Solar and Stellar Astrophysics
A Systematic Gaia–ZTF Search for Short-Period Blue Compact-Binary Candidates
Jiamao Lin, Liangliang Ren, Yilong Li et al. (+7 more)
We present a catalog of 147 short-period (10.34–106.46~min) blue compact-binary candidates, identified by combining Gaia DR3 astrometry and photometry with ZTF DR23 light curves via a Gaia selection, period searches, and machine-learning morphology ranking. Of these, 111 lack prior compact-binary classifications. Multiwavelength data (DESI DR1, GALEX, AllWISE) reveal a heterogeneous sample: on the Gaia colour–magnitude diagram, 52 sources lie on the white-dwarf locus, 69 in the hot-subdwarf region, and 26 are intermediate. Among 26 sources with DESI spectra, only about one third follow the white-dwarf cooling sequence; the rest are more luminous blue
stars with white-dwarf-like low-resolution spectra. We highlight a prioritized subset of new white-dwarf-locus candidates for follow-up, including ten with periods below 40~min and none with existing radial-velocity data. Under fiducial binary assumptions, 17 of these newly identified white-dwarf-locus candidates would exceed the adopted LISA signal-to-noise threshold (led by a 37~pc white dwarf), with the count depending on chirp mass (9 for $0.15\,M_\odot$, 17 for $0.3\,M_\odot$, 21 for $0.6\,M_\odot$), assuming orbital modulation. However, for most of the white-dwarf-locus sample, observed modulation amplitudes exceed any plausible ellipsoidal signal by three to five orders of magnitude, implying that rotating
magnetic or chemically inhomogeneous single white dwarfs offer a viable alternative that ZTF photometry alone cannot rule out—the catalog includes at least one confirmed case. We release the full 147-source catalog, including periods, Gaia/spectroscopic classifications, harmonic/ellipsoidal diagnostics, and supplementary tables of fiducial GW estimates and UV–IR photometry.
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All authors Jiamao Lin, Liangliang Ren, Yilong Li, Bo Ma, Di-Chang Chen, Zi-Heng Yu, Sen Yang, Shun-Jia Huang, Yi-Ming Hu, Chengyuan Li
Solar and Stellar Astrophysics
Correlations with Magnetic Activity in the Solar Near-Surface Shear Layer. II. Radial Shear
M. Cristina Rabello Soares, Sarbani Basu, Richard S. Bogart et al. (+1 more)
Using Helioseismic and
Magnetic Imager ring-diagram measurements and building on the rotation-rate $\Omega$ inferences presented in Paper I for depths of 1-17 Mm, we examine the properties of the dimensionless radial shear $\partial\ln\Omega/\partial\ln r$. In the radial range overlapping global-mode analyses, the inferred shear agrees with previous results. The near-surface shear layer exhibits a three-region shear structure with an enhanced-shear middle layer, and the largest residual variations occur in the two shallowest regions not accessible to global-mode analyses. We parameterize the enhanced-shear layer by the depth of maximum shear, its amplitude, and its width, and find all three to be strongly correlated with a
magnetic activity index; increasing activity corresponds to a shallower, stronger, and modestly narrower layer, indicating that the flows and
magnetic fields are interconnected in these layers. This behavior is consistent with expectations that sufficiently strong toroidal fields can enhance the near-surface rotational shear and with inferences of a near-surface toroidal-field concentration near the radius where we observe the strongest shear. Moreover, the observed strengthening and upward shift of the strong-shear layer toward solar-cycle maximum suggest a corresponding solar-cycle dependence in the location of the strong toroidal field. We also highlight the importance of finite-resolution effects and instrumental calibration in interpreting small variations in the results.
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All authors M. Cristina Rabello Soares, Sarbani Basu, Richard S. Bogart, Charles S. Baldner
Solar and Stellar Astrophysics
Correlations with Magnetic Activity in the Solar Near-Surface Shear Layer. I. Rotation
M. Cristina Rabello Soares, Sarbani Basu and Richard S. Bogart
We used data from the Helioseismic and
Magnetic Imager to determine the rotation rate of the near-surface shear layer and its time variation. We applied the ring-diagram analysis technique allowing us to probe the layer between the depths of 1 Mm and 17 Mm. We find that the rotation rate increases inwards; it reaches values consistent with those inferred from global helioseismic analyses in the deeper layers, however, there are differences in the rotation rate of the northern and southern hemispheres. We show that the time variation of the rotation rate can be determined even without subtracting the time-averaged rotation rate from each epoch; however, such a subtraction is needed to get the canonical “torsional oscillation” signal. We find that even at depths as shallow as 1 Mm, the rotation rate shows the typical torsional oscillation pattern. The cumulative zonal displacement inferred from the residual flows exhibits a pronounced high-latitude hemispheric asymmetry and varies on solar-cycle timescales; at $75^\circ$ it shows an apparent temporal association with the polar
magnetic field. We find significant correlations between the cumulative displacement and
magnetic activity at a subset of latitudes, with multi-year lags: the displacement leads activity by ~5 years near $15^\circ$, whereas at higher latitudes activity leads by ~4 years. At mid to high latitudes, the inferred lags show a hemispheric dependence, with activity tending to lead in the north and lag in the south, suggesting possible hemispheric differences in the timing of cycle
evolution and motivating longer time series to test cycle-to-cycle variation.
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Solar and Stellar Astrophysics
Responses of the X-ray spectrometer/imager STIX onboard Solar Orbiter
Hualin Xiao, Olivier Limousin, Ewan Dickson et al. (+1 more)
Solar
flares are explosive events that release X-rays from hot
plasma and accelerated electrons. The STIX instrument on the Solar Orbiter provides imaging spectroscopy of solar X-ray emissions from 4 to 150 keV. To interpret the STIX data accurately, understanding the instrument's response is crucial. Given the complexity of interactions of X-rays with the instrument, we developed a detailed Monte Carlo model for STIX based on Geant4. The model accurately depicts the instrument's components, such as grids, detectors, X-ray windows, and collimators, with their responses. We studied various effects, including grid shadowing, fluorescent X-rays emitted by materials in STIX, and grid transmission, to assess their impacts on STIX's scientific goals. Model validation was performed using Crab Nebula observations, a standard calibration source that provides reliable ground truth for X-ray instruments. Our simulations align with the Crab Nebula observations within the uncertainties, thereby validating the accuracy of the Geant4 model and showcasing its potential for interpreting STIX data. With the help of the generated response
matrices, which are indispensable for solar spectroscopy, we discuss the applications and limitations of the model for future STIX data analysis.
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All authors Hualin Xiao, Olivier Limousin, Ewan Dickson, Säm Krucker
Solar and Stellar Astrophysics · Cross-listed from astro-ph.IM
Microlensify: a Transformer Based Machine Learning Classifier for Microlensing Events Trained on TESS Light Curves
Atousa Kalantari, Somayeh Khakpash, Sedighe Sajadian et al. (+3 more)
Microlensing can reveal populations of faint compact objects that are otherwise difficult to detect. Depending on their design, all-sky surveys have the potential to search for these objects across the sky. The Transiting
Exoplanet Survey Satellite (TESS), primarily designed to detect transiting
exoplanets, also provides near all-sky coverage with high cadence. In this work, we use TESS data to search for microlensing candidates using both traditional and machine-learning methods and to identify associated false positives in high-cadence surveys. Microlensify is a physics-informed,
transformer-based variational autoencoder trained on simulated single-lens microlensing light curves and real TESS Sector 12 data. The model classifies events, reconstructs light curves, and estimates microlensing event durations. Applied to $\sim 5.6$ million TESS light curves, it identified between $0.036\%$ and $1.89\%$ as microlensing candidates across different TESS pipelines. After applying microlensing detection metrics and cross-matching with SIMBAD, we obtained a final list of candidates and identified false positives including long-period variables, Mira variables, cataclysmic variables, red giants, and transients. We also found Gaussian-like peaks caused by asteroid crossings, a potential source of false positives in high-cadence microlensing surveys. The model also predicts event duration with an accuracy of $R^2 = 0.97$. The model was further tested on published events from different ground-based microlensing surveys, confirming 92.7% as microlensing, demonstrating its applicability across surveys with different cadences.
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All authors Atousa Kalantari, Somayeh Khakpash, Sedighe Sajadian, Hosein Haghi, Willow Fox Fortino, Rosanne Di Stefano
Solar and Stellar Astrophysics · Cross-listed from astro-ph.HE
Modeling Relativistic Tidal Disruptions of MESA Stars
Liam M. Wang, Giovanni Maria Tomaselli and Zihan Zhou
Tidal disruption events (TDEs) occur when a
star passes so close to a black hole that its self-
gravity is overcome by the external tidal field. As the
star passes, it initially deforms, then is ripped apart, and some of its material eventually falls back on bound orbits, forming an
accretion disk around the black hole. A Newtonian model of TDEs, based on stellar perturbation theory of MESA
stars, was recently introduced as an alternative to computationally intensive hydrodynamical simulations. In this work, we add relativistic corrections to the model, incorporating equatorial Kerr geodesics, relativistic tidal fields, and relativistic fallback times. Compared to the Newtonian case, we find that
stars are disrupted earlier in their orbit, which gives them less time to accumulate physical deformations. Additionally, we find that the increased distance from the black hole at the time of disruption makes the fallback time longer. However, the black hole
spin has a negligible impact on fallback time, except for orbits with exceptionally close pericenter. Our results allow for a more accurate calculation of fallback rates than the Newtonian model, while also remaining computationally cheap. The code is available on GitHub.
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Solar and Stellar Astrophysics
Early Planet Formation in Embedded Disks (eDisk). XXIV: Systematic Investigation of Disk Structures based on Visibility Analysis
Mayank Narang, Jerry Xu, Leslie W. Looney et al. (+11 more)
The dust continuum emission from young protostellar disks encodes key information about their mass distribution and early
evolution, yet uniform high-resolution comparative studies remain limited. We present a systematic uv-plane analysis of parametric intensity models applied to ALMA Band-6 (1.3 mm) observations of 23 disks (19 protostellar systems with 4 being in binary) from the eDisk sample, spanning Gaussian profiles to power-law cores with exponential tails (PLCT), including asymmetric extensions. Gaussian models generally fail to reproduce the centrally peaked emission and extended outer structure observed in most disks, whereas the PLCT framework provides a significantly improved description of radial brightness profiles. Incorporating azimuthal asymmetries further reduces residuals in 15 of 17 inclined disks, indicating that departures from axisymmetry are common at early stages. Only two disks, L1489 IRS and Oph IRS63, exhibit clear gap and ring substructures, while most appear smooth at the spatial resolution and sensitivity of our observations. These systems are among the most evolved in the sample, and the absence of flat-spectrum sources limits the evolutionary range probed, {suggesting that the detection of prominent gaps and rings is not common} in the earliest phases of disk
evolution. Using a uniform definition of disk radius based on the 95% enclosed flux, we find a positive correlation with stellar mass, $R_{\rm disk} \propto M_{\star}^{1.5 \pm 0.1}$, with disks in binary systems systematically smaller than those around isolated protostars. While the models capture overall morphology and large-scale asymmetries, distinguishing intrinsic structures from radiative transfer effects in optically thick regions remains challenging.
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All authors Mayank Narang, Jerry Xu, Leslie W. Looney, Nagayoshi Ohashi, Anika Khandavalli, Patrick Sheehan, Jonathan P. Williams, Shigehisa Takakuwa, Jes K. Jørgensen, Ilseung Han, Woojin Kwon, Zhi-Yun Li, Nguyen Thi Phuong, John J. Tobin
Solar and Stellar Astrophysics
ALMA high resolution observations of Betelgeuse: Persistent structure spanning the inner atmosphere
W.R.F. Dent, A.M.S. Richards, G.M. Harper et al. (+2 more)
The extended atmosphere of red supergiants (RSGs) forms an important link in the process of mass loss and the subsequent enrichment of the interstellar medium. Large-scale convection is thought to play a significant role, which is likely to result in irregularities in the surface. High resolution, high contrast sub-mm images of Betelgeuse - one of the closest RSGs - are used to probe the structure and temporal stability of the inner 1-2$R_\star$ of its atmosphere. Using ALMA in the longest baseline configuration, continuum emission and lines of SiO and CO and their isotopomers were observed at $\lambda$0.6-1.4mm, giving beamwidths down to 7mas at the shortest wavelengths. These were compared with a similar observation taken at 0.9mm approximately 7 years earlier. The observed continuum emission arises mostly from an optically-thick mm/sub-mm photosphere of radius 1.1-1.3$R_\star$ with a relatively constant temperature of $\sim$2300K, but with two hotter patches to the NE and SW. The brightest of these has a temperature enhancement of $\sim$800K, and its location and intensity appears relatively unchanged since the 2015 observation. The sub-mm photosphere shows deviations of up to $\pm$ 6% in radius, with weaker continuum extending out to $\sim$2.5$R_\star$ - similar to the extent of clumpy emission in SiO and CO. The hot regions of gas and deviations from radial
symmetry are thought to be associated with active shocks driven by underlying convective
cells, although their lifetimes appear longer than model predictions. They lie near the proposed poles of the
star, which might suggest enhanced and relatively stable polar convection. The present data show no clear evidence for stellar rotation in the extended line emission or absorption against the photosphere, although the structure of the gas emission has changed significantly since 2015.
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All authors W.R.F. Dent, A.M.S. Richards, G.M. Harper, L.D. Matthews, E. O'Gorman
Solar and Stellar Astrophysics · Cross-listed from astro-ph.EP
Substructure evolution from protoplanetary to debris disks driven by mutually gravitating planetesimals and implications on Kepler resonances and free-floating planets
Yinuo Han, Konstantin Batygin and Fei Dai
Motivated by recent observations suggesting rings found in debris disks are wider than those in protoplanetary disks, we consider a picture in which planetesimals formed in radially narrow dust traps radially diffuse into debris rings via mutual scattering. Under this picture, evolving the fractional widths ($\Delta r/r$) of resolved debris rings back to a few Myr according to the theoretical $t^{1/5}$ evolutionary trajectory reproduces the protoplanetary ring distribution. We inferred the product of the ring mass and individual planetesimal mass required to reach the observed debris ring widths at their ages, finding that $M_\mathrm{disk}\times m$ ranges from $10^{-3}$ to $10^{3} \, M_\oplus^2$. The distribution of $M_\mathrm{disk} \times m$ appears to correlate with the stellar mass, peaking at 1.5 to 2 $M_\odot$, which resembles the stellar mass dependence of the giant
exoplanet occurrence rate. The population of resolved debris rings lie close to the $\Delta r / r = 10 \, h$ equipartition relation expected of a planetesimal ring that formed narrow, with typical resolved debris disks still expected to be broadening radially and vertically at present. If sufficiently massive ($\sim$10 $M_\oplus$), this radial broadening can send a few Mercurys to the terrestrial region within 10 Myr, making debris disks a plausible source of planetesimals disrupting resonant chains among Kepler
planets. Within Gyr timescales, outer planetesimal belts can also eject $\sim$1% of their mass into interstellar space if they consist of Moon-sized bodies or above, suggesting that the slow and steady intrinsic
evolution of massive debris disks could contribute to the interstellar free-floating population of terrestrial-
planet-sized bodies.
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Solar and Stellar Astrophysics
Multi-lane type II radio bursts: Insights into shock propagation in the corona
Nadiya K., Divya Paliwal and Anshu Kumari
Type II solar
radio bursts are considered as the signatures of the coronal shocks. These bursts are generated from
plasma waves excited by magnetohydrodynamic (MHD) shocks, and then converted into
radio waves at the local
plasma frequency and/or its harmonics. Hence, these bursts often have fundamental-harmonic (FH) and band-splitting (SB) structures, which provide insights into shock generation and propagation in the corona, hence, in turn, the corresponding coronal conditions. In the present study, we analysed an unusual multi-lane type II burst observed with ground-based solar
radio spectrographs on May 29, 2024, between 14:24 and 14:43 UT. The start and end frequencies of the type II burst were 450 MHz and 25 MHz, respectively. By combining spectral information with
radio imaging data, we found that
radio waves were escaping from the corona via emissions from distinct shock regions. In addition, along with the traditional FH and SB, there were multi-lane structures in the type II bursts. Our analysis suggests complex, inhomogeneous shock dynamics near the leading edge (LE) of the coronal mass ejection (CME). This indicates that the
plasma material compresses more strongly in these forefront regions. This was confirmed by
radio imaging observations, which showed that the higher-frequency emission occurred at a higher altitude than the lower-frequency emission. Our results suggest that the shock geometry and
plasma inhomogeneity play an important role in the generation of type II bursts, leading to traditional fundamental-harmonic split-band (FH-SB) pairs with additional splitting in the type II bands.
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Solar and Stellar Astrophysics
Asteroseismology of the multiperiodic field SX Phe pulsator BL Camelopardalis
W. Szewczuk, J. Daszyńska-Daszkiewicz, P. Walczak et al. (+1 more)
BL Camelopardalis (BL Cam) is the most metal-poor SX Phoenicis
star known in the Galactic field, making it an excellent test bed for studies of Population II stellar structure and
evolution, as well as for investigating the formation channels of blue straggler
stars. We aim to constrain fundamental stellar parameters and pulsational properties of BL Cam and identify the nature of its observed oscillation modes. We analysed high-precision space-based data from the TESS mission and long-term ground-based observations from the Zwicky Transient Facility (ZTF) survey. The ZTF data were primarily used to derive the orbital parameters of the system, while the TESS light curves enabled us to extract a rich oscillation spectrum. We identified multiple pulsation frequencies and performed seismic modelling using a
Bayesian approach. We detected numerous pulsation frequencies, including a dominant radial mode and additional non-radial components. We predicted all fitted modes in our seismic models as excited. The models reproduced the two highest amplitude-independent frequencies (i.e. the radial fundamental mode and a dipole mode) and suggested the possible presence of additional radial overtones. The inferred stellar parameters confirm the extremely low
metallicity of BL~Cam. We also confirm its binary nature, with an orbital period of 144 days. BL Cam provides a valuable
benchmark for testing stellar models of metal-poor pulsators. The combination of space-based photometry and
Bayesian seismic modelling enables robust constraints to be placed on its internal structure and pulsation properties.
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All authors W. Szewczuk, J. Daszyńska-Daszkiewicz, P. Walczak, E. Rodríguez
Solar and Stellar Astrophysics
The Ultrafast Line-Driven Wind from the Double-Degenerate Merger Remnant WD J005311
Kazuma Kato and Kazumi Kashiyama
We systematically construct steady-state wind solutions for double-degenerate merger remnants consisting of a degenerate oxygen-neon core and an optically thick expanding envelope powered by carbon-shell burning, with winds accelerated by radiation pressure including line driving. For a given envelope composition, each solution is characterized by two
eigenvalues: the degenerate core mass, $M_{\rm WD}$, and the total envelope and wind mass, $\Delta M$. We find that wind solutions exist for $M_{\rm WD} \gtrsim 1.0\,M_\odot$. For a given $M_{\rm WD}$, the solutions transition with decreasing $\Delta M$ from slow, continuum-driven winds to ultrafast, line-driven winds, forming a sequence that can be interpreted as the temporal
evolution of a merger remnant. We apply these solutions to WD J005311, a Galactic double-degenerate merger-remnant candidate with an ultrafast wind of $v_{\rm w} \sim 0.05\,c$. Its luminosity, effective temperature, and mass-loss rate are consistently reproduced with $M_{\rm WD} \sim 1.15-1.25\,M_\odot$ and $\Delta M \sim (1.8-5.7)\times 10^{-3}\,M_\odot$. Combining our evolutionary analysis with observations of the surrounding nebula Pa 30 and historical records of SN 1181, we argue that WD J005311 began launching a continuum-driven wind $400-650$ yr after the putative merger and transitioned to the ultrafast-wind phase approximately $100$ yr ago. This phase is expected to continue for another $\sim 1000$ yr, during which the WD will remain below the Chandrasekhar mass and avoid collapse into a
neutron star. Before the continuum-driven wind phase, the remnant may have passed through a more bloated, hydrostatic giant phase with a slower but more massive wind. Future observations of the wind nebula could test this scenario by revealing signatures of interactions between the slow, massive wind and the ultrafast wind.
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Solar and Stellar Astrophysics
Quadrupole White-light Sources in an X1.2 Flare Observed by ASO-S/LST/WST and SDO/HMI
Zhichen Jing, Ying Li, Dechao Song et al. (+2 more)
We present observations of an X1.2 white-light
flare on 2023 January 6, which exhibits a rare quadrupolar white-light source configuration. This event was observed by the White-light Solar
Telescope (WST; 3600 Å) aboard the Advanced Space-based Solar Observatory and the Helioseismic and
Magnetic Imager (HMI; 6173 Å) aboard the Solar Dynamics Observatory. Four
flare-related footpoints (labeled as FP1–FP4) were nearly simultaneously identified in both WST 3600 Å\ and HMI 6173 Å\ continua, associated with a quadrupolar
magnetic configuration and a failed filament eruption. The inner sources of FP1 and FP2 showed a similar enhancement of $\sim$65%/10% in the WST/HMI continuum, while the outer sources of FP3 and FP4 exhibited weaker responses. The inner footpoints had earlier responses in UV and EUV bands and were spatially coincident with the hard X-ray (HXR) footpoint sources. The two southern footpoints (FP2 and FP4) showed stronger HXR and white-light emissions than their northern counterparts (FP1 and FP3), with FP4 uniquely exhibiting a distinct HXR emission above 60 keV, in contrast to the absence of such an emission at FP3. Notably, faint WST 3600 Å\ enhancements at FP4 were observed during the gradual phase, temporally consistent with the fallback of filament material. This X1.2
flare presents a novel quadrupolar white-light structure, enriching our understanding of the generation and
evolution of white-light
flares.
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All authors Zhichen Jing, Ying Li, Dechao Song, Qiao Li, Zhengyuan Tian
Solar and Stellar Astrophysics · Cross-listed from astro-ph.EP
A metallicity sweet spot for disc fragmentation and planet formation
Ethan J. Carter, Dimitris Stamatellos, George Blaylock-Squibbs et al. (+2 more)
Fragmentation of gravitationally unstable discs offers an alternate formation mechanism for gas giant
planets and brown dwarfs on wide orbits.
Metallicity plays a key role in disc
evolution from the onset of gravitational instability to the formation of
planets. We aim to determine the effect of
metallicity on disc fragmentation and on the properties of disc-instability
planets. We model gravitationally unstable discs with varying
metallicity ($0.01-10 \,\rm Z_{\odot}$) using the Smoothed Particle Hydrodynamics code PHANTOM. Our simulations reveal a "sweet spot" for fragmentation at $0.3 \,\rm Z_{\odot}$, where cooling is most efficient, with fragmentation also happening less vigorously at higher and lower
metallicities. However, further away from the sweet spot, fragmentation becomes more difficult and is eventually suppressed at extreme low and high
metallicities ($0.01 \,\rm Z_{\odot}$ and $10 \,\rm Z_{\odot}$, respectively), where the disc cools inefficiently. Discs with
metallicities close to the sweet spot form more
planets per disc, faster, and with lower initial masses than fragmenting discs with higher or lower
metallicities. Our results may explain the slight overabundance of wide-orbit giant
planets observed around metal-poor
stars; these
planets may have formed via disc fragmentation.
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All authors Ethan J. Carter, Dimitris Stamatellos, George Blaylock-Squibbs, Alison Young, Ken Rice
Solar and Stellar Astrophysics · Cross-listed from physics.hist-ph
Could John Ellard Gore have pre-empted the Hertzsprung-Russell diagram?
Jeremy Shears
John Ellard Gore (1845-1910) was an Irish amateur astronomer, prolific science writer and civil engineer. He was an inaugural member of the British Astronomical Association when it was founded in 1890 and was invited to become the first Director of its Variable
Star Section. Through careful
reasoning, Gore reached remarkably modern conclusions about the nature of
stars, including their sizes, distances and luminosities. This paper explores whether he might have been able to produce an early form of what is now known as the Hertzsprung-Russell (H-R) diagram.
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Solar and Stellar Astrophysics
A generalized quadratic balance relation for nonradial nonadiabatic pulsations
Jan Zalewski
We derive a generalized quadratic balance relation for linear nonadiabatic, nonradial stellar pulsations, starting from a sesquilinear amplitude analogue of the pressure-volume-rate work. The derivation requires neither weak nonadiabaticity nor averaging over a pulsation cycle. The relation is expressed in terms of work, generalized norm and boundary contributions and is subsequently recast into kinetic-energy-power form $\mathcal{P}+\Delta B=2\Re(\sigma)E_{\rm kin}$. The volume power is decomposed into a thermodynamic exchange term and response terms associated with compression, horizontal-area deformation and gravitational stratification effects. The equivalent forms of the relation provide diagnostics for checking the computed eigenfrequencies and estimating mode excitation rates. The properties of the balance relation for various types of modes in an envelope of a model AGB
star are examined. We analyze the terms entering the power $\mathcal{P}$ for radial and nonradial p-modes, strange modes as well as examples of low frequency outer-envelope
gravity modes and thermal modes. The results show that the magnitude of mode driving is not determined solely by the thermodynamic work term.
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Solar and Stellar Astrophysics
An Empirical Effective-Temperature Calibrations for Galactic B/A Supergiants
N.L.Vaidman, A.S.Miroshnichenko, Sh.T.Nurmakhametova et al. (+9 more)
We present empirical effective temperature Teff calibrations for Galactic supergiants of spectral types B5-A5 based on optical spectra. The relationships were derived from a reference sample with adopted literature temperatures and use equivalent widths, central line depths, and ratios of selected spectral features as temperature indicators. Quadratic relationships are established for individual diagnostics and their ratios. Collectively, the calibrations span a Teff interval from 8 400 K to 14 700K, while the validity range of each relationships is individually specified. Detailed quantitative atmospheric analyzes remain indispensable for deriving physically consistent stellar parameters. However, their application to extensive spectroscopic samples is observationally and computationally demanding. The empirical relationships presented here provide a homogeneous and readily applicable temperature scale for the characterization of Galactic BA supergiants. The complete calibration tables, including fitted coefficients and uncertainty information, together with an interactive Python tool to apply the relationships, are publicly available through Zenodo. The reduced continuum-normalized spectra and associated metadata are published through a VO–compliant service of the Kazakhstan National Virtual Observatory.
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All authors N.L.Vaidman, A.S.Miroshnichenko, Sh.T.Nurmakhametova, S.Danford, S.A.Khokhlov, I.M.Izmailova, Ch.T.Omarov, S.V.Zharikov, D.E.Yakhiya, A.T. Agishev, A.A.Khokhlov, D.T.Agishev
Solar and Stellar Astrophysics
Investigating the properties of nearby young moving groups using GaiaDR3
Mamta Lad, Ujjwal Krishnan, Blesson Mathew et al. (+4 more)
Moving groups, which are gravitationally unbound collections of
stars spread over large portions of the sky, pose challenges to their identification. Analyzing the three-dimensional spatial motion of
stars is one method to identify their members. Despite several studies in the past, a reliable and conclusive catalog of moving group
stars is currently lacking. Our objective is to present a most recent and updated catalog of nearby young moving group (NYMG) candidates in the solar neighborhood and investigate their properties using updated science data from the Gaia Data Release 3 (DR3). We searched for candidates of twelve NYMGs within a distance of 150 pc using Gaia DR3. To determine the membership, we employed the
Bayesian algorithm BANYAN-Sigma. We compiled a total list of 3,153 NYMG candidates, of which 1,651 were new candidates. We also assessed the credibility of the literature defined 'Good-box' criterion with the latest comprehensive catalog of NYMGs from our study. We homogeneously estimated the ages of the NYMG candidates using Gaia DR3 photometry data. The analysis revealed that our NYMG candidates display a large scatter on the CMDs resulting in a large range of estimated ages from isochrones. Additionally, we conducted an infrared (IR) excess analysis to identify disk candidates among our final sample. Our spectral energy distribution (SED) analysis found 51
stars with IR excess. We present a largely inclusive list of all the NYMG candidates within 150 pc of Solar neighbourhood using Gaia DR3. The wide range of ages obtained from isochrone fitting underscores the need for more robust age analysis techniques to accurately determine the ages of NYMG members. The presence of IR excess in the 51
stars confirms the existence of disks indicating that they could be potential candidates for
exoplanet detections.
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All authors Mamta Lad, Ujjwal Krishnan, Blesson Mathew, Raksha Olakal, Arun Roy, Sreeja Kartha, Vineeth Valsan
Solar and Stellar Astrophysics · Cross-listed from astro-ph.GA
Kinematics and Dynamics of the Open Cluster NGC 2302
Yuna Lee, Jongsuk Hong and Beomdu Lim
Open clusters are ideal observational testbeds to understand the dynamics of stellar systems. We present a dynamical study of the young open cluster NGC 2302. The latest Gaia data and $UBVIJHK_s$ photometric data are used in this study. A total of 117
stars are selected as the genuine members using the Gaia data. This cluster is, on average, reddened by $<E(B-V)> = 0.24 \pm 0.06$ (s.d.). The ratio of total-to-selective extinction ($R_V$) in the direction of NGC 2302 is $2.8 \pm 0.1$. The cluster distance is determined to be $1.16 \pm 0.08$ kpc using Gaia parallaxes. Theoretical isochrone fitting for $Z = 0.008$ on color-magnitude diagrams yields an age of $80 \pm 20$ Myr. The relative proper motions of individual members show no significant radial expansion or contraction. NGC 2302 contains a total stellar mass of $333 \pm 48 M_{\odot}$. The one-dimensional velocity dispersion is approximately 0.26 km s$^{-1}$, which is comparable to the viral velocity dispersion of 0.27 km s$^{-1}$ derived from its total mass. Its relaxation time is estimated to be approximately 90 Myr, which is similar to the age of the cluster within the uncertainty in age estimation. Finally, we report a pattern of mass segregation in the radial distribution of stellar masses. Our results suggest that NGC 2302 is virialized and currently approaching a state of dynamical relaxation. However, because no definitive evidence of kinetic energy equipartition is found, the possibility of the in-situ formation of high-mass
stars within the central region should be carefully considered.
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Solar and Stellar Astrophysics · Cross-listed from astro-ph.GA
Beyond Idealized PAHs: Infrared Signatures of Carbon-Chain Defects from Shock Synthesis
Xiaoting Tan, Zhao Wang, Zu-Jia Lu et al. (+2 more)
Polycyclic aromatic hydrocarbons (PAHs) are widely recognized as carriers of the aromatic infrared bands (AIBs). However, most spectral models rely on idealized structures that fail to capture the energetic environments of interstellar PAH formation. This work investigates the infrared (IR) signatures of PAHs formed under shock conditions and explores whether produced defective structures can explain observational features unpredicted by standard, idealized models. We combine two-stage reactive molecular dynamics simulations of PAH formation via condensation and shock processing with density functional theory spectral calculations, and compare our theoretical results with James Webb Space
Telescope (JWST) observations of NGC 7023 and MRK 1066. Shock processing produces PAHs featuring fullerene-like carbon skeletons and linear carbon-chain attachments. These structural defects yield distinct IR signatures, including prominent carbon-chain stretching features at 4.6-5.5 micron that is absent in ideal PAHs, and significantly enhanced out-of-plane skeletal modes in the 14.5-20 micron regime. Our findings attribute the observed 5.2 micron band in NGC 7023 and MRK 1066 to carbon-chain vibrations and the 15-18 micron emission to curved skeletal modes, providing observational support for the prevalence of defective, shock-formed PAHs in the interstellar medium.
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All authors Xiaoting Tan, Zhao Wang, Zu-Jia Lu, Houda Haidar, Dimitra Rigopoulou
Solar and Stellar Astrophysics · Cross-listed from astro-ph.EP
Stellar Abundances as Probes of Rocky Exoplanet Interiors: The Mantle Composition and Mineralogy of GJ 486b
Harshit Krishna, Asmit Gupta, Sneha Bhowmik et al. (+3 more)
Over the past three decades, hundreds of rocky
exoplanets have been discovered. Some of these show atmospheric signatures indicative of diverse chemical compositions. Interpreting these atmospheres requires a physically grounded understanding of planetary interiors, as interior composition and mineralogy govern the formation and
evolution of secondary atmospheres. Rocky terrestrial
exoplanets are expected to inherit the refractory composition of their host
stars, providing a direct pathway to constrain their bulk composition and mineralogy. However, a large fraction of these
planets orbit M-type
stars, whose compositions remain poorly constrained because of limited and uncertain stellar abundance measurements. Here, we present a physically consistent framework that connects stellar abundances to the interior structure and mineralogy of rocky
exoplanets by combining stellar abundance inference, devolatilization modeling to estimate bulk and mantle elemental abundances, interior structure calculations to derive pressure-temperature profiles, and thermodynamic
equilibrium modeling of mantle mineralogy. We first
benchmark the framework against Earth and then apply it to the super-Earth GJ 486b using chemically consistent abundances derived from ensembles of similar M-dwarf hosts. We find that GJ 486b likely hosts an iron-rich and silica-poor mantle relative to Earth while preserving the major mantle phase transitions. Sensitivity analyses show that the overall mineralogical structure is robust to variations in bulk composition and pressure-temperature profiles, with temperature primarily modulating phase proportions near key transitions. Finally, our results show that stellar-abundance inference combined with devolatilization models constrains the interior composition of rocky
exoplanets and provides a foundation for linking planetary interiors to atmospheric characterization.
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All authors Harshit Krishna, Asmit Gupta, Sneha Bhowmik, Chandan K. Sahu, Sudipta Mridha, Liton Majumdar