On the Number of Comets Around White Dwarf Stars: Orbit Survival During the Late Stages of Stellar Evolution

The accretion of comets onto DA white dwarfs can produce observable metal absorption lines. We show here that comet systems around the progenitor main sequence star are vulnerable to being lost during asymptotic giant branch mass loss, if the mass loss is sufficiently asymmetric to impart modest linear momentum to the white dwarf. This may have bearing on the frequency of observation of heavy elements in white dwarf stars, and on inferences regarding the frequency of comet systems, if the imparted linear velocities of white dwarfs can be estimated.