New BVRI light curves of the eclipsing binary system 1SWASP J160156.04+202821.6 have been obtained with the 1.88 meter telescope of Kottamia Astronomical Observatory (KAO), Egypt on June, 2013. New twenty times of minima of the system J1601 and new ephemeris have been reduced and derived from the present photometry. A preliminary determination of the geometric and photometric element parameters of the system J1601 has been derived.

We want to compare masses and radii of Red Giant (RG) stars derived from detached Eclipsing Binaries (dEBs) (KIC 8410637: Frandsen et al. 2013) with those derived from asteroseismology, and to classify the RG as a hydrogen- or helium-burning or as an asymptotic giant branch (AGB) star. The Kepler satellite has provided unique data, that allows asteroseismology to be carried out on RG stars. Among the many RGs are a small set of dEBs, where accurate masses and radii can be measured from an analysis of observations of the binary system.

We present the results of an all sky survey for binary systems among the massive stars that we made with the HST Fine Guidance Sensors. The sample of 225 stars is comprised mainly of Galactic O- and B-type stars and Luminous Blue Variables, plus a few luminous stars in the LMC. The FGS TRANS mode observations are sensitive to detection of companions with an angular separation of 0.01–1 arcsec and brighter than △m = 5 mag. The FGS observations resolved 52 binary and 6 triple star systems and detected partially resolved binaries in 7 additional targets, yielding a companion detection frequency of 29%. We also gathered literature results on the numbers of close spectroscopic binaries and wider astrometric binaries among the sample. These results confirm the high multiplicity fraction. The period distribution is essentially flat in increments of log P, although there remains an observational gap in detections for periods of years and decades.

DV Cam is a triple system showing the diversity of the physics of photospheres of B-type stars at a common age: an SPB star in a wide orbit around a close binary consisting of an ultra-slowly rotating helium-weak star and a much faster rotating mid-B star.

The ESA space mission Gaia, planned to be launched at the end of 2013, will make astrometric, photometric and spectroscopic measurements of about 1 billion sources in our Galaxy. Amongst these sources will be numerous multiple systems. In the processing chain eclipsing binaries (EBs) will be detected and, if possible, their period and characteristics determined. Here we summarize the various steps that are foreseen to automatically classify and characterise these EBs.

Dome A, on the Antarctica plateau, offers a new window for uninterrupted and consecutive observations of variable targets. CSTAR deployed at Dome A had been operated for four consecutive years since 2008 and collected vast mass of frames. For each polar winter, the observational time can span over 100 days which means to cover hundreds of periods of most eclipsing binary stars. We represent here the first result of four eclipsing binary stars, CSTAR 36162, CSTAR 38663, CSTAR 55495 and CSTAR 57775, using the data of CSTAR 2008 in i and 2009 in g and r bands. The further works are in progress, including fundamental parameters of those targets using the WD's code and investigation of period change from O − C diagrams.

Fabritius discovered the first variable star, Mira, in 1596. Holwarda determined the 11 months period of Mira in 1638. Montanari discovered the next variable star, Algol, in 1669. Its period, 2.867 days, was determined by Goodricke (178). Algol was associated with demon-like creatures, “Gorgon” in ancient Greek and “ghoul” in ancient Arab mythology. This indicates that its variability was discovered much before 1669 (Wilk 1996), but this mythological evidence is ambiguous (Davis 1975). For thousands of years, the Ancient Egyptian Scribes (AES) observed stars for timekeeping in a region, where there are nearly 300 clear nights a year. We discovered a significant periodicity of 2.850 days in their calendar for lucky and unlucky days dated to 1224 BC, “the Cairo Calendar”. Several astrophysical and astronomical tests supported our conclusion that this was the period of Algol three millennia ago. The “ghoulish habits” of Algol could explain this 0.017 days period increase (Battersby 2012).

The Binary star DataBase (BDB, http://bdb.inasan.ru) is created to provide liasons between binary star catalogue data of various origin. Information on different observational types of binaries is obtained from heterogeneous sources of data – astronomical catalogues and surveys. The database allows a variety of query options useful for selected stars investigation purposes, for binary observations planning, and for construction and examination of binary datasets with certain characteristics.

The complete set of orbital elements of binary and multiple systems can be only determined from complementary observables. In spectral disentangling the orbital elements are optimised along with simultaneous determination of the individual spectra of components. Therefore, a posteriori combination with some other observables, i.e. astrometric measurements or historic RVs is principally incorrect. With advances in the instrumentation more and more binary and multiple systems are spatially and spectroscopically resolved which makes the solution of orbital elements more firm. Following this advances, we have developed a wrapper with optimisation routine which enables spectral disentangling of time-series of spectra with the constraints from interferometric (astrometric) measurements.

We present the results of analysis of 1764 eclipsing binary stars (EBs) in the Large Magellanic Cloud (LMC) contaminating the sample of candidate Classical Cepheids (CCs) from the EROS-2 survey. These binaries have the same periods and luminosities as Classical Cepheids, but their colors are bluer. These EBs contain hot massive Main Sequence components and could be used as tracers of regions of recent star formation activity.

Multi-epoch, high-resolution (R ∼ 50 000) optical spectrosco-py of the O-type (O9 III – IV) star HD 152246 suggests that it is a triple system where a close inner pair (Aa–Ab) with a circular orbit and a period of 6 days is in a 53–d eccentric orbit (e = 0.68) with a third component Ac. The mass ratios for the inner and outer system are 0.10 and 0.96, respectively. The strengths of various He lines classify Aa and Ac as late O-type stars while Ab is invisible in our spectra.

Cyg OB2 #5, #8A, and #9 are binary or multiple massive stars in the Cyg OB2 association displaying several peculiarities, such as bright X-ray emission and non-thermal radio emission. Our X-ray monitoring of these stars reveals the details of their behaviours at high energies, which can be directly linked to wind-wind collisions (WWCs). In addition, the X-ray emission of Cyg OB2 #12, an evolved massive star, shows a long-term decrease, which could hint at the presence of a companion (with associated colliding winds) or indicate the return to quiescence of the star following a recent eruption.

V444 Cyg is a short-period (4 d) binary composed of two massive objects, a WN star and an O star. The winds of the two massive components collide, generating X-ray emission. A monitoring campaign in the high-energy domain was performed using Swift and XMM-Newton, with surprising results on the collision geometry (wide shock opening angle, clear Coriolis deflection). Polarimetric data further help to understand the system properties. This new information places strong constraints on the physical parameters of the two stars.

We present a thorough modeling of new multicolor light curves of the low amplitude W UMa type binary system FI Boo obtained at the University of Patras Observatory “Mythodea”, in spring 2012, in view of the presence of a detected third body. The absolute properties of the components were derived with the phoebe software and were tested extensively by heuristic scanning with parameter kicking in order to check the solution uniqueness.

From newly list of times of maximae of the HADS, we were able to determine the binary nature of these stars. With uvby − β photometry we determined their physical parameters.

We introduce our PhD project in which we focus on pulsating stars in eclipsing binaries. The combination of high-precision Kepler photometry with high-resolution hermes spectroscopy allows for detailed descriptions of our sample of target stars. We report here the detection of three false positives by radial velocity measurements.

We present a Bayesian method that simultaneously takes all available observables for a given star, their uncertainties and prior knowledge like the initial mass function into account to determine probability distributions of the stellar parameters based on grids of stellar evolutionary models. This allows to homogeneously analyse stars, to determine stellar parameters including robust uncertainties and to identify stars that cannot be reproduced by current stellar models. Our code is available through an easy-to-use web-interface.

PG1544+488 is a short-period spectroscopic binary containing two subdwarf B stars and is exceptional because the surfaces of both components are extremely helium-rich. We present a new spectroscopic analysis to obtain improved orbital parameters, including the period P = 0.496 ± 0.002 day, mass ratio q = 0.933 ± 0.016, and the atmospheric parameters of each component.

A large fraction of the Wolf-Rayet stars reside in binary or multiple systems. While multiple systems provide information which is not accessible for single stars, their composite spectra are harder to analyze. For this reason, quantitative spectral analyses of WR binaries have been vastly excluded so far. We present first attempts in analyzing multiple systems using the non-LTE Potsdam Wolf-Rayet (PoWR) model atmosphere code.

Our survey of long-baseline infrared and optical interferometry measurements is producing considerable numbers of directly determined stellar angular sizes. We use our sample of 124 high-precision (5%) angular stellar diameter values and correlate them with stellar magnitude values from the literature to produce empirical relations for main-sequence stars between observed apparent magnitudes, stellar colors, and angular sizes (surface brightness relations). We find a significant dependence on stellar metallicity for (B − V) colors. The scatter in the calculated relations is small (∼5%), which makes them a robust tool for the prediction of main-sequence stellar angular sizes based on photometry. We apply these relations via the calculation of the radius of the multiplanet host star GJ 667 C.