SdBs, Synchronization, and Evolution: The Benefits of Pulsations in Binaries
Universite de Montreal
Subdwarf B (sdB) stars are evolved helium burning stars that have masses of around 0.5 Msun. Their formation therefore requires significant mass loss typically due to binary evolution. sdB stars found in close binaries (P< 10 days) have gone through the Common Envelope formation channel where much of the primaries star's mass is ejected as the companion spirals in. With the onset of Kepler it became possible to monitor these very faint binary systems for extended periods of time. This along with near micro-magnitude photometric precision has allowed for significant advancements in the asteroseismic analysis of these stars. Specifically, this has led to an dramatic increase in the number of observed pulsation modes which has enabled the calcuation of rotation periods for many of these stars. In this talk I will discuss the derivation of rotation periods in three close sdB binaries and the implications on the synchronization state of these systems. I will then discuss the consequences for all close sdB binaries and how these systems can be used to place constraints on the common envelope phase of binary evolution.
Date: Thursday, 16 January 2014 Time: 11:30 Where: Université de Montréal Pavillon Roger-Gaudry, local D-460 Contact: Tony Moffat