Chromospheric emission of planet candidate systems - a way to identify false positives

TL;DR

This study investigates chromospheric emission in Kepler planet candidate systems, finding that enhanced emission is likely linked to false positives such as eclipsing binaries rather than genuine giant planets.

Contribution

It provides evidence that chromospheric emission can be used to identify false positives in planet candidate systems, especially distinguishing binaries from true planets.

Findings

Giant planet candidates show emission enhancement, which disappears when binaries are removed.

False positives, likely tidally interacting binaries, exhibit strong chromospheric emission.

Chromospheric emission correlates with orbital period in eclipsing binary candidates.

Abstract

It has been hypothesized that the presence of closely orbiting giant planets is associated with enhanced chromospheric emission of their host stars. The main cause for such a relation would likely be enhanced dynamo action induced by the planet. We present measurements of chromospheric emission in 234 planet candidate systems from the Kepler mission. This ensemble includes 37 systems with giant planet candidates, which show a clear emission enhancement. The enhancement, however, disappears when systems which are also identified as eclipsing binary candidates are removed from the ensemble. This suggests that a large fraction of the giant planet candidate systems with chromospheric emission stronger than the Sun are not giant planet system, but false positives. Such false-positive systems could be tidally interacting binaries with strong chromospheric emission. This hypotesis is supported by an analysis of 188 eclipsing binary candidates that show increasing chromospheric emission as function of decreasing orbital period.