A Planet in a 0.6-AU Orbit Around the K0 Giant HD 102272

TL;DR

This paper reports the discovery of a planet orbiting the K0 giant star HD 102272 at 0.6 AU, providing evidence that planetary orbits around intermediate-mass giants are influenced by formation and stellar evolution.

Contribution

First detection of a close-in planet around a GK-giant, showing the impact of stellar evolution on planetary orbit sizes.

Findings

Minimum planet mass is 5.9 Jupiter masses.

Planet's orbit has a semi-major axis of 0.61 AU and eccentricity of 0.05.

Evidence suggests stellar evolution affects planetary orbit sizes.

Abstract

We report the discovery of one or more planet-mass companions to the K0-giant HD 102272 with the Hobby-Eberly Telescope. In the absence of any correlation of the observed periodicities with the standard indicators of stellar activity, the observed radial velocity variations are most plausibly explained in terms of a Keplerian motion of at least one planet-mass body around the star. With the estimated stellar mass of 1.9M$_\odot$, the minimum mass of the confirmed planet is 5.9M$_J$. The planet's orbit is characterized by a small but nonzero eccentricity of $e$=0.05 and the semi-major axis of 0.61 AU, which makes it the most compact one discovered so far around GK-giants. This detection adds to the existing evidence that, as predicted by theory, the minimum size of planetary orbits around intermediate-mass giants is affected by both planet formation processes and stellar evolution. The currently available evidence for another planet around HD 102272 is insufficient to obtain an unambiguous two-orbit solution.