A SEMI-EMPIRICAL MASS-LOSS RATE IN SHORT-PERIOD CATACLYSMIC VARIABLES

作者：Sirotkin Fedir V^*; Kim Woong Tae

来源：Astrophysical Journal, 2010, 721(2): 1356-1367.

DOI：10.1088/0004-637X/721/2/1356

• binaries: close
• binaries: eclipsing
• novae, cataclysmic variables
• stars: dwarf novae
• stars: fundamental parameters
• stars: low-mass
• white dwarfs

The mass-loss rate of donor stars in cataclysmic variables (CVs) is of paramount importance in the evolution of short-period CVs. Observed donors are oversized in comparison with those of isolated single stars of the same mass, which is thought to be a consequence of the mass loss. Using the empirical mass-radius relation of CVs and the homologous approximation for changes in effective temperature T(2), orbital period P, and luminosity of the donor with the stellar radius, we find the semi-empirical mass-loss rate M. 2 of CVs as a function of P. The derived M. 2 is at similar to 10(-9.5)-10(-10) M(circle dot) yr(-1) and weakly depends on P when P > 90 minutes, while it declines very rapidly toward the minimum period when P < 90 minutes, emulating the P-T(2) relation. Due to strong deviation from thermal equilibrium caused by the mass loss, the semi-empirical M. 2 is significantly different from and has a less-pronounced turnaround behavior with P than suggested by previous numerical models. The semi-empirical P-M. 2 relation is consistent with the angular momentum loss due to gravitational wave emission and strongly suggests that CV secondaries with 0.075M(circle dot) < M(2) < 0.2M(circle dot) are less than 2Gyr old. When applied to selected eclipsing CVs, our semi-empirical mass-loss rates are in good agreement with the accretion rates derived from the effective temperatures T(1) of white dwarfs, suggesting that M. 2 can be used to reliably infer T2 from T1. Based on the semi-empirical M(2), SDSS 1501 and 1433 systems that were previously identified as post-bounce CVs have yet to reach the minimal period.

• 出版日期2010-10-1