AAS 205th Meeting, 9-13 January 2005
Session 120 Studies of Variable and Moving Objects with the SDSS
Special Session, Wednesday, January 12, 2005, 10:00-11:30am, Royal Palm 1-3

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[120.05] The Evolution of Low Mass Stars in Close Binary Systems

N. M. Silvestri, S. L. Hawley, P. Szkody, J. J. Bochanski, A. A. West, O. J. Fraser, K. R. Covey, M. A. Wolfe (University of Washington), K. M. Vanlandingham (Steward Observatory), L. C. Dang (Whitman College), SDSS Collaboration

We report on our extensive investigation of the evolution of low mass stars in close binary systems with white dwarfs. Cataclysmic variables (CVs), which are the most numerous UV and X-ray sources in the Galaxy, and Type Ia supernovae, which are standard candles for cosmology, are believed to be the end products of these close binary systems, but little is known about their evolution before they reach the CV stage. In particular, we are studying the influence of the binary environment on the evolution of the low mass secondary star (typically an M dwarf), and investigating how the properties of the M dwarf are impacted by the presence of the white dwarf primary. Using our growing sample of over 700 M dwarf-white dwarf close binary systems identified spectroscopically in the Sloan Digital Sky Survey, we determine spectral types and magnetic activity properties of the M dwarfs, and effective temperatures and gravities of the white dwarfs, which allows us to determine their ages. Candidate systems with very active secondaries are then observed using time-series spectroscopy on the ARC 3.5m to find their orbital periods. Candidates are also observed using photometric time-series on the MDM 2.4m to search for variability (eclipses, rotational modulation). We have now compiled a sample of systems with a wide range of orbital period and age, and will discuss our results on the properties of the secondary stars, and compare them to recent field M dwarf studies (e.g. West et al. 2004).

This work was supported in part by NSF Grant AST02-05875.

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