We present a comprehensive catalog, in the Sloan i and Harris V filters, of long-period variable (LPV) stars in the spheroidal dwarf satellites of the Andromeda galaxy based on a dedicated survey for variable stars in Local Group dwarf systems. Using photometric time-series data obtained with the Wide Field Camera on the 2.5 m Isaac Newton Telescope, we identify approximately 2800 LPV candidates across 17 Andromeda satellites, spanning a broad range in luminosity and variability amplitude. This study is accompanied by a public data release that includes two comprehensive catalogs, a catalog of the complete stellar populations for each galaxy, and a separate catalog listing all identified LPV candidates. Both are available through CDS/VizieR and provide a valuable resource for investigating quenching timescales, stellar mass distributions, and the effects of mass loss and dust production in dwarf galaxies. We derive updated structural parameters, including newly measured half-light radii, and determine distance moduli using the tip of the red giant branch method with Sobel filter edge detection, yielding values between 23.38 +/- 0.06 and 25.35 +/- 0.06 mag.

Recent detections of α Orionis B, the putative companion to Betelgeuse, have been reported using multiple instruments and techniques. These include, most recently, a >6σ detection using VLT/SPHERE reported by Montarges+2026. The authors infer a bright companion (∼10^-3× Betelgeuse's luminosity) with a mass of 2-3 M_⊙ and T_eff≈10-12,000 K, loosely consistent with the uppermost bounds of Howell+2025's recent mass estimate from speckle-imaging. However, it is in tension by a factor of two with the reported mass-exclusion limits via non-detection from a recent HST far-UV campaign (Goldberg+2025). While mass identification from isochrone-fitting (conducted in all cases) is prone to uncertainty, the restrictive HST upper limit on FUV flux precludes the hot, blue emission of a ≳2 M_⊙ main-sequence star. This discrepancy is reconciled by the following hypothesis: these detections observe the reflection of Betelgeuse's own luminosity scattered off the companion's bow shock and wake as it traverses the dusty circumstellar medium. To evaluate the feasibility of this scenario, we draw from custom, filter-specific stellar models computed with MESA, as well as Athena++ simulations of the companion's bow shock in idealized conditions. Importantly, the expansive bow shock from a stellar-mass object necessarily subtends a sizable portion of Betelgeuse's outgoing flux. We find that optical luminosity ratios of ∼10^-3-10^-4 are straightforward to resolve within reasonable assumptions about the companion mass and circumstellar dust, and disfavor a hot 3 M_⊙ companion. We thereby reconcile competing mass hypotheses across observational campaigns through proper attribution of the observed brightness, motivating future multi-wavelength campaigns to further characterize this enigmatic system.

Blue large-amplitude pulsators (BLAPs) are a recently discovered group of hot pulsating stars whose evolutionary status remains uncertain. Their proposed progenitors are either ≃0.3 M _⊙ shell H-burning stars or ≃1.0 M _⊙ core He-burning stars, both relying on mass loss or a merger event in a (rarely observed) close interacting binary system. With the goal of understanding the stellar masses of BLAPs, we therefore carried out a linear nonadiabatic analysis of a grid of models computed using mesa-rsp , with appropriate input stellar parameters ZXMLT _eff and convection parameter sets. We discuss the impact of stellar mass, metallicity, helium abundance, and convection parameters on the theoretical instability regions of BLAPs. We also derive new theoretical period relations; those based on low stellar masses show better agreement with the observed period relations. Although only two BLAPs have been observed to be multiperiodic oscillators so far, we analyse theoretical P _1O / P _F ratios and compare these values with other classical pulsators. Furthermore, we provide the first asteroseismic mass estimate for the triple-mode pulsator OGLE-BLAP-030, which seems to be well constrained in the range of 0.62–0.64 M _⊙ with a high metallicity of Z = 0.07, albeit with a few sources of uncertainty involved. This would place the BLAP star intermediate to the two proposed mass scenarios so far.

Abstract I revisit the contradictory claims regarding the detection of low-frequency extra modes in the RR Lyrae star HH Puppis. A Research Note by T. Love noted that the star shows no extra signals in the Transiting Exoplanets Survey Satellite (TESS) observations. In a response, M. Chadid attributed this to the limitations of the TESS mission over their longer dataset collected with the PAIX instrument they used. Here I show that some of the capabilities of TESS have been underestimated, and the claims made could be verified with a more detailed analysis (and public release) of the PAIX data.

Mass loss in low-mass stars during the red giant branch (RGB) and early asymptotic giant branch (EAGB) phases plays a key role in shaping stellar evolution, yet its dependence on stellar parameters such as metallicity remains poorly constrained, with observational studies yielding conflicting trends. We present the first asteroseismic analysis of RGB and EAGB stars in NGC 5897, the most distant and metal-poor globular cluster observed by the Kepler space telescope during the K2 mission. We detected solar-like oscillations and derived the frequency of maximum power excess, ν_ max, for 20 RGB and 6 EAGB stars. Using asteroseismic scaling relations, we derived mean masses of M_ RGB = 0.74±0.01 M_⊙ and M_ EAGB=0.65± 0.03 M_⊙. The inferred integrated mass loss between the two phases is ΔM_ RGB-EAGB=0.08± 0.03 M_⊙. We present an updated mass-loss–metallicity relation for Type I globular clusters, extending it to the very metal-poor regime and supporting decreasing integrated RGB mass loss with decreasing metallicity.

We present a systematic survey of strange mode pulsations in Cepheids using MESA and for the linear stability analysis, MESA RSP. Our model grid spans 2-15 M circle dot in mass and [Fe/H] = -0.95-0.17 (Z = 0.0015-0.0200) in metallicity, with four convective overshoot prescriptions. Strange modes were identified in a relatively small fraction (similar to 5-12.5%) of models, occurring at npg = 5-9, with npg = 6-7 as the most frequent radial modes. No unstable solutions were identified beyond npg = 9, in contrast to earlier studies reporting strange modes at npg = 10-12. We quantified the duration of the instability crossing phase (tau IS), the strange mode phase (tau s), and their ratio Ps=tau s/tau IS . Toward higher masses, both tau IS and tau s decrease, yet their ratio shows no systematic trend with mass in models that include convective core overshoot. The absolute timescales for strange modes remain short, typically tau s similar to 104.5-106 yr, while tau IS is often an order of magnitude shorter, implying that these stars may spend a larger fraction of their life in the strange mode phase than in the instability strip itself. The extended duration of the strange mode phase may enhance the detectability of strange mode pulsators, provided that observational precision is sufficient to capture their low-amplitude variability. The predicted periods (0.6-6.3 days) are well covered by a single 27-day TESS sector, making strange mode pulsators potentially detectable with current space-based photometry, although blending with nearby sources may pose challenges.

The diversity of Type IIn supernovae is largely driven by the properties of the circumstellar material (CSM) they explode into. We examine the temporal evolution of SN 2019vxm, an interacting supernova that belongs to the class of long-lasting Type IIn events, using multicolor photometry spanning the ultraviolet, optical and near-infrared wavelengths, including over 650 days of optical and 1500 days of IR coverage. The evolution of the spectral energy distribution and bolometric luminosity, as well as the effective temperature and radius of the photosphere, indicates that the supernova was initially surrounded by an optically thick CSM, which was heated and pushed outward by the forward shock of the impacting ejecta. About 80-100 days after the explosion the forward shock and the photosphere decouples, and we observe the receding photosphere of the H-recombination front within the now thinned CSM. Near-IR measurements reveal long-lasting, slowly cooling emission from circumstellar dust around SN 2019vxm and an IR rebrightening about one year after explosion, which we tentatively identify as a signature of an outer CSM region. We find that due to the moving photosphere and the transition from optically thick to partially thin inner CSM, modeling the explosion and subsequent interaction of the ejecta with the CSM to infer progenitor and CSM masses faces difficulties. Nevertheless, the inferred high masses and extremely high mass-loss rates point to a massive progenitor undergoing intense pre-supernova mass loss.

Abstract In this work, we investigate the applicability of asteroseismic scaling relation correction factors inferred from the comparison of APOKASC-3 seismic and Gaia radii of stars. Our findings suggest that applying these corrections beyond the scaling relation for the radius, e.g., in order to calculate stellar masses, requires a careful treatment of the underlying physical assumptions as well as further calibrations.

Interstellar extinction is a major obstacle in determining accurate stellar parameters from photometry near the Galactic disk. It is especially true for globular clusters at low galactic latitudes, which suffer from significant amounts of spatially variable reddening. Although differential reddening maps are available for tens of clusters, establishing and validating the absolute zero-point of relative maps is a challenge. In this study, we present a new approach to determine and evaluate absolute reddening zero-points for Galactic globular clusters by combining 3D reddening maps with Gaia DR3 RR Lyrae data. As a first case study, we investigate the low-latitude globular cluster M9. We compare the Gaia photometry and color data of the cluster member RR Lyrae stars to field RR Lyrae stars with accurate parallaxes and whose photometric metallicities match that of M9, as well as to theoretical models. We calculate the dereddened Gaia colors for the M9 stars based on three zero points. We confirm that the original SFD map by D. J. Schlegel et al. (1998) appears to be overcorrecting the reddening for at least some RR Lyrae stars, albeit not excessively. In contrast, the 3D Bayestar map and the recalibrated version of the SFD map provide physically plausible reddenings, which we accept as lower and upper limits for M9, respectively. Our results provide a physically motivated reddening range for M9 and outline a methodology that can be directly extended to other globular clusters that are accessible to the Gaia mission, and to other multicolor sky surveys, such as the Rubin Observatory.

Context. γ Persei is a long-period eclipsing binary system (P≈ 14.6 years) containing a red giant primary, and it is well known for its multi-faceted classification as a visual and spectroscopic binary. Its brightness and binary nature together make it a valuable target for both photometric and spectroscopic studies, particularly in the context of asteroseismology and stellar evolution, as the primary star likely formed through a stellar merger. Aims. We aim to determine the seismic parameters ν_ max, Δν, and the oscillation amplitudes of the primary component, an evolved giant, to estimate its seismic mass - which we can compare to its estimated dynamic mass. Methods. We use Transiting Exoplanet Survey Satellite (TESS) data obtained during Sectors 58, 85, and 86 and to complement the space-based observations, we incorporate high-resolution RV measurements acquired by the Stellar Observations Network Group (SONG) during two distinct epochs; 2017 and 2024. Results. We successfully detect solar-like oscillations in γ Per and infer a seismic mass of 3.25±0.13 M_⊙, which is slightly below the dynamical mass. We find the photometric oscillation amplitudes to be significantly lower than predicted from scaling relations, but in line with other high-mass red giants. We also find that radial velocity amplitudes along the Hertzsprung-Russell diagram cannot be fitted uniformly with current scaling relations.

We used MIST isochrone fitting and a dedicated grid of stellar evolution models computed with MESA to constrain the ages of the components of the gamma Persei binary system. While individual stars can be matched to the models at specific metallicities, no joint isochrone solution reproduces both the observed masses and evolutionary states. The stellar evolutionary tracks calculated by MESA reveal a clear evolutionary mismatch. The primary component of the system is in a post-main-sequence phase consistent with the red giant branch or red clump. In contrast, the lighter secondary component lies near the turn-off point of the main sequence or is in the early phase of the subgiant branch. This discrepancy can be overcome by assuming that the gamma Persei system was born as a triple and the primary component is a rejuvenated star formed through a merger of a close-by pair of main-sequence stars. We show that the merger must have occurred no later than a few hundred megaryears after system formation, and the progenitor masses of the merging stars are restricted by a combination of stars that fall within a narrow band in the (M-1,M- a, M-1,M- b) plane, corresponding to M-1,M- a similar or equal to 0.9-2.1 M-circle dot and M-1,M- b similar or equal to 2.3-2.5 M-circle dot.

Shock breakout and, in some cases, jet-driven high-energy emission are increasingly recognized as key signatures of the earliest phases of core-collapse supernovae, especially in Type IIn systems due to their dense, interaction-dominated circumstellar environments. We present a comprehensive photometric analysis of SN 2019vxm, a long-duration, luminous Type IIn supernova, MV=-21.41 +/- 0.05mag , observed from X-ray to near-infrared. SN 2019vxm is the first superluminous supernovae Type IIn to be caught with well-sampled TESS photometric data on the rise and has a convincing coincident X-ray source at the time of first light. The high-cadence TESS light curve captures the early-time rise, which is well described by a broken power law with an index of n = 1.41 +/- 0.04, significantly shallower than the canonical n = 2 behavior. From this, we constrain the time of first light to within 7.2 hr. We identify a spatial and temporal coincidence between SN 2019vxm and the hard X-ray/gamma-ray transient GRB 191117A, corresponding to a 3.3 sigma association confidence. Both the short-duration X-ray event and the lightcurve modeling are consistent with shock breakout into a dense, asymmetric circumstellar medium, indicative of a massive, compact progenitor such as a luminous blue variable transitioning to Wolf-Rayet phase embedded in a clumpy, asymmetric environment.

We present a new method and a corresponding code to compress the color magnitude diagram of a globular cluster into a representative curve, called a ridgeline, that can be more readily compared to isochrone models, among other applications. This compression method preserves the physical properties of the cluster, including the morphology of the CMD.

We present new theoretical light curves in the Rubin-LSST filters for a fine grid of BL Her models computed using MESA-RSP. We also derive new theoretical period-luminosity (PL) and period-Wesenheit (PW) relations in the Rubin-LSST filters with the goal to study the effect of convection parameters and metallicity on these relations. The grid of BL Her models was computed with the input stellar parameters: metallicity (-2.0 dex≤[Fe/H]≤ 0.0 dex), stellar mass (0.5M_⊙-0.8M_⊙), stellar luminosity (50L_⊙-300L_⊙), and effective temperature (across the full extent of the instability strip; in steps of 50K) and using four sets of convection parameters. Bolometric correction tables from MIST were used to transform the theoretical bolometric light curves of the BL Her models into the Rubin-LSST ugrizy filters. The PL relations of the BL Her models exhibit steeper slopes but smaller dispersion with increasing wavelengths in the Rubin-LSST filters. The PL and PW slopes for the complete set of BL Her models computed with radiative cooling (sets B and D) are statistically similar across the grizy filters. The BL Her models exhibit weak or negligible effect of metallicity on the PL relations for wavelengths longer than the g filter for both the cases of the complete set of models as well as the low-mass models. However, we find significant effect of metallicity on the PL relation in the u filter. Strong metallicity effects are observed in the PWZ relations involving the u filter and are found to have significant contribution from the high-metallicity BL Her models. Due to negligible metallicity effect for relations involving the Wesenheit indices W(i,g-i), W(z,i-z) and W(y,g-y), we recommend these filter combinations for BL Her stars when observed with the Rubin-LSST to be used as reliable standard candles.

Context. In the era of precision stellar astrophysics, classical pulsating stars play a crucial role in determinations of the cosmological distance scale thanks to their period-luminosity (PL) relations. Therefore, it is important to constrain their stellar evolution and pulsation models not only through a comparison of empirical and theoretical PL relations and properties at mean light, but also using their light curve structure over the complete pulsation cycle. Aims. We carried out an extensive light curve comparison of BL Her stars using observations from Gaia DR3 and stellar pulsation models computed using MESA-RSP with the goal of obtaining the best-matched observed-model pairs for BL Her stars in the Large Magellanic Cloud (LMC). Methods. We used the Fourier decomposition technique to analyze the light curves in the G band obtained from Gaia DR3 and from MESA-RSP and used a robust light-curve-fitting approach to score the observed-model pairs with respect to their pulsation periods and over their Fourier parameter space. Results. We obtain the best-fit models for 48 BL Her stars in the LMC and thereby provide the stellar parameter estimates of these stars, 30 of which we classify as our “gold sample” due to their superior light curve fits. We find a relatively flat distribution of stellar masses between 0.5 and 0.65 M⊙ for the gold sample of observed-model pairs. An interesting result is that the majority of the best-matched models in the gold sample were computed using the convection parameter sets without radiative cooling. The period-Wesenheit (PW) relation for the best-matched gold sample of 30 BL Her models has a slope of −2.805 ± 0.164 and the corresponding period-radius relation a slope of 0.565 ± 0.035, both in good agreement with the empirical PW and period-radius slopes from BL Her stars in the LMC, respectively. We also used the Wesenheit magnitudes of the 30 best-matched observed-model pairs to estimate a distance modulus of μLMC = 18.582 ± 0.067 to the LMC, which lies within the bounds of previous literature values. We also discuss the degeneracy in the stellar parameters of the BL Her models that result in similar pulsation periods and light curve structure, and highlight that caution must be exercised while using the stellar parameter estimates.

Hilda asteroids, which orbit in a 3:2 resonance with Jupiter, serve as key indicators of dynamical processes in the early solar system. Their spin rates, an important probe of these mechanisms, can constrain their density and collisional evolution, offering valuable insights into their origin. In this paper, we report on the identification of three fast-rotating Hilda asteroids with spin periods in the 3.2--3.7 h range using data from the Transiting Exoplanet Survey Satellite. These rotation periods are significantly shorter than the previous $\sim$5.0 h shortest rotation periods obtained from ground-based observations in the $\sim$10 km size range, and are comparable with the $\sim$3.0 h breakup limit of Hildas a few km in size, derived from the FOSSIL survey. These fast-rotating asteroids require either considerable cohesion (in the order of a few kPa), or densities $\rho$ $\gtrsim$1.5 $gm^{-3}$, in contrast to the typically assumed $\rho$ $\lesssim$1 $gm^{-3}$, to prevent rotational break-up. C-type asteroids, which are common in the outer main belt, have densities of $\rho$ $\approx$1.5 $gm^{-3}$ and are known to comprise a small but notable fraction of Hildas. The observed occurrence rate of the $\leq$4 h rotation periods may be explained by the 10-15% fraction of C-type asteroids, likely mixed into these populations from the outer main belt during giant planet dynamical interactions in the early solar system.

The ∼2100 daylong secondary period of Betelgeuse’s optical lightcurve and radial velocity motivated the prediction of a low-mass stellar companion, expected to be at maximal apparent separation from Betelgeuse around 2024 December. We carried out Director’s Discretionary Time observations with the Chandra X-ray Observatory to identify any X-ray emission from the companion and constrain its nature as either a compact object or young stellar object (YSO). Past X-ray observations occurred at the wrong phase of the companion’s orbit for optimal detection prospects and/or lacked the deep exposure required to constrain the typical X-ray luminosities of YSOs. In our 41.85 ks exposure with Chandra, we do not detect an X-ray source at the position of Betelgeuse. For an estimated hydrogen column density N _H = 6 × 10 ^22 cm ^−2 , we place a limit on the X-ray luminosity L _X ≲ 2 × 10 ^30 erg s ^−1 (≲4.7 × 10 ^−4 L _⊙ ) in 0.5–8 keV for a 10 MK plasma temperature spectral model, or L _X ≲ 5 × 10 ^29 erg s ^−1 (≲1.2 × 10 ^−4 L _⊙ ) for an absorbed power law with photon index Γ = 2. These limits robustly exclude an accreting compact object (white dwarf or neutron star) as the companion. Solar-mass YSOs with an age similar to Betelgeuse (∼10 Myr) display a range of X-ray luminosities (10 ^28−32 erg s ^−1 ), and we can place upper bounds within this range for most absorbing columns. Based on these considerations, we conclude that the companion to Betelgeuse is likely a low-mass YSO.

Aims. We report the serendipitous discovery of two RR Lyrae stars that exhibit significant s-process element enrichment, a rare class previously represented solely by TY Gruis. Our goal is to characterise these objects chemically and dynamically, and explore their origins and evolutionary histories. Methods. Using high-resolution spectroscopy from HERMES@AAT and UVES@VLT, we derived detailed chemical abundances of key s-process elements (Y, Ba, La, Ce, Nd, and Eu) and carbon, along with alpha elements (Ca, Mg, and Ti). We also employed Gaia Data Release 3 astrometric data to analyse their kinematics, orbital properties, and classify their Galactic population membership. We compared observational results with theoretical asymptotic giant branch (AGB) nucleosynthesis models to interpret their enrichment patterns. Results. Both stars exhibit clear signatures of s-process enrichment, with significant overabundances in second-peak elements such as Ba and La compared to first-peak Y and Zr. Comparison with AGB nucleosynthesis models suggests their progenitors experienced pollution of s-process-rich material, consistent with early binary interactions. However, notable discrepancies in dilution factors highlight the need for more refined low-metallicity AGB models. We also explore and discuss alternative scenarios, including sub-luminous post-AGB-like evolution or double episodes of mass transfer. In the latter case, the star initially undergoes a mass transfer when it is on the main sequence, accreting material from a former AGB companion. Subsequently, as the star evolves along the red giant branch, it may again transfer mass to its companion before becoming an RR Lyrae star. Conclusions. Our findings confirm the existence of s-process-enhanced RR Lyrae stars and demonstrate the importance of combining chemical and dynamical diagnostics to unveil their complex evolutionary pathways. Future detailed binary evolution modelling and long-term orbital monitoring are essential to resolve their formation scenarios and assess the role of binarity in the evolution of pulsating variables.

γ Persei is a long-period (P ≈ 14.6 yr) eclipsing binary system. Its period makes it a difficult target to fully understand: so far, only two primary eclipses are known in the literature, from 1990 and from 2019, whereas the 2005 one was missed due to its closeness to the Sun at the time. We aimed to fill in this gap by processing the quasi-continuous photometry collected by the Solar Mass Ejection Imager (SMEI) between 2003 and 2011, which was ideally positioned to observe such a bright targets. In order to do that, we first determined a color-dependent conversion formula from the SMEI measurements into Gaia G magnitudes. We applied various corrections to the photometry and provide the longest continuous light curve of γ Persei. We successfully detected the 2005 primary eclipse of the system, with the yearly observations ending during the egress of the companion. We predicted the position of a possible secondary eclipse by forward modeling the binary system with PHOEBE, and successfully recovered the secondary eclipse in the 2006 SMEI observations. The existence of the secondary eclipse puts strong constraints on the orbital configuration, which will be an important constraint for future studies of the system.

The existence of dynamically young and metal-rich RR Lyrae stars challenges conventional notions of these variable stars. One possible scenario for their formation and evolution is via binary channels involving mass transfer. This study presents the detection of nine fundamental-mode RR Lyrae stars residing in the thin disk of the Milky Way with metallicities higher than [Fe/H] > -1.0 dex and showing proper motion anomalies. Our thin disk classification is based on kinematics and supported by α-element abundances, where possible. We searched for indications of the light-travel time effect (LTTE) in the available literature sources and the TESS photometric data of the stars but found no signs of periodic variations induced by companions within the expected period range. This could be because of a lack of observations as well as sparse measurements and large gaps in the data. We propose a continued search for signs of binarity and a subsequent long-term follow-up of nine targets that satisfy all of our search criteria. Beyond these targets, we also report the detection of slow phase changes in the Blazhko star ST Pic, which could be compatible with the LTTE.