Thomas Erchul, M.S. 2007

M.S. Plan B Project

How the M Dwarf in a Post-Common Envelope Binary is affected by Close Binary Evolution

by Thomas Erchul

Under the supervision of Dr. Robert Gehrz & Dr. Roberta Humphreys

ABSTRACT

What physical processes once affected and continue to affect the M dwarf star in a post-common envelope binary (PCEB)? To determine the influence of close binary evolution on an M dwarf with a white dwarf (WD) primary, I pull together the significant theory and models describing the energy dissipation and angular momentum loss (AML) during the common envelope (CE) and PCEB phases. Hydrodynamical models representing the effects of gravitation during the CE phase and calculations modeling AML by magnetic braking during the PCEB phase are key elements of this study. Sandquist et al. (1998) provide a complete simulation of the CE phase (occurring on the order of years), and Silvestri et al. (2006) provide a more complete picture of M dwarf secondary behavior based on observational data comparing close binary WD-M dwarf magnetic activity to field M dwarf activity from West et al. (2004). The relevance of this new data to the test for disrupted magnetic braking in PCEBs (Politano and Weiler 2006), and the DMB model itself by Rappaport, Verbunt, and Joss (1983), is pointed out.