Eclipsing binary stars provide highly accurate measurements of the fundamental physical properties of stars. They therefore serve as stringent tests of the predictions of evolutionary models upon which most stellar age determinations are based. Models generally perform very well in predicting coeval ages for eclipsing binaries with main-sequence components more massive than ~1.2 Msun; relative ages are good to ~5% or better in this mass regime. Low-mass main-sequence stars (M < 0.8 Msun) reveal large discrepancies in the model predicted ages, primarily due to magnetic activity in the observed stars that appears to inhibit convection and likely causes the radii to be 10-20% larger than predicted. In mass-radius diagrams these stars thus appear 50-90% older or younger than they really are. Aside from these activity-related effects, low-mass pre--main-sequence stars at ages ~1 Myr can also show non-coevality of ~30% due to star formation effects, however these effects are largely erased after ~10 Myr.
Age constraints are most often placed on globular clusters by comparing their CMDs with theoretical isochrones. The recent discoveries of detached, eclipsing binaries in such systems by the Cluster AgeS Experiment (CASE) provide new insights into their ages and, at the same time, much needed tests of stellar evolution models. We describe efforts to model the properties of the detached, eclipsing binary V69 in 47 Tuc and compare age constraints derived from stellar evolution models of V69A and B with ages obtained from fitting isochrones to the cluster CMD. We determine, under reasonable assump…
New complete light and radial velocities curves were obtained for the eclipsing binaries CC Her and CM Lac. The data are analysed with modern techniques in order to derive the physical parameters of the systems and study their present evolutionary status. We found that CC Her is a classical Algol type binary, while CM Lac is a detached system with two Main Sequence stars in asynchronous orbit.
We have developed a procedure for the classification of eclipsing binaries from their light-curve parameters and spectral type. The procedure was tested on more than 1000 systems with known classification, and its efficiency was estimated for every evolutionary status we use. The procedure was applied to about 4700 binaries with no classification, and the vast majority of them was classified successfully. Systems of relatively rare evolutionary classes were detected in that process, as well as systems with unusual and/or contradictory parameters. Also, for 50 previously unclassified cluster bi…
We present an analysis of the detached eclipsing binaries V44 and V54 belonging to the globular cluster M55. For V54 we obtain the following absolute parameters: $M_p=0.726\pm 0.015\,M_\odot$, $R_p=1.006\pm 0.009\,R_\odot$, $L_p=1.38\pm 0.07\,L_\odot$ for the primary, and $M_s=0.555\pm 0.008\,M_\odot$, $R_s=0.528\pm 0.005\,R_\odot$, $L_s=0.16\pm0.01\,L_\odot$ for the secondary. The age and apparent distance modulus of V54 are estimated at 13.3 - 14.7 Gyr and $13.94\pm0.05$ mag, respectively. This age is substantially larger than ages we have derived from the analysis of binary systems in 47 Tu…
Binary systems, in particular eclipsing binaries, are essential sources of our knowledge of the fundamental properties of stars. The ages of binaries, members of open clusters, are constrained by their own fundamental properties and by those of the hosting cluster. The ages of eleven open clusters are here found by constructing models for the components of twelve eclipsing binaries. The difference between the ages we found and the ages of the clusters derived from isochrone fitting is up to 40%. For the binary system V497 Cep in NGC 7160, the difference is about 100%. Binary systems whose prim…
The recent discovery and analysis of a classical Cepheid in the well detached, double-lined, eclipsing binary OGLE-LMC-CEP0227, has provided the first determination of the dynamical mass of a classical Cepheid variable to an unprecedented 1% accuracy. We show here that modern stellar evolution models widely employed to study Galactic and extragalactic stellar systems, are able to match simultaneously mass and radius (and effective temperature) of the two components with a single value for the age of the system, without any specific fine-tuning. Our conclusion is that there is no discrepancy be…
First photometric study for the newly discovered systems USNO-B1.0 1091-0130715 and GSC-03449-0680 were applied by means of recent windows interface version of the Wilson and Devinney code based on model atmospheres by Kurucz (1993). The accepted models reveal some absolute parameters for both systems, which used in adopting the spectral type of the systems components and follow their evolutionary status. Distances to each systems are and physical properties are estimated. Comparisons of the computed physical parameters with stellar models are discussed.
Eclipsing binary systems are unique stellar objects to examine and understand the stellar evolution and the formation. Thanks to these systems, the fundamental stellar parameters (mass, radius) can be obtained very precisely. The existence of metallic-line (Am) stars in binaries is noticeably common. However, the known number of Am stars in eclipsing binaries is less. The Am stars in eclipsing binaries are extremely useful to deeply investigate the properties of Am stars, as the eclipsing binaries are the only tool to directly derive the fundamental stellar parameters. Additionally, the atmosp…
We present the first detailed analysis of the detached eclipsing binary V15 in the super-metal rich open cluster NGC 6253. We obtain the following absolute parameters: M_p=1.303+-0.006 Msun, R_p=1.71+-0.03 Rsun, L_p=2.98+-0.10 Lsun for the primary, and M_s=1.225+-0.006 Msun, R_s=1.44+-0.02 Rsun, L_s=2.13+-0.06 Lsun for the secondary. Based on Dartmouth isochrones, the age of NGC 6253 is estimated to be 3.80 - 4.25 Gyr from the mass-radius diagram and 3.9 - 4.6 Gyr from color-magnitude diagram (CMD) fitting. Both of these estimates are significantly higher than those reported so far. The derive…
We have compiled a catalogue of eclipsing variable stars, the largest catalogue, containing classified eclipsing binaries. A procedure for the classification of eclipsing binaries, based on the catalogued data, is also developed. It was applied to unclassified eclipsing binaries. In this paper we discuss eclipsing binaries, which can not be classified with the procedure. Some of them belong to marginal evolutionary classes. Observational data for others are too contradictory, and additional observations are needed to attribute them to one or another evolutionary class.
Low-mass eclipsing binaries show systematically larger radii than model predictions for their mass, metallicity and age. Prominent explanations for the inflation involve enhanced magnetic fields generated by rapid rotation of the star that inhibit convection and/or suppress flux from the star via starspots. However, derived masses and radii for individual eclipsing binary systems often disagree in the literature. In this paper, we continue to investigate low-mass eclipsing binaries (EBs) observed by NASA's {\it Kepler} spacecraft, deriving stellar masses and radii using high-quality space-base…
We present an orbital solution study for the newly discovered system 1SWASP J080150.03+471433.8 by means of new CCD observations in VRI bands. Our observations were carried out on 25 Feb. 2013 using the Kottamia optical telescope at NRIAG, Egypt. 12 new times of minima were estimated and the observed light curves were analysed using the Wilson-Devinney code. The accepted orbital solution reveals that the primary component of is more massive and hotter than the secondary one by about 280K. The system is an over-contact one with fillout ratio ~ 29% and is located at a distance of 195 Pc. The evo…
The ages of the components in very short period pre-main sequence (PMS) binaries are essential to an understanding of their formation. We considered a sample of 7 PMS eclipsing binaries (EBs) with ages 1 to 6.3 MY and component masses 0.2 to 1.4 Msun The very high precision with which their masses and radii have been measured, and the capability provided by the {\it Modules for Experiments in Stellar Astrophysics (MESA)} to calculate their evolutionary tracks at exactly the measured masses, allows the determination of age differences of the components independent of their luminosities and effe…
We determine the age of the eclipsing binary V380 Cygni, whose components have a significant mass ratio, $M_B/M_A\approx$ 0.6. Because this binary exhibits spectral lines of both components, the values of masses and radii could be determined with a very high accuracy. Assuming that both components are on the main sequence, we derive the age of about 16 Myr. However, in this case the primary needs a large overshooting from the convective core ($f_{\rm{ov}} \approx 0.04$) and higher metallicity ($Z \approx 0.02$). It is difficult to tell whether such a high value of overshooting from the convect…
The field of the metal-rich open cluster NGC 6253 has been surveyed in a search for variable stars. A total of 25 new variables were detected, 14 of which are bright stars with 13<V<15 mag. This domain was not covered in an earlier work by de Marchi et al. (2010). Four variables, including three short-period eclipsing binaries, are candidate blue straggler stars. Two new detached eclipsing binaries at the turnoff of the cluster and another one on the subgiant branch were identified. These three systems deserve a detailed follow-up study aimed at a determination of the age and distance of NGC 6…
We use photometric and spectroscopic observations of the detached eclipsing binaries V40 and V41 in the globular cluster NGC 6362 to derive masses, radii, and luminosities of the component stars. The orbital periods of these systems are 5.30 and 17.89 d, respectively. The measured masses of the primary and secondary components ($M_p$, $M_s$) are (0.8337$\pm$0.0063, 0.7947$\pm$0.0048) M$_\odot$ for V40 and (0.8215$\pm$0.0058, 0.7280$\pm$0.0047) M$_\odot$ for V41. The measured radii ($R_p$, $R_s$) are (1.3253$\pm$0.0075, 0.997$\pm$0.013) R$_\odot$ for V40 and (1.0739$\pm$0.0048, 0.7307$\pm$0.004…
Aims: We aim to derive the absolute parameters of the components of AD And, AL Cam, and V338 Her, interpret their orbital period changes and discuss their evolutionary status. Methods: New and complete multi-filter light curves of the eclipsing binaries AD And, AL Cam, and V338 Her were obtained and analysed with modern methods. Using all reliably observed times of minimum light, we examined orbital period irregularities using the least squares method. In addition, we acquired new spectroscopic observations during the secondary eclipses for AL Cam and V338 Her. Results: For AL Cam and V338 Her…
We aim to unravel the interior mixing profile of the pulsating eclipsing binary KIC9850387 by comparing its dynamical parameters and the parameters derived through a combination of evolutionary and asteroseismic modelling. We created a grid of stellar evolutionary models using the stellar evolutionary code \textsc{mesa} and performed an isochrone-cloud (isocloud) based evolutionary modelling of the system. We then generated a grid of pulsational models using the stellar pulsation code \textsc{gyre} based on the age constraints from the evolutionary modelling. Finally, we performed asteroseismi…
We use photometric and spectroscopic observations of the eclipsing binaries V65, V66 and V69 in the field of the globular cluster M4 to derive masses, radii, and luminosities of their components. The orbital periods of these systems are 2.29, 8.11 and 48.19 d, respectively. The measured masses of the primary and secondary components (Mp and Ms) are 0.8035+-0.0086 and 0.6050+-0.0044 Msun for V65, 0.7842+-0.0045 and 0.7443+-0.0042 Msun for V66, and 0.7665+-0.0053 and 0.7278+-0.0048 Msun for V69. The measured radii (Rp and Rs) are 1.147+_0.010 and 0.6110+-0.0092 Rsun for V66, 0.9347+_0.0048 and 0…
We present a photometric, spectroscopic, asteroseismic, and evolutionary analysis of the Algol-type eclipsing binary KIC 12268220. We find the O'Connell effect and anticorrelated eclipse timing variations in the Kepler light curve, revealing the presence of large starspots. Radial velocities and atmospheric parameters are obtained from ground-based spectroscopic observations. Combined with the radial velocity measurements and Gaia-derived total luminosity, our light-curve modeling yields the solution of the physical parameters for both the primary and secondary components. We find 14 independe…
We analyze multicolor light curves of six totally eclipsing, short-period W UMa binaries and derive, for the first time, their orbital and stellar parameters. The mass ratios are established robustly through an automated q-search procedure that performs a heuristic survey of the parameter space. Five stars belong to the W and one to the A subtype. The mass ratios range from 0.23 to 0.51 and the fillouts from 10 to 15%. We estimate the ages and discuss the evolutionary status of these objects in comparison with a sample of other short-period W UMa binaries from the literature.
Detached eclipsing binaries are the primary tool used to measure precise masses and radii of stars. In our previous paper estimating the parameters of more than 30,000 detached eclipsing binaries, we identified 766 eclipsing binaries with additional features in their All-Sky Automated Survey for Supernovae (ASAS-SN) and Transiting Exoplanet Survey Satellite (TESS) light curves. Here, we characterize these "extra-physics" systems, identifying eclipsing binaries with spotted stars, pulsating components, and candidate triple/quadruple systems. We use the Gaia, ATLAS, ZTF, and ASAS-SN variable sta…
We present a detailed study of the G0V detached eclipsing binary EW Ori, based on new photometric and spectroscopic observations. Masses and radii that are precise to 0.9% and 0.5%, respectively, have been established for both components. The 1.12 Msun secondary component reveals weak Ca II H and K emission and is probably mildly active; no signs of activity are seen for the 1.17 Msun primary. We derive an [Fe/H] abundance of +0.05 +/- 0.09 and similar abundances for Si, Ca, Sc, Ti, Cr, and Ni. Yonsai-Yale and Granada solar-scaled evolutionary models for the observed metal abundance reproduce …
Eclipsing binaries serve as a valuable source of stellar masses and radii that inform stellar evolutionary models and provide insight into additional astrophysical processes. The exquisite light curves generated by space-based missions such as Kepler offer the most stringent tests to date. We use the Kepler light curve of the 4.8-day eclipsing binary KIC 5739896 with ground based optical spectra to derive fundamental parameters for the system. We reconstruct the component spectra to determine the individual atmospheric parameters, and model the Kepler photometry with the binary synthesis code …
Aims. We present the results of our detailed spectroscopic and photometric analysis of two previously unknown < 1 M{_\sun} detached eclipsing binaries: ASAS J045304-0700.4 and ASAS J082552-1622.8. Methods. With the HIgh Resolution Echelle Spectrometer (HIRES) on the Keck-I telescope, we obtained spectra of both objects covering large fractions of orbits of the systems. We also obtained V and I band photometry with the 1.0-m Elizabeth telescope of the South African Astronomical Observatory (SAAO). The orbital and physical parameters of the systems were derived with the PHOEBE and JKTEBOP codes.…
Diversity in Evolutionary Status and Magnetic Activity among Solar-Type Twin Detached Eclipsing Binaries
Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台）；University of Chinese Academy of Sciences（中国科学院大学）；Department of Astronomy, School of Physics and Astronomy, Yunnan University（云南大学物理与天文学院天文学系）；National Astronomical Research Institute of Thailand（泰国国家天文研究所）；Department of Astronomy and Space Sciences, Atatürk University, Faculty of Science（阿塔图尔克大学理学院天文学与空间科学系）；Türkiye National Observatories, DAG（土耳其国家天文台）
We aim at constraining evolutionary models at low mass and young ages by identifying interesting transiting system members of the nearest OB association to the Sun, Upper Scorpius, targeted by the Kepler mission. We produced light curves for M dwarf members of the USco region surveyed during the second campaign of the Kepler K2 mission. We identified 'by eye' a transiting system, UScoJ161630.68-251220.1 (=EPIC203710387) with a combined spectral type of M5.25 whose photometric, astrometric, and spectroscopic properties makes it a member of USco. We conducted an extensive photometric and spectro…
We present the first modern analysis of two young, eclipsing binaries, EK Cep and HS Her, based on new, ground-based, CCD multicolour light curves as well as the TESS observations, radial velocity curves, and eclipse timing measurements. The orbital and stellar parameters of the stars are determined by Roche modelling, and their evolutionary status is examined using a grid of isochrones and evolutionary tracks. We find that HS Her is 25-32 Myr old and its components are on the zero-age main sequence; at the age of 16-20 Myr, the primary of EK Cep is also on the ZAMS, but its secondary is a pre…
We present a new Bayesian approach to constrain the intrinsic parameters (stellar mass, age) of the eclipsing binary system CEP0227 in the LMC. We computed evolutionary models covering a broad range in chemical compositions and in stellar mass. Independent sets of models were constructed either by neglecting or by including a moderate convective core overshooting (beta=0.2) during central H-burning phases. Models were also constructed either by neglecting or by assuming a canonical (eta=0.4,0.8) or an enhanced (eta=4) mass loss rate. The solutions were computed in three different planes: lumin…
We present a new analysis of the multiple star V1200 Centauri based on the most recent observations for this system. We used the photometric observations from the Solaris network and the TESS telescope, combined with the new radial velocities from the CHIRON spectrograph and those published in the literature. We confirmed that V1200 Cen consists of a 2.5-day eclipsing binary orbited by a third body. We derived the parameters of the eclipsing components, which are $M_{Aa} = 1.393\pm0.018\,$M$_\odot$, $R_{Aa} = 1.407\pm0.014\,$R$_\odot$ and $T_{{\rm eff},Aa} = 6\,588\pm58\,$K for the primary, an…
Eclipsing binaries in star clusters offer more stringent tests of stellar evolution theory than field binaries because models must not only match the binary properties, but also the radiative properties of all other cluster members at a single chemical composition and a single age. Here we report new spectroscopic observations of the G type, detached eclipsing binary EPIC 219394517 in the open cluster Ruprecht 147 ([Fe/H] = +0.10), which was observed in late 2015 by the K2 mission. A joint analysis of our radial-velocity measurements and the K2 light curve shows the 6.5 day orbit to be very ne…
About 3196 EA-type binaries (EAs) were observed by LAMOST by June 16, 2017 and their spectral types were derived. Meanwhile stellar atmospheric parameters of 2020 EAs were determined. In the paper, those EAs are catalogued and their physical properties and evolutionary states are investigated. The period distribution of EAs suggests that the period limit of tidal locking for the close binaries is about 6 days. It is found that the metallicity of EAs is higher than that of EWs indicating that EAs are generally younger than EWs and they are the progenitors of EWs. The metallicities of long-perio…
We use photometric and spectroscopic observations of the eclipsing binary V69-47 Tuc to derive the masses, radii, and luminosities of the component stars. Based on measured systemic velocity, distance, and proper motion, the system is a member of the globular cluster 47 Tuc. The system has an orbital period of 29.5 d and the orbit is slightly eccentric with e=0.056. We obtain Mp=0.8762 +- 0.0048 M(Sun), Rp=1.3148 +-0.0051 R(Sun), Lp=1.94 +- 0.21 L(Sun) for the primary and Ms=0.8588 +- 0.0060 M(Sun), Rs=1.1616 +- 0.0062 R(Sun), Ls=1.53 +- 0.17 L(Sun) for the secondary. These components of V69 a…
New BVRI CCD observations of the semi-detached eclipsing binary EG Cep are presented. The observed light curves are analyzed with the Wilson-Devinney program and new geometrical and photometric elements are derived. These elements are used to compute the physical parameters of the system in order to study its evolutionary status.
We use photometric and spectroscopic observations of the eclipsing binary E32 in the globular cluster 47 Tuc to derive the masses, radii, and luminosities of the component stars. The system has an orbital period of 40.9 d, a markedly eccentric orbit with e = 0.24, and is shown to be a member of or a recent escaper from the cluster. We obtain Mp = 0.862(5) Msun , Rp = 1.183(3) Rsun , Lp = 1.65(5) Lsun for the primary and Ms = 0.827(5) Msun , Rs = 1.004(4) Rsun , Ls = 1.14(4) Lsun for the secondary. Based on these data and on an earlier analysis of the binary V69 in 47 Tuc we measure the distanc…
Gaia22ayj (=ZTF19aagmvuk) was detected as a transient on 2022 March 3 both by the Gaia satellite and the Zwicky Transient Facility (ZTF). I analyzed the past public ZTF data and found that Gaia22ayj showed coherent large-amplitude double-wave variations with a period of 0.00649910257(13) d = 9.36 min. The period can be either from the spin period of the white dwarf or the orbital period of the binary. I consider the latter possibility more likely based on the light curve resembling an eclipsing binary and on the stability of the profile. The presence of an outburst lasting at least ~1 d sugges…
The field of the globular cluster M12 (NGC 6218) was monitored between 1995 and 2009 in a search for variable stars. $BV$ light curves were obtained for 36 periodic or likely periodic variables. Thirty-four of these are new detections. Among the latter we identified 20 proper-motion members of the cluster: six detached or semi-detached eclipsing binaries, five contact binaries, five SX~Phe pulsators, and three yellow stragglers. Two of the eclipsing binaries are located in the turnoff region, one on the lower main sequence and the remaining three among the blue stragglers. Two contact systems …
Observational mapping of the mass discrepancy in eclipsing binaries. A new self-contained framework for concurrent analysis of photometric and spectroscopic time series
The study of eclipsing binaries is our primary source of measured properties of normal stars, achieved through analysis of light and radial velocity curves of eclipsing systems. The study of oscillations and pulsations is increasingly vital for determining the properties of single stars, and investigating the physical phenomena active in their interiors. Combining the two methods holds the promise of establishing stringent tests of stellar evolutionary theory, and of calibrating model-dependent asteroseismology with empirically measured stellar properties. I review recent advances and outline …
Based on over 5400 BV images of 47 Tuc collected between 1998 and 2010 we obtained light curves of 65 variables, 21 of which are newly detected objects. New variables are located mostly just outside of the core in a region poorly studied by earlier surveys of the cluster. Among them there are four detached eclipsing binaries and five likely optical counterparts of X-ray sources. Two detached systems are promising targets for follow-up observations. We briefly discuss properties of the most interesting new variables.
Altough both components of the bright eclipsing binary $α$ Dra having been resolved using long baseline interferometry and the secondary component shown to contribute some 15\% of the total flux, a spectroscopic detection of the companion star was so far unsuccessful. To achieve our goals, we use a combined data set from interferometry with the Navy Precision Optical Interferometer (NPOI), photometry with the TESS space observatory, and high-resolution spectroscopy with the HERMES fibre-fed spectrograph at the La Palma observatory. We use the method of spectral disentangling to search for the …
The field of the globular cluster NGC 6362 was monitored between 1995 and 2009 in a search for variable stars. BV light curves were obtained for 69 periodic variables including 34 known RR Lyr stars, 10 known objects of other types and 25 newly detected variables. Among the latter we identified 18 proper-motion members of the cluster: seven detached eclipsing binaries (DEBs), six SX Phe stars, two W UMa binaries, two spotted red giants, and a very interesting eclipsing binary composed of two red giants - the first example of such a system found in a globular cluster. Five of the DEBs are locat…
We report photometric observations of the eclipsing close binary CSS21055 (SDSS J141126+200911) that strongly suggest that the companion to the carbon-oxygen white dwarf is a brown dwarf with a mass between 0.030 and 0.074 Msun. The measured orbital period is 121.73min and the totality of the eclipse lasts 125s. If confirmed, CSS21055 would be the first detached eclipsing WD+BD binary. Spectroscopy in the eclipse could provide information about the companion's evolutionary state and atmospheric structure.
We present the first evidence for the binarity of four targets in the TESS field. The temperatures are estimated by SED analysis and the orbital periods are determined. The TESS light curves of the systems are analysed and the orbital and the absolute parameters are derived. The targets are also compared to well-studied binary systems with the same morphological type and their evolutionary states are discussed. Our results indicate that the stars belong to the class of eclipsing detached binary systems.
We present new photometric and spectroscopic observations and analyses for the eclipsing binary systems V1241 Tau and GQ Dra. Our photometric light and radial velocity curves analyses combining with the TESS light curves show that both are conventional semi-detached binary systems. Their absolute parameters are also derived. We present the $O-C$ analyses of the systems and we propose the most possible orbital period modulating mechanisms. Furthermore, Fourier analyses are applied to the photometric residual data of the systems to check for the pulsational behavior of the components. We conclud…
We present the results of an analysis aimed at testing the accuracy and precision of the PARSEC v1.2S library of stellar evolution models, in a Bayesian framework, to infer stellar parameters. We mainly employ the online DEBCat catalogue by Southworth, a compilation of detached eclipsing binary systems with published measurements of masses and radii to $\sim$ 2 per cent precision. We select a sample of 318 binary components, with masses between 0.10 and 14.5 Msun, at distances between 1.3 pc and ~ 8 kpc for Galactic objects and ~ 44-68 kpc for extragalactic ones. The Bayesian analysis applied …
KIC 9851944 is a short period ($P=2.16$ days) eclipsing binary in the {\it Kepler} field of view. By combining the analysis of {\it Kepler} photometry and phase resolved spectra from Kitt Peak National Observatory and Lowell Observatory, we determine the atmospheric and physical parameters of both stars. The two components have very different radii ($2.27R_{\odot}$, $3.19R_{\odot}$) but close masses ($1.76 M_{\odot}$, $1.79M_{\odot}$) and effective temperatures ($7026$K, $6902$K), indicating different evolutionary stages. The hotter primary is still on the main sequence (MS), while the cooler …
We present fundamental parameters of 4 massive eclipsing binaries in the young massive cluster Westerlund 1. The goal is to measure accurate masses and radii of their component stars, which provide much needed constraints for evolutionary models of massive stars. Accurate parameters can further be used to determine a dynamical lower limit for the magnetar progenitor and to obtain an independent distance to the cluster. Our results confirm and extend the evidence for a high mass for the progenitor of the magnetar.
The field of the globular cluster NGC 3201 was monitored between 1998 and 2009 in a search for variable stars. $BV$ light curves were obtained for 152 periodic or likely periodic variables, 57 of which are new detections. Thirty-seven newly detected variables are proper motion members of the cluster. Among them we found seven detached or semi-detached eclipsing binaries, four contact binaries, and eight SX Phe pulsators. Four of the eclipsing binaries are located in the turnoff region, one on the lower main sequence and the remaining two slightly above the subgiant branch. Two contact systems …
Pulsation periods reveal tension between theoretical and empirical radii for classical Cepheids in eclipsing binary systems
Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（尼古拉·哥白尼天文中心，波兰科学院）；Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange（蔚蓝海岸大学，蔚蓝海岸天文台，法国国家科学研究中心，拉格朗日实验室）
Eclipsing binary stars are rare and extremely valuable astrophysical laboratories that make possible precise determination of fundamental stellar parameters. Investigation of early-type chemically peculiar stars in eclipsing binaries provides important information for understanding the origin and evolutionary context of their anomalous surface chemistry. In this study we discuss observations of eclipse variability in six mercury-manganese (HgMn) stars monitored by the TESS satellite. These discoveries double the number of known eclipsing HgMn stars and yield several interesting objects requiri…
We present the analysis of an eccentric, partially eclipsing long-period ($P=19.23$ d) binary system KIC 9777062 that contains main sequence stars near the turnoff of the intermediate age open cluster NGC 6811. The primary is a metal-lined Am star with a possible convective blueshift to its radial velocities, and one star (probably the secondary) is likely to be a $γ$ Dor pulsator. The component masses are $1.603\pm0.006$(stat.)$\pm0.016$(sys.) and $1.419\pm0.003\pm0.008 M_\odot$, and the radii are $1.744\pm0.004\pm0.002$ and $1.544\pm0.002\pm0.002 R_\odot$. The isochrone ages of the stars are…
We revisit the problem of low-mass pre-main-sequence (PMS) stellar evolution and its observational consequences for where stars fall on the Hertzsprung-Russell diagram (HRD). In contrast to most previous work, our models follow stars as they grow from small masses via accretion, and we perform a systematic study of how the stars' HRD evolution is influenced by their initial radius, by the radiative properties of the accretion flow, and by the accretion history, using both simple idealized accretion histories and histories taken from numerical simulations of star cluster formation. We compare o…
O-stars are known to experience a wide range of variability mechanisms originating at both their surface and their near-core regions. Characterization and understanding of this variability and its potential causes are integral for evolutionary calculations. We use a new extensive high-resolution spectroscopic data set to characterize the variability observed in both the spectroscopic and space-based photometric observations of the O+B eclipsing binary HD~165246. We present an updated atmospheric and binary solution for the primary component, involving a high level of microturbulence ($13_{-1.3…
First spectroscopic and new photometric observations of the eclipsing binary FM Leo are presented. The main aims were to determine orbital and stellar parameters of two components and their evolutionary stage. First spectroscopic observations of the system were obtained with DDO and PST spectrographs. The results of the orbital solution from radial velocity curves are combined with those derived from the light-curve analysis (ASAS-3 photometry and supplementary observations of eclipses with 1 m and 0.35 m telescopes) to derive orbital and stellar parameters. JKTEBOP, Wilson-Devinney binary mod…
Older Ages for 23 Pre-Main Sequence Stars in Upper Scorpius Using Dynamical Mass-Constrained Stellar Evolutionary Models
University of Arizona（亚利桑那大学）；National Radio Astronomy Observatory（国家射电天文台）；California Institute of Technology（加州理工学院）；National Taiwan Normal University（台湾师范大学）
Parameter regions in which stars can become pulsationally unstable are found throughout the Hertzsprung-Russel diagram. Stars of high, intermediate, low and very low masses may cross various instability regions along their paths of evolutionary sequences. In describing them, I give special consideration to hybrid pulsational characteristics that are particularly valuable for asteroseismic investigations, to Pdot measurements that allow us to directly follow the stellar evolutionary changes in some stars, and to new research results that stand out with respect to previous consensus.
