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M. Politano (Ariz. St. U.), U. Kolb (Open U.), I. Baraffe (Ecole Normale--Lyon)
We present new results from our continuing population synthesis study of the formation of cataclysmic variables (CVs) with brown dwarf (BD) secondaries and their subsequent evolution. We have incorporated results from the latest detailed models for brown dwarfs in the CV formation code. The secular evolution of the CV is calculated by using a grid of full evolutionary sequences which utilize the same BD models as in the formation code, rather than by using a polytropic approximation for the secondary star. To our knowledge, this is the first self-consistent treatment of the formation and evolution of CVs with BD secondaries. This work will address the following goals: 1) to calculate the number and distribution of systems which form below the observed orbital period minimum for CVs (78 mins) with an attempt to provide a model for a system like V485 Cen, which has an orbital period of 59 min; 2) to possibly resolve the long-standing discrepancy between the observed period minimum for CVs and the theoretically-predicted one (~65 mins); and 3) to test different input progenitor mass ratio distributions for ZAMS star + BD binaries and to potentially constrain the formation of binaries containing a MS star and a brown dwarf in relatively wide orbits (10--1000 days). We note that it is currently unfeasible to provide this latter constraint observationally, yet this constraint is important in estimating the contribution of BDs to the Galactic mass budget.
This work was funded in part by NASA grants NAG 5-3892 and NAG 5-8481 to Arizona State University.