Tracking Advanced Planetary Systems (TAPAS) with HARPS-N. VI. HD 238914 and TYC 3318-01333-1 - two more Li-rich giants with planets

TL;DR

This study reports the discovery of planetary systems around Li-rich giant stars, suggesting a potential link between planetary companions and lithium enrichment, based on high-resolution spectroscopic observations and radial velocity measurements.

Contribution

First detection of planets around Li-rich giants, with detailed spectral analysis and orbital characterization, indicating a possible connection between planetary presence and lithium enhancement.

Findings

Two new planetary systems discovered around Li-rich giants

Planet frequency in Li-rich giants is twice that of the general sample

Most planetary orbits are highly eccentric

Abstract

We present the latest results of our search for planets with HARPS-N at the 3.6 m Telescopio Nazionale Galileo under the Tracking Advanced Planetary Systems project: an in-depth study of the 15 most Li abundant giants from the PennState - Toru\'n Planet Search sample. Our goals are first, to obtain radial velocities of the most Li-rich giants we identified in our sample to search for possible low-mass substellar companions, and second, to perform an extended spectral analysis to define the evolutionary status of these stars. Methods. This work is based on high-resolution spectra obtained with the Hobby-Eberly Telescope and its High Resolution Spectro- graph, and with the HARPS-N spectrograph at the Telescopio Nazionale Galileo. Two stars, HD 181368 and HD 188214 , were also observed with UVES at the VLT to determine beryllium abundances. We report i) the discovery of two new planetary systems around the Li-rich giant stars: HD 238914 and TYC 3318-01333- 1 (a binary system); ii) reveal a binary Li-rich giant, HD 181368 ; iii) although our current phase coverage is not complete, we suggest the presence of planetary mass companions around TYC 3663-01966-1 and TYC 3105-00152-1 ; iv) we confirm the previous result for BD+48 740 and present updated orbital parameters, and v) we find a lack of a relation between the Li enhancement and the Be abundance for the stars HD 181368 and HD 188214 , for which we acquired blue spectra. We found seven stars with stellar or potential planetary companions among the 15 Li-rich giant stars. The binary star frequency of the Li-rich giants in our sample appears to be normal, but the planet frequency is twice that of the general sample, which suggests a possible connection between hosting a companion and enhanced Li abundance in giant stars. We also found most of the companions orbits to be highly eccentric.