Searching for the secondary eclipse of CoRoT-Exo-2b and its transit timing variations

TL;DR

This study searches for the secondary eclipse of CoRoT-Exo-2b using extensive CoRoT data, tentatively detects it, and investigates transit timing variations, finding no significant periodic TTVs larger than 10 seconds.

Contribution

It introduces a technique to detect the secondary eclipse in active star data and assesses transit timing variations, accounting for stellar activity effects.

Findings

Tentative 2.5 sigma detection of the secondary eclipse.

No significant periodic transit timing variations larger than 10 seconds.

Stellar activity influences transit timing measurements.

Abstract

With more than 80 transits observed in the CoRoT light curve with a cadence of 32 s, CoRoT-Exo-2b provides an excellent case to search for the secondary eclipse of the planet, with an expected signal of less than 10^-4 in relative flux. The activity of the star causes a modulation on the flux that makes the detection of this signal challenging. We describe the technique used to seek for the secondary eclipse, that leads to a tentative 2.5 sigma detection of a 5.5x10^-5 eclipse. If the effect of the spots are not taken into account, the times of transit centers will also be affected. They could lead to an erroneous detection of periodic transit timing variations of ~20 s and with a 7.45 d period. By measuring the transit central times at different depths of the transit (transit bisectors), we show that there are no such periodic variations in the CoRoT-Exo-2b O-C residuals larger than ~10 s.