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RE: Beta Lyrae
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Sheliak is at minimum brightness at 1:30 UT, 7th February, 2012.



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Beta Lyrae (Sheliak) is at minimum brightness on the 25th January, 2012.



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Beta Lyrae ( Lyr / Lyrae) is a binary star system approximately 882 light-years away in the constellation Lyra. Beta Lyrae is traditionally named Sheliak which is Arabic for "tortoise" or "harp."

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Beta Lyrae variables are a class of close binary stars. Their total brightness is variable because the two component stars orbit each other, and in this orbit one component periodically passes in front of the other one, thereby blocking its light. The two component stars of Beta Lyrae systems are quite heavy (several solar masses each) and extended (giants or supergiants). They are so close, that their shapes are heavily distorted by mutual gravitation forces: the stars have ellipsoidal shapes, and there are extensive mass flows from one component to the other.

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Position(2000): RA  18 50 04.7947, Dec  +33 21 45.601

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Title: First Resolved Images of the Eclipsing and Interacting Binary Beta Lyrae
Authors: M. Zhao (1), D. Gies (2), J. D. Monnier (1), N. Thureau (3), E. Pedretti (3), F. Baron (4), A. Merand (2), T. ten Brummelaar (2), H. McAlister (2), S. T. Ridgway (5), N. Turner (2), J. Sturmann (2), L. Sturmann (2), C. Farrington (2), P. J. Goldfinger (2) ((1). University of Michigan, (2). The CHARA Array, Georgia State University, (3). University of St. Andrews, Scotland, UK, (4).University of Cambridge, UK, (5).National Optical Astronomy Observatory, NOAO)

We present the first resolved images of the eclipsing binary Beta Lyrae, obtained with the CHARA Array interferometer and the MIRC combiner in the H band. The images clearly show the mass donor and the thick disk surrounding the mass gainer at all six epochs of observation. The donor is brighter and generally appears elongated in the images, the first direct detection of photospheric tidal distortion due to Roche-lobe filling. We also confirm expectations that the disk component is more elongated than the donor and is relatively fainter at this wavelength. Image analysis and model fitting for each epoch were used for calculating the first astrometric orbital solution for Beta Lyrae, yielding precise values for the orbital inclination and position angle. The derived semi-major axis also allows us to estimate the distance of Beta Lyrae; however, systematic differences between the models and the images limit the accuracy of our distance estimate to about 15%. To address these issues, we will need a more physical, self-consistent model to account for all epochs as well as the multi-wavelength information from the eclipsing light curves.
 
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