Mutual occurrence ratio of planets – I. New clues to reveal origins of hot and warm Jupiter from the RV sample

Abstract

ABSTRACT Many studies have analysed planetary occurrence rates and their dependence on the host’s properties to provide clues to planet formation, but few have focused on the mutual occurrence ratio of different kinds of planets. Such relations reveal whether and how one type of planet evolves into another, e.g. from a cold Jupiter (CJ) to a warm Jupiter (WJ) or even hot Jupiter (HJ), and demonstrate how stellar properties impact the evolution history of planetary systems. We propose a new classification of giant planets, i.e. CJ, WJ, and HJ, according to their position relative to the snow line in the system. Then, we derive their occurrence rates (ηHJ, ηWJ, ηCJ) with the detection completeness of radial velocity (RV) surveys (HARPS and CORALIE) considered. Finally, we analyse the correlation between the mutual occurrence ratios, i.e. ηCJ/ηWJ, ηCJ/ηHJ, or ηWJ/ηHJ, and various stellar properties, e.g. effective temperature Teff. Our results show that the ηHJ, ηWJ, and ηCJ are increasing with the increasing Teff when Teff ∈ (4600, 6600] K. Furthermore, the mutual occurrence ratio between CJ and WJ, i.e. ηCJ/ηWJ, shows a decreasing trend with the increasing Teff. But, both ηCJ/ηHJ and ηWJ/ηHJ are increasing when the Teff increases. Further consistency tests reveal that the formation processes of WJ and HJ may be dominated by orbital change mechanisms rather than the in situ model. However, unlike WJ, which favours gentle disc migration, HJ favours a more violent mechanism that requires further investigation.