The Perils of Pdot

Abstract

Schaefer (2024) has recently published observations of binary period derivatives $\dot P$ for 52 cataclysmic variables, and concluded that these strongly conflict with all proposed evolutionary pictures for these systems. We point out once again that using measurements of $\dot P$ is likely in practice to produce misleading evolutionary constraints in almost every case. The one identified exception to this is probably the recently-born X-ray binary SN 2022jli, because of its extremely high mass transfer rate.