wavelengths are shifted by different redshifts. Hence each quasar is characterised by an emission line redshift and the absorption lines redshifts are all less than the emission line redshift. The distribution of observed absorption line redshifts ($z_{abs}$) with respect to emission line redshift ($z_{em}$) for a large sample of quasars shows a systema…

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astro-ph.SR

Pulsation periods reveal tension between theoretical and empirical radii for classical Cepheids in eclipsing binary systems

O. Ziółkowska, R. Smolec, R. Singh Rathour, V. Hocdé

Context. With their precisely determined physical parameters, classical Cepheids in eclipsing binary systems are often used to constrain stellar evolution and pulsation theories. To this end, their position in the HR diagram, effective temperature and luminosity, and radius are commonly used when matching best-fitting evolutionary models. However, the pulsation period of Cepheids, the most precise observable, is rarely used in such studies. Aims. We explore how including the pulsation period as…

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astro-ph.GA

The Radcliffe Wave is not alone in the Local System

V. V. Bobylev, A. T. Bajkova

The spatial distribution of open star clusters (OSCs) younger than 30 million years old in the Local System was studied. It was shown for the first time that a significant number of OSCs belong to the recently discovered Vela Ridge gas and dust supercloud. The most intriguing property of this sample of OSCs is the presence of periodic perturbations in their vertical coordinates with a maximum amplitude of 47 pc and a wavelength of 1.1 kpc. Thus, the discovered chain of young OSCs is analogous to…

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astro-ph.GA

The Radcliffe Wave is not alone in the Local System

V. V. Bobylev, A. T. Bajkova

The spatial distribution of open star clusters (OSCs) younger than 30 million years old in the Local System was studied. It was shown for the first time that a significant number of OSCs belong to the recently discovered Vela Ridge gas and dust supercloud. The most intriguing property of this sample of OSCs is the presence of periodic perturbations in their vertical coordinates with a maximum amplitude of 47 pc and a wavelength of 1.1 kpc. Thus, the discovered chain of young OSCs is analogous to…

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