Disproval of the validated planets K2-78b, K2-82b, and K2-92b

TL;DR

This study re-evaluates three validated exoplanets from K2 data and finds they are false positives caused by background eclipsing binaries, emphasizing the need for careful validation and independent confirmation.

Contribution

It demonstrates that K2-78b, K2-82b, and K2-92b are not planets but background eclipsing binaries, highlighting potential pitfalls in exoplanet validation processes.

Findings

The supposed planets are actually background eclipsing binaries.

Validation processes can mistakenly confirm false positives.

Independent confirmation is crucial for reliable exoplanet validation.

Abstract

Transiting super-Earths orbiting bright stars in short orbital periods are interesting targets for the study of planetary atmospheres. While selecting super-Earths suitable for further characterization from the ground among a list of confirmed and validated exoplanets detected by K2, we found some suspicious cases that led to us re-assessing the nature of the detected transiting signal. We did a photometric analysis of the K2 light curves and centroid motions of the photometric barycenters. Our study shows that the validated planets K2-78b, K2-82b, and K2-92b are actually not planets but background eclipsing binaries. The eclipsing binaries are inside the Kepler photometric aperture, but outside the ground-based high resolution images used for validation. We advise extreme care on the validation of candidate planets discovered by space missions. It is important that all the assumptions in the validation process are carefully checked. An independent confirmation is mandatory in order to avoid wasting valuable resources on further characterization of non-existent targets.