Since 2010, a program to explore new eclipsing binary systems identified from STEREO photometry has been in progress. Our first results are presented here: light curves and high resolution spectra taken with Coudé spectrograph (National Astronomical Observatory Rozhen) and ARC Échelle spectrometer (ARCES, Apache Point Observatory).

We present a code which can be used to simulate the light curve of a binary system harbouring a non-circular accretion disk, and show that such a system geometry can produce light curves with asymmetric minima and different heights of the maxima. We have applied this code to check for the possible existence of a non-circular accretion disk, as suggested by Smak & Plavec (1997), in the Algol-type binary KU Cyg. We compare the best solutions for two sets of multicolour light curves, obtained within circular and non-circular disk models.

With the precision of space-borne photometers better than 100 ppm (i.e. MOST, CoRoT and Kepler), the derived stellar properties often suffer from systematic offsets due to the values used for solar mass, radius and luminosity, and to fundamental astrophysical constants. Stellar parameters are often expressed in terms of L⊙, M⊙ and R⊙, but the actual values used vary from study to study. Here, we propose to adopt a nominal set of fundamental solar parameters that will impose consistency across published works and eliminate systematics that stem from inconsistent values. We further implore the community to rigorously use the official values of fundamental astrophysical constants set forth by the Committee on Data for Science and Technology (CODATA).

I. Hubeny Today, the discussion will be open to the general audience. In Sessions C, D, and E, we have talked about models and modelling techniques so I expect the discussion will focus on these topics.

The techniques of disentangling were originally developed to separate spectra of individual components from time series of spectra of binaries and, simultaneously, to determine either the corresponding radial velocities or directly to solve for orbital parameters.

Generalizations of the disentangling method enable us to include also intrinsic line-profile variability of the component spectra into the underlying model, and thus to solve for additional physical parameters of the stars (either single or components of multiple systems). Depending on the problem in question, it may also be helpful to constrain the space of separated spectra by templates or to bound the solution in the parameter space by photometry, interferometry or other observational data.

The method of spectral disentangling has now created the opportunity for studying the chemical composition in previously inaccessible components of binary and multiple stars. This in turn makes it possible to trace their chemical evolution, a vital aspect in understanding the evolution of stellar systems. We review different ways to reconstruct individual spectra from eclipsing and non-eclipsing systems, and then concentrate on some recent applications to detached binaries with high-mass and intermediate-mass stars, and Algol-type mass-transfer systems.

Essential assumptions and features of the Broadening Function (BF) technique are presented. A distinction between BF determination and the BF concept and utilization is made. The BF's can be determined in various ways. The approach based on linear deconvolution involving stellar templates, as used during the DDO program (1999 – 2008) is described, but the LSD technique would also give excellent results. The BF concept to prove and/or verify photometric light-curve solutions has so far been very limited to only a few W UMa-type binaries, with AW UMa giving particularly unexpected results.

TODCOR is a TwO-Dimensional CORrelation technique to measure radial velocities of the two components of a spectroscopic binary. Assuming the spectra of the two components are known, the technique correlates an observed binary spectrum against a combination of the two spectra with different shifts. TODCOR measures simultaneously the radial velocities of the two stars by finding the maximum correlation. The main use of the technique has been to turn single-lined binaries into double-lined systems. This helps to explore the binary mass-ratio distribution, especially the low-mass regime, where the secondaries are usually very faint and therefore hard to detect. The technique has been generalized to study multi-order spectra, and also triple- and quadruple-lined systems. It has several applications in studying extrasolar planets and in the future may even help to dynamically measure stellar masses of binaries through relativistc effects.

In this talk I will review the Rossiter-McLaughlin (RM) effect; its history, how it manifests itself during stellar eclipses and planetary transits, and the increasingly important role its measurements play in guiding our understanding of the formation and evolution of close binary stars and exoplanet systems.

The Rossiter-McLaughlin effect occurs during the eclipse or transit of an object in front of another one. In our case, it appears as an anomaly on the radial velocity Doppler reflex motion. The modelling of that effect allows one to measure the sky-projected angle between the rotation spin of the primary and the orbital spin of the secondary. In the case of exoplanets, it gave clues about the formation of the hot Jupiters. In this paper, I will talk about how the data are acquired, how models are adjusted to them, and which results have been made.

We present a versatile method appropriate for the period analyses of observations containing phase information of all kinds of periodic or nearly periodic variable stars on the basis of phenomenological modelling of their phase curves and phase functions. The approach is based on rigorous application of a non-linear weighted least-squares method exploiting all available observational data and does not need an O-C diagram as an intermediate stage for period analyses. However, this approach enables us to determine precise times of extrema of light curves, to calculate ephemerides and construct plausible O-C diagrams. We substantiate the general applicability of the method on eclipsing binaries research.

We introduce a new computer program that is able to determine the flux ratio between the components of SB2 stars from time series of composite spectra. The spectra of the components are decomposed using the KOREL program and compared to synthetic spectra computed on a grid of fundamental stellar parameters. In the result, we obtain the optimized stellar parameters together with the flux ratio. The program is tested and applied to the oscillating eclipsing binary KIC 10661783 observed by the Kepler satellite mission.

Binaries are not always neatly aligned. Previous observations of the DI Herculis system showed that the spin axes of both stars are highly inclined with respect to one another and the orbital axis. Here, we report on our ongoing survey to measure relative orientations of spin-axes in a number of eclipsing binary systems.

These observations will hopefully lead to new insights into star and planet formation, as different formation scenarios predict different degrees of alignment and different dependencies on the system parameters. Measurements of spin-orbit angles in close binary systems will also create a basis for comparison for similar measurements involving close-in planets.

The enigmatic long period (P = 27.1 yr) eclipsing binary, ε Aurigae, recently emerged from its 2009–2011 eclipse. We have analyzed out-of-eclipse observations (Chadima et al. 2010) obtained over the past 17 years: 306 medium-resolution, high S/N, spectroscopic observations from 6300–6700 Å. Of these, 105 spectra were obtained at the Dominion Astrophysical Observatory (DAO) near Victoria, Canada, from 1994–2010, and 201 spectra were obtained at Ondřejov Observatory (OND), from 2006–2010. Analyzing these data, Chadima et al. (these proceedings) reported on a positive, but ultimately spurious, detection of a secondary spectrum. Their attempts at disentangling the binary spectra were foiled by line profile variations of the F star primary. The 6300-6700 Å spectral region contains several strong stellar lines but space limitations allow us to present only the results for Si II 6347 Å. We examine the centroids and higher moments of this prominent F star spectral line for any evidence of a secondary spectrum. Even if secondary contributions are blended with the F star lines, contamination by the secondary star should produce a centroid shift that is anti-correlated with the orbit of the F star primary.

During our recent spectroscopic study of ε Aur (Chadima et al. 2011), we made an attempt to detect weak spectral lines of the secondary, hidden in a dark disk, using the spectral disentangling technique of Simon & Sturm (1994) and Hadrava (1995, 1997, 2004). We used the Dominion Astrophysical Observatory (DAO) and Ondřejov (OND) red electronic spectra, which cover more than one half of the orbital period. To our surprise, two different programs that disentangled the spectrum in Fourier space, KOREL (Hadrava 1995, 2004) and FDBINARY (Ilijić et al. 2001), both yielded apparently good, similar reconstructions of two well-defined spectra for mass ratios near unity. The results (Solution 1) are shown in Fig. 1 (left panels) and Table 1 (left column). This result is hard to accept as real given the existing knowledge about the system: ε Aur is an F-type star with an unseen companion embedded in a cool, dark disk (temperature ~ 500–600 K). A detailed search for any trace of spectral signatures of the secondary in the spectra was carried out (see Bennett et al., these proceedings). Although they found line profile variations that were correlated with orbital phase, these variations were not consistent with the presence of a secondary.

VO-KOREL is a web service exploiting the technology of the Virtual Observatory for providing astronomers with the intuitive graphical front-end and distributed computing back-end running the most recent version of the Fourier disentangling code KOREL.

The system integrates the ideas of the e-shop basket, conserving the privacy of every user by transfer encryption and access authentication, with features of laboratory notebook, allowing the easy housekeeping of both input parameters and final results, as well as it explores a newly emerging technology of cloud computing.

While the web-based front-end allows the user to submit data and parameter files, edit parameters, manage a job list, resubmit or cancel running jobs and mainly watching the text and graphical results of a disentangling process, the main part of the back-end is a simple job queue submission system executing in parallel multiple instances of the FORTRAN code KOREL. This may be easily extended for GRID-based deployment on massively parallel computing clusters.

The short introduction into underlying technologies is given, briefly mentioning advantages as well as bottlenecks of the design used.

The spectral disentangling technique makes possible separation of individual component spectra in binary or multiple systems, and determination of the orbital elements in a self-consistent way. Since its introduction, a number of variants of their basic idea have been implemented. We present yet another ‘direct’ approach using optimization by genetic algorithm. Starting with an initial random flux distribution representing individual spectra, genetic optimization returns both individual component spectra and an optimal set of orbital parameters only constrained by time-series of the observed composite spectra of the binary system. Benchmark tests on V453 Cyg, which is an eclipsing binary with total eclipse, as well as tests on the artificial time-series spectra, have proven that ‘constrained genetic disentangling’ is performing correctly and efficiently, albeit with high demand on CPU time. Since genetic optimization can be easily parallelized, we expect our second release to run on cluster in a less time-consuming way.

Binary stars provide an excellent calibration of the success or otherwise of star formation simulations, since the reproduction of their statistical properties can be challenging. Here, I summarise the direction that the field has taken in recent years, with an emphasis on binary formation in the cluster context, and discuss which observational diagnostics are most ripe for meaningful theoretical comparison. I focus on two issues: the prediction of binary mass ratio distributions and the formation of the widest binaries in dissolving clusters, showing how in the latter case the incidence of ultra-wide pairs constrains the typical membership number of natal clusters to be of order a hundred. I end by drawing attention to recent works that include magnetic fields and which will set the direction of future research in this area.

Various processes can lead to non-conservative evolution in binary stars. Under conservative mass transfer, both the total mass and the orbital angular momentum of the system are conserved. Thus, the transfer of angular momentum between the orbit and the spins of the stars can represent one such effect. Stars generally lose mass and angular momentum in a stellar wind so, even with no interaction, evolution is non-conservative. Indeed, a strong wind can actually drive mass transfer. During Roche lobe overflow itself, mass transfer becomes non-conservative when the companion cannot accrete all the material transferred by the donor. In some cases, material is simply temporarily stored in an accretion disc. In others, the companion may swell up and initiate common envelope evolution. Often the transferred material carries enough angular momentum to spin the companion up to break-up, at which point it could not accrete more. We investigate how this is alleviated by non-conservative evolution.

Protoplanetary disks are ubiquitously observed around young solar-mass stars and are considered to be not only natural by-products of stellar evolution but also precursors of planet formation. If a forming star has close companions, the protoplanetary disk may be seriously influenced. It is important to consider this effect because most stars form as multiples. Thus, studies of protoplanetary disks in multiple systems are essential to describe the general processes of star and planet formation.

We present the direct image of an interacting binary protoplanetary system. We obtained an infrared image of a young multiple circumstellar disk system, SR24, with the Subaru 8.2-m Telescope. Both circumprimary and circumsecondary disks are clearly resolved with a 0.1 arcsecond resolution. The binary system exhibits a bridge of infrared emission connecting the two disks and a long spiral arm extending from the circumprimary disk. A spiral arm would suggest that the SR24 system rotates counter-clockwise. The orbital period of the binary is 15,000 yr. Numerical simulations reveal that the bridge corresponds to gas flow and a shock wave caused by the collision of gas rotating around the primary and secondary stars. The simulations also show that fresh material streams along the spiral arm, confirming the theoretical proposal that gas is replenished from a circum-multiple reservoir. These results reveal the mechanism of interacting protoplanetary disks in young multiple systems. Furthermore, our observations provide the first direct image that enables a comparison with theoretical models of mass accretion in binary systems. The observations of this binary system provide a great opportunity to test and refine theoretical models of star and planet formation in binary systems.