The resonant B1II+B1II binary BI108

BI108 is a luminous variable star in the Large Magellanic Cloud classified B1II. The variability consists of two resonant periods (3:2), of which only one is orbital, however. We discuss possible mechanisms responsible for the second period and its resonant locking.Comment: 2 pages, 1 figure, IAUS 272 - Active OB Stars: Structure, Evolution, Mass Loss and Critical Limit

The interacting binary V 393 Scorpii: another clue for Double Periodic Variables

We give a brief report on spectroscopic properties of V 393 Scorpii. H alfa emission and shape and radial velocity of He I 5875 are modulated with the long cycle. The long cycle is explained as a relaxation cycle in the circumprimary disc, that cumulates the mass transferred from the donor until certain instability produces disc depletion.Comment: 2 pages, 2 figures in encapsulated postscript format. To be published in Proceedings IAU Symposium No.262, 200

Optical spectroscopy of DPVs and the case of LP Ara

We present preliminary results of our spectroscopic campaign of a group of intermediate mass interacting binaries dubbed "Double Periodic Variables" (DPVs), characterized by orbital light curves and additional long photometric cycles recurring roughly after 33 orbital periods (Mennickent et al. 2003, 2005). They have been interpreted as interacting, semi-detached binaries showing cycles of mass loss into the interstellar medium (Mennickent et al. 2008, Mennickent & Kolaczkowski 2009). High resolution Balmer and helium line profiles of DPVs can be interpreted in terms of mass flows in these systems. A system solution is given for LP Ara, based on modeling of the ASAS V-band orbital light curve and the radial velocity of the donor star.Comment: To be published in the proceedings book of the IAUS 272, Cambridge University Press. Editors C. Neiner, G. Wade, G. Meynet and G. Peter

The Araucaria Project. Determination of the LMC Distance from Late-Type Eclipsing Binary Systems: I. OGLE-051019.64-685812.3

We have analyzed the double-lined eclipsing binary system OGLE-051019.64-685812.3 in the LMC which consists of two G4 giant components with very similar effective temperatures. A detailed analysis of the OGLE I-band light curve of the system, radial velocity curves for both components derived from high-resolution spectra, and near-infrared magnitudes of the binary system measured outside the eclipses has allowed us to obtain an accurate orbit solution for this eclipsing binary, and its fundamental physical parameters. Using a surface brightness-(V-K) color relation for giant stars we have calculated the distance to the system and obtain a true distance modulus of 18.50 mag, with an estimated total uncertainty of ~ 3 %. More similar eclipsing binary systems in the LMC which we have discovered and for which we are currently obtaining the relevant data will allow us to better check on the systematics of the method and eventually provide a distance determination to the LMC accurate to 1 percent, so much needed for the calibration of the distance scale.Comment: ApJ accepte

The Surface Brightness-color Relations Based on Eclipsing Binary Stars: Toward Precision Better than 1% in Angular Diameter Predictions

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