Planetary engulfment events have long been proposed as a lithium ( Li ) enrichment mechanism contributing to the population of Li-rich giants ( A ( \mathrm { Li } ) \geq 1.5 dex ) .
Using GALAH survey data and MESA stellar models , we calculate the strength and duration of the Li enrichment signature produced in the convective envelope of a host star that has engulfed a hot Jupiter ( HJ ) companion .
We consider solar-metallicity stars in the mass range of 1.0 M _ { \odot } – 2.0 M _ { \odot } and the Li supplied by a HJ of 1.0 M _ { J } .
We explore engulfment events that occur near the main sequence turn-off ( MSTO ) and out to orbital separations of R _ { \star } \sim~ { } 0.1 ~ { } \mathrm { AU } ~ { } = ~ { } 22 R _ { \odot } .
We map our results onto the Hertzsprung-Russell ( H-R ) Diagram , revealing the parameter space where planetary engulfment events produce significant Li enrichment signatures .
We also map the associated survival times of these signatures , which range across 9 orders of magnitude .
Our calculations indicate that if the HJ engulfment event occurs near the MSTO or on the subgiant branch , Li enrichment can be measured at a 5 \sigma confidence level and with strengths that exceed meteoritic abundance measurements .
Moreover , for stars of 1.4 M _ { \odot } these signatures are predicted to survive for up to 1 Gyr .
We determine that Li enrichment beyond the subgiant branch must be produced by other mechanisms , such as the Cameron–Fowler process or the accretion of material from an AGB companion .