Planetary companion candidates around the K giant stars 42 Dra and HD 139357

TL;DR

This study reports the detection of planetary companions around two K giant stars, 42 Dra and HD 139357, using precise radial velocity measurements over three years, demonstrating the presence of exoplanets around intermediate-mass stars.

Contribution

First detection of planetary companions around the K giant stars 42 Dra and HD 139357 through long-term RV monitoring, expanding knowledge of planet occurrence around evolved intermediate-mass stars.

Findings

Periodic RV variations indicating planets with periods of 479.1 and 1125.7 days.

Radial velocity signals consistent with Keplerian motion.

Confirmation of planets around intermediate-mass giant stars.

Abstract

For the past 3 years we have been monitoring 62 K giant stars using precise stellar radial velocity (RV) measurements with the 2m Alfred Jensch telescope of the Th\"uringer Landessternwarte Tautenburg (TLS). To probe the dependence of planet formation on stellar mass by finding planets around intermediate-mass giant stars. We present high accuracy RV measurements of the K1.5 III star 42 Dra and the K4 III star HD 139357. The wavelength reference for the RV measurements was provided by an iodine absorption cell placed in the optical path of the spectrograph. Our measurements reveal that the time series of the radial velocity of 42 Dra shows a periodic variation of 479.1 days. HD 139357 shows periodic RV variations of 1125.7 days. Keplerian motion is the most likely explanation for the observed radial velocity variations for these stars. Thus the K giant stars 42 Dra and HD 139357 host extrasolar planets.