Evidence for a lost population of close-in exoplanets

TL;DR

This paper explores how evaporation influences the distribution of close-in exoplanets, suggesting a lost population closer to stars explains observed correlations between planetary properties.

Contribution

It introduces a simple evaporation model that accounts for the absence of certain close-in exoplanets and explains observed correlations as a linear cutoff in specific planetary parameter space.

Findings

Survival of known planets aligns with the evaporation model.

A lost population of closer-in planets could explain observed correlations.

Distribution in the M^2/R^3 vs a^-2 plane matches model predictions.

Abstract

We investigate the evaporation history of known transiting exoplanets in order to consider the origin of observed correlations between mass, surface gravity and orbital period. We show that the survival of the known planets at their current separations is consistent with a simple model of evaporation, but that many of the same planets would not have survived closer to their host stars. These putative closer-in systems represent a lost population that could account for the observed correlations. We conclude that the relation underlying the correlations noted by Mazeh et al. (2005) and Southworth et al. (2007) is most likely a linear cut-off in the M^2/R^3 vs a^-2 plane, and we show that the distribution of exoplanets in this plane is in close agreement with the evaporation model.