Some close binary formation theories require the presence of a third body so that the binary orbit can shrink over time. Tidal friction and Kozai cycles transfer energy from the binary to its companion, resulting in a close inner binary and a wide third body orbit. Spectroscopy and imaging studies have found 40% of binaries with periods less than 10 days, and 96% with periods less than 3 days, have a wide tertiary companion. With recent advancements in large photometric surveys, we are now beginning to detect many of these triple systems by observing tertiary eclipses or through the effect they have on the eclipse timing variations (ETVs) of the inner-binary. In the sample of 2600 Kepler EBs, we have detected the possible presence of a third body in ∼20%, including several circumbinary planets. Some multiple systems are quite dynamical and feature disappearing and reappearing eclipses, apsidal motion, and large disruptions to the inner-binary. phoebe is a freely available binary modeling code which can dynamically model all of these systems, allowing us to better test formation theories and probe the physics of eclipsing binaries.

In-depth analysis of eclipsing binary (EB) observational data collected for several decades can inform us about a lot of astrophysically interesting processes taking place in the systems. We have developed a wide-ranging method for the phenomenological modelling of eclipsing binary phase curves that enables us to combine even very disparate sources of phase information. This approach is appropriate for the processing of both standard photometric series of eclipses and data from photometric surveys of all kind. We conclude that mid-eclipse times, determined using the latest version of our “hi-fi” phenomenological light curve models, as well as their accuracy, are nearly the same as the values obtained using much more complex standard physical EB models.

We present distance determinations to the LMC and SMC based on long period eclipsing binary systems composed of giants. Our LMC distance provides the best zero point for the whole extragalactic distance scale, while the precise relative distance between the LMC and SMC offers unique opportunity to study populational effects on the stellar distance indicators. Apart from distances, analysis of these systems allowed us to measure with a very good accuracy basic stellar parameters (1–2% radii, masses, effective temperature, etc.) of relatively large sample of giants. This catalog provides unique opportunity to calibrate evolutionary models of giant stars.

The status of our work on binary classical cepheid systems in the Large Magellanic Cloud is presented. We report on results from our follow up of two eclipsing binary cepheids OGLE-LMC-CEP-0227 and OGLE-LMC-CEP-1812. Here we presented for the first time confirmation that a third cepheid OGLE-LMC-CEP-2532 is a true eclipsing binary cepheid with a period of 800 days. Two other very good candidates for eclipsing binaries detected during OGLE-IV survey are also discussed.

Open clusters are laboratories for testing theories of binary evolution and dynamics against detailed observations. As part of the WIYN Open Cluster Study (WOCS), we are currently observing several open clusters spanning a wide range in age and metallicity, with primary goals of determining the binary frequencies and distributions of binary orbital parameters for their solar-type stars. Currently, the three WOCS clusters with the most complete data sets are M35 (0.15 Gyr), M67 (4 Gyr) and NGC 188 (7 Gyr). Despite the large differences in age, we find that all three of these rich clusters have remarkably similar solar-type binaries that are also consistent with comparable binaries in the Galactic field. These data have been critical for guiding our sophisticated open cluster N-body simulations, which enable us to investigate the dynamical evolution of rich binary populations and the production of exotic stars, like blue stragglers, within open clusters.

After a brief introduction into the asteroseismic modelling of stars, we provide a compilation of the current seismic estimates of the core overshooting parameter and of the rotational frequency of single and binary massive stars. These important stellar parameters have meanwhile become available for eleven OB-type stars, among which three spectroscopic pulsating binaries and one magnetic pulsator. We highlight the potential of ongoing and future analyses of eclipsing binary pulsators as essential laboraties to test stellar structure and evolution models of single and binary stars.

A short description of Dynamic Eclipse Mapping methodology is given. These tools are designed for mapping the surface patterns of non-radial oscillations on eclipsing binary components, using the effective surface sampling of the eclipses. I present two approaches to the problem, an image reconstruction (EM) and a direct model fitting (DF) method, review their capabilities and limitations, then report about the status of their application on real data, with emphasis on the encountered difficulties and caveats.

We discuss the potential role that tidal flows in asynchronous binary stars may play in transporting chemically enriched material from deep layers towards the surface and the corresponding observational consequences of these processes. We suggest that the time-dependent velocity field induced by asynchronous rotation may contribute significantly to the mixing, thus providing a channel for the formation of chemically enriched slowly rotating massive stars.

We present the analysis of HD 181068 which is one of the first triply eclipsing triple system discovered. Using Kepler photometry, ground based spectroscopic and interferometric measurements, we determined the stellar and orbital parameters of the system. We show that the oscillations observed in the red giant component of the system are tidally forced oscillations, while one of the most surprising results is that it does not show solar-like oscillations.

Red giant stars can be stripped of their outer layers by stellar collisions or mass transfer in binary star systems such as low mass X-ray binaries. If the star is stripped on or before its first ascent of the red giant branch it will eventually become a very low mass white dwarf composed almost entirely of helium. Very low mass white dwarfs are well known in binary milli-second pulsars and many have recently been found in surveys such as the Sloan Digital Sky Survey, but the precursor phase during which the remnant evolves to higher effective temperature at nearly constant luminosity has rarely been observed. The cooling timescale for very low mass white dwarfs is very uncertain because they are thought to be born with thick hydrogen envelopes which can sustain weak but stable p-p shell burning, but unstable phases of CNO burning (shell flashes) can remove this hydrogen envelope. The predicted number of shell flashes (if any) is dependent on the mass and composition of the star and other details of the models used. In this talk I present new observations of a bright eclipsing binary star recently discovered in the WASP archive in which a stripped red giant is eclipsed by an A-type dwarf star. These observations were used to derive precise masses and radii for both stars and have be used to test the formation scenario outlined above. In addition, I present the main characteristics of 17 new eclipsing binary stars that are also likely to contain the precursors of very low mass white dwarfs.

SuWt 2 is a planetary nebula (PN) consisting of an edge-on thin bright ionized ring, and perpendicular fainter bipolar lobes. The central star (12th magnitude) is an eclipsing binary, which is however too cool to ionize the PN; IUE spectra show no evidence for a hot, evolved PN central star, that could have first created and then ionised the nebula. We followed the central binary of SuWt 2 (NSV 19992) for over a decade with photometry and spectroscopy, and from these data obtained light and radial velocity curves and built an SED, from all of which we measured the stellar and system parameters. The two components are nearly identical A1 V stars, each of mass ∼2.7 M⊙. Both are in the short-lived “blue-hook” evolutionary phase that occurs between the main sequence and the Hertzsprung gap, with an age of about 520 Myr. One puzzle is that the stars' rotational velocities are different from each other, and considerably slower than synchronous with the orbital period. We find that it is possible that the center-of-mass velocity of the eclipsing pair is varying with time, suggesting that there is an unseen third orbiting body in the system.

2M0535−05 is a one-of-a-kind eclipsing binary (EB) comprising two brown dwarfs (BDs), and is an important benchmark for understanding the fundamental properties of BDs and low-mass stars. Because 2M0535−05 presents a peculiar reversal of temperatures with mass (the higher mass, magnetically active BD in the system is cooler than the lower mass companion BD), 2M0535−05 is particularly important as a case study for the effects of magnetic activity on the properties of low-mass objects. Using a large number of low-mass M-dwarfs and EBs in the field, we have developed empirical relations for determining the amount by which the temperatures and radii–and therefore the estimated masses–of low-mass stars and BDs are altered due to chromospheric activity. The relations link the amount by which an active object's temperature is suppressed, and its radius inflated, to the strength of its Hα emission. These relations are found to approximately preserve bolometric luminosity. Applying these relations to 2M0535−05 brings the activity-corrected radii and temperatures of 2M0535−05 into precise agreement with theoretical isochrones for inactive stars. The relations that we present are applicable to BDs and low-mass stars with masses below 0.8 M⊙ and for which the activity, as measured by Hα, is in the range − 4.6 < log LHα/Lbol < −3.3. We discuss implications of this work for determinations of young cluster IMFs, and discuss competing ideas for the physical mechanism by which magnetic fields alter the temperatures and radii of low-mass stars.

We present optical broad-band (UBVRI) aperture polarimetry of 52 post-AGB stars, selected from De Ruyter et al. (2006) and the Torun Catalog, based on the shape of their SED and near-infrared excess. We find 10 (19%) of the stars in our sample to have high polarization (P > 5%), 30 (56%) intermediate/low polarization (1% < P < 5%) and 13 (25%) very low (or non–polarized) polarization (P < 1%). Our observations show clear evidence of asymmetric circumstellar envelopes or equatorial density enhancement around post-AGB stars, probably formed at the beginning of the AGB phase. Some stars exhibit wavelength-independent polarization suggesting scattered light by large dust grains or free electrons (Thomson scattering), while others show wavelength-dependent polarization originated from scattering by small dust grains (Rayleigh scattering). Finally, we conclude that highly polarized sources (P > 3%), show systematically [12] − [25] > 1.5, J − H > 0.5 and J − K > 0.5, clearly separated from the group of RV Tauri stars, which are found to have very low polarization (P < 3%).

V2107 Cyg is located in the direction of Cyg OB1 stellar association. The eclipsing system consists of an early-B primary and a late-B type secondary component contributing about 6% of the total light. Line profile variability and photometry suggest strongly it is a β Cep type non-radial pulsator. A signature of the faint secondary component is for the first time identified through spectra disentangling.

We present the first results of a comprehensive photometric O-star survey performed with a robotic twin refractor at the Universitätssternwarte Bochum located near Cerro Armazones in Chile. For three high-mass stars, Pismis 24-1, CPD − 51∘ 8946, and HD 319702, we determined the period through the Lafler-Kinman algorithm and modelled the light curves within the framework of the Roche geometry. We introduce a newly discovered eclipsing high-mass binary HD 319702 that shows well-defined eclipses favouring a detached configuration with a period of 2.0 days and an orbital inclination of 67.5∘. Combining our photometric result with the primary spectral type O8 III(f) (T1 = 34 000 K) we derive a temperature of T2 = 25 200 K for the secondary component.

As part of our project for studying bright (V < 10 mag) eclipsing binaries discovered using images from the NASA STEREO mission we are accumulating follow-up observations with the goal of complete characterization of the systems. The full complement of data consist of light curves extracted from STEREO photometry, wide coverage Echelle spectra obtained at Apache Point Observatory for stellar characterization and Coude spectra obtained at NAO Rozhen for radial velocity curves. Here we present physical parameters-masses and radii- for six short period (P < 3 d) single line binary systems containing low-mass components.

Period analysis of eclipsing binaries can be performed effectively when using fine-tuned phenomenological models. The combination of regression analysis and genetic algorithms is a powerful tool for such astrophysical tasks as light curve analysis, mid-eclipse time determination and O − C diagram investigation – even apsidal motion and light time effect can be resolved.

In the era of staggering Kepler data and sophisticated approach of the automatic analysis, how obsolete are the traditional object-by-object multiwavelength photometric observations? Can we apply the new tools of classification, light curve modeling and timing analysis to study the newly detected or/and most interesting EBs or to detect circumbinary bodies? In this paper, we present the contribution of “Mythodea” Observatory University of Patras to DWARF project that promises additional useful science of binary stars within an extensive network of relatively small to medium-size telescopes with apertures of ∼20–200 cm.

We present the preliminary results of modeling of the optical counterparts of the ROSAT X-ray sources identified by ASAS survey data for detached systems (Szczygieł et al. 2008, ASAS.ROSAT.cat) in the framework of the optical variability campaign for strong X-ray sources among eclipsing binaries that was launched in summer 2012, with the 14′′ telescope at the University of Patras“Mythodeia” Observatory.

We present a spectroscopc study of the hot Algol-type system u Her (68 Her, B2 IV + B8 III). A new set of high-resolution échelle spectra has been obtained at Calar Alto Observatory. Spectral disentangling allowed isolation of the individual spectra of the components. A detailed spectroscopic analysis of the primary star indicates an abundance pattern resulting from CNO processing.