Did Lithium Rich Giant Star KIC 9821622 eat its Exoplanets?

KIC 9821622: An interesting lithium-rich giant in the Kepler field

Authors:

Jofré et al

Abstract:

We report the discovery of a new exceptional young lithium-rich giant, KIC 9821622, in the Kepler field exhibiting unusually large enhancement of α, Fe-peak and \textit{r}-process elements. From high-resolution spectra obtained with GRACES at Gemini North, we derived fundamental parameters and detailed chemical abundances of 23 elements from both equivalent widths and synthesis analysis. Combining atmospheric stellar parameters with available asteroseismic data we obtained the stellar mass, radius and age. The data analysis reveals that KIC 9821622 is a Li-rich (A(Li)NLTE = 1.80 ± 0.2) intermediate-mass giant star (M = 1.64 M⊙) located at the RGB near the luminosity bump. We find unexpected elevated abundances of Fe-peak and \textit{r}-process elements. Also, as previously reported, we find that this is a young star (2.37 Gyr) with unusual high abundances of α-elements ([α/Fe] = 0.31). The evolutionary status of KIC 9821622 suggests that its Li-rich nature is result of internal freshly Li synthesized through the Cameron-Fowler mechanism near the luminosity bump. However, its peculiar enhancement of α, Fe-peak and \textit{r}-process elements opens the possibility of external contamination by material enriched by a supernova explosion. Although less likely, planet accretion cannot be ruled out.