THEORETICAL STATISTICS OF ZERO-AGE CATACLYSMIC VARIABLES

Abstract

The distribution of the white-dwarf masses, the distribution of the mass ratios, and the distribution of the orbital periods in cataclysmic variables which are forming at the present time are calculated. These systems are referred to as cataclysmic variables. The results show that 60% of the systems being formed contain helium white dwarfs and 40% contain carbon-oxygen white dwarfs. The mean white-dwarf mass in those systems containing helium white dwarfs is 0.34 33IO. The mean white-dwarf mass in those systems containing carbonoxygen white dwarfs is 0.75 3KO. The distribution of white-dwarf masses in zero-age cataclysmic variables is similar to the distribution of masses in single white dwarfs for masses above approximately 0.6 37io. The distribution of white-dwarf masses in zero-age cataclysmic variables is not sufficient to account for the observed high white-dwarf masses in cataclysmic variables, emphasizing the possible importance of selection effects. The orbital period distribution identifies four main classes of zero-age cataclysmic variables: (1) short-period systems containing helium white dwarfs, (2) systems containing carbon-oxygen white dwarfs whose secondaries are convectively stable against rapid mass transfer to the white dwarf, (3) systems containing carbon-oxygen white dwarfs whose secondaries are radiatively stable against rapid mass transfer to the white dwarf, and (4) long-period systems with evolved secondaries. The ranges of progenitor lobe-filling giant masses and radii are also better identified.