AAS 201st Meeting, January, 2003
Session 120. Cataclysmic Variables
Poster, Thursday, January 9, 2003, 9:20am-4:00pm, Exhibit Hall AB

## [120.06] The Formation of Cataclysmic Variables with Brown Dwarf Secondaries

M. Politano (Marquette Univ.)

The formation of cataclysmic variables (CVs) with brown dwarf (BD) secondaries is investigated using a population synthesis technique. Results from the latest, detailed models for BDs have been incorporated into the population synthesis code. The orbital period distribution of CVs that form with BD secondaries is calculated. For our models, we find that CVs with BD secondaries form with orbital periods in the range 46 min to 2.5 hrs. The dependence of the formation rate of CVs with BD secondaries as a function of the common envelope efficiency parameter, \alphaCE, is also investigated for three different assumed mass ratio distributions in ZAMS binaries. We find that even for the most unfavorable ZAMS mass ratio distribution, the common envelope process must be extremely inefficient (\alphaCE < 0.1) in order for CVs with BD secondaries not to be formed. These results are examined in the context of V485 Cen, a CV with an orbital period of 59 minutes, and 1RXS J232953.9+062814, a CV with an orbital period of 64 minutes. In addition, these results are discussed with regard to non-standard prescriptions for \alphaCE and with regard to the so-called ''brown dwarf desert.''

This work was funded in part by NASA grant NAG 5-8481 and NSF grant AST-0098742 to Arizona State University and Marquette University.

Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.