Ground-based photometry of space-based transit detections: Photometric follow-up of the CoRoT mission

TL;DR

This paper discusses the methods and effectiveness of ground-based photometric follow-up of CoRoT space mission transit detections, emphasizing high spatial resolution to identify false positives like eclipsing binaries.

Contribution

It introduces a dedicated ground-based follow-up approach using 'on'-'off' photometry to validate CoRoT transit candidates and demonstrates its application in confirming or rejecting potential exoplanets.

Findings

Ground-based follow-up effectively identifies contaminating eclipsing binaries.

'On'-'off' photometry is a practical technique for transit validation.

Application to CoRoT-7b confirmed the planetary nature of the candidate.

Abstract

The motivation, techniques and performance of the ground-based photometric follow-up of transit detections by the CoRoT space mission are presented. Its principal raison d'\^{e}tre arises from the much higher spatial resolution of common ground-based telescopes in comparison to CoRoT's cameras. This allows the identification of many transit candidates as arising from eclipsing binaries that are contaminating CoRoT's lightcurves, even in low-amplitude transit events that cannot be detected with ground-based obervations. For the ground observations, 'on'-'off' photometry is now largely employed, in which only a short timeseries during a transit and a section outside a transit is observed and compared photometrically. CoRoT planet candidates' transits are being observed by a dedicated team with access to telescopes with sizes ranging from 0.2 to 2 m. As an example, the process that led to the rejection of contaminating eclipsing binaries near the host star of the Super-Earth planet CoRoT-7b is shown. Experiences and techniques from this work may also be useful for other transit-detection experiments, when the discovery instrument obtains data with a relatively low angular resolution.