High Order Harmonics in Light Curves of Kepler Planets

TL;DR

This paper investigates high order harmonic signals in Kepler light curves, confirming their reality, exploring their origins, and warning about potential impacts on exoplanet parameter estimations.

Contribution

It identifies and confirms the presence of high order harmonics in Kepler light curves and discusses their possible origins and implications.

Findings

Harmonics are real signals, not processing artifacts.

Harmonics likely originate from non-sinusoidal periodic signals.

Potential misestimations in planet properties due to harmonics.

Abstract

The Kepler mission was launched in 2009 and has discovered thousands of planet candidates. In a recent paper, Esteves et al. (2013) found a periodic signal in the light curves of KOI-13 and HAT-P-7, with a frequency triple the orbital frequency of a transiting planet. We found similar harmonics in many systems with a high occurrence rate. At this time, the origins of the signal are not entirely certain. We look carefully at the possibility of errors being introduced through our data processing routines but conclude that the signal is real. The harmonics on multiples of the orbital frequency are a result of non-sinusoidal periodic signals. We speculate on their origin and generally caution that these harmonics could lead to wrong estimates of planet albedos, beaming mass estimates, and ellipsoidal variations.