Planets around Giant Stars

TL;DR

This study reports on a radial-velocity survey of 373 giant stars, confirming known planets, finding a correlation between metallicity and planet occurrence, and discovering brown dwarf companions around nu Oph, suggesting disk formation.

Contribution

It provides new observational data on planets around giant stars, including confirmation of previous planets and discovery of brown dwarf companions, highlighting formation mechanisms.

Findings

Confirmed planets iota Dra b and Pollux b.

Detected increased planet frequency with higher metallicity.

Found two brown dwarfs orbiting nu Oph in a 6:1 period ratio.

Abstract

We present results from a radial-velocity survey of 373 giant stars at Lick Observatory, which started in 1999. The previously announced planets iota Dra b and Pollux b are confirmed by continued monitoring. The frequency of detected planetary companions appears to increase with metallicity. The star nu Oph is orbited by two brown dwarf companions with masses of 22.3 M_Jup and 24.5 M_Jup in orbits with a period ratio close to 6:1. It is likely that the two companions to nu Oph formed in a disk around the star.