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Session 76 - Cataclysmic Variables and Accretion Disks.
Display session, Wednesday, January 15
Metropolitan Ballroom,
Models of the present-day, intrinsic population of cataclysmic variables (CVs) predict that 99% of these systems should be of short orbital period (P_orb \la 2.5 hr). The Galaxy is old enough so that \sim 70% of these will have already reached their period minimum and will be evolving back toward longer periods. Mass transfer rates in these highly evolved binaries are predicted to be \la 10^-11 M_ødot yr^-1 leading to M_V's of \sim 10 or fainter. Recent observations of a group of low-luminosity dwarf novae (TOADs) provide evidence which indicates that some of these stars may indeed be the above theoretically- predicted old CVs. Theory suggests that these intrinsically faint dwarf novae are likely to contain degenerate (brown dwarf) secondaries having masses between 0.02-0.06 M_ødot (\sim 40 Jupiter masses) and radii near 0.1 R_ødot. We explore the possible connection between TOADs and CVs with degenerate secondaries in greater detail. Assuming TOADS are CVs with degenerate secondaries, then these systems may be used to set a lower limit on the age of the Galaxy and may provide an important complement to our understanding of brown dwarfs.
