A Substellar Companion to the Intermediate-Mass Giant 11 Com

TL;DR

This paper reports the discovery of a substellar companion, likely a brown dwarf, orbiting the intermediate-mass giant star 11 Com, based on precise Doppler measurements, contributing to understanding substellar companions around such stars.

Contribution

First detection of a substellar companion around 11 Com, providing statistical insights into brown dwarf occurrence around intermediate-mass giants from a joint China-Japan survey.

Findings

Companion mass is approximately 19.4 Jupiter masses.

Orbital period is about 326 days with an eccentricity of 0.231.

Detection rate of brown dwarf candidates is comparable to that around solar-type stars.

Abstract

We report the detection of a substellar companion orbiting the intermediate-mass giant star 11 Com (G8 III). Precise Doppler measurements of the star from Xinglong station and Okayama Astrophysical Observatory (OAO) revealed Keplerian velocity variations with an orbital period of 326.03 +/- 0.32 days, a semiamplitude of 302.8 +/- 2.6 m/s, and an eccentricity of 0.231 +/- 0.005. Adopting a stellar mass of 2.7 +/- 0.3 M_solar, the minimum mass of the companion is 19.4 +/- 1.5 M_Jup, well above the deuterium burning limit, and the semimajor axis is 1.29 +/- 0.05 AU. This is the first result from the joint planet search program between China and Japan aiming at revealing statistics of substellar companions around intermediate-mass giants. 11 Com b emerged from 300 targets of the planet search program at OAO. The current detection rate of a brown dwarf candidate seems to be comparable to that around solar-type stars within orbital separations of $\sim$3 AU.