astro-ph.SR

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astro-ph.SR 2026-05-15 Recognition

Convex hulls reveal propagating sausage waves in irregular solar pores

Analysing the highly irregular boundaries of solar pores

Fundamental sausage and kink modes stay detectable while higher fluting modes are suppressed by boundary irregularity.

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Solar pores possess irregular and evolving boundaries that are often far from the ideal circular flux tubes assumed in many magnetohydrodynamic (MHD) oscillation models. To tackle this irregularity in a consistent way for wave analysis, we introduce a framework that employs the convex hull of the pore boundary - derived from intensity minimum error thresholding - as the domain to perform further analysis. Using the modal assurance criterion, we find the range of pore shapes for which this approximation is valid. We demonstrate the usefulness of this framework by applying it to multi-height, high-cadence observations (4170 angstrom continuum, G-band, Na~\textsc{i}, and Ca~\textsc{ii}~K) of a solar pore, and apply Proper Orthogonal Decomposition of the convex hull to determine wave modes. The fundamental sausage ($m=1$) and kink ($m=2$) mode is found to remain reliable, while higher-order fluting modes ($m\ge3$) are strongly degraded by small-scale boundary irregularity. As expected, sausage-like modes dominate the variance at all heights and exhibit a systematic upward shift in frequency, consistent with freely propagating compressive waves. In contrast, the kink-like motions appear weak, confined to a persistent low-frequency peak, and most plausibly interpreted as a forced response to granular buffeting rather than a propagating mode. Together, these results establish a practical methodology for boundary-mode analysis in real, highly structured pores and provide new constraints on the nature and height evolution of MHD waves in the lower solar atmosphere.

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astro-ph.SR 2026-05-15 1 theorem

Reconnection at HCS produces observed ion power-law energies

The Role of Magnetic Reconnection in Energizing Protons and Heavier Ions at the Heliospheric Current Sheet

Simulations yield spectral indices and E_max scaling with Q/M that match PSP data for multiple species.

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During near-Sun crossings of the heliospheric current sheet (HCS), Parker Solar Probe (PSP) observed populations of high-energy protons and heavier ions indicating possible energization by magnetic reconnection up to 10s -- 100s keV nucleon$^{-1}$. Here we study ion acceleration by magnetic reconnection at the HCS. To estimate ion energization, we solve the Parker transport equation coupled to a large-scale 2D MHD reconnection simulation. We find that multiple ion species develop power-law distributions with both spectral index and high-energy cutoff $E_{\text{max}}$ consistent with in-situ data. By accounting for the injection physics determined by kinetic simulations, we confirm that the charge-to-mass ratio scales as $E_{\text{max}} \propto (Q/M)^{\alpha}$ with $\alpha \sim 0.8-1.1$, approximately consistent with PSP measurements in the broader range $\alpha \sim 0.6-1.7$. In the limit where ions are injected at the same energy per nucleon, $\alpha$ can be as low as $\sim 0.3$. These findings further support the role of magnetic reconnection in producing high-energy heavy ions at the HCS.

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astro-ph.SR 2026-05-15 2 theorems

V486 Car binary has 2.1 and 0.4 solar masses plus third companion

The Close Binary V486 Carinae

Photometry and timing data give the physical parameters of this near-contact system and indicate a 0.3 solar-mass star a few AU away.

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The hitherto neglected close binary V486 Car is studied with the aid of newly applied satellite photometry (HIPPARCOS and TESS), high dispersion spectrometry (HERCULES) and ground-based B and V photometry. While the sinusoidal light variations are suggestive of a near-contact system, the stars have only shallow eclipse, so highly confident parametrization becomes challenging. We find: $M_1 = 2.1 \pm 0.1$, $M_2 = 0.4 \pm 0.1$; $R_1 = 3.20 \pm 0.02$, $R_2 = 1.48 \pm 0.01$; (${\odot}$); $T_{e1} = 10000 \pm 500$, $T_{e2} = 6200 \pm 200$ (K); distance = 162 $\pm$ 12 (pc). New times of minima for V486 Car have been examined, including recent observations from TESS. The role of the relatively significant O'Connell effect is examined. As well as the conspicuous asymmetry from the main effect of about 0.036 mag (V), a jitter, with amplitude of about 0.005 V mag and quasi-period of order $\sim$ 10 d is noticed. There is a tendency for such photometric excursions at one maximum to precede those at the other. As well, the O -- C data indicate the presence of a low mass star $\sim$0.3 M$_{\odot}$ in an orbit separated by a few AU from the close binary. More accurate and plentiful spectroscopic data would be requisite for further investigations. A brief discussion reviews possible approaches to understanding the system in the context of near-contact binary scenarios.

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astro-ph.SR 2026-05-14 2 theorems

Half of blue stragglers sit near the end of their main-sequence phase

The Distribution of Blue Straggler Stars in the Color-Magnitude Diagrams of Old Open Clusters

In old open clusters, helium enrichment from accretion places them in late evolutionary stages on the color-magnitude diagram.

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We examine the blue straggler star (BSS) populations of six old ($\geq$4 Gyr) open clusters: M67, NGC 188, NGC 6791, Berkeley 32, Berkeley 39, and Trumpler 19. We find that 50% of BSSs have color-magnitude diagram (CMD) locations corresponding to single stars in the final third of their main-sequence lifetimes. This build-up of BSSs near the terminal-age main sequence (TAMS) is primarily, but not solely, driven by more massive BSSs. Eleven of the BSSs have white dwarf companions with measured cooling ages; their evolution age distributions indicate that more massive BSSs typically form far from the zero-age main sequence, whereas lower mass BSSs can form at every evolutionary age. We show that inferred core helium amounts (above primordial) of late-evolution-age BSSs correspond to the core helium fused by cluster main-sequence stars near the turnoffs. We also find that the masses of asymptotic giant branch (AGB) mass-transfer BSSs require evolved main-sequence accretors and conservative mass transfer. These findings indicate that helium enrichment of progenitor accretors leads to the prevalence of BSSs near the TAMS. We further classify the evolutionary stages of the progenitor donors in M67 and NGC 188 and find mass transfer during the AGB accounts for at least half of the BSSs. We trace how the main-sequence binary population of NGC 188 evolves, and find that only 30-40% of interacting binaries create BSSs and that progenitor orbits must change to match current BSS periods.

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astro-ph.SR 2026-05-14 2 theorems

Rotation barely affects Cepheid blue loop luminosities

Toward a Comprehensive Grid of Cepheid Models with MESA. IV. Modest Effects of Rotation on Blue Loops

MESA models find increases of at most 0.04 dex, insufficient to resolve the mass discrepancy without core overshooting.

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Evolutionary tracks for $2-8M_\odot$ stars, with metallicities of $Z=0.014$, $0.006$, and $0.002$, including rotation, are computed with Modules for Experiments in Stellar Astrophysics (MESA). We study how rotation impacts the evolutionary properties of classical Cepheids. We examine whether rotation can offer a plausible explanation for the mass discrepancy problem when it is included in the evolutionary code using the fully diffusive approximation for rotationally induced mixing processes. We find that rotation barely influences the appearance and luminosity levels of the blue loops. While luminosity increases with increasing initial rotation rate, the increase does not exceed 0.04 dex, a fraction of the increase resulting from including the main sequence (MS) core overshooting of $0.2H_p$. As a consequence, rotation alone cannot resolve the mass discrepancy problem without simultaneously requiring significant MS core overshooting. Similar to the mass-luminosity relation, the period-radius and period-luminosity relations are barely affected by rotation, while the period-age relation predicts Cepheid ages to be only a few per cent longer compared with models without rotation. The predicted surface rotational velocities are too large compared with observations. These results are in contrast with those obtained with the Geneva code, which implements rotational mixing using the advective-diffusive scheme. In that approach, the luminosity levels of the loops are significantly higher, their luminosity extent increases, and the predicted rotation velocities are lower, compared with MESA models. The differences between the two approaches arise from significantly more efficient rotation-induced mixing during the MS evolution in models computed with the advective-diffusive scheme.

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astro-ph.SR 2026-05-14 2 theorems

Switchbacks show non-zero electric fields in plasma frame

Direct Evidence of Non-Ideal Dissipative Dynamics in Solar Wind Magnetic Switchbacks

Parker Solar Probe data proves these structures follow Hall-MHD physics and dissipate energy locally.

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Magnetic switchbacks, large-amplitude, localized Alfvenic like rotations of the solar wind magnetic field, have been the subject of intensive investigation, with approximately 200 refereed papers published in the last decade. Yet, fundamental controversies persist regarding whether switchbacks can be described with Ideal MHD (magnetohydrodynamic) physics or Hall-MHD physics and whether their origin is at the solar surface or in the solar wind. To settle these controversies, we present Parker Solar Probe electric field measurements between 13 and 40 solar radii, which show that switchbacks have non-zero electric fields in the plasma frame, a finding that definitively settles the physics controversy by proving that switchbacks are Hall-MHD, not Ideal MHD, structures. Along with these electric fields, there are enhanced Poynting vectors having three components with similar magnitudes that exist only inside the switchbacks. These facts contradict the view of switchbacks as simple outward-propagating pulses. Together, they resolve one controversy by showing that switchbacks in the young solar wind are a non-MHD process. They contribute to the second (source) controversy by identifying switchbacks as sites of active, in-situ, evolution. These findings provide a new framework for understanding energy transport and dissipation in astrophysical plasmas.

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astro-ph.SR 2026-05-14 Recognition

Dust and gamma-ray escape explain SN2023ixf's late fading

SN2023ixf: ultraviolet-to-infrared radiative-transfer modeling of the nebular-phase evolution until 1000 days

Models with fixed ejecta parameters match observations to 1000 days only after adding dust in the cold dense shell and greater gamma-ray

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We present non-local thermodynamic equilibrium radiative-transfer modeling of SN2023ixf during the nebular phase out to 1000d, using the same ejecta that matched its photospheric evolution, namely a partially stripped red-supergiant star of initially 15Msun whose terminal explosion yielded ejecta with 7-8Msun, kinetic energy of 1.2e51erg, and 56Ni mass of 0.05Msun, augmented with a cold dense shell (CDS) of 0.2Msun at 8000km/s. Interaction with circumstellar material persists at all epochs, powering the ultraviolet (UV) flux at all times, but dominating the optical only after ~600d. Matching the V-band light curve requires invoking both enhanced gamma-ray escape and dust formation after ~200d, first in the CDS and eventually in the inner ejecta as well. Depending on where they form relative to the dust, emission lines are uniformly attenuated or skewed with a blue-red asymmetry. Our models suggest a rising dust mass (chosen as an C-rich and Si-rich mixture) in the CDS and inner ejecta, possibly reaching 1e-4Msun at 700d, while an external cold dust component is required to match the mid-infrared emission. The UV radiation, largely unaffected by dust, is influenced by the emission and absorption from Fe lines, together with strong, blueshifted emission from Lyalpha and MgII2800, both present at >~200d and with a strengthening fractional flux thereafter. Optical-depth effects play a critical role for the UV flux, and most notably on Lyalpha whose strength depends strongly on the CDS structure (mass and extent) and the treatment of power injection. The CDS is continuously slowing down from 8000km/s at 112d to ~6500km/s at 998d, suggesting a growth in mass of several 0.1Msun. SN2023ixf shares many similarities with SN1993J at 1-3yr, but it is eventually fainter due to dust extinction and cooler (i.e., weak [NII] and no [OIII] lines) likely as a result of greater CDS and ejecta masses.

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astro-ph.SR 2026-05-14 Recognition

ET Cru secondary shows deep CNO-cycle exposure

Spectral Disentangling Reveals Deep CNO-cycle Exposure in ET Cru

Spectral disentangling measures carbon depletion and nitrogen enrichment far beyond classical Algols, confirming advanced stripping of the 6

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Binary stars undergoing mass transfer provide unique laboratories for testing stellar evolution. Here, we present a comprehensive photometric and spectroscopic analysis of the semi-detached system ET Cru. Using spectral disentangling, we independently determined the effective temperatures and chemical abundances of both components with high precision, including nine elements (eleven species). We find masses of $13.41\,M_\odot$ and $6.00\,M_\odot$ for the primary and secondary, respectively, with uncertainties of only $\sim$1.3%. The radii are $5.58\,R_\odot$ and $5.68\,R_\odot$, measured to within 0.4% and 0.5%. Surface gravities are constrained to better than 1%, while effective temperatures are determined to within 3-5%. The secondary exhibits extreme chemical anomalies, with severe carbon depletion and nitrogen enrichment far exceeding those reported in classical Algol systems. Multi-wavelength spectral energy distribution modelling yields a distance of $\sim$2.5 kpc, inconsistent with the $Gaia$ DR3 parallax, suggesting systematic astrometric uncertainties in the parallax distance. Together, these results establish ET Cru as a benchmark Algol-type binary, revealing direct spectroscopic evidence of deep CNO-cycle exposure in the donor and confirming the primary star as a rejuvenated gainer. ET Cru thus provides a chemically and dynamically illustrative case for understanding advanced binary interactions and the late evolutionary stages of massive-star evolution.

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astro-ph.SR 2026-05-14 Recognition

Procyon models point to higher core overshoot in evolution

Analysis of DQZ White Dwarf Evolution through Procyon

Best fits reproduce masses and give a 2.23 Gyr system age while mapping the white dwarf to a 1.9-2.6 solar mass progenitor.

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Procyon is a great system to probe stellar evolution of non-interacting binaries. We present an extensive grid of MESA (Modules for Experiments in Stellar Astrophysics) evolutionary tracks to constrain the evolution of Procyon A and B. We systematically vary the initial parameters of our grid anchored by precise dynamical masses and spectroscopic determinations of effective temperature (T$_{eff}$) and luminosity ($L$) to match the stars' positions on the H-R Diagram. Our goal is two-fold: (i) to quantify how the inferred system age and the progenitor mass of Procyon B depend on metallicity ($Z$), mixing length ($\alpha$), and core overshoot ($\beta$), and (ii) to determine the best fitting model of Procyon B within a model-based initial-to-final mass relationship (IMFR) for hydrogen-deficient white dwarfs. Our best-fit models reproduce the observed properties for both components, yielding $M_\mathrm{A}=1.487 \pm 0.095$ M$_{\odot}$, $M_\mathrm{B}=0.592\pm 0.082$ M$_{\odot}$, a system age of $2.23 \pm 0.90$ Gyr, and a white dwarf cooling age of $1.20\pm0.49$ Gyr for Procyon B, consistent with independent determinations. Our results point to higher core overshoot than the standard adopted range, with the best fits ranging from $\beta=0.5-1.0$. From our model grid, we map Procyon B to the initial-to-final mass relationship for H-deficient white dwarfs in the $1.9\!-\!2.6$ M$_{\odot}$ progenitor range. Additionally, we implement the accretion of heavy metals onto the surface of the WD and fit our isotopic abundances to spectroscopic observations. We outline the physics used in our analysis.

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astro-ph.SR 2026-05-14 2 theorems

Gaia light curves give RR Lyrae metallicities to 0.26 dex

Photometric metallicity of Galactic RR Lyrae stars in the Gaia DR3 era

A period and Fourier-phase relation calibrated on spectroscopic ground truth assigns metallicities to thousands of stars without new spectra

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We present a new, calibrated $G$-band relationship between pulsation period $P$, Fourier parameter $\phi_{31}$, and metallicity [Fe/H] for galactic RR Lyrae stars from the Gaia survey. A set of 72 fundamental mode RR Lyrae stars were identified for deriving the relation in the $G$-band, after visual examination of their light curves. Unlike recent large-scale calibrations, our relation prioritizes calibration purity by anchoring exclusively to a homogeneously analyzed sample of high-resolution spectroscopic metallicities from the literature. Our best fit relation is $\text{[Fe/H]} = (-6.93 \pm 0.58) - (6.04 \pm 0.37)P + (1.65 \pm 0.11)\phi_{31}$. We compare the [Fe/H] predicted by our relation for the stars in our calibration sample with that obtained from previously established relations in the $G$-band using different approaches. Our calibrated $G$-band $P$-$\phi_{31}$-[Fe/H] relationship demonstrates high reliability when validated against spectroscopic data, achieving a negligible bias of $0.00$ dex and an empirical RMS scatter of 0.26 dex. Furthermore, by applying an Orthogonal Distance Regression (ODR) routine that fully propagates parameter covariance, we establish a mathematically strict empirical baseline whose theoretical uncertainties perfectly align with this observed dispersion. We find that the inclusion of the $R_{21}$ Fourier parameter offers no significant improvement in metallicity estimation. Comparisons with literature confirm that our linear relation aligns closely with other Gaia DR3-based studies, while offering improved precision over older DR2-based relations.

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astro-ph.SR 2026-05-14 Recognition

New formula links RR Lyrae period and shape to metallicity

Photometric metallicity of Galactic RR Lyrae stars in the Gaia DR3 era

Calibrated on 72 stars with homogeneous spectra, the G-band relation returns zero bias and 0.26 dex scatter.

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We present a new, calibrated $G$-band relationship between pulsation period $P$, Fourier parameter $\phi_{31}$, and metallicity [Fe/H] for galactic RR Lyrae stars from the Gaia survey. A set of 72 fundamental mode RR Lyrae stars were identified for deriving the relation in the $G$-band, after visual examination of their light curves. Unlike recent large-scale calibrations, our relation prioritizes calibration purity by anchoring exclusively to a homogeneously analyzed sample of high-resolution spectroscopic metallicities from the literature. Our best fit relation is $\text{[Fe/H]} = (-6.93 \pm 0.58) - (6.04 \pm 0.37)P + (1.65 \pm 0.11)\phi_{31}$. We compare the [Fe/H] predicted by our relation for the stars in our calibration sample with that obtained from previously established relations in the $G$-band using different approaches. Our calibrated $G$-band $P$-$\phi_{31}$-[Fe/H] relationship demonstrates high reliability when validated against spectroscopic data, achieving a negligible bias of $0.00$ dex and an empirical RMS scatter of 0.26 dex. Furthermore, by applying an Orthogonal Distance Regression (ODR) routine that fully propagates parameter covariance, we establish a mathematically strict empirical baseline whose theoretical uncertainties perfectly align with this observed dispersion. We find that the inclusion of the $R_{21}$ Fourier parameter offers no significant improvement in metallicity estimation. Comparisons with literature confirm that our linear relation aligns closely with other Gaia DR3-based studies, while offering improved precision over older DR2-based relations.

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astro-ph.SR 2026-05-14 2 theorems

Neural network finds 50 fast wave train candidates in solar radio

Detector for fast wave trains in the solar radio emission

The method expands the sample of rare events used to diagnose energy release scales and plasma structures in the corona.

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Quasi-periodic fast propagating (QFP) wave trains observed in the solar corona after some energetic events (solar flares, coronal mass ejections, jets) open possibilities for diagnostics of spatial and temporal scales of the impulsive energy release processes, that are absent in the standard model of a solar flare. Besides, the dynamics of the wave trains and their characteristic spatial and temporal signatures allow to localize the initial energy release volume magenta and to perform fine diagnostics of the transverse structures of plasma inhomogeneities in the solar corona. However, the small number of such events registered significantly limits their promising diagnostic potential. The aim of this paper is to perform an automatic search for fast wave trains in radio data. We apply classifying neural network/machine learning methods. Dynamic radio spectra obtained by HiRAS radio spectrographs within the 20 MHz -- 2.5 GHz frequency band during 2011 were used. We consider 50 global coronal EUV waves as marker events for more a targeted search in HiRAS data. Our automatic detector revealed 50 independent QFP-candidates events with the temporal signatures similar to that of the fast wave trains, with 13 candidates connected with the global waves.

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astro-ph.SR 2026-05-14 Recognition

Stokes V asymmetries diagnose waves tied to FIP bias

Spectropolarimetric analysis of waves linked to FIP

The method uses polarization profile imbalances to probe Alfvénic perturbations that fractionate elements in the solar atmosphere.

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High-resolution spectropolarimetry has opened new avenues for understanding how chromospheric waves shape coronal plasma composition. All modeling efforts so far highlight wave activity and, in particular, the ponderomotive force associated to Alfv\'enic perturbations, as a key ingredient. Over recent years, studies based on spectropolarimetric measurements in the solar chromosphere have identified magnetic perturbations associated to waves linked to regions in the corona with enhanced FIP bias. Building on this established framework, the present work explores the diagnostic potential of Stokes V amplitude asymmetries as an alternative diagnostic tool for investigating wave behavior relevant to compositional fractionation processes.

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astro-ph.SR 2026-05-14 2 theorems

Post-AGB disc inner rims show diverse substructures

VLTI/PIONIER imaging of post-AGB binaries. An INSPIRING hunt for inner rim substructures in circumbinary discs

Images of eight systems find only one explained by inclination alone; four show unexpected azimuthal enhancements and one has large and fine

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We image the detailed inner rim morphology for a sample of post-AGB circumbinary discs observed using NIR interferometry. At resolutions down to ~1-2 mas (corresponding to ~1-10 AU), we aim to reveal potential substructures that may trace perturbations from the binary or embedded substellar companions, or that arise from hydrodynamical instabilities. We developed an image reconstruction workflow using the SPARCO approach together with the ORGANIC reconstruction algorithm. This was applied to VLTI/PIONIER data of eight diverse post-AGB binaries, providing high-fidelity images of dust continuum emission at the inner rim. Extensive tests were applied to assess the robustness of the recovered image features. The dusty disc rim is well-resolved for all targets. Only one of the images can be fully accounted for by simple radiative transfer effects due to disc inclination, while in several others indications of potential substructures are detected. Strikingly, four exhibit robust azimuthal brightness enhancements at locations not expected from inclination effects alone. These can indicate strong radiative or dynamical responses to the binary, or vortices formed via hydrodynamical instabilities. One target displays an even more puzzling morphology, showing a single large-scale outer flux arc and several small-scale arcs closer to the binary, possibly revealing accretion streams onto the binary, a misaligned innermost disc, or a spiral feature located in the disc or in an outflow. This work presents the first homogeneous interferometric imaging survey of the inner regions of post-AGB circumbinary discs, enabling direct comparison of inner rim morphologies across a representative sample. The inner disc regions are highly diverse and dynamic, harbouring a significant amount of substructure candidates. Multi-wavelength and time-series imaging will be essential in uncovering their physical origins.

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astro-ph.SR 2026-05-14 2 theorems

Standard NLTE suffices for Ca II H&K and IR triplet lines

Full non-LTE multi-level radiative transfer II. The case of a 5-level Ca ii atom with broadened excited levels

In a simplified atmosphere the full non-LTE treatment is unnecessary even after including velocity-changing collisions.

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The so-called full non-local thermodynamic equilibrium (FNLTE) radiative transfer problem allows us to take into account not only deviations of the radiation field from the Planckian but also deviations of the densities and velocity distributions of massive particles from Maxwell-Boltzmann statistics. This article discusses the extension of this formalism to physically realistic multi-level atoms, including natural broadening of the excited levels. In practice, we must solve self-consistently a coupled set of kinetic equations and determine, for each line, an emission and absorption profile by convolving a non-Lorentzian atomic profile with a non-Maxwellian velocity distribution at each iteration. To solve this numerically challenging problem, we have developed a new efficient iterative method based on well-known approximate operator techniques. After validating our numerical strategy, we present the results obtained for the H & K lines and the infrared triplet of the Ca II. Under the conditions studied, for this particular atomic model and for a simplified atmosphere, we find that the standard NLTE with partial redistribution is sufficient to describe the formation of Ca II spectral lines. The more exact treatment of FNLTE is unnecessary in the case of Ca II H & K, and infrared triplet lines, even when accounting for velocity-changing collisions.

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astro-ph.SR 2026-05-14 Recognition

Equal-mass twin binaries show divergent evolution and activity

Diversity in Evolutionary Status and Magnetic Activity among Solar-Type Twin Detached Eclipsing Binaries

Four G-type systems span main-sequence, subgiant, and red-giant stages with differing magnetic activity levels.

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We present a combined photometric and spectroscopic analysis of four detached eclipsing binaries (KIC 8957954, KIC 10593759, KIC 8302455, and TIC 207398432), all of which exhibit composite G-type spectra and nearly equal mass ratios. Based on survey data and our own observations, we measured radial velocities with the broadening function method, applied the fd3 program for spectral disentangling, and modeled the light curves with the Wilson-Devinney code to determine accurate absolute parameters. The results reveal significant differences in evolutionary stages and magnetic activity despite their nearly equal masses. Both components of KIC 8957954 and KIC 8302455 are on the main sequence; KIC 10593759 has evolved to the subgiant stage; and in TIC 207398432, the secondary has entered the red giant phase. Stronger magnetic activity is observed in KIC 10593759 and TIC 207398432, characterized by rapid O'Connell Effect Ratio variations, with the latter also exhibiting multiple superflare events. In addition, the spectral characteristics of TIC 207398432 suggest that it may be part of a hierarchical triple system. This study provides precise absolute parameters for twin binaries and offers important observational evidence for understanding their evolutionary diversity, magnetic activity, and the possible presence of tertiary companions.

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astro-ph.SR 2026-05-14 Recognition

Review unifies data and models on protostellar mass accretion

The Accretion Process on Protostars

Compares measurement methods and gaps to clarify how stars gain most of their mass before the T Tauri stage.

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The process of mass accretion onto Young Stellar Objects (YSOs) plays a fundamental role in determining the final stellar mass and setting the initial conditions for planet formation. Despite its critical role, our understanding of accretion remains fragmented, particularly for what concerns the earliest, protostellar phases (Class 0/I). While the community has consolidated a comprehensive knowledge of the accretion process of the later-stage Classical T Tauri Stars (CTTSs), a similar level of understanding is critically lacking for the protostellar phase, where the bulk of the mass is assembled. This work aims to review recent major results, both from the observational and numerical point of view, bridging the gap between the two approaches and providing an updated, complete assessment of accretion in protostellar sources. We present different techniques to measure accretion on protostars, analyze how methodological differences affect parameter estimation, discuss the caveats in comparing with numerical models, and suggest the next steps to take towards an ever more exhaustive picture of the protostellar phase.

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astro-ph.SR 2026-05-14

654 white-dwarf FGK binaries isolated from UV excess sources

Discovery and Characterization of White Dwarf-FGK Main-Sequence Binaries within the Optical Main-Sequence Locus

LAMOST spectra and Gaia data yield mostly low-mass hot white dwarfs paired with G-type stars in close systems.

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White dwarf main-sequence (WDMS) binaries provide important laboratories for studying binary evolution and the formation of low-mass white dwarfs. In this work, we identify 654 reliable WDMS candidates with FGK-type companions from an initial set of 772 ultraviolet-excess sources, selected using stellar atmospheric parameters from LAMOST spectroscopy and subsequently refined with \textit{Gaia} DR3 astrometry and photometry together with ultraviolet data from \textit{GALEX}. Candidates were selected based on ultraviolet excess relative to the \textit{Gaia} main-sequence locus and refined using isochrone constraints to exclude systems inconsistent with MS companions. Binary spectral energy distribution fitting yields effective temperatures and radii for both components, as well as distance and extinction estimates. The MS companions are dominated by G-type stars ($\sim52\%$), with comparable fractions of F- and K-type companions, and no A-type primaries. Using white-dwarf evolutionary cooling models, we find that the WD components are predominantly low-mass ($M_{\rm WD}\,\sim\,0.2\text{--}0.4\,M_\odot$), including a substantial population of extremely low-mass ($<0.3\,M_\odot$) WDs likely produced through binary interaction. The WDs are generally hot ($\sim1.5\times10^4\,\mathrm{K}$), consistent with the ultraviolet selection bias favoring luminous, large-radius WDs. Multi-epoch LAMOST radial velocities show larger amplitudes than those of a comparison sample of MS stars, supporting the close-binary nature of these systems. Although subject to strong selection effects, the catalog offers a clean and well-characterized sample of FGK+WD binaries.

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astro-ph.SR 2026-05-14 2 theorems

Resonant instability in supersonic plasma shear flows vanishes for sharp edges

Resonant shear-flow instability in anisotropic supersonic plasmas with heat flux

The growth peaks when wave phase velocity equals flow velocity and weakens at high Mach numbers, offering a candidate for solar wind temp. 0

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This work is devoted to the study of the influence of temperature anisotropy and parallel heat flux on the stability of supersonic shear flow in collisionless plasmas. Within a fluid-based framework, we employ the 16-moment transport equations -- derived from the Vlasov-Maxwell system -- to describe the plasma dynamics. By performing a modal analysis we investigate the oblique propagation of linear disturbances within a magnetized plasma characterized by a shear flow of arbitrary profile aligned with the ambient magnetic field. In the unperturbed state, both the plasma density and the magnetic field are assumed to be homogeneous. For a smooth, hyperbolic velocity profile representing supersonic shear, the governing wave equation is reduced to a form amenable to an exact analytical solution. Analytical solutions are expressed in terms of special functions that yield an infinite discrete spectrum of complex eigenfrequencies ($n = 0, 1, 2, \dots$). The instability is identified as resonant, peaking when the wave phase velocity matches the mean flow velocity, with the growth rate decreasing for higher-order modes. The results indicate that, while heat flux exerts a negligible influence under conditions of supersonic flow, the growth rate decreases and approaches an asymptotic value as the Mach number increases. Notably, the instability vanishes in the vortex sheet limit, distinguishing it from the classical Kelvin-Helmholtz mechanism. These findings suggest that this specific instability holds significant potential for explaining the problem of observed boundaries between isotropic and anisotropic proton temperature regions in a low-beta solar wind plasma.

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astro-ph.SR 2026-05-14

Solar wave cutoff frequency rises from 3 to 8.5 mHz with height

Height Variations of Magnetoacoustic Cutoff Frequency in the Solar Atmosphere

IRIS spectra show the threshold for upward-propagating magnetoacoustic waves increasing from photosphere to chromosphere.

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The determination of the cutoff frequency in real solar observations under different local physical conditions is an important and insufficiently explored aspect of waves in solar physics. This work utilizes the near ultraviolet (NUV) spectrum of the QS, observed by the Interface Region Imaging Spectrograph (IRIS) on November 16th, 2013, in sit-n-stare mode. It contains several absorption and emission lines that form at different heights between the photosphere and chromosphere. Cross-wavelet analysis is performed on Doppler velocity time series of pairs of spectral lines sampling different atmospheric layers to estimate the cutoff frequency at six different heights between the photosphere and chromosphere. It is found that the cutoff frequency increases with height from around 3.0 mHz at 0.38 Mm (photosphere) to around 8.5 mHz at 1.2 Mm (chromosphere). Higher chromospheric heights show indications of standing oscillations. The presented observational results are compared with those previously obtained, and serve as a benchmark to refine theoretical models that predict variations of cutoff frequencies in the solar atmosphere.

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astro-ph.SR 2026-05-14 2 theorems

Lens dust monitoring cuts coronagraph noise by 67 percent

Forward Modeling of Dust-Induced Stray Light in Ground-Based Coronagraphs: A Dual-Path Monitoring Approach for High-Precision Inner Corona Observations

Dual-path imaging and physical modeling restore accurate inner corona profiles and expected 2 MK temperature decay.

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High-precision ground-based observations of the inner corona (1.05-2.0 R_sun) are fundamentally constrained by instrumental stray light, particularly the additive background from dynamic dust accumulation on the objective lens. To address this issue, we propose a correction method for the Spectral Imaging Coronagraph (SICG) based on dual-path real-time monitoring and forward physical modeling. By simultaneously imaging the objective lens surface, we obtain deterministic prior information on dust distribution. We construct a physical point-spread function using optical defocus parameters and reconstruct the nonuniform scattering background via convolution. Model parameters are retrieved through data-driven inversion constrained by polar coronal holes. The method demonstrates excellent robustness under varying contamination conditions. After correction, the rms noise in the polar background is reduced by approximately 67% on average, and the signal-to-background ratio improves by a factor of up to 3.7 under heavy contamination conditions. Comparisons with space-based Solar Dynamics Observatory/Atmospheric Imaging Assembly observations indicate that the corrected images recover the morphological structures of streamers with high fidelity. Further radial intensity analysis reveals that the correction process successfully restores the hydrostatic exponential decay characteristic of inner coronal radiation. The fitted decay coefficient corresponds to a plasma temperature of approximately 2.0 MK, consistent with the characteristic formation temperature of the Fe XIV 530.3 nm line. These results demonstrate that the method effectively eliminates the dominant systematic bias in ground-based observations, providing a reliable data foundation for high-precision coronal thermodynamic and dynamic research with the SICG.

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astro-ph.SR 2026-05-13

Near-IR lines distinguish FUOr disks from normal stars

Quantitative Spectroscopic Diagnostics for FU Orionis-Type Young Stellar Objects

Atomic equivalent widths and molecular band ratios place outbursting young stars in distinct parameter spaces from dwarfs and evolved stars.

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We present near-infrared spectroscopic diagnostics that can be used to identify FU Orionis stars (FUOrs). FUOrs are young stellar objects (YSOs) that are currently in a state of extreme outburst, caused by enhanced mass {inflow} from their accretion disks. The disks give FUOrs a distinct multi-temperature optical and infrared spectrum. Considering both the predicted spectrum from a disk atmosphere model, and existing spectral diagnostics from the literature, we identify key atomic and molecular features for characterizing FUOrs. Some of the chosen features are proxies for temperature, others are sensitive to surface gravity, and still others probe disk winds. Using the Palomar Observatory/Hale Telescope TripleSpec spectrograph, we gathered near-infrared spectra of 28 known FUOrs. We use standard equivalent widths to determine the strength of atomic lines and we design several band ratios for measuring molecular features. We compare the measurements between our spectra and a control sample of late-type dwarfs and evolved stars from the Infrared Telescope Facility Spectral Library. By considering the relative distributions of these samples in our defined spectral diagnostics, we propose a number of parameter spaces that can distinguish FUOr disks from normal stars. The rate of discovery of FUOr candidates has increased significantly in recent years, largely due to the increasing prevalence of time-domain surveys. Our proposed diagnostics will allow new photometric candidates to be confirmed or refuted as such.

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astro-ph.SR 2026-05-13 2 theorems

New dwarf nova below period minimum shows 72-minute superhumps

A New WZ Sagittae-type Dwarf Nova KSP-OT-202104a Near the Period Minimum from the KMTNet Supernova Program

KSP-OT-202104a adds a rare short-period example with low mass transfer that may evolve into an AM CVn star.

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We present photometric and spectroscopic studies of a new WZ Sagittae (Sge)-type dwarf nova (DN) KSP-OT-202104a discovered by the Korea Microlensing Telescope Network Supernova Program. The source exhibits outburst amplitudes of $\sim 8$ mag with a duration of $\sim 28.5$ days in the $V$-band. It is a type D DN among WZ Sge-types, and we estimate the superhump period to be $P_{\rm sh} \approx 71.7$ minutes ($=0.04978$ days). Its spectrum shows blue continuum as often found in optically-thick accretion disks of DNe during outbursts with hydrogen absorption lines from H$\beta$ to H$\zeta$. Since the orbital period in WZ Sge-type DNe is typically very close to the superhump period, we consider that this target would belong to the small sample of DNe below the period minimum and may be evolving toward AM Canum Venaticorum (AM CVn) stars. This system therefore adds an example of a short-period dwarf nova with a low mass-transfer rate to the known sample.

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astro-ph.SR 2026-05-13 Recognition

Catalog supplies ages for 659 HWO stars but covers only 25 percent

The HAges Catalog: Stellar Ages for High Priority HWO Target Stars

Asteroseismic ages exist for 5 percent and gyrochronal ages for 20 percent, showing the scale of work still needed before launch.

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Precise stellar ages (uncertainties $\lesssim 1$ Gyr, or $\sim 20\%$ at solar age) are required to discern evolutionary trends in atmospheric biosignatures of terrestrial habitable zone exoplanets surveyed by the Habitable Worlds Observatory (HWO) and will aid in constraining planetary interior evolution and target prioritization. We present a catalog of stellar ages for Tier 1 and Tier 2 targets in the HWO Target Stars and Systems (TSS) sub-working group's TSS25 list, compiling published literature ages derived from high-precision methods. The sample comprises 659 stars likely to be observed by HWO, independent of the final mission architecture. This initial catalog focuses on asteroseismology and gyrochronology, which can achieve $\sim 20\%$ precision for the majority of these stars. We find that only $\sim 5\%$ of the sample have asteroseismic ages and $\sim 20\%$ have gyrochronal ages, with just $\sim 2\%$ having constraints from both methods. For stars with multiple published measurements, the median reported statistical uncertainties are slightly smaller than the systematic uncertainties: $\sim 9\%$ versus $\sim 12\%$ for asteroseismology and $\sim 16\%$ versus $\sim 18\%$ for gyrochronology. The scarcity of precise stellar ages in this sample highlights the need for a concerted effort to obtain robust age constraints in advance of HWO; this catalog is intended as a living resource that will be regularly updated in the lead-up to the mission.

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astro-ph.SR 2026-05-13

18 hot Ariel stars receive uniform parameters

Ariel stellar characterisation IV. Fundamental parameters of 18 hot stars in the Ariel mission candidate sample

Mass and metallicity correlations with planetary radii now confirmed for early-type hosts as well

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The characterisation of exoplanetary systems depends on the accurate determination of host star parameters. The Ariel mission will probe the atmospheres of a statistically significant sample of exoplanets, and so requires a precise characterisation of the stellar properties well before its launch in 2029. The homogeneous determination of stellar parameters for Ariel will enable both the optimisation of the final target list and set roots for a reliable interpretation of the formation and evolution of planetary systems. Such a homogeneous characterisation has thus far only been carried out for the cool (\teff\ $\lesssim 7000\,$K) host stars among the Ariel target candidates. We present a uniform determination of fundamental stellar parameters for 18 hot stars in the Tier 1 candidate list of the Ariel mission candidate sample. We adopted an iterative spectro-trigonometric approach optimised for high-temperature stars. High-resolution spectra were analysed using the \textsc{zeeman} code with $\chi^2$ minimisation, combining model fits to metal and Balmer lines. Surface gravity was refined using photometry-based radii and masses from stellar evolutionary tracks. We derived effective temperatures, surface gravities, projected rotational velocities, microturbulent velocities, overall metallicities, iron abundances, stellar masses, and radii for our sample of $18$ hot stars. Our results were validated against a set of benchmark stars previously presented in the literature. The derived parameters provide an internally consistent basis for studying the link between stellar properties and planetary characteristics in intermediate-mass stars. Building on our previous work on FGK host stars, we show that correlations between stellar mass, metallicity, and planetary radii also extend to early-type stars, and stellar properties influence the architecture of multi-planet systems.

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astro-ph.SR 2026-05-13 Recognition

The paper presents a chemical abundance analysis of the eclipsing binary V505 Per using…

Elemental Abundances in the Binary Star V505 Per

Abundance analysis of V505 Per shows mostly solar [X/Fe] ratios with manganese deficiency and effective temperatures positioning both stars…

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We present a detailed chemical abundance analysis of the eclipsing binary system V505 Per. High resolution spectra were analyzed using the MOOG spectrum analysis code, and we determined abundances not only for iron and lithium but also for Si, Na, Ca, Mn, and Ni, elements that have not previously been analyzed in detail for this system. Abundances were computed across 15 temperature points using model atmospheres, with stellar parameters refined by minimizing abundance trends with excitation potential. We determined effective temperatures of T_eff = 6650 +/- 50 K for the primary and T_eff = 6550 +/- 50 K for the secondary, with iron abundances of [Fe/H] = -0.10 +/- 0.06 and [Fe/H] = -0.19 +/- 0.07, respectively. Most [X/Fe] ratios are consistent with solar values, though manganese is deficient. Our analysis of the effective temperatures shows that both stars lie on the hot edge of the lithium dip, consistent with Koenigsberger et al. (2025), which may help resolve the inconsistency noted of the stars lithium abundance within the dip by Baugh et al. (2013).

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astro-ph.SR 2026-05-13 1 theorem

Joint index of depth and plasma coupling tracks young star rotation

How plasma coupling and convective-zone depth shape the rotation of solar-mass stars

Moderate correlation holds in first two-thirds of main-sequence life for solar-mass stars, then fades as plasma effects gain weight.

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Stellar rotation on the main sequence is a complex function of mass and age, displaying multiple regimes whose physical origin remains only partially understood. In particular, the connection between the diversity of observed rotation rates and the internal structure and thermodynamic properties of stellar interiors is still unclear. We investigated how the depth of the convective zones and the degree of plasma coupling, quantified through the plasma coupling parameter, relate to the observed rotation rates of solar-mass stars. We used a grid of $1 \, M_\odot$ MESA stellar models with a wide range of metallicities to identify the best-matching models for 243 main-sequence stars with measured rotation periods. We then examined correlations between their rotation rates and both the structural properties of the convective zones and the corresponding convective plasma coupling parameter. For this sample, rotation rates show only weak correlations with either the convective-zone depth or the plasma coupling parameter when considered independently. However, during the first two-thirds of the main-sequence lifetime, the correlation strengthens when both factors are considered jointly through a combined convective coupling index, indicating a moderate and statistically significant relationship. For older stars, these correlations weaken and lose significance, although the thermodynamic component becomes relatively more influential. These trends suggest that microphysical plasma properties may contribute to the regulation of angular momentum loss and may be connected to the onset of weakened magnetic braking.

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astro-ph.SR 2026-05-13 Recognition

Flares leave decayless kink oscillations in loops unchanged

Effect of Solar Flares on Decayless Kink Oscillations in Nearby Coronal Loops

Average amplitudes stay the same across 130 B-to-X events, implying flare processes do not supply the oscillation energy.

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We present a statistical study of 130 solar flares (B to X class) that lack soft X-ray quasi-periodic pulsations and show no kink oscillations of nearby coronal loops visible in SDO/AIA 171~\AA~images. The aim is to investigate whether decayless kink oscillations of coronal loops respond to nearby flaring activity. Using the Fractional Anisotropy-based Video Motion Magnification technique, we detected low-amplitude decayless oscillations in all 130 loops before, during, and after each flare, confirming their ubiquitous nature. Oscillation periods are found to range from 122~s to 268~s, and the projected displacement amplitudes are 0.023--0.111~Mm. No amplitude--period correlation is found. For each event, we estimated the amplitude before, during, and after the flare. Across all flare classes, the average amplitude remains unchanged. However, in some specific cases, the oscillation amplitude may exhibit minor changes. For B-, C-, and M-class flares, the fraction of events with an amplitude change exceeding 10% is approximately 23%, 41%, and 36%, respectively. In M-class flares, such minor amplitude increases occur four times more often than decreases; in X-class flares (only six events), decreases dominate by a factor of three. The fraction of events that exhibit an increase in the amplitude of more than 20% appears to be highest when the loop centre is located at a distance of 100--120~Mm from the flare site, reaching 33% (6 out of 18 events). Overall, the amplitude of decayless kink oscillations does not undergo a major change in response to nearby flares, especially for less powerful classes, suggesting that flare-related processes such as blast waves and reconnection inflows have little effect on the energy supply to oscillating loops.

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astro-ph.SR 2026-05-13 2 theorems

First eclipsing binary found among carbon-enhanced stars

An eclipsing CEMP candidate discovered in a search for dwarf carbon stars in post-common envelope binaries

A 1.224-day period and 30 percent eclipse depth identify a halo post-common-envelope system, supporting wind-capture pollution before Roche-

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Dwarf carbon stars are dominated by members of the Galactic halo and are thus likely carbon-enhanced metal-poor stars. In this work, a sample of 879 bona fide dwarf carbon stars are characterized by their ground-based light curves, and p<15 d modulation is found to be significant in 31 objects (3.5%), consistent with starspots and rotation in tidally-locked, post-common envelope binaries. Among these is an unambiguous halo star that is eclipsing every 1.224 d, and where the 30% eclipse depth rules out a white dwarf occulter. Available Gaia data do not indicate any tertiary in the eclipsing system, but this remains a possibility and follow-up data are necessary to determine the evolutionary history of this first eclipsing binary among carbon-enhanced stars. Four of the variable sources exhibit clear multi-year, quasi-sinusoidal trends indicative of magnetic-activity and starspot cycles in rapidly-rotating, dynamo-rejuvenated stars. These data support a picture where carbon pollution results from wind capture prior to Roche lobe overflow, and the orbital period distribution appears to be moderately shifted to longer periods than carbon-normal, low-mass stars in similar binaries. The band-combined approach adopted in this work may be more sensitive than prior work using single-bandpass light curves, where at most 19 of 34 binary candidates published by Roulston et al. (2021) are independently confirmed here.

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astro-ph.SR 2026-05-13 1 theorem

Starspot maps of UX Arietis reveal weak anti-solar shear

Starspot activity and surface differential rotation on UX Arietis

Mid-to-high latitude features shift over seven years while the equator stays locked to the binary orbit.

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We present new Doppler images of the K0 subgiant primary component of the RS CVn-type binary UX Arietis (UX Ari), derived from time-series spectra obtained in November--December of 2017 and 2024. Observations demonstrate that some spectral lines of the K0 IV component exhibit rapid changes on timescales of 1-2 hours, which seem not to be resulting from spot activity, meanwhile other spectral lines show no such fast variations. Through an investigation, we find that the Ca I 6439 $\unicode{x212B}$ profile shows variation that follows the rotational modulation of spots. Using this line as a reference, we derive the least-squares deconvolution (LSD) profile from the selected lines of each spectrum so as to generate a more reliable Doppler image, which is consistent with the shape of the corresponding Ca I 6439 $\unicode{x212B}$ line. The Doppler images are separately reconstructed from the Ca I 6439 $\unicode{x212B}$ and the LSD profiles for each dataset, and the surface maps are in good agreement with each other. All of the surface maps show dominant starspot structure at mid-to-high latitudes with appendages extending to the equator, while their locations differ by about 0.5 in the rotational phase between 2017 and 2024. In 2017 November-December, the main starspot group appears to be spatially associated with a large flare event just half a month later. Through the cross-correlation method, we have derived a weak anti-solar differential rotation for the primary component of UX Ari, while its equator belt is well tidally locked.

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astro-ph.SR 2026-05-13 1 theorem

Helicity ratio reaches 0.38 at solar eruption onset

An investigation of magnetic energy and helicity thresholds at the onset of solar eruptions based on numerical simulations

Simulations across topologies show only 10 percent variation, outperforming other energy and helicity metrics

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Identifying universal, topology-independent thresholds in the coronal magnetic fields at onset of solar eruptions is crucial for physics-based prediction of eruptions. To this end, we systematically analyze the evolution of magnetic energy and helicity in twelve high-fidelity 3D magnetohydrodynamic simulations where eruptions are triggered by magnetic reconnection. The simulations encompass a comprehensive parameter space, including bipolar and quadrupolar configurations, sheared arcades and pre-existing flux ropes, and various photospheric driving motions. We find that the ratio of current-carrying helicity to total relative helicity $(H_j/H_r)$ exhibits a remarkably consistent threshold of $0.38 \pm 0.04$ at eruption onset across all cases, with a coefficient of variation of only $\sim 10$\%. This threshold specifically characterizes the critical conditions at eruption onset and is largely independent of the subsequent temporal evolution, making it the most robust eruptivity indicator identified. In contrast, other normalized helicity and energy metrics show greater scatter. Crucially, we further find that $H_j/H_r$ does not necessarily achieve its peak at the eruption onset time and its post-eruption evolution diverges based on magnetic topology: it continues to increase in bipolar configurations due to tether-cutting reconnection, which transforms sheared arcade into the erupting current-carrying magnetic flux, but decreases in quadrupolar configurations as breakout reconnection peels off the erupting flux. These results highlight the helicity ratio as a promising and consistent eruptivity indicator and provide new insights into its dynamic evolution due to different reconnections.

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astro-ph.SR 2026-05-12 Recognition

Engulfed planets dissolve steadily inside stars

Continuous mass ablation of planets engulfed in stellar envelopes

Simulations reveal continuous ablation by surface instabilities, enabling full dissolution and lithium release rather than destruction at a临

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Most stars host short-period planets that are expected to be engulfed during post-main-sequence expansion. The dissolution of engulfed planets has been proposed as a possible mechanism for producing stars enriched in lithium and refractory elements. We perform three-dimensional hydrodynamical simulations of a Jupiter-like planet engulfed within a stellar envelope using the Seven-League Hydro code. Unlike previous studies that represent the planet as a point mass or rigid sphere, we adopt a wind-tunnel setup that resolves the planet's gaseous structure. We find that a continuous mass-ablation process operates during planetary engulfment, contrary to the common assumption that destruction occurs at a specific depth due to ram pressure, tidal forces, or thermal evaporation. The ablation rate scales nearly linearly with the wind momentum flux and is largely insensitive to the Mach number, consistent with an analytical model based on Kelvin-Helmholtz instability developing at the planetary surface. We define efficiency coefficients for drag and ablation, finding pressure-drag coefficients of 0.44-0.56 and smaller ablation efficiencies of 0.054-0.11. Applying these coefficients to a numerically integrated inspiral through a stellar profile, we find that continuous ablation could lead to complete dissolution of the planet within the convective envelope, producing observable lithium enrichment at the stellar surface. Our results provide prescriptions for drag and mass loss that enable large parameter-space studies of planetary engulfment and suggest that chemical enrichment may occur over a broader range of stellar parameters than previously thought.

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astro-ph.SR 2026-05-12 Recognition

Planet-hosting binaries show diverse Tc abundance trends

Chemical signatures of planetary systems in their host stars. Near-infrared spectroscopy of four planet-hosting wide binaries

Four observed systems display varied differential patterns versus condensation temperature, indicating multiple processes rather than one,

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An important open question in exoplanet studies is whether planets leave detectable chemical fingerprints on their host stars. While several studies have suggested possible planetary chemical signatures in planet-hosting stars, their origin remains debated because of stellar birth conditions and evolutionary effects. Wide binaries, whose components share a common formation environment, provide an ideal testbed for identifying planetary signatures. Such signatures are often characterized by differential abundance trends with condensation temperature (Tc), which traces the partitioning between gaseous and rocky planetary material. We investigate whether these trends are associated with planetary architectures in wide binaries. We obtained high-resolution NIR spectra of four planet-hosting wide binaries. We measured abundances for both components and analyzed differential abundances in each system. We also compiled literature measurements for planet-hosting and non-hosting wide binaries and compared their Tc trends. WASP-160 A/B and WASP-127/TYC 4916-897-1 exhibit significant abundance trends with Tc, while HD 20782/HD 20781 shows a weaker correlation and K2-54/K2-54 B is consistent with a flat relation. The trends are diverse, including both volatile- and refractory-enhanced patterns in planet-hosting stars. Literature comparisons indicate that extreme Tc slopes may occur more frequently among planet-hosting wide binaries, particularly at large separations, although the statistics remain limited by sample size and definition. Our results indicate that chemical signatures in planet-hosting wide binaries are not universal but vary across systems. While planetary architectures may be associated with some host-star abundance patterns, multiple processes are likely to contribute. Larger samples are essential for disentangling planetary signatures from stellar and binary effects.

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astro-ph.SR 2026-05-12 2 theorems

s+r mix fits CEMP star abundances better than i-process

Observational Signatures and Constraints on the Intermediate Neutron-Capture Process. The Case of the CEMP star TYC 6044-714-1 (RAVE J094921.8-161722)

High-precision analysis of TYC 6044-714-1 shows standard slow and rapid captures explain the pattern without needing the intermediate route.

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Observational abundances of CEMP stars with patterns in between those produced by the rapid and slow nucleosynthesis processes (CEMP-rs stars) are currently invoked as evidence of synthesis via the intermediate process in the early AGB evolutionary phase of metal-poor low mass stars. Nevertheless, discriminating between r+s- and i-process hypotheses requires high-precision abundances obtained through advanced spectral modelling techniques. Theoretical models of the i-process have become more robust, incorporating refined stellar modelling and nuclear reaction physics, providing ranges of probable elemental abundances and isotopic ratios predictions to be confronted with observational determinations. We performed a new analysis of a high resolution and high S/N UVES spectrum of TYC 6044-714-1. We derived accurate effective temperature and highly precise atmospheric parameters, element abundances, and isotopic ratios using state-of-the-art 1D non-LTE and 3D non-LTE spectral line modelling. Using the latest AGB nucleosynthesis models, we assessed the possibility of the i-process to act aside the s-process. We find that TYC~6044-714-1 was likely born as a normal in-situ halo star about 13 Gyr ago, pre-enriched by the r-process through a standard Galactic chemical-evolution pathway. The s+r model provides the best overall reproduction of the observed heavy-element abundance pattern and Ba isotopic ratios, yielding excellent agreement across all three s-process peaks. While i+s+r models with increasing overshooting efficiency improve the fit for specific elements, they do not consistently reproduce the full abundance pattern. The i+s+r models require extreme and physically implausible conditions, and predict s-process Ba fractions inconsistent with those inferred from isotopic ratios of the 4934 \AA\ resonance line. We conclude that the pure s+r scenario is the most plausible explanation.

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astro-ph.SR 2026-05-12 1 theorem

Gaia zero points for bolometric corrections fixed at 0.87

Spectroscopic Bolometric Corrections and Empirical Zero-point Constants of textit{Gaia} Magnitudes, G, G_{rm BP}, and G_{rm RP}, from textit{Gaia} XP Spectra

Averages from 88 XP spectra link G, GBP and GRP magnitudes to total stellar luminosity using IAU standards.

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The International Astronomical Union 2015 Resolution B2 (IAU2015GARB2) has resolved the long-standing problem of zero-point constants for the absolute and apparent bolometric magnitude scales and opened a new window in fundamental astrophysics. The empirical zero-point constants of the bolometric corrections, $C_2(\xi)$, and the absolute/apparent magnitudes, $C_\xi/c_\xi$, for the {\it Gaia} passbands were obtained from 88 {\it Gaia} XP spectra, and absolute bolometric/filtered magnitudes. The individual zero-point constants $\langle C_{\rm 2}\rangle$ of the bolometric corrections ($BC_\xi$) for each star revealed weighted averages of $\langle C_{\rm 2}(G)\rangle=0.8677\pm0.0109$ mag, $\langle C_{\rm 2}(G_{\rm BP})\rangle=1.0449\pm0.0116$ mag, and $\langle C_{\rm 2}(G_{\rm RP})\rangle=2.0510\pm0.0087$ mag. Furthermore, $C_{\rm Bol}=71.197425...$ mag and $c_{\rm Bol} =-18.997351...$mag announced by IAU2015GARB2, and using the definition of $C_{\rm 2}=C_{\rm Bol}-C_{\xi}=c_{\rm Bol}-c_{\xi}$, where the subscript $2$ indicate the wavelength ranges of two in which one is for bolometric and the other for one of the three filters, the zero-point constants of magnitudes for {\it Gaia} filters as $C_{\rm G}=70.1525\pm0.0109$ mag and $c_{\rm G}=-19.8651\pm0.0105$ mag, $C_{\rm G_{\rm BP}}=70.1525\pm0.0116$ mag and $c_{\rm G_{\rm BP}}=-20.0423\pm0.0116$ mag, and $C_{\rm G_{\rm RP}}=69.1464\pm0.0087$ mag and $c_{\rm G_{\rm RP}}=-21.0484\pm0.0087$ mag, if $L_{\xi}$ and $f_{\xi}$ are in SI units in case no extinctions. Lastly, spectroscopic $BC$s for {\it Gaia} magnitudes of 88 stars and the spectroscopic $BC-T_{\rm eff}$ relation for each {\it Gaia} filter are presented.

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astro-ph.SR 2026-05-12 2 theorems

Cross-directed emergences create shearing PIL that triggers repeated X-class flares

Magnetic Evolution of Highly-Sheared Region in Active Region 13842 Producing Large X9.0 Flare

In AR 13842, opposing motions of emerging patches built a narrow collisional line where flux cancelled and ropes formed, producing the cycle

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Shearing motion and magnetic flux cancellation around the polarity inversion line (PIL) play significant roles in the build-up of free magnetic energy and magnetic flux rope (MFR) in source region of major solar flares. Here we investigate the magnetic evolution of a highly-sheared PIL in active region (AR) 13842, hosting the largest X9.0 flare of Solar Cycle 25. Since 2024 September 29, a positive-polarity pore persistently drifted northward along the western side of the AR's main negative-polarity sunspot. The main sunspot remained stationary until negative-polarity patches successively emerged to its east and approached. Rear-ended by these same-polarity patches, the sunspot then began moving westward toward the opposite-polarity pore around October 1, forming a collisional PIL. Meanwhile, on the PIL's other side, the pore was also rear-ended by same-polarity patches sequentially emerging behind it, accelerating the shearing motion around the PIL, where frequent flux cancellations were also observed. Synchronous rapid accumulation of free magnetic energy and formation of MFR were then observed in the PIL, where multiple major flares successively occurred within two days. Before these large flares, the area and total free energy of the high-free-energy-density PIL region gradually decreased in the photosphere, which could be caused by the initial ascent of MFR before eruption and serve as a precursor of solar eruptions. These results suggest that persistent flux emergences with cross separation directions facilitates rapid formation of collisional shearing PIL and frequent flux cancellations, leading to repeated MFR formations and multiple large flares in a relatively short time.

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astro-ph.SR 2026-05-12 2 theorems

Hα spectra distinguish filament eruption locations on Sun

Can We Distinguish the Source Region Location of Filament/Prominence Eruptions from the Sun-as-a-star Hα Spectrum?

Blueshifted emission, absorption, and line-center sequences differ for disk versus limb and active versus quiet-Sun events, giving a way to

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Solar filament/prominence eruptions can significantly perturb geospace when originating from favorable source locations and directions. While stellar analogs have been recently reported, the disk locations and magnetic environments of their source regions remain spatially unresolved on other stars. To bridge this gap, we investigate the typical Sun-as-a-star H$\alpha$ temporal spectral characteristics of solar filament/prominence eruptions with different source region locations (on-disk vs. limb, active region vs. quiet-Sun region). It is revealed that limb eruptions are characterized by blueshifted/redshifted emission caused by the bright off-limb erupting structures, whereas on-disk eruptions may show blueshifted absorptions due to the dark erupting filaments. Among the limb eruptions, front-side limb eruptions usually display line center emission before the blueshifted/redshifted emission, while far-side limb eruptions show the opposite sequence. Moreover, the magnetic environment at source also shapes the spectral characteristics. On-disk filament eruptions from active region exhibit much more intense flare-ribbon-dominated line center emission features compared with those from quiet-Sun region. Limb active region eruptions often show single-wing emissions, whereas large-scale quiet-Sun region (quiescent) prominence eruptions frequently display expansion-induced emission in both wings followed by line center absorption due to the disappearance of bright prominence. These distinct Sun-as-a-star H$\alpha$ spectral characteristics, dependent on eruption location, provide a diagnostic basis for inferring source regions of stellar filament/prominence eruptions from spatially unresolved H$\alpha$ spectra.

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astro-ph.SR 2026-05-12 2 theorems

Strange modes produce irregular pulsations in ε Ori

On the origin of variability in α Cygni variable ε Ori (HD 37128) using TESS observations and modelling

Nonlinear simulations link linear instabilities to the envelope inflation and finite-amplitude variability observed in this α Cygni star.

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$\epsilon$ Ori (HD 37128) is an $\alpha$ Cygni variable characterized by irregular and small amplitude variations. From TESS observations, we find the presence of stochastic low-frequency variability in this star. We have constructed a sequence of models for this star in the mass range of 30 to 70 M$_{\odot}$, using recently derived values of luminosity (log $(L/L_{\odot})$ = 5.92) and effective temperature. In these considered models, both radial and non-radial linear stability analyses have been performed. Low-order radial modes are excited in models having mass below 62 M$_{\odot}$. These radially excited modes have periods ranging from 6.8 days for the fundamental mode to a few hours for higher-order modes. Similar to the case of radial modes, several non-radial modes are found to be unstable in models having higher luminosity-to-mass ratios. Linear stability analysis for the case of $l$ = 2 and $l$ = 4 reveals the presence of a strongly unstable mode in models having a mass below 40 M$_{\odot}$. This mode is found to be unstable in all the considered models and the strength of the instability varies as a function of harmonic degree. The non-adiabatic reversible approximation reveals that the origin of instabilities associated with the low-order modes is indeed linked with strange modes. To find out the consequence of radial instabilities, non-linear numerical simulations have been performed in selected models of $\epsilon$ Ori. In the non-linear regime, these instabilities lead to the envelope inflation, finite amplitude regular and irregular pulsations consistent with an $\alpha$ Cygni variable.

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astro-ph.SR 2026-05-12 2 theorems

Kinetic Alfven waves redirect energy at solar transition region

Transition region-induced kinetic Alfven wave conversion. Electric displacement field

Coupling via transverse wavenumber boosts normal electric fields and creates a zone where ponderomotive forces accelerate plasma upward.

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The transition region is a thin inhomogeneous region where Alfven waves' energy fluxes generated elsewhere in the solar atmosphere are effectively converted. Large-scale kinetic Alfven wave propagations, transmission, and reflection processes across the transition region are examined. The two-fluid model is adopted, and a study is conducted of how the kinetic Alfven wave electric displacement field changes across the transition region. The analysis outcomes are: the kinetic Alfven wave and electrostatic ion sound waves are coupled by the transverse wavenumber; wave electric field components (normal to the transition region) become enhanced up to two orders; the energy fluxes of transmitted kinetic Alfven waves are re-directed almost horizontally along the transition region, an evanescent electric field zone of enhanced intensity is induced tightly beyond the transition region; the ponderomotive force that emerges in that zone due to the reflected kinetic Alfven waves accelerates plasma particle upwards compared to their initial energy in the upper chromosphere.

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astro-ph.SR 2026-05-12 2 theorems

CME signatures replace HCS for 48-hour sector reversal

Coronal Mass Ejection and Heliospheric Current Sheet Interaction Causing a Long-Duration Magnetic Field Sector Transition

October 2024 data show a fast halo CME and companions locally supplant the current sheet near Earth, extending the magnetic transition over

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We present a study that combines remote-sensing and in-situ observations of coronal mass ejections (CMEs) interacting with the nearby heliospheric current sheet (HCS). The sequence of eruptive events under study culminates in the largest directly observed flare of solar cycle 25 on 3 October 2024, producing a fast halo CME. Their source region can be linked to a so-called nested active region (or active longitude) that persisted over several solar rotations. Such long-lived regions reflect deep-seated magnetic structures that shape the global magnetic field configuration. By applying the drag-based CME propagation model, we connect the near-Sun observations from several CMEs during that activity period with in-situ measurements. While one of the CMEs propagated on the opposite side of the HCS from Earth, and therefore did not produce in-situ signatures near Earth, we detect, over the period October 5-10, 2024, a complex of HCS and CME structures propagating together with a shock ahead of them. The HCS seems to be locally replaced by the CME signatures, leading to a long-duration sector reversal of more than 48 hours. This event highlights the intrinsic connection between solar surface structures, the global magnetic field, and the evolution of complex eruptive events.

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astro-ph.SR 2026-05-12 1 theorem

Gaussian separation checks coronal currents in solar models

Validating Coronal Magnetic Field Models Using Gaussian Separation

Partitioning photospheric vector fields reveals how well NLFFF models match observed currents above the surface in AR 11429.

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Nonlinear Force-free Field (NLFFF) models are widely used to investigate coronal magnetic field structure in solar active regions, but methods to validate them remain limited. Here, we use Gaussian separation, recently applied to solar vector magnetogram data, to assess the accuracy of NLFFF models constructed with two methods: optimization and the current-field iteration (CFIT) implementation of the Grad-Rubin method. Gaussian separation partitions the photospheric vector magnetic field into three components associated with currents flowing below, above, and passing through the photosphere, respectively. Comparing the photospheric field components due to coronal currents in an NLFFF model with those in the original vector magnetogram data provides a check on the accuracy of the model's coronal currents. We consider NLFFF models constructed for the active region AR 11429. The photospheric signatures of coronal currents in both the models and the vector magnetogram data indicate currents flowing above and parallel to central, sheared polarity inversion lines (PILs), consistent with other recent studies. We find that while both models reproduce the coronal current signatures along the upper section of the main PIL, the CFIT model significantly alters the signature of a flux rope along the lower section of the PIL, including shifting its positive-polarity footpoint. These differences arise from modifications to the vector magnetogram boundary data when solving the NLFFF equations, and from the assumptions underlying the models. We propose Gaussian separation as a useful tool to validate coronal magnetic field models, in addition to existing methods.

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astro-ph.SR 2026-05-11 2 theorems

GNN predicts 3D non-LTE Ca populations million times faster

Accelerating 3D Non-LTE Synthesis with Graph Neural Networks

Model matches full solutions with over 0.99 correlation in key layers and under 2 percent profile residuals.

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Spectropolarimetric interpretation of chromospheric lines requires solving the radiative transfer problem under non-local thermodynamic equilibrium (non-LTE) conditions. This means computing atomic-level populations self-consistently with the radiation field. While traditional inversion codes employ 1.5D approximations, they neglect horizontal radiative transfer, which can be significant near magnetic structures and in the chromosphere. We present a method to solve 3D atomic-level populations using Graph Neural Networks (GNNs), extending prior 1.5D work to the full 3D domain. By discretizing the solar atmosphere as a directed graph, in which nodes encode physical properties and edges encode spatial distances, an Encode-Process-Decode GNN propagates information to efficiently capture radiative coupling. The network is trained on a Bifrost simulation using Ca II populations from Multi3D as ground truth. The trained GNN accurately predicts populations of the five-level Ca II atom plus continuum. Correlations exceed 0.99 in the photosphere and mid-chromosphere; errors in the upper chromosphere remain unbiased. Inference is $\sim 10^6$ times faster than traditional iterative solvers. Spectral synthesis of the Ca II 8542 \AA\ line yields intensity profiles with $< 2 \%$ mean residuals relative to the full 3D solution. This framework bypasses the computational bottleneck of iterative solvers while preserving essential non-LTE physics, including horizontal transfer, paving the way toward routine 3D non-LTE inversions.

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astro-ph.SR 2026-05-11 Recognition

Large superhump excess identifies new AH Pic nova-like

GSC 08227-00723: An Unusually Large PSH Excess AH Pic Candidate

Recurrent 30-50 day outbursts and 0.19 excess in GSC 08227-00723 point to tidal driving in high-accretion disks.

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Nova-like variables are high-accretion-rate cataclysmic variables (CVs) that, in contrast to dwarf novae, do not undergo outbursts caused by thermal-viscous instability. However, a small group of nova-likes, classified as AH Pic-type stars, show recurrent small-amplitude outbursts, which are unexpected by the classical disk instability model. The physical mechanisms underlying these outbursts are not clear. In this study, we present a comprehensive time-domain analysis of the CV candidate GSC 08227-00723 using photometric data from ASAS-SN and TESS. The long-term light curves reveal a sequence of low-amplitude, recurrent stunted outbursts with recurrence times ranging from 30 to 50 days. Notably, these outbursts are frequently preceded by precursor brightenings, a feature reminiscent of super-outbursts in SU UMa stars driven by tidal instability. Period analysis of high-cadence TESS data identifies a coherent periodic modulation at 0.297 d, likely the orbital period, and a persistent positive superhump signal at 0.352 d. The latter corresponds to an exceptionally large superhump excess of $\epsilon^+ \approx 0.19$, surpassing typical values seen in CVs. Additionally, we detect short-timescale variability resembling quasi-periodic oscillations in the TESS light curves. Based on the outburst properties and photometric behavior, we classify GSC 08227-00723 as a new member of the AH Pic subclass of nova-like stars. We discuss how tidal effects may be involved in the observed behavior, although the exact mechanism is still unclear.

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astro-ph.SR 2026-05-11 1 theorem

SAGES releases DDO51 photometry separating dwarfs from giants

The Stellar Abundances and Galactic Evolution Survey (SAGES). V. The First Data Release of the DDO51 Band

First data cover 2500 square degrees with 10 million sources and confirm surface-gravity sensitivity for late-type stars.

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We present the first public data release of DDO51 band from the Stellar Abundances and Galactic Evolution Survey (SAGES), based on Nanshan One-meter Wide-field Telescope (NOWT) observations obtained between 2023 September and 2024 January. This release initiates the DDO51-band component of the survey, covering $\sim$ 2,500 deg$^2$ of the northern sky and including more than 10 million sources. The DDO51 filter is centered near the \ion{Mg}{1}~$b$ triplet and the adjacent MgH feature, offering sensitivity to stellar surface gravity. The data reduction pipeline incorporates an improved astrometric solution anchored to Gaia DR3 and a photometric calibration strategy tied to synthetic photometry from Gaia XP spectra. These procedures yield a point-source depth of $\sim$18.9 mag at S/N$\sim$10 and an internal photometric precision $\approx$6-7 mmag at the bright end. A preliminary color--color analysis using Gaia broadband photometry confirms the expected sensitivity of the DDO51 band to stellar surface gravity, demonstrating a clear photometric separation between dwarf and giant sequences for late-type stars. This dataset, when combined with existing SAGES photometry in other bands, provides a crucial tool for disentangling the substructures of the Milky Way. All data products from this release upon publication will be available.

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astro-ph.SR 2026-05-11 2 theorems

OGLE finds 30 stars eclipsed by circumbinary dust disks

Thirty Circumbinary Disk Occultation Systems (KH 15D-like stars) from the OGLE Project

Decades-long light curves track evolving eclipse shapes in these KH 15D analogs, supplying a larger sample for disk studies.

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We present a catalog of 30 stars that are candidates for KH 15D-like binary systems, in which the observed brightness variations are caused by a circumbinary dusty disk that periodically obscures at least one of the stellar components as it moves along its orbit. Thanks to the regular observations conducted within the Optical Gravitational Lensing Experiment (OGLE) project, we provide unique light curves in the I and V bands with very long time baselines, in some cases beginning as early as 1997 and extending to the present day. Such long-term monitoring allows us to identify changes in eclipse widths, amplitudes, and light-curve shapes on timescales of many years. We highlight several circumbinary disk occultation (CBO) systems of particular interest and present spectra for three of them.

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astro-ph.SR 2026-05-11 Recognition

Deep learning infers red-giant seismic parameters from short TESS data

Inferring Asteroseismic Parameters from Short Observations Using Deep Learning: Application to TESS and K2 Red Giants

The model succeeds for half of one-month Kepler samples but only 23% of TESS sectors, and yields reliable period spacings for 200 K2 stars.

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Asteroseismology is the study of resonant oscillations of stars to infer their internal structure and dynamics. It is also a powerful tool for precisely determining stellar parameters such as mass, radius, surface gravity, and age. The ongoing TESS mission, with its nearly complete sky coverage, presents a unique opportunity to uniformly probe stellar populations across the Milky Way. TESS is estimated to have observed more than 300,000 oscillating red giants, most of which have one to two months of observations. Given the scale of this dataset, we need a fast, efficient, and robust way to analyse the data. In this work, our objective is to develop a machine learning (ML) based method to infer asteroseismic parameters from short-duration observations. Specifically, we focus on two global seismic parameters, the large frequency separation ($\Delta\nu$) and the frequency at maximum power ($\nu_{\mathrm{max}}$), from one-month-long TESS observations of red giants. Meanwhile, for K2 data, our focus extends to inferring the period spacings of dipolar gravity modes ($\Delta\Pi_{1}$), in addition to $\Delta\nu$ and $\nu_{\mathrm{max}}$. Our findings demonstrate that our machine learning algorithm can accurately infer $\Delta\nu$ and $\nu_{\mathrm{max}}$ for approximately 50% of samples created by taking one-month Kepler and K2 observations. For TESS one sector data however, we recover reliable $\Delta\nu$ for only about 23% of the stars. Additionally, we get reliable $\Delta\Pi_{1}$ inferences for about 200 young red-giants from K2. For these $\Delta\Pi_{1}$ inferences, we see a good match with the well known $\Delta\nu-\Delta\Pi_{1}$ degenerate sequence observed in Kepler red-giants.

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astro-ph.SR 2026-05-11 2 theorems

Pre-flare oscillations detected hours ahead of X9 solar flare

Investigating Pre-flare Signatures in Spectroscopic Observations of an X9-class Solar Flare

IRIS data show 7-21 minute periods and steady parameter increases consistent with slow magnetic destabilization before rapid reconnection.

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On October 3rd, 2024, the Sun emitted an X9.0-class flare from active region NOAA 13842. The event was recorded by multiple space-based instruments, beginning hours before the eruption, granting a unique opportunity to provide insight into the flare's pre-flare phase. In this study, we employ analysis of Interface Region Imaging Spectrograph (IRIS) spectroscopic data to investigate pre-flaring phenomena associated with this flare. We present time-series and wavelet analysis of non-thermal velocity, Doppler velocity, and line intensity quantities of the IRIS Si IV 1403 angstrom line. We find two ranges of periodic oscillations during the pre-flare phase: ~7-10 min and ~18-21 min oscillations, with local enhancements occurring near the polarity inversion line. We also find a steady rise in Si IV line parameters beginning 3 hours before the flare in the same region, transitioning into strong non-thermal velocities and blueshifts ~15 minutes before onset. These findings are consistent with a slow destabilization of the coronal magnetic field, possibly driven by the gradual activation of a flux rope, followed by a rapid shift to intense reconnection activity leading to flare onset.

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astro-ph.SR 2026-05-08 Recognition

H2 winds disperse disks in 2-3 million years

Characterizing the Extended Molecular Hydrogen Winds in Protoplanetary Disks from the JWST Disk Infrared Spectroscopic Chemistry Survey

JWST survey measures median wind mass-loss rates of 10^-9 solar masses per year, matching observed protoplanetary disk lifetimes.

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We present a comprehensive analysis of extended H$_2$ emission from 34 protoplanetary disks observed with the JWST Disk Infrared Spectroscopic Chemistry Survey (JDISCS), supplemented by archival data. We investigated the morphology, kinematics, excitation conditions, and mass dynamics of H$_2$. Extended emission from pure rotational H$_2$ lines is found to be common, with 16 sources exhibiting clear signatures of disk winds. These include monopolar and bipolar structures in inclined disks and ring-like or bubble-like morphologies in face-on systems features indicative of wide-angle disk winds. Our analysis shows that the H$_2$ is consistent with slow {(4.2$^{+6.7}_{-3.0}$ km s$^{-1}$)} MHD driven winds. For ten disks, we model the wind morphology and find a median half-opening angle of $45\arcdeg^{+5}_{-4}$ and a characteristic power-law index of $\alpha \sim$ 1.6. Excitation analysis yields a median gas temperature of 624 $\pm$ 130 K and a column density of $\log(N_{\mathrm{tot}}\,[\mathrm{cm}^{-2}]) = 18.6 \pm 0.6$. The median wind mass-loss rate, ${\rm log_{10}}(\dot{\rm M}_{\rm wind}^{\rm tot}) = -9_{-0.4}^{+0.8}\,{\rm M_\odot\,yr^{-1}}$, implies that, if molecular winds are the dominant mechanism responsible for disk dispersal, a typical disk with a mass of $2-3\,M_{\rm Jup}$ would dissipate on a $\sim$2-3 Myr timescale, consistent with observed disk lifetimes. The $\dot{\rm M}_{\mathrm{\rm wind}}^{\rm tot}$ span a relatively narrow range ($\sim$2 dex) and do not correlate strongly with accretion rates onto the star, suggesting that the mass loss rate and the accretion rates are probing different timescales. Our findings demonstrate that spatially extended warm H$_2$ emission is a widespread and reliable tracer of molecular disk winds in protoplanetary systems.

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astro-ph.SR 2026-05-08 Recognition

Protostellar jets keep massive stars below critical spin

On the origin of the rotation of massive stars

Outflows remove angular momentum so accretion ends with sub-critical rotation, with final rate set by initial cloud conditions.

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We explore the origin of the rotation rates of massive stars. Contrary to their low-mass siblings, most massive stars do not have detectable magnetic fields, so that star-disk interaction models used for the formation of rotating low-mass stars do not apply. We investigate whether the magnetic fields of protostellar jets present in the parent molecular cloud prevent the protostar from reaching the critical angular velocity. Starting from the gravitational collapse of a molecular cloud, we run two two-dimensional radiation-gravito-magnetohydroynamical simulations to study the formation of an accretion disk and the launching of magnetically-driven protostellar outflows (of particular interest is the formation of a magnetocentrifugal jet originating from the protostar and inner disk). We then study the angular momentum transfer from the disk and jet onto the protostar. Finally, we compute one-dimensional stellar evolution models of the pre-main sequence including our results from the disk-jet simulations and follow the angular momentum redistribution within the structure of the protostar. We find that the angular momentum transported outwards by the magnetically-driven protostellar outflows is sufficient for keeping the protostar below the critical speed at all times. Moreover, we are able to link the strength of the jet, and thus the rotation rate at the end of the accretion epoch, to the initial conditions for star formation. Our results show that the jet strength produces a variety of stellar rotation rates, suggesting that protostellar jets fix the rotation rate of massive stars.

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astro-ph.SR 2026-05-08 Recognition

Consistent envelope energies shift compact binary merger rates by over 10x

The impact of envelope binding energies on the merger rate density of binary compact objects

PARSEC v2.0 binding energies fed into SEVN produce order-of-magnitude changes from standard fitting formulas.

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The common envelope (CE) phase plays a key role in the formation of binary compact object systems. Its final outcome strongly depends on the envelope binding energy, but this quantity is often estimated using fitting formulas that are not fully consistent with the underlying stellar evolution models adopted in population-synthesis codes. Here, we investigate envelope binding energies across the most extensive stellar grid considered to date. Our stellar tracks, evolved with PARSEC v2.0, include hydrogen (H) -rich stars with metallicities ranging from $Z = 10^{-11}$ (Population III stars) to $Z = 0.03$, and initial masses between 2 and 2000 M$_\odot$, as well as pure-helium stars with masses from 0.36 to 350 M$_\odot$. We examine the sensitivity of the envelope binding energies to the selected core-envelope boundary definition and to different internal energy source contributions. For H-rich stars, we find that internal energy sources can alter the envelope binding energy by more than an order of magnitude, whereas the core boundary criteria play a secondary role. In contrast, for pure helium stars, the core-boundary criterion becomes the dominant factor. The envelope binding energies derived from different stellar tracks can show deviations of several orders of magnitude, with larger differences for more massive stars and higher metallicities.Finally, by implementing our new envelope binding energy prescriptions into the binary population synthesis code SEVN, we show that the predicted merger rate densities of compact binaries can differ by more than an order of magnitude compared to previous models. Our results highlight the importance of using envelope binding energies that are consistent with the underlying stellar evolution models and caution against extrapolating empirical fits beyond the considered parameter space.

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astro-ph.SR 2026-05-08 2 theorems

No radio change in protostar during luminosity burst

Radio Continuum and Water Maser Monitoring of the Outburst in HOPS 373: Free-Free Emission Does Not Respond to the Outburst

VLA data show steady 5 cm free-free emission from HOPS-373 despite a fourfold luminosity jump, hinting at neutral outflows or delayed timing

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We present VLA C-band (5~cm) continuum, K-band (1.3~cm) continuum, and water maser (22.235 GHz) monitoring of the protostar HOPS-373. We additionally present the contemporaneous monitoring for 95 sources within the 5~cm field of view for over two years during the peak of the HOPS-373 outburst and an additional epoch in 2026. HOPS-373 is a binary Class 0 protostar located in the Orion star forming region that was found to have a $\sim$4$\times$ luminosity burst from the JCMT Transient Survey and NEOWISE monitoring. We do not find evidence for a change in the free-free emission traced by VLA 5~cm continuum during the peak of its outburst or during the decline. Moreover, the 1.3~cm continuum does not show significant variability between the NE and SW components of the HOPS-373 binary. The water maser emission is highly variable toward HOPS-373, multiple velocity components are detected at different (or the same) times and the maser spots are located close to the 1.3~cm continuum source of HOPS-373-SW. There is tentative evidence for the water maser spots to be propagating away from the source, but there is not a robust connection between the outburst and the observed maser activity. The lack of correlation between outburst and free-free emission from HOPS-373 indicates that the free-free emission may not directly respond to increases in the accretion rate and subsequently the outflow rate. The lack of a link could be due to the outflow mostly being neutral, or there may be offsets in the timescale for the free-free response.

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astro-ph.SR 2026-05-08

Solar flare footpoints show 8.2μm peaking 0.3-0.45s before 5.2μm

First time delay observation between two mid-infrared channels in solar flare footpoints

The lag matches RADYN models where ionization alters opacity differently at each wavelength, tracing energy deposition timing in the chromo

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The strong correlation between energy injection and mid-infrared (mid-IR) emission observed during solar flares can be used to probe energy deposition throughout the chromosphere, since the IR tracks prompt flare-induced changes in electron density. Despite its diagnostic value, solar mid-IR observations are relatively recent, with sporadic campaigns over the last decade resulting in only a few recorded flares. Earlier studies found time lags between mid-IR emissions from spatially resolved footpoints, offering clues about flare energy transport. Building on this, we analyse the time lags between emissions at two wavelengths (5.2 micrometers and 8.2 micrometers) for each footpoint. Using a local cross-correlation function, we show for the first time that the 8.2 micrometers emission channel peaks 0.3 s-0.45 s before the 5.2 micrometer channel. We investigate the origin of this lag, obtaining infrared emission estimates using results from the RADYN radiation hydrodynamics code. The theoretical lag values fall within the range of the observed ones. Variations in opacity-primarily due to flare-induced ionization-explain the wavelength-dependent temporal shift between emission maxima. In particular, longer wavelengths exhibit a smaller lag between the peak of energy injection and peak of intensity. These results contribute to a better understanding of how energy deposition during a flare affects the chromospheric layers of the atmosphere. Future observations with higher temporal resolution could exploit measurements of these time lags to more fully characterize the dynamics of energy deposition during solar flares, opening a new avenue for studying heating and energy transport processes in the solar atmosphere.

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astro-ph.SR 2026-05-08

Nested MHD runs follow CME from active region to beyond 1 AU

Modeling of Coronal Mass Ejection Originated from a Sheared Arcade of Realistic Active-Region Scale and Its Propagation in the Heliosphere: Methodology

High-resolution modeling captures shearing-driven eruption, flux-rope structure, and southward Bz interval at Earth distance.

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Simulating coronal mass ejections (CMEs) from their origin in active regions (ARs) to their propagation to Earth remains challenging, particularly when aiming to resolve AR scales and employ realistic magnetic field strengths without compromising computational efficiency. Here we present a methodology for end-to-end CME modeling that addresses these challenges. Three nested magnetohydrodynamic simulations are coupled to jointly cover the heliosphere from solar surface to beyond $1.5$ au. A block-structured adaptive mesh refinement scheme is employed to achieve $\sim 700$ km resolution in the low corona, allowing AR scales to be resolved while maintaining the total grid count below $10^8$ across the entire computational domain. A semi-relativistic Boris correction combined with a relativistic mass-density factor is used to handle magnetic field strengths up to $10^3$ G without prohibitively small time steps. Using this model, we simulate the emergence of a bipolar AR into the corona, the initiation of a CME by shearing of the AR core field and the subsequent evolution. Our simulation captures its pre-eruption energy buildup, triggering by magnetic reconnection, rapid acceleration, and propagation to 1 au and beyond. The simulated CME exhibits a three-part structure in synthetic coronagraph images and a torus-shaped flux rope in the heliosphere, with synthetic in-situ observations showing shock formation, density compression, and a prolonged southward $B_z$ component at 1 au. The entire simulation requires about one day on a moderately sized cluster (e.g., $600$ processors), while the simulated CME takes three days to arrive at $1$ au, offering a lead time of two days if used for forecasting.

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astro-ph.SR 2026-05-08

Leading coronal hole edges hotter and smoother than trailing

Investigating the Relationship Between Physical Properties and Spatial Irregularities at Coronal Hole Boundaries

Single-event study ties the contrast to large organized loops on one side versus scattered bipoles on the other.

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Coronal hole boundaries are the interfaces between closed and open magnetic field regions in the solar atmosphere. Many fundamental processes take place at these regions, including magnetic reconnection that is responsible for solar wind release and restructuring of the solar magnetic field. In this paper, we present a case study in which we investigate the physical properties of the boundary of a large low-latitude coronal hole. Differential Emission Measure analysis is used to derive the plasma properties of these regions. We also apply correlation dimension mapping analysis to measure the irregularities of the coronal hole boundary. We find that the leading boundary of this coronal hole has a slightly higher average plasma temperature, is associated with a stronger and more unipolar magnetic field, and has a smoother boundary line than the trailing counterpart. These differences are hypothesised to be direct consequences of the local magnetic field configurations of the coronal hole boundary: the leading boundary corresponds to large, well-organised coronal loops, and the trailing boundary corresponds to more dispersed, randomly orientated small magnetic bipoles. Hence, we suggest that the surrounding magnetic field structure and the nature of magnetic reconnection influence the properties of coronal hole boundaries.

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astro-ph.SR 2026-05-08

ALMA maps high-v SiO lines in AGB envelopes

ATOMIUM: Inner circumstellar envelopes of oxygen-rich AGB stars as revealed by highly excited SiO lines

Observations of 14 stars find arcs, clumps and velocity gradients that trace mass-loss geometry.

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Silicon monoxide (SiO) traces the physical conditions and dynamics in the circumstellar envelopes (CSEs) of AGB stars. We present high-resolution ALMA Band 6 observations of highly excited SiO emission in 14 oxygen-rich AGB stars. We cover transitions from v = 0 to v = 8, including first detections of 28SiO v = 3, 4, 8, J = 6-5, 29SiO v = 6, J = 6-5, and 30SiO v = 4, 5, J = 6-5, some of which are masers. The v = 8 transition is the highest v-state observed in an AGB star yet. Masers in v = 0 are detected clearly in V PsA and IRC+10011 and tentatively in T Mic. R Hya exhibits the richest SiO spectrum. SiO J = 6-5 absorption is seen in R Aql, R Hya, S Pav, and T Mic, with features indicative of both infalls and outflows, and tentative detection of 28SiO v = 8, J = 6-5 absorption is found towards S Pav and R Aql. Highly excited SiO emission is often distributed in arcs or clumps with velocity gradients; components in R Hya and U Her align with predicted shock fronts. Detection rates show no significant difference between low and high mass-loss rate stars, although line overlap may affect some intensities. Maser detections appear uncorrelated with pulsation period or phase. The radius enclosing 90 per cent of compact SiO emission shows a tentative correlation with mass-loss rate. These results highlight the role of mass loss and CSE geometry in shaping high-excitation SiO emission.

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astro-ph.SR 2026-05-08

Old RR Lyrae star likely has neutron star companion

IY Lyr: A Thick-Disk first-overtone RR Lyrae Star with a Possible Neutron Star Companion

Timing analysis and kinematics of IY Lyr reveal a 1.37-solar-mass companion in a 4-year eccentric orbit consistent with a neutron star.

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IY Lyr, historically misclassified as an eclipsing binary, is now established as a first-overtone RR Lyrae star (RRc star). Using multi-band photometry (ASAS-SN, ZTF, TESS, and our BVRI data), LAMOST spectroscopy, and Gaia astrometry, we investigate its pulsation, binarity, and Galactic population. From O-C analysis, we detect a long-term period decrease and a light-travel time effect with an orbital period of 3.94 years, eccentricity of 0.46, and a mass function of 0.65 M$_{\odot}$. The companion is independently confirmed by radial velocity residuals and Gaia proper motions. Combined constraints yield an orbital inclination of 94.8$^{\circ}$ and a companion mass of 1.37 M$_{\odot}$. Chemical abundances ([Fe/H] $\simeq$ -1.0, [$\alpha$/Fe] $\simeq$ +0.27, Xiang et al. 2019) and dynamics ($L_{\rm z}$ $\simeq$ 1250 kpc km s$^{-1}$, $Z_{\rm max}$ $\simeq$ 1.31 kpc) identify IY Lyr as an old, high-$\alpha$, thick-disk star. The companion mass lies at the peak of the neutron star mass distribution, and the system's age excludes a main-sequence star; we conclude the companion is most likely a typical neutron star, although a massive white dwarf near the Chandrasekhar limit cannot be ruled out. IY Lyr is among the few RRc binaries with a compact companion verified by multiple methods, and it has important implications for thick-disk binary evolution and neutron star formation.

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astro-ph.SR 2026-05-08

Microwave polar brightening tracks coronal hole area

Microwave Polar Brightening and Its Connection to Polar Coronal Holes

Nobeyama 17 GHz data from 1992-2018 shows strong correlation with polar magnetic field strength across the solar cycle.

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Polar brightening (PB) observed at microwave frequencies serves as an important probe to study the thermal and magnetic properties in the Sun's polar regions. Building on earlier studies that linked microwave PB to polar faculae, small-scale loops, and the polar coronal holes (PCHs), we present a comprehensive analysis of the long-term behaviour of 17 GHz microwave PB and its relation to polar magnetic field and coronal hole evolution. Using daily Nobeyama Radioheliograph observations spanning 1992 to 2018, we quantify microwave PB peak temperature variations and compare them with the temporal evolution of PCH area extracted from SDO/AIA-based SPoCA coronal hole catalogues during the period 2010-2018. We also examine the correspondence between microwave PB and the polar magnetic field to assess the nature of their association. Our results show a strong correlation between microwave PB peak temperature and PCH area, as well as with the polar magnetic-field strength. In addition, we found that regions of enhanced microwave emission are frequently associated with small-scale loop structures, consistent with Coronal Bright Points (CBPs), which are often associated with the eruption of jets. Overall, this study aims to investigate the impact of coronal holes, polar magnetic fields, and small-scale polar activity on polar brightening observed at 17 GHz and its long-term evolution.

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astro-ph.SR 2026-05-08

Helium lines in Type Ia remnants flag abundance differences

Helium emission from Balmer-dominated shocks in Type Ia supernova remnants provides constraints to their progenitor systems

Detections of narrow and broad He lines in three LMC shocks show some remnants enriched in helium while others match primordial levels.

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Balmer-dominated shocks in Type Ia supernova remnants offer powerful probes into collisionless shock physics and hints towards supernova progenitor environments. Prior studies focused on the hydrogen Balmer lines, which manifest as a superposition of broad and narrow emission lines. Using integral-field spectroscopy with MUSE, we discovered broad and narrow helium emission lines from Balmer-dominated filaments of three Type Ia supernovae remnants in the Large Magellanic Cloud: SNR 0509-67.5, SNR 0519-69.0 and N103B. We detect broad and narrow He~\textsc{i} 5876~\AA~,7065~\AA\ emission in SNR 0519 and N103B and He \textsc{ii} 8236~\AA\ in SNR 0519. In SNR 0509 we detect narrow He~\textsc{i} 5015~\AA, 6678~\AA, 7065~\AA\ and 7281~\AA, with only 7065~\AA~ exhibiting a broad component. The detection of narrow He\,\textsc{ii} challenges existing shock models, where such emission is not expected, and may indicate either incomplete ion-ion equilibration behind the shock or an origin in shock precursors. For SNR 0509 and N103B, the neutral He/H line ratios indicate enhanced helium abundances, whereas SNR 0519 is consistent with the primordial He/H value. We therefore propose helium emission in Balmer-dominated shocks as a new diagnostic of shock physics and Type Ia supernova circumstellar environments. Although our modeling is primarily a proof of concept, it demonstrates the possibility to infer the total He-to-H abundance ratio, with dominant uncertainties arising from the assumed initial ionization fractions. Despite the uncertainties, we demonstrate that narrow helium lines can serve as effective probes of circumstellar conditions and progenitor evolution when analysed alongside reliable constraints on the preshock neutral H/He abundance ratio.

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astro-ph.SR 2026-05-07

TRAPPIST-1 flares follow one power law across four energy orders

A single power law for the TRAPPIST-1 flare distribution across four orders of magnitude in energy

Unified JWST and Kepler data converted to TESS energies show rare large events set the average high-energy output.

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TRAPPIST-1 is an ultra-cool dwarf that flares frequently. These flares shape the surrounding planets' high-energy irradiation environments, with consequences for atmospheric chemistry and escape, and they can contaminate transmission spectroscopy of those planets. A quantitative flare-frequency distribution (FFD) spanning the full energy range is therefore essential for both interpreting JWST spectra and modeling the planets' irradiation histories. Here we present a unified FFD over four orders of magnitude in energy by jointly analyzing $\approx$87\,hr of JWST/NIRISS and JWST/NIRSpec time-series spectroscopy together with $\approx$74\,days of \textit{Kepler}/K2 photometry. To enable a consistent comparison across these heterogeneous datasets, we convert all events to energies in the TESS bandpass. For the Kepler-to-TESS conversion we adopt a cooler flare continuum appropriate for ultra-cool dwarfs ($T_{\rm flare}=3500$\,K). After correcting for flare-detection sensitivities, the combined JWST+K2 cumulative FFD is consistent with a single power law, $N(\ge E_\mathrm{TESS})\propto E_\mathrm{TESS}^{-\beta}$, with $\beta=0.753$ over $E_{\rm TESS}\simeq10^{29}$-$10^{33}$\,erg. The slope of the distribution indicates that the time-averaged flare energy budget is dominated by rare, high-energy events rather than by the more numerous low-energy flares. This bandpass-consistent FFD provides a practical basis for JWST transit-spectroscopy planning and for modeling the flare-driven irradiation environment of the TRAPPIST-1 planets.

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astro-ph.SR 2026-05-07

Double-horned lines trace ring-like gas around supernova

The Eye of Sauron in SN 2025ngs: a Short-plateau Cousin of SN 1998S with Evidence for a Ring-like Circumstellar Medium

Early spectra of short-plateau SN 2025ngs show shock interaction with a disk of material from its supergiant progenitor, resembling but f

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Interacting supernovae probe the twilight years of massive stars, exhibiting signatures of interaction between the supernova ejecta and surrounding material expelled from the progenitor. We present the peculiar interacting supernova, SN\,2025ngs in NGC5961 (37.8 Mpc). This transient toes the line between strongly interacting supernovae (type IIn) and type IIP supernovae. SN 2025ngs presents photometrically as a short-plateau supernova, with a plateau duration, t$_{\mathrm{PT}}^{}\approx70$ days. Interaction features subside within a week post-explosion, consistent with the growing number of flash supernovae, giving way to a short period where a typical IIP spectrum is exhibited. Towards the drop off the plateau, interaction features re-emerge, exhibiting complex H$\alpha$ profiles throughout the rest of the transient evolution. We compare with models of early spectra, finding the abundances generally consistent with a supergiant progenitor with a high mass-loss rate (10$^{-3}$ M$_\odot$ yr$^{-1}$). Early, high-resolution spectra reveal a double-horned H$\alpha$ profile, providing strong evidence for shock interaction with a proximate disk-like circumstellar medium. Spectroscopically, SN 2025ngs closely resembles the luminous SN 1998S, despite photometric differences, with SN 2025ngs having a relatively modest peak magnitude of $M_\mathrm{V}=-17.9$ mag, adding another member to the surprisingly diverse 98S-like group.

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astro-ph.SR 2026-05-07

Stronger radiation yields more massive protostellar discs

The Impact of Radiation Environment on the Evolution and Fragmentation of Protostellar Discs

Simulations show high-radiation environments produce hotter, denser discs whose fragments can destroy the system rather than form planets.

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We present high-resolution zoom-in simulations of molecular clouds exposed to an interstellar radiation field and cosmic ray ionisation rate up to 1000 times stronger than that of the solar neighbourhood. We detail the evolution of the accretion discs that form around the first protostar in each simulation, for a total of 7 discs, for up to 100 kyr. The use of a zoom-in procedure allows for the au-scale discs to be well resolved (with resolution < 0.25 au) whilst retaining the structure of the wider parsec-scale molecular cloud. We find that discs exposed to a stronger radiation field tend to be more massive, hotter and denser. Similarly, their host stars grow to become more massive as a result of accreting more rapidly from their surroundings. All the discs show evidence of recurrent instability during the simulations, but only some of them fragment. We investigate whether stability metrics, such as the Toomre $Q$, $\alpha$ viscosity, and $\beta$ cooling parameter, can predict fragmentation by calculating them just before the discs fragment. We find that the metrics are generally unable to do so, as the discs appear stable even up to a few hundred years before fragmenting. In solar-like environments fragments are typically of planetary mass and often migrate to the centre of the disc, whereas fragments in a high-radiation environment are massive ($\rm > 0.1 \, M_\odot$) and fully disrupt/accrete from the progenitor disc. We conclude that the evolution and properties of circumstellar discs depend on both their radiation and physical environment.

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astro-ph.SR 2026-05-07

New Ag I model raises solar silver abundance by 0.19 dex

Ag I model atom and the 3D non-LTE solar silver abundance

3D non-LTE analysis of the 328 and 338 nm lines shrinks the gap with meteoritic value to 0.06 dex.

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Silver is an important light neutron-capture element whose stellar abundances help constrain the origin of the weak r-process. The Sun is an important reference point for such studies; moreover, being a moderately volatile element in CI chondrites, the solar silver abundance is interesting as a diagnostic for the debated Sun-CI abundance vs. condensation temperature trend. These studies require accurate silver abundances that go beyond the commonly used assumptions of 1D atmospheres and local thermodynamic equilibrium (LTE); however, no consistent 3D non-LTE analysis of silver has been available to date. We present a new Ag I model atom built from carefully curated radiative and collisional data, including newly computed oscillator strengths using an ab initio multi-configurational Hartree-Fock method and inelastic hydrogen collision rates based on a combined asymptotic and free-electron model approach. We assess modelling uncertainties via targeted sensitivity tests, finding the results most sensitive to hydrogen collision data. Applying the model to the solar Ag I 328 and 338 nm resonance lines, we find severe positive abundance corrections from coupled 3D and non-LTE effects. Using revised equivalent width measurements, we derive a recommended solar 3D non-LTE silver abundance of 1.15 +/- 0.08. This is an increase of 0.19 dex relative to the current reference value. Our ab initio model significantly reduces the discrepancy with the meteoritic value from 0.25 to 0.06 dex; moreover, this residual offset is consistent with recent results for other moderately volatile elements. The Sun provides the benchmark test for the first Ag I non-LTE model atom presented here. In subsequent work, this model will be applied to determine 3D non-LTE silver abundances in metal-poor dwarfs and giants, enabling improved constraints on Galactic chemical evolution and weak r-process nucleosynthesis.

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astro-ph.SR 2026-05-07

Most massive open clusters show extended turnoffs

Stellar rotation and binaries in open clusters with Gaia DR3

Analysis of Gaia DR3 finds eMSTO in clusters over 1000 solar masses and a new way to count blue stragglers by mass and age.

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Stellar rotation is a fundamental ingredient in shaping the evolution of stars and it can also be used to trace past stellar interactions. Yet, systematic studies of stellar rotation in large samples of stars belonging to different populations have only recently been made possible, thanks to spectroscopic surveys. We profit from the catalogue of rotational broadening and rotation periods released with Gaia DR3. We focus on open clusters to study the rotational behaviour of several interesting populations including, among others, blue stragglers and extended main sequence turnoffs (eMSTO). We use literature lists of almost a million member stars in several thousand open clusters in the Milky Way. We collect properties of stars and clusters from large surveys, including Gaia, and from various literature sources. We include a comprehensive collection of known variables and binary stars from various databases. We manually select (exotic) stellar populations from the color-magnitude diagrams of individual clusters and study their rotational properties. Our catalogue contains more than 44 000 rotationally characterised stars, almost 57 000 variables (excluding binaries) and more than 22 000 binary stars. We find several interesting results, including a few hundred new blue stragglers, several fast rotating red giants, and we increase the number of clusters with an eMSTO to 96. We discover that most clusters more massive than $10^3$ $M_{\odot}$ display an eMSTO. We present a new parametrization of the number of blue stragglers as a function of cluster mass and age. We find that the percentage of binary stars in the equal-mass binary sequence and in the main sequence are similar. We present the first large-scale statistical exploration of stellar rotation in open clusters, which already yielded new interesting results and which can be used as the basis for several detailed follow-up studies.

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astro-ph.SR 2026-05-07

Catalogs map white dwarf mergers to LISA sources

The diverse outcomes of binary white dwarf mergers and connections to Galactic LISA sources

Public simulations show how binary evolution uncertainties set rates of AM CVn stars, magnetars and supernovae from galactic white dwarf bin

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In the coming decade, the millihertz gravitational wave observatory LISA will provide the best constraints yet on the tens of thousands of close white dwarf binaries in the Milky Way, yielding unprecedented insights into the most abundant class of compact object binaries. Following inspiral via gravitational wave emission, interacting white dwarf binary pairs can lead to a multitude of outcomes, including AM Canum Venaticorum (AM CVn) binaries, R Coronae Borealis stars, young, rapidly-spinning single white dwarfs, (millisecond) magnetars, and a variety of explosive transients, most notably Type Ia supernovae. Current and future electromagnetic observations of these various outcomes coupled with the forthcoming flood of data from LISA place us on the precipice of a significant advance in our understanding of the long-term fate of white dwarf binaries. In this paper, we present a suite of mock catalogs of the Milky Way's white dwarf merger history, created using the population synthesis code $\texttt{COSMIC}$. We summarize the various merger outcomes expected (based upon varying white dwarf masses and chemical compositions) and explore ways the rates of these outcomes may vary with model uncertainties pertaining to binary evolution. We publicly release these merger catalogs as a tool for facilitating connections between gravitational wave science and white dwarf binary astrophysics.

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astro-ph.SR 2026-05-07

Fast tides transfer energy to convective flow at u'^2 over t_conv

Turbulent damping of fast tidal oscillations by three-dimensional Rayleigh-B\'enard convection with a radiating free surface

Three-dimensional simulations reveal systematic kinetic energy transfer from tidal oscillations to mean flow through velocity correlations,

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We present three-dimensional Dedalus simulations of Rayleigh-B\'enard convection with a blackbody-radiating free upper surface, subject to a low-amplitude oscillatory forcing that mimics tidal perturbations in convective envelopes of stars and planets. The forcing period is 10-100 times shorter than the convective timescale, $t_{\rm conv}$. Using a Reynolds decomposition of the velocity field averaged over one oscillation period, in which the tidal oscillations naturally constitute the fluctuating field and convection the mean flow, we elucidate the kinetic energy exchange between the two. Provided the oscillatory Reynolds number exceeds a modest threshold, we find that the oscillations systematically transfer kinetic energy to the mean flow at a volume-averaged rate $D_R \sim u'^2 t_{\rm conv}^{-1}$, where $u'$ is the rms fluctuation velocity. This reflects strong, order-unity correlations between the fluctuation velocities and the mean flow. These arise because the oscillatory forcing displaces fluid elements that are then redirected by buoyancy and incompressibility in the same manner as the mean flow. The transfer is dominated by correlations involving vertical velocity fluctuations and vertical gradients of the mean flow. The resulting energy transfer rate is consistent, within the equilibrium-tide framework, with the observed tidal circularisation of solar-type binaries and with the orbital evolution of moons of Jupiter and Saturn. This validates the formalism proposed by Terquem (2021) for the dissipation of fast tides, a longstanding problem. Replacing the free surface with a rigid upper boundary significantly and artificially modifies the correlations.

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astro-ph.SR 2026-05-07

Simulations show faster shocks in young supernova remnants

Multi-Dimensional MHD simulations of young Core-Collapse Supernova Remnants

Accounting for structured circumstellar material from evolved stars accelerates forward shocks beyond analytic predictions in the first few

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Supernova remnants (SNRs) play a central role in shaping the interstellar medium. Core-Collapse Supernova (CCSN) progenitors are massive stars, which produce a dense circumstellar medium (CSM) through intense mass loss in post-main sequence evolution. The subsequent CCSN produces a strong shock which expands into a highly structured, complex magnetised environment. Magnetohydrodynamic (MHD) consideration of pre- and post-CCSN evolution in multi-D are desirable to further our understanding of non-thermal aspects. We aim to determine how detailed stellar evolution treatment influences the shock propagation, focusing on Red Supergiants (RSGs) and Wolf-Rayet (WR) stars. We use the PION code to perform 3D MHD simulations of these CCSN progenitors. We use a detailed stellar evolution prescription to accurately and self-consistently model the pre-SN CSM and initialise CCSN explosions to investigate the surrounding environment. Our 2D and 3D treatment, inclusion of radiative cooling and assumption of full photoionization produces CSM features not identified in previous work. In the WR model we produce a coherent set of fast reflected shocks. In both cases we find faster forward shocks than predicted by analytic theory due to additional wind acceleration from photoionization for the RSG case, and accounting for the CSM expansion in the WR case. Model predictions of slowly rotating RSG and WR stars results in weakly magnetised wind bubbles, limiting potential for their SNRs to become PeV particle accelerators. Detailed multi-D MHD treatment of the CSM is needed to account for SNR evolution beyond the wind termination shock, where dynamic instabilities can be important. Including self-consistent stellar evolution is important for determining the CSM density and magnetic field structure close to the star, which govern the shock properties and SNR evolution for the first few hundred yr. (Abridged)

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astro-ph.SR 2026-05-07

Tertiary star spectrum isolated in EM Boo at 300 pc

Spectroscopic Disentangling Revealed the Tertiary Component in the Multiple System EM Boo

Disentangling and SED fitting agree on distance while Gaia underestimates due to multiplicity

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We present a comprehensive photometric and spectroscopic study of the triple stellar system EM\,Boo. The system is composed of detached, low-mass components, and for the first time in the literature, the spectrum of the tertiary component has been successfully disentangled from the composite spectrum using the \texttt{KOREL} code. Synthetic spectra were generated for each disentangled component, allowing determination of their atmospheric parameters. The depth of the H$_\alpha$ line in the tertiary spectrum indicates that it is an intermediate-temperature star, consistent with spectral types between A and F, and its effective temperature was determined to be 7000~K. By analyzing the radial velocity and light curves simultaneously, the fundamental physical parameters of the system were derived, and its detailed evolutionary status was investigated using \texttt{MESA} models. The \textit{HIPPARCOS} trigonometric parallax ($\varpi_{\rm Hip}=1.33\pm1.45$ mas) and \textit{Gaia} DR3 trigonometric parallax ($\varpi_{\rm Gaia}=3.9699\pm0.1812$ mas) show a significant discrepancy, most likely related to the system's multiplicity and the limitations of single-star astrometric solutions. To provide independent distance estimates, we modeled the spectral energy distribution (SED) using multi-wavelength flux data, yielding $E(B-V)=0.05$ mag and a trigonometric parallax $\varpi_{\rm SED}=3.2$ mas, corresponding to $d_{\rm SED}=313$ pc. Furthermore, photometric distance estimates based on the components' absolute magnitudes yield $d_{1}=299$ pc and $d_{2}=301$ pc, in good agreement with the SED-based distance. Both the SED-based and photometric distances converge around $d=300$ pc, indicating that the \textit{Gaia} trigonometric parallax underestimates the true distance of EM\,Boo.

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astro-ph.SR 2026-05-07

Be stars show magnetic fields of hundreds of gauss

The magnetic fields in Be stars are stronger than previously suggested

Measurements in seven stars detect fields up to 460 G, contradicting earlier claims of weak fields and calling for revised binary-formation

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Recent observational studies suggest that Be stars most likely are formed through the process of mass transfer in binary systems. In view of the wide consensus that the origin of the magnetic field in stars with radiative envelopes involves binary interaction processes, searching for magnetic fields in Be stars appears especially promising. As a pilot project, we searched for the presence of magnetic fields in a sample of seven well-known Be stars. We used high-resolution HARPSpol spectra to measure the mean longitudinal magnetic field, employing the least squares deconvolution technique. A dedicated measurement procedure introduced by our group in recent years was applied. Opposite to previous spectropolarimetric studies reporting that magnetic fields in Be stars are weak and usually below 100 G, our study presents the first observational evidence that magnetic fields in Be stars can be as strong as a few hundred gauss. Magnetic fields are detected in all studied Be stars, with the strongest magnetic field being about -460 G for the B0.5 III star HD 184915. Magnetic fields in the range between 338 and 380 G (in absolute values) are detected in three other Be stars, HD 209409, HD 209522, and HD 224686. Due to the fact that magnetic fields in Be stars are stronger than previously believed, we must re-evaluate our understanding of the initial conditions of massive binaries to be able to determine the origin of such systems.

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astro-ph.SR 2026-05-07

Fast waves steepen and dissipate before reaching coronal null points

Nonlinear steepening of a fast magnetoacoustic wave in the vicinity of a coronal magnetic null point

The drop in fast speed near the null amplifies nonlinear deformation, so the wave breaks at a distance away.

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The interaction of a fast magnetoacoustic wave with a magnetic null point is studied in the context of the sympathetic flare phenomenon. Attention is paid to steepening the wave caused by the finite-amplitude effects in a non-uniform plasma environment. The null point is modelled by a potential magnetic configuration without a guiding field. The equilibrium plasma density and temperature are taken to be constant. The fast wave is excited by an impulsive point source outside the distance at which the local Alfv\'en and sound speeds are equal to each other. The incoming fast wave approaches the null point along the bisector of the magnetic configuration, i.e., across the local field. The fast-speed non-uniformity around the null point causes the refraction of the incident fast wave. However, the segment of the incoming wave, which approaches the null point is locally plane. The decrease in the fast speed towards the null point amplifies the nonlinear deformation of the incoming wave. Hence, the fast wave can become subject to nonlinear dissipation at a distance from the null point and not reach it.

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astro-ph.SR 2026-05-06

CME input errors drive 2-8 hour arrival spreads at Earth

Ensemble modeling of Coronal Mass Ejection dynamics and forecasts at 1 AU with a semi-analytic flux-rope model

Monte Carlo ensembles of a flux-rope model map how eruption and wind uncertainties affect forecasts for six events

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This study quantifies how uncertainty in physically meaningful coronal mass ejection (CME) and solar-wind inputs propagates into forecast-relevant diagnostics from eruption to 1 AU. We use a semi-analytic erupting flux rope (EFR) model to simulate CME initiation and Sun-to-1 AU propagation under Lorentz, gravitational, and drag forces, driven by a prescribed time-dependent poloidal-flux injection. Relative to the original EFR formulation, we include sheath and pile-up effects through an effective mass and update the drag term for CME solar-wind coupling. The model is embedded in a Monte Carlo framework with truncated-normal sampling of key eruption and background solar-wind inputs. Across six CME events, the ensembles show event-dependent dispersion in the 1 AU diagnostics. For +/- 20% input sampling, all spreads are 1-sigma ensemble standard deviations. The time-of-arrival spread is 2.4-7.7 h and is mainly controlled by the poloidal-flux injection history, upstream wind speed, and drag coefficient. The leading-edge speed spread is 28-53 km/s and is primarily controlled by background-flow properties. Magnetic-field diagnostics show two regimes: the sheath field is relatively tightly distributed, with a spread of 1-3.5 nT and sensitivity to upstream wind, size, and expansion scaling, whereas the internal flux-rope field has a larger spread of 1-7.6 nT and is governed mainly by eruption-driving and flux-content parameters. The impact-duration spread is 2.4-6.3 h and is controlled mostly by geometric size and expansion scaling, with additional sensitivity to the driving timescale. These results establish a quantitative link between EFR input uncertainties and the resulting spread in CME arrival and impact diagnostics, identifying the physical parameters that most strongly limit forecast precision at 1 AU.

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astro-ph.SR 2026-05-06

Flare continuum calibrates EIS and shows inverse FIP bias

Modeling Flare Continuum Emission Observed by Hinode/EIS: Instrument Calibration and Element Composition Results

Observed-to-modeled continuum ratio gives effective area curves without fine structure and Fe/H abundance 0.57 times photospheric at 10 MK.

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Continuum emission from a solar flare observed with the Extreme ultraviolet Imaging Spectrometer (EIS) on board the Hinode satellite is used to obtain the radiometric calibration of the instrument. The flare had a GOES class of M8, and peaked at 23:59 UT on 2024 September 30. The continuum is modeled by computing a differential emission measure curve using EIS emission lines and atomic data from the CHIANTI database. The ratio of the observed continuum to model continuum yields effective area curves for the instrument. The new curves confirm earlier findings that the EIS long-wavelength channel has degraded by a factor two compared to the short-wavelength channel. However, no evidence is found for the fine-scale structure in the effective area curves that has been presented by previous authors. In order to reproduce both the emission line intensities and the continuum, it is found that the plasma must be depleted in elements with low first ionization potentials (FIPs), i.e., the so-called inverse FIP-effect. In particular, the Fe/H relative abundance is found to be a factor 0.57 below the photospheric value at a temperature of 10 MK. This is confirmed by analysis of soft X-ray spectra from the Solar X-ray Monitor on Chandrayaan-2, which yields an Fe/H FIP bias of 0.55 averaged over the entire flare.

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astro-ph.SR 2026-05-06 2 theorems

M-dwarf binary gets dynamical mass of 0.46 solar masses from radio and RV data

Orbital motion and dynamical mass of the complex periodic variable binary system 2MASS J05082729-2101444

VLBA resolves both components in an eccentric 2.19-year orbit, yielding a total mass slightly above model estimates for young stars.

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We uses very long baseline interferometry to constrain the orbit of the binary system 2MASS J05082729-2101444. We observed the system with the VLBA in three epochs at a frequency of 4.85 GHz, which provides an angular resolution of about 3 mas. We combined the three radio astrometric observations, 119 RVs (60 VIS and 59 NIR) obtained with the CARMENES high-resolution spectrograph over a period of 8.1 years, and a relative astrometric measurement of an archival H-band Keck NIRC adaptive optics image to fit the orbital motion of the binary system. The VLBA observations resolved the binary system and show emission from both stellar components, with similar flux density levels (0.34-0.67 mJy) and showing slight temporal flux variations. The emission appears quiescent, with no significant circular polarization, and with no flare events. We obtained a fit of the orbital motion of this binary system, which has an eccentric orbit (e = 0.71) with an orbital period of 2.19 yr and a semimajor axis of 26.964 mas (1.3 au). The VLBA observations made it possible to resolve the binary system and identify both stars as radio-loud sources. The combined fit shows that 2M0508-21 is an M-dwarf binary with a total dynamical mass of $0.459\pm0.007$ M$_{\odot}$, assuming Gaia parallax. This mass is slightly larger than those estimated from the luminosity and theoretical evolutionary models. The upper limit of the circular polarization at 4.85 GHz ($\lesssim$10\%), the persistence of the quiescent emission, and the relatively low brightness temperatures are consistent with a gyro-synchrotron or synchrotron origin for the radio emission. Further VLBA observations are needed to obtain the individual masses of the stars, as well as to verify Gaia's parallax of the system. A complete characterization of the system will help improve evolutionary models for young objects at the substellar boundary.

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astro-ph.SR 2026-05-06 2 theorems

Radiative damping speeds brown dwarf inspiral by 25-110 Myr

The Tale of a Hungry Subgiant and Its Brown Dwarf: Interior Radiative Damping Dominates the Tidal Evolution of TOI-5882

Coupled MESA and GYRE-tides models show classical equilibrium tides miss most angular momentum transfer in this subgiant system.

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We present a self-consistent tidal evolution framework that couples binary evolution from MESA to the full linear tidal response from GYRE-tides. Applying this framework to TOI-5882, a subgiant hosting a short-period brown dwarf, we show that interior radiative damping dominates the system's tidal evolution, with the classical equilibrium tidal model significantly underestimating the star's angular momentum evolution by several orders of magnitude. Consequently, our combined framework predicts a 2--6 fold reduction in the engulfment timescale, accelerating the companion's inspiral by roughly 25--110 Myr. By modeling angular momentum transport through the star as it evolves, we demonstrate that the early inspiral is driven by the non-resonant dissipation of internal gravity waves, before transitioning into a regime dominated by resonance crossings as the system approaches Roche-lobe overflow. We highlight the necessity of reframing the historical dichotomy between equilibrium and dynamical tides and instead propose categorizing tidal interactions around their dissipation mechanisms: radiatively and viscously damped tides. Our framework is broadly applicable to the tidal modeling of a wide class of star-companion systems, from binary stars to hot Jupiters, in a self-consistent and computationally feasible manner.

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astro-ph.SR 2026-05-06

Mg II triplet wings flag Ellerman bombs in IRIS NUV

IRIS NUV diagnostics for Ellerman bombs: spectral properties, thermodynamics, and formation height

Detection rule using NUV signatures recovers 14 of 18 Hα events and estimates formation height.

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Context. Ellerman bombs (EBs) are observational signatures of small-scale magnetic reconnection, key to understanding the lower solar atmosphere. While their role in active regions has been widely studied using the H$\alpha$ line, near-ultraviolet (NUV) spectra routinely observed by the Interface Region Imaging Spectrograph (IRIS) offer a promising alternative for EB identification, enabling large-scale studies. Aims. We aim to identify the most important spectral signatures of EBs in the IRIS NUV spectra. With this, we seek to develop a robust criterion for their detection solely using the IRIS NUV spectra. In parallel, we determine the typical atmospheric stratification associated with EBs. Methods. We used four coordinated observations between the Swedish 1-m Solar Telescope (SST) and IRIS. Using the H$\alpha$ line as a reference, we detected 18 different EBs and studied their associated IRIS NUV spectra. In addition, we used the IRIS$^{2+}$ inversion tool to infer the temperature, line-of-sight velocity, and non-thermal broadening from the EB spectra. Results. The defining feature of EBs in the IRIS NUV is the enhancement of the wings of the subordinated Mg II triplet in between the Mg II h&k lines. Inversions reveal that these signatures are produced by localized temperature increase of $\Delta$ T~1650 K around log$\tau$=-3.8. Using only the Mg II triplet signatures, we found a detection criterion that successfully recovered 14 of 18 H$\alpha$-detected EBs. In addition, the shape of the Mg II h&k lines in relation to the Mg II triplet can serve as a proxy for the EB formation height. Conclusions. The NUV spectrum observed by IRIS is a good candidate for detecting EBs, opening the doors to large-scale studies across the extensive IRIS database, removing the dependence on H$\alpha$ observations.

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astro-ph.SR 2026-05-06

Unstable modes spectrum unifies star mixing theories

Unifying Transport Models of Thermohaline Convection in Stars

Thermohaline diffusion now interpolates between models that differed by orders of magnitude when both slow and fast growing modes are

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Thermohaline convection is a standard chemical mixing process in stellar interiors, yet its mixing efficiency is not fully settled. Competing theories predict turbulent diffusion coefficients, $D_\mu$, that can differ by orders of magnitude, leading to uncertainties in stellar models and interpretations of observations. This paper explores a potential resolution to existing discrepancies. We first complete the linear stability theory and identify two types of unstable modes: slow growing modes at large length scales and fast growing modes at small length scales. We then reevaluate $D_\mu$ considering the full spectrum of unstable modes and find that it can self-consistently interpolate between previously proposed theoretical scalings across the instability parameter space. The question of thermohaline mixing efficiency in stars may be settled by future simulations that quantify the scale-dependent contributions of fast and slow modes to $D_\mu$ and determine how the modes dominating the transport change across parameter space.

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astro-ph.SR 2026-05-06

15265 super-Nyquist frequencies identified in 1309 delta Scuti stars

Identification and characterization of 15265 super-Nyquist frequencies in 1309 {δ} Scuti stars from Kepler photometry

Sliding periodogram method flags aliases in Kepler long-cadence data and supplies a cleaned frequency catalog for asteroseismic modeling.

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The frequency of pressure (p) mode in $\delta$~Scuti stars can exceed the Nyquist limit of \textit{Kepler} long-cadence photometry. {These 'super-Nyquist frequencies' (SNFs) are observed as 'reflected' peaks at lower frequencies, i.e., they are Nyquist aliases that pose} a threat to asteroseismic diagnostics. Their impact on $\delta$~Scuti p modes has yet to be comprehensively explored. We performed a systematic survey to search for SNFs in 1,838 \textit{Kepler} $\delta$~Scuti stars through a novel technique based on sliding Lomb-Scargle periodogram, identifying 15,265 confirmed SNFs in 1,309 stars, from a total of 259,883 frequencies. We observe that the total number of detected frequencies per star remains featureless across the $\delta$~Scuti instability strip; however, young stars pulsate in higher frequencies and so have significantly more SNFs on average. Both the number and the rate of SNFs diminishes accordingly as $\delta$~Scuti stars become more evolved, which is consistent with both observation and stellar models. Furthermore, our method detects a greater fraction of modes as SNFs at higher frequencies, rising from approximately 1\% at 20 $\mu $Hz to 23\% at the Nyquist limit. The rate of underdetection is highest amongst low-amplitude modes. The SNF modulation patterns can be well distinguished from phase modulations induced by binarity or nonlinear mode interactions. We provide a frequency catalog for future asteroseismic studies of $\delta$~Scuti stars, wherein we identify each peak as being real or an alias, enabling further investigations into regular patterns of pulsation modes, linear combination frequencies, and theoretical modeling.

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astro-ph.SR 2026-05-06 3 theorems

Flare electrons precipitate six times more in weak polarity

Data-Constrained Modeling of Electron Transport and Asymmetric Precipitation in the 2011 August 4 Solar Flare

3D model of 2011 August 4 event ties magnetic mirror ratios to observed two-ribbon structure and strong asymmetry.

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Energetic electrons accelerated at coronal reconnection sites during solar flares precipitate into the lower solar atmosphere, generating nonthermal emissions and regulating energy deposition. However, how their transport and precipitation are jointly governed by the three-dimensional (3D) magnetic topology, turbulent scattering, and Coulomb collisions remains unclear. Here, we aim to disentangle these physical processes by using a data-constrained 3D particle transport model for the 2011 August 4 flare. The simulated distribution of precipitated electrons aligns closely with photospheric quasi-separatrix layers and reproduces the observed two-ribbon morphology in 1700~\AA. We reveal a strong polarity asymmetry, with the 10~s precipitation fraction about six times higher in the weak positive polarity. This arises primarily from distinct mirror ratios of different polarities under the 3D magnetic configuration and can be understood via a modified escape probability for an asymmetric magnetic bottle. Varying strengths of turbulent scattering lead to a rise-then-fall trend and a pronounced energy dependence in the precipitation fraction. Coulomb collisions globally suppress precipitation, especially at low energies, and further amplify the polarity asymmetry. This integrated modeling framework bridges detailed transport physics to observable flare emissions and advances the development of quantitative models for realistic solar flare events.

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astro-ph.SR 2026-05-06

Flare electrons precipitate six times more into weak magnetic polarity

Data-Constrained Modeling of Electron Transport and Asymmetric Precipitation in the 2011 August 4 Solar Flare

Three-dimensional magnetic mirror ratios create strong asymmetry in where electrons deposit energy during the 2011 August 4 event.

abstract click to expand

Energetic electrons accelerated at coronal reconnection sites during solar flares precipitate into the lower solar atmosphere, generating nonthermal emissions and regulating energy deposition. However, how their transport and precipitation are jointly governed by the three-dimensional (3D) magnetic topology, turbulent scattering, and Coulomb collisions remains unclear. Here, we aim to disentangle these physical processes by using a data-constrained 3D particle transport model for the 2011 August 4 flare. The simulated distribution of precipitated electrons aligns closely with photospheric quasi-separatrix layers and reproduces the observed two-ribbon morphology in 1700~\AA. We reveal a strong polarity asymmetry, with the 10~s precipitation fraction about six times higher in the weak positive polarity. This arises primarily from distinct mirror ratios of different polarities under the 3D magnetic configuration and can be understood via a modified escape probability for an asymmetric magnetic bottle. Varying strengths of turbulent scattering lead to a rise-then-fall trend and a pronounced energy dependence in the precipitation fraction. Coulomb collisions globally suppress precipitation, especially at low energies, and further amplify the polarity asymmetry. This integrated modeling framework bridges detailed transport physics to observable flare emissions and advances the development of quantitative models for realistic solar flare events.

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astro-ph.SR 2026-05-06

Evolving magnetic fields change solar wind in full Sun-to-Earth runs

COCONUT: Toward practical time-evolving Sun-to-Earth magnetohydrodynamic modeling

Single implicit MHD model from corona to 1 AU yields differences from steady-state and supports four-day L5 forecasts at Earth.

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Due to computational efficiency and numerical stability limitations, coronal simulations constrained by static magnetograms are typically performed first and then used to drive inner-heliosphere (IH) models. In this paper, we calculate the Sun-to-Earth coronal and wind evolutions using a single time-evolving MHD model, showing that implicit MHD models have the potential to meaningfully simplify and improve the overall Sun-to-Earth modelling pipeline. We extend the implicit time-evolving coronal MHD model COCONUT out to 1 AU, and utilise it to investigate solar coronal and wind evolutions around a solar maximum Carrington rotation (CR). We compare quasi-steady-state and time-evolving Sun-to-Earth simulations to evaluate the impact of the inner-boundary magnetic field evolution, which is neglected in steady-state simulations, on background plasma parameters. Comparisons with commonly used coupled Sun-to-Earth simulations are also conducted to further validate and assess the Sun-to-Earth model COCONUT. The results show that the time-evolving implicit MHD modelling approach yields noticeable differences compared to oversimplified steady-state simulations, and is efficient enough for practical applications. Modelling the solar corona and wind using a single MHD model simplifies the modelling pipeline and avoids uncertainties associated with coupling different coronal and IH models. The noticeable differences in the temporal evolution of plasma parameters at the L1 and L5 points highlight the need to use continuously evolving, synchronised magnetic field observations to improve global coronal and solar wind simulations, whereas the overall consistent evolutionary trend reveals the reliability of using L5 observations to forecast solar wind conditions near Earth about four days in advance.

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astro-ph.SR 2026-05-06

TESS Cycle 7 yields 73 rapid stellar oscillators

A Search for High Frequency Oscillations in TESS Cycle 7

Short-cadence data from 39,000 light curves adds 24 white dwarfs, 31 subdwarfs, and 18 A-F stars with frequencies above 50 cycles per day.

abstract click to expand

High-quality, short-cadence photometry from TESS enables the detection of rapid oscillators with unprecedented sensitivity. In this work, we conduct a homogeneous search for high-frequency variability using 20-second cadence light curves from TESS Cycle 7 (Sectors 84--96). From $\sim 3.9\times10^{4}$ light curves, we compute Lomb-Scargle periodograms and select candidates exhibiting at least one significant signal with $\mathrm{FAP}\le 10^{-4}$ at frequencies $f\ge 50~\mathrm{d^{-1}}$. After excluding previously reported objects and performing pixel-level and light-curve vetting to mitigate contamination, we identify 73 rapid oscillators, including 24 pulsating white dwarfs, 31 hot subdwarfs, and 18 A-F stars. Using an iterative prewhitening procedure, we carry out a detailed frequency analysis for each target and derive the oscillation frequencies and amplitudes. We further investigate the physical origins of the detected frequency content and present statistical characterizations of the rapid-oscillator sample. We highlight one white dwarf and one subdwarf that exhibit clear frequency multiplets consistent with rotational splitting. This work enlarges the sample of rapid oscillators accessible with TESS data and provides a uniformly measured frequency-amplitude catalog, establishing a consistent basis for future asteroseismic and population studies.

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