The Pan-Pacific Planet Search. VIII. Complete results and the occurrence rate of planets around low-luminosity giants

TL;DR

This study presents the final results of a 5-year radial velocity survey of low-luminosity giant stars, estimating a planet occurrence rate of about 7.8%, aligning with rates around main-sequence A-type stars.

Contribution

It provides the complete data set and refined occurrence rate estimates for planets around low-luminosity giant stars, filling a gap in stellar population studies.

Findings

Estimated giant planet occurrence rate: 7.8%

Detected six potential substellar companions

Results align with planet frequencies around main-sequence A-type stars

Abstract

Our knowledge of the populations and occurrence rates of planets orbiting evolved intermediate-mass stars lags behind that for solar-type stars by at least a decade. Some radial velocity surveys have targeted these low-luminosity giant stars, providing some insights into the properties of their planetary systems. Here we present the final data release of the Pan-Pacific Planet Search, a 5-year radial velocity survey using the 3.9m Anglo-Australian Telescope. We present 1293 precise radial velocity measurements for 129 stars, and highlight six potential substellar-mass companions which require additional observations to confirm. Correcting for the substantial incompleteness in the sample, we estimate the occurrence rate of giant planets orbiting low-luminosity giant stars to be approximately 7.8$^{+9.1}_{-3.3}$\%. This result is consistent with the frequency of such planets found to orbit main-sequence A-type stars, from which the PPPS stars have evolved.