Rate and nature of false positives in the CoRoT exoplanet search

TL;DR

This study assesses the false positive rates in CoRoT's exoplanet search, revealing that most initial detections are false positives, with a small fraction confirmed as planets, and compares results with theoretical predictions.

Contribution

It provides an empirical analysis of false positive rates in CoRoT data and compares these with semiempirical models, highlighting discrepancies at low transit depths.

Findings

83% of initial detections are false positives.

12% of follow-up candidates are confirmed planets.

False positive rate distribution aligns with predictions except below 0.4% transit depth.

Abstract

Context. The CoRoT satellite searches for planets by applying the transit method, monitoring up to 12 000 stars in the galactic plane for 150 days in each observation run. This search is contaminated by a large fraction of false positives, caused by different binary configurations that might be confused with a transiting planet. Aims. We evaluate the rates and nature of false positives in the CoRoT exoplanets search and compare our results with semiempirical predictions. Methods. We consider the detected binary and planet candidates in the first three extended CoRoT runs, and classify the results of the follow-up observations completed to verify their planetary nature. We group the follow-up results into undiluted binaries, diluted binaries, and planets and compare their abundances with predictions from the literature. Results. 83% of the initial detections are classified as false positives using only the CoRoT light-curves, the remaining 17% require follow-up observations. Finally, 12% of the follow-up candidates are planets. The shape of the overall distribution of the false positive rate follows previous predictions, except for candidates with transit depths below about 0.4%. For candidates with transit depths in the range from 0.1 - 0.4%, CoRoT detections are nearly complete, and this difference from predictions is probably real and dominated by a lower than expected abundance of diluted eclipsing binaries.