The Pan-Pacific Planet Search III: Five companions orbiting giant stars

TL;DR

This paper reports the discovery of a new giant planet and four stellar companions orbiting giant stars, providing updated orbital data and discussing the nature of some companions near the brown dwarf threshold.

Contribution

It presents new planetary and stellar companions from the Pan-Pacific Planet Search and refines the orbit of a previously discovered planet, expanding knowledge of substellar companions around giants.

Findings

Discovery of a new giant planet HD 155233b with specific orbital parameters.

Identification of four stellar-mass companions with masses from 0.066 to 0.33 M_sun.

Updated orbit data for HD 47205b (7 CMa b).

Abstract

We report a new giant planet orbiting the K giant HD 155233, as well as four stellar-mass companions from the Pan-Pacific Planet Search, a southern hemisphere radial velocity survey for planets orbiting nearby giants and subgiants. We also present updated velocities and a refined orbit for HD 47205b (7 CMa b), the first planet discovered by this survey. HD 155233b has a period of 885$\pm$63 days, eccentricity e=0.03$\pm$0.20, and m sin i=2.0$\pm$0.5 M_jup. The stellar-mass companions range in m sin i from 0.066 M_sun to 0.33 M_sun. Whilst HD 104358B falls slightly below the traditional 0.08 M_sun hydrogen-burning mass limit, and is hence a brown dwarf candidate, we estimate only a 50% a priori probability of a truly substellar mass.