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Published February 2023 | Supplemental Material + Published
Journal Article Open

Planet engulfment signatures in twin stars


Planet engulfment can be inferred from enhancement of refractory elements in the photosphere of the engulfing star following accretion of rocky planetary material. Such refractory enrichments are subject to stellar interior mixing processes, namely thermohaline mixing induced by an inverse mean-molecular-weight gradient between the convective envelope and radiative core. Using ᴍᴇsᴀ stellar models, we quantified the strength and duration of engulfment signatures following planet engulfment. We found that thermohaline mixing dominates during the first ∼5-45 Myr post-engulfment, weakening signatures by a factor of ∼2 before giving way to depletion via gravitational settling on longer time-scales. Solar metallicity stars in the 0.5-1.2 M_⊙ mass range have observable signature time-scales of ∼1 Myr-8 Gyr, depending on the engulfing star mass and amount of material engulfed. Early type stars exhibit larger initial refractory enhancements but more rapid depletion. Solar-like stars (M = 0.9-1.1 M_⊙) maintain observable signatures (>0.05 dex) over time-scales of ∼20 Myr-1.7 Gyr for nominal 10 M_⊕ engulfment events, with longer-lived signatures occurring for low-metallicity and/or hotter stars (1 M_⊙, ∼2-3 Gyr). Engulfment events occurring well after the zero-age main sequence produce larger signals due to suppression of thermohaline mixing by gravitational settling of helium (1 M_⊙, ∼1.5 Gyr). These results indicate that it may be difficult to observe engulfment signatures in solar-like stars that are several Gyr old.

Additional Information

© 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model) AB acknowledges funding from the National Science Foundation Graduate Research Fellowship under grant no. DGE1745301. This work benefited from involvement in ExoExplorers, which is sponsored by the Exoplanets Program Analysis Group (ExoPAG) and NASA's Exoplanet Exploration Program Office (ExEP). DATA AVAILABILITY. The data underlying this article will be uploaded to Zenodo.org at https://zenodo.org/communities/mesa upon acceptance for publication.

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August 22, 2023
October 25, 2023