White dwarf natal-kick conjecture in Gaia wide binaries

Establish whether impulsive or asymmetric mass loss during the asymptotic giant branch (AGB) phase imparts weak velocity kicks (≲0.75 km s−1) to newly formed white dwarfs that unbind the widest binaries, thereby explaining the steeper decline in the separation distribution of Gaia-resolved white dwarf–main-sequence and white dwarf–white dwarf binaries relative to main-sequence binaries.

Background

Analyses of Gaia wide-binary samples have shown that systems containing white dwarfs (either white dwarf–main sequence or white dwarf–white dwarf) exhibit a steeper drop in the separation distribution at large separations than binaries composed of two main-sequence stars. This feature has been hypothesized to arise from small velocity kicks imparted to white dwarfs during the late stages of stellar evolution, which would preferentially disrupt the widest binaries.

Confirming or refuting this mechanism requires connecting population-level features in the Gaia separation distributions with a physical model for mass-loss-induced kicks on AGB stars, including their magnitudes and occurrence rates. Establishing this would clarify whether the observed break is a signature of white dwarf natal kicks rather than selection effects or other dynamical processes.