Simulations of planetary engulfment in MESA: envelope hydrodynamics, light curves, and prospects for survival

The engulfment of planets by their host stars is a frequent occurrence, especially among post-main-sequence stars. The discovery of short-period giant planets around white dwarfs has prompted interest in whether a planet can ever survive engulfment. Engulfment also affects the host star’s rotation, composition, luminosity, and color. We present simulations of planetary engulfment events using the Modules for Experiments in Stellar Astrophysics software instrument, in which the planetary orbit evolves simultaneously with a 1D spherical hydrodynamical stellar model in a coupled manner. We present selected results for 1-10M_Jup planets engulfed by 1-1.5M_Sun stars on the red giant branch and asymptotic giant branch (AGB). We obtain the stellar luminosity and effective temperature during and after an engulfment event, which may aid searches for such events in time-domain surveys. For AGB hosts, engulfment of a sufficiently massive planet triggers significant expansion of the envelope, sometimes accompanied by an outgoing shock wave. However, the planet fills its Roche lobe before the envelope is lost, casting doubt on whether it can survive in orbit around the white dwarf.