BD+48 740 - Li overabundant giant star with a planet. A case of recent engulfment?

TL;DR

This paper reports the discovery of BD+48 740, a lithium-rich giant star with a highly eccentric planet, suggesting recent planetary engulfment and providing insights into planetary system evolution around evolved stars.

Contribution

It presents the first detailed case linking lithium overabundance in a giant star with a highly eccentric planetary companion, indicating recent planetary engulfment.

Findings

BD+48 740 hosts a 1.6 M_J planet with high eccentricity (e=0.67).

The star shows an unusually high lithium abundance for a giant.

Possible evidence of recent planetary engulfment event.

Abstract

We report the discovery of a unique object, BD+48 740, a lithium overabundant giant with A(Li)=2.33 +/- 0.04 (where A(Li) = log(n_Li/n_H) + 12), that exhibits radial velocity (RV) variations consistent with a 1.6 M_J companion in a highly eccentric, e = 0.67 +/- 0.17 and extended, a=1.89 AU (P=771 d), orbit. The high eccentricity of the planet is uncommon among planetary systems orbiting evolved stars and so is the high lithium abundance in a giant star. The ingestion by the star of a putative second planet in the system originally in a closer orbit, could possibly allow for a single explanation to these two exceptional facts. If the planet candidate is confirmed by future RV observations, it might represent the first example of the remnant of a multiple planetary system possibly affected by stellar evolution.