Title:  A Survey of Planet Engulfment Amongst Planet Host Systems

Abstract:  Dynamical evolution within planetary systems can cause planets to be engulfed by their host stars. Following engulfment, the stellar photosphere abundance pattern will reflect accretion of rocky material that composes planetary cores by exhibiting refractory enhancements in order of condensation temperature. Multi-star systems are excellent environments to search for such abundance trends because stellar companions share the same natal gas cloud and primordial chemical composition to within 0.05 dex. Thus, refractory differences above 0.05 dex that trend with condensation temperature between stellar companions constitute a signpost of planet engulfment. Such abundance measurements have been made for a few systems, and have occasionally yielded robust engulfment signatures, but only a handful of observations targeted systems with known planets. To address this gap, we carried out a survey of 36 multi-star systems where one star is a known planet host with the Keck High Resolution Echelle Spectrometer. Among the 36 systems observed, none exhibit engulfment patterns that are indicative of engulfment events. This agrees with our modeling efforts that indicate observable refractory enrichments from engulfment will not last on timescales greater than ~1 Gyr for solar-like stars. We consider the implications of these results for planetary system dynamical evolution, as well as chemical homogeneity amongst bound stellar companions and assumptions that underpin galactic archaeology.

Host:  Jiayin "DJ" Dong

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