Planets Around the K-Giants BD+20 274 and HD 219415

TL;DR

This paper reports the discovery of two planet-mass companions orbiting giant stars, using radial velocity measurements, including the longest period planet detected by the survey, highlighting the potential for finding planets around evolved stars.

Contribution

First detection of planet-mass companions around two giant stars using the Hobby-Eberly Telescope, including the longest period planet found in this survey.

Findings

One planet with a 578-day orbit around BD+20 274.

A Jupiter-mass planet with a 5.7-year eccentric orbit around HD 219415.

Detection demonstrates the survey's capability to find long-period planets around giant stars.

Abstract

We present the discovery of planet-mass companions to two giant stars by the ongoing Penn State- Toru\'n Planet Search (PTPS) conducted with the 9.2 m Hobby-Eberly Telescope. The less massive of these stars, K5-giant BD+20 274, has a 4.2 MJ minimum mass planet orbiting the star at a 578-day period and a more distant, likely stellar-mass companion. The best currently available model of the planet orbiting the K0-giant HD 219415 points to a Jupiter-mass companion in a 5.7-year, eccentric orbit around the star, making it the longest period planet yet detected by our survey. This planet has an amplitude of \sim18 m/s, comparable to the median radial velocity (RV) "jitter", typical of giant stars.