Lifetime of Binary Stars

Abstract
Changes in orbital elements of a binary star by a distant stellar encounter and their cumulative effects are calculated by a similar method to that by Lyttleton and Yabushita for planetary orbits. For close encounters the equations of motion for three bodies with finite masses are integrated numerically on an IBM 7090 for randomly chosen initial conditions which are generated by a Monte Carlo method. For binary stars with total masses equal to one M equally shared by the components, the probabilities of disruption due to encounters with passing stars with one M and impact parameters less than the semimajor axes before the encounters are found to be 0.227, 0.O28 and < 0.002 for binaries with the semimajor axes 10 2 , 10 3 and 10 4 a.u., respectively. If the mean stellar density is taken to be 0.1 star/pc as in the solar neighbourhood, the lifetime turns out to be 2.92 × 10 12 , 2.46 × 10 11 and > 3 × 10 10 years, respectively.

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