Jie Yu

A possible planet formation imprint: chemically depleted stars are magnetically more active

Chemical abundance anomalies in stars have long been considered tell-tale signs of interactions between stars and planets. Recent studies have suggested that such signals are prevalent, though the nature of these planet-related signatures remains under debate. On one hand, exoplanet formation may induce chemical depletion in host stars by locking up refractory elements. On the other hand, exoplanet engulfment can result in chemical enrichment, both processes potentially producing similar differential signals. In this study, we aim to observationally disentangle these processes by measuring the magnetic activity of 125 co-moving star pairs with high SNR, high-resolution spectra from the Magellan, Keck, and VLT telescopes using Ca II infrared triplet lines. We find that binary systems in which the two stars exhibit significant chemical abundance differences also show differences in their magnetic activity, in the sense that that chemically depleted stars are magnetically more active. Furthermore, the strength of this correlation between differential chemical abundances and differential magnetic activity increases with condensation temperature. These observations indicate that the chemical anomaly signature may be linked to planet formation, wherein refractory elements are drawn from the planetary disk, and the host stars become more active due to more efficient contraction during the pre-main-sequence phase or star–planet tidal and magnetic interactions.