Abstract

We present a study of the evolutionary stage of the interacting binary and Double Periodic Variable AU Mon. A multi-parametric chi(2) minimization is made between the observed parameters and those predicted by the grid of nonconservative and conservative evolutionary models by Van Rensbergen et al., finding the model that best represents the current stellar and system parameters. According to this model, the system started with initial masses 4 M-circle dot and 3.6 M-circle dot and orbital period 3.0 days, 196 million years ago, and at present undergoes a Case-B mass-exchange episode. This evolutionary stage is consistent with the reported existence of a circumprimary accretion disk. However, the implied high mass transfer rate contrasts with the absence of significant orbital period change if the mass exchange is conservative. We show that this can occur if the system has recently entered a nonconservative stage of mass transfer and the efficiency of mass and angular momentum loss satisfy certain conditions.