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The mass of a star is the most fundamental parameter for its structure, evolution, and final fate. It is particularly important for any kind of stellar archaeology and characterization of exoplanets. There exist a variety of methods in astronomy to estimate or determine it. In this review we present a significant number of such methods, beginning with the most direct and model-independent approach using detached eclipsing binaries. We then move to more indirect and model-dependent methods, such as the quite commonly used isochrone or stellar track fitting. The arrival of quantitative asteroseismology has opened a completely new approach to determine stellar masses and to complement and improve the accuracy of other methods. We include methods for different evolutionary stages, from the pre-main sequence to evolved (super)giants and final remnants. For all methods uncertainties and restrictions will be discussed. We provide lists of altogether more than 200 benchmark stars with relative mass accuracies between [0.3,2]% for the covered mass range of M∈[0.1,16]M⊙, 75% of which are stars burning hydrogen in their core and the other 25% covering all other evolved stages. We close with a recommendation how to combine various methods to arrive at a “mass-ladder” for stars.

Observations and analyses of V500 Pegasi taken at the Dark Sky Observatory (DSO), the SARA North Observatory and the Dominion Astrophysical Observatory are presented. V500 Peg is an eclipsing binary with a period of 0.57983 d. The light curves have the appearance of a detached or semi-detached binary. Spectroscopy reveals that it is of F5V-type. A continuous 14-year period study may show an orbital period increase is occurring. This may be due to weak matter transfer with the primary component as the gainer. The light curve has a large difference in primary and secondary amplitudes that is typical of this class of binary. The final solution shows a total secondary eclipse. The solution is that of a classical Algol system (semi-detached with the secondary component filling its Roche lobe), but it is of solar type, with a magnetic spot. This may mean that magnetic braking is interfering in the nuclear evolution. The secondary component has a temperature of ∼4700 K (K3), which means it is somewhat overluminous for its mass.

The Eclipsing Binaries Minima (BIMA) 2.0 Monitoring Project is a continuation of the previous BIMA program that was initiated by the collaboration of Bosscha Observatory - Lembang, Indonesia and The National Astronomical Research Institute of Thailand (NARIT) in 2012. This project aims to build an open database of eclipsing binary minima and establish each system’s orbital period and its variations in a time of minima (ToM) photometric observation using the Thai Robotic Telescope (TRT) network. In this work, we will present the progress of our monitoring program during 3 ∼ months of observations using TRT with proposal ID TRTC11A_009. We have collected ToM data at least once on 18 samples of contact binary stars and carried out O-C diagram analysis on three selected objects: IR Car, V1370 Tau, and GY Pup. We obtained six, three, and four primary minima on IR Car, V1370 Tau, and GY Pup, respectively. These three objects were chosen due to the lack of ToM data in recent years. We also use the TESS space mission ToM data to increase data coverage. Preliminary results show a significant change in O-C values and indicate mass transfer in this system.

Four color light curves of the EW type eclipsing binary V441 Lac were presented and analyzed by the W–D code. It is found that V441 Lac is an extremely low mass ratio ( q = 0.093±0.001) semi-detached binary with the less massive secondary component filling the inner Roche lobe. Two dark spots on the primary component were introduced to explain the asymmetric light curves. By analyzing all times of light minimum, we determined that the orbital period of V441 Lac is continuously increasing at a rate of d P /d t = 5.874(±0.007) × 10 −7 d yr −1 . The semi-detached Algol type configuration of V441 Lac is possibly formed by a contact configuration destroyed shallow contact binary due to mass transfer from the less massive component to the more massive one predicted by the thermal relaxation oscillation theory.

In this study, we present the results obtained from the analysis of KOI-7234’s photometric data obtained by the Kepler satellite. For the first time in the literature, the light curve analysis of the system was carried out and it seems that the system was composed of two low mass components with the masses of 0.574 M⊙ and 0.442 M⊙ in radii of 0.598 R⊙ and 0.529 R⊙ with the semi-major axis of 17.390 R⊙. In total, 195 flares have been detected from the short cadence data. Over these parameters, two different OPEA models were obtained for the system, and Plateau values were calculated as 1.578 ± 0.117 s for the first model and 1.735 ± 0.099 s for the second, while the half-time values were calculated as 1826.87 s and 1138.10 s. The general flare frequency of the system was calculated as 0.02345 h−1.

We present the design and commissioning of Project Solaris, a global network of autonomous observatories. Solaris is a Polish scientific undertaking aimed at the detection and characterization of circumbinary exoplanets and eclipsing binary stars. To accomplish this, a network of four fully autonomous observatories has been deployed in the Southern Hemisphere: Solaris-1 and Solaris-2 in the South African Astronomical Observatory in South Africa; Solaris-3 in Siding Spring Observatory in Australia; and Solaris-4 in Complejo Astronomico El Leoncito in Argentina. The four stations are nearly identical and are equipped with 0.5-m Ritchey-Crétien (f/15) or Cassegrain (f/9, Solaris-3) optics and high-grade 2 K × 2 K CCD cameras with Johnson and Sloan filter sets. We present the design and implementation of low-level security; data logging and notification systems; weather monitoring components; all-sky vision system, surveillance system; and distributed temperature and humidity sensors. We describe dedicated grounding and lighting protection system design and robust fiber data transfer interfaces in electrically demanding conditions. We discuss the outcomes of our design, as well as the resulting software engineering requirements. We describe our system's engineering approach to achieve the required level of autonomy, the architecture of the custom high-level industry-grade software that has been designed and implemented specifically for the use of the network. We present the actual status of the project and first photometric results; these include data and models of already studied systems for benchmarking purposes (Wasp-4b, Wasp-64b, and Wasp-98b transits, PG 1663-018, an eclipsing binary with a pulsator) as well J024946-3825.6, an interesting low-mass binary system for which a complete model is provided for the first time.

Three light curves of the V1059 Cep eclipsing binary obtained in 2012, 2013, and 2021 were analyzed. We found the rapid apsidal motion in this system at the rate per year. Assuming the equality of observed and theoretical apsidal motion rates we estimated physical characteristics of the components based on the data on their temperatures from the literature. According to our calculations the components are two very similar stars of the B7V–B7.5V spectral type with masses and age million years.

In this work, we quantify the performance of the Large Synoptic Survey Telescope (LSST) on the detection of eclipsing binaries. We use Kepler observed binaries to create a large sample of simulated pseudo-LSST binary light curves. From these light curves, we attempt to recover the known binary signal. The success rate of period recovery from the pseudo-LSST light curves is indicative of LSST's expected performance. Using an off-the-shelf analysis of variance routine, we successfully recover 71% of the targets in our sample. We examine how the binary period impacts recovery success and see that for periods longer than 10 days, the chance of successful binary recovery drops below 50%.

We investigated the evolution of HS Hya system’s inclination based on analysis of its light curves in the period 1964–2021. HS Hya is EA type eclipsing binary star, belonging to separate group with changing orbital inclination. We used our recent observations as well as the data from sky surveys.

V393 Scorpii is a member of the subclass of Algols dubbed double periodic variables (DPVs). These are semi-detached binaries with B-type primaries showing a long photometric cycle, lasting on average 33 times the orbital period. We describe the behavior of unreported metallic emission lines in the cool stellar component of this system. The emissions can be single or double for a same line, and they sometimes show velocity shifts regarding the velocity of the center of mass of the star. In addition, these lines are stronger during the high state. This behavior suggests the presence of active regions in the surface of the rapidly rotating A7 donor covering a fraction of the visible hemisphere, which have larger emissivity during the high state. Our finding supports the recently proposed dynamo model for the long cycle of DPVs proposed by Schleicher & Mennickent. The model predicts an increase of the dynamo number of the donor during epochs of mass transfer in this system, and a theoretical long/orbital period ratio very close to the observed one at the present system age.