Theoretical Models for the Late Thermal Pulse in Post-asymptotic Giant Branch Stars: The Case of DY Cen

Abstract We present theoretical predictions of the born-again scenario for post-asymptotic giant branch stars. An extensive model grid for born-again objects has been constructed, particularly including models for the very late thermal pulse with and without convective overshooting and also including models for the late thermal pulse. We constructed a large parameter space to analyze the dependencies of the born-again model on core mass, hydrogen-envelope mass, and overshoot parameters, and we analyzed how changes in these parameters affect the models’ evolution. We applied our grid of models to interpret observations of DY Cen, a star exhibiting characteristics similar to confirmed born-again stars. We compared DY Cen with models from multiple aspects, including heating rate, evolutionary tracks, and surface abundances. Ultimately, we concluded that none of our born-again models could match all of the observed properties of DY Cen, especially its surface chemistry; DY Cen is therefore an unlikely born-again star.