Mutual Occurrence Ratio of Planets. I. New Clues to Reveal Origins of Hot- and Warm-Jupiter from the RV Sample

Abstract

Many studies have analyzed 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 to a warm or even hot Jupiter, and demonstrate how stellar properties impact the evolution history of planetary systems. We propose a new classification of giant planets, i.e. cold Jupiter(CJ), warm Jupiter(WJ), and hot Jupiter(HJ), according to their position relative to the snow line in the system. Then, we derive their occurrence rates(${\eta}_{\rm HJ}$, ${\eta}_{\rm WJ}$, ${\eta}_{\rm CJ}$) with the detection completeness of RV(Radial Velocity) surveys(HARPS$\&$ CORALIE) considered. Finally, we analyze the correlation between the mutual occurrence ratios, i.e. ${\eta}{_{\rm CJ}} / {\eta}_{\rm WJ}$, ${\eta}{_{\rm CJ}} / {\eta}_{\rm HJ}$ or ${\eta}{_{\rm WJ}}/{\eta}_{\rm HJ}$, and various stellar properties, e.g. effective temperature $T_{\rm eff}$. Our results show that the ${\eta}_{\rm HJ}$, ${\eta}_{\rm WJ}$ and ${\eta}_{\rm CJ}$ are increasing with the increasing $T_{\rm eff}$ when $T_{\rm eff}\in (4600,6600] K$. Furthermore, the mutual occurrence ratio between CJ and WJ, i.e. ${\eta}{_{\rm CJ}} /{\eta}_{\rm WJ}$, shows a decreasing trend with the increasing $T_{\rm eff}$. But, both ${\eta}{_{\rm CJ}}/{\eta}_{\rm HJ}$ and ${\eta}{_{\rm WJ}}/{\eta}_{\rm HJ}$ are increasing when the $T_{\rm eff}$ 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 favors gentle disk migration, HJ favors a more violent mechanism that requires further investigation.