Kaitlyn Lane, Alexander P. Stephan, Melinda Soares-Furtado, Keivan G. Stassun, Ricardo Yarza
Abstract The engulfment of planets by their host stars is an expected outcome of various dynamical processes and has been invoked to explain a variety of observed stellar properties, such as rapid rotation, chemical abundance abnormalities, and other transient phenomena. Recent observations support engulfment as the cause of such signatures; however, many details of the engulfment process remain uncertain. Here, we present a model for determining the chemical signatures produced due to the pollution of main-sequence stars by rocky planets, a common engulfment scenario given the high frequency of observed short-period rocky exoplanets. A key novel aspect of our model is that we calculate the gradual evaporation of the planet due to drag interactions with the stellar envelope, which can lead to observable pollution on the stellar surface even if the bulk of the planet is only destroyed below the star’s outer convective zone. Our results indicate that rocky planet pollution is most easily measurable for stars in the 1.0–1.4 M ⊙ range and that elements such as aluminium, calcium, and vanadium, in addition to lithium, are most suited for its detection. We predict that, for some stellar hosts, it may also be possible to differentiate between the engulfment of one massive planet and multiple small planets with the same total pollution mass. We find that rocky planet engulfment events typically unfold over timescales ranging from years to about a decade for most stars. Our results can guide future observational campaigns aimed at identifying sites of past or ongoing engulfment events.