Survival Function Analysis of Planet Orbit Distribution and Occurrence Rate Estimate

TL;DR

This study uses survival function analysis on Kepler data to reveal distribution patterns of exoplanets, identifying different regimes based on size and orbital distance, and enabling precise occurrence rate estimates and TESS yield predictions.

Contribution

It introduces a novel application of survival function analysis to orbital and size distributions, uncovering distinct regimes and migration effects in exoplanet populations.

Findings

All exoplanets are uniformly distributed in ln a or ln P.

Inner cut-off at 0.05 AU, varying by planet type.

Different distribution slopes suggest migration and irradiation effects.

Abstract

Applying survival function analysis to the planet orbital period (P) and semi-major axis (a) distribution from the Kepler sample, we find that all exoplanets are uniformly distributed in (ln a) or (ln P), with an average inner cut-off of 0.05 AU to the host star. More specifically, this inner cut-off is 0.04 AU for rocky worlds (1-2 Earth radii) and 0.08 AU for water worlds (2-4 Earth radii). Moreover, the transitional planets (4-10 Earth radii) and gas giants (>10 Earth radii) have a change of slope of survival function at 0.4 AU from -1 to -1/2, suggesting a different statistical distribution uniform in \Sqrt[a] inside 0.4 AU, compared to small exoplanets (<4 Earth radii). This difference in distribution is likely caused by the difference in planet migration mechanism, and susceptibility to host stellar irradiation, for gas-poor (<4 Earth radii) versus gas-rich (>4 Earth radii) planets. Armed with this knowledge and combined with the survival function analysis of planet size distribution, we can make precise estimates of planet occurrence rate and predict the TESS mission yield.