The Pan-Pacific Planet Search. II. Confirmation of a two-planet system around HD 121056

TL;DR

This paper confirms a two-planet system around the evolved star HD 121056 using precise radial velocity measurements, highlighting its significance as the most-evolved star known to host multiple planets with diverse orbital periods.

Contribution

First confirmation of a multi-planet system around an evolved giant star, demonstrating the presence of both short- and long-period planets around HD 121056.

Findings

Inner planet has a period of 89.1 days and mass of 1.35 Mjup.

Outer planet has a mass of 3.9 Mjup and orbits at 2.96 AU.

HD 121056 is the most-evolved star with a confirmed multiple-planet system.

Abstract

Precise radial velocities from the Anglo-Australian Telescope confirm the presence of a rare short-period planet around the K0 giant HD 121056. An independent two-planet solution using the AAT data shows that the inner planet has P=89.1+/-0.1 days, and m sin i=1.35+/-0.17 Mjup. These data also confirm the planetary nature of the outer companion, with m sin i=3.9+/-0.6 Mjup and a=2.96+/-0.16 AU. HD 121056 is the most-evolved star to host a confirmed multiple-planet system, and is a valuable example of a giant star hosting both a short-period and a long-period planet.