Close Binary Stars that Interact: What Spacecraft Observations Have Revealed about Mass Transfer
Geraldine J. Peters
Space Sciences Center & Dept. of Physics & Astronomy
University of Southern California
Astronomical spacecraft have made it possible to investigate mass transfer in interacting binary systems in time domains and spectral regions not possible with ground-based telescopes. In this talk I will discuss the observations and modeling of long-term, quasi-periodic variations in the light curve of WX Dra (A8V + K0IV; P=1.8 d) that was observed nearly continuously for four years with the Kepler spacecraft from 2009-12. In this system the ratio of the light from the leading hemisphere on the primary (L) to its trailing hemisphere’s light (T) varies by +/- 3% in a period of about 2 years. The variability could be due to either a migrating hot accretion spot on the primary or cool spotted regions on the secondary. The FUSE spacecraft observation of a hot accretion spot on the primary of the U Cep system (B7V + G6III-IV; P=2.49 d) is also presented. Finally our quest to find sdO companions to bright Be binary systems with long periods is discussed. In the latter project archival data from the IUE spacecraft are analyzed. These sdO objects are the stripped-down remnants of originally massive stars that have transferred most of their material to the Be star and spun it up in the process. So far we have confirmed sdO objects in the f Per, FY CMa, 59 Cyg, and HR 2142 systems.
