A Massive Substellar Companion to the Massive Giant HD 119445

TL;DR

This paper reports the discovery of a massive brown dwarf companion orbiting a giant star, providing evidence that more massive stars tend to host more massive substellar companions, which informs formation theories.

Contribution

First detection of a brown dwarf-mass companion around an intermediate-mass giant star using precise radial velocity measurements.

Findings

The companion has a minimum mass of 37.6 Jupiter masses.

It orbits at 1.71 AU with a period of 410.2 days.

This is the most massive substellar companion found within 3 AU of such a star.

Abstract

We detected a brown dwarf-mass companion around the intermediate-mass giant star HD 119445 (G6III) using the Doppler technique. This discovery is the first result from a Korean-Japanese planet search program based on precise radial velocity measurements. The radial velocity of this star exhibits a periodic Keplerian variation with a period, semi-amplitude and eccentricity of 410.2 days, 413.5 m/s and 0.082, respectively. Adopting a stellar mass of 3.9 M_solar, we were able to confirm the presence of a massive substellar companion with a semimajor axis of 1.71 AU and a minimum mass of 37.6 M_Jup, which falls in the middle of the brown dwarf-mass region. This substellar companion is the most massive ever discovered within 3 AU of a central intermediate-mass star. The host star also ranks among the most massive stars with substellar companions ever detected by the Doppler technique. This result supports the current view of substellar systems that more massive substellar companions tend to exist around more massive stars, and may further constrain substellar system formation mechanisms.