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

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.

accepted for publication in A&A

References in corpus (10)

• The Transiting Exoplanet Survey Satellite
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• The K2 Mission: Characterization and Early results
• A Technique for Extracting Highly Precise Photometry for the Two-Wheeled Kepler Mission
• Modeling Kepler transit light curves as false positives: Rejection of blend scenarios for Kepler-9, and validation of Kepler-9d, a super-Earth-size planet in a multiple system
• EVEREST: Pixel Level Decorrelation of K2 Light curves
• 197 Candidates and 104 Validated Planets in K2's First Five Fields
• PASTIS: Bayesian extrasolar planet validation. I. General framework, models, and performance
• New planetary and EB candidates from Campaigns 1-6 of the K2 mission
• Transit Shapes and Self Organising Maps as a Tool for Ranking Planetary Candidates: Application to Kepler and K2

Cited by in corpus (14)

• The K2-138 System: A Near-Resonant Chain of Five Sub-Neptune Planets Discovered by Citizen Scientists
• Discovery and Vetting of Exoplanets I: Benchmarking K2 Vetting Tools
• MuSCAT2 multicolour validation of TESS candidates: an ultra-short-period substellar object around an M dwarf
• Precise masses for the transiting planetary system HD 106315 with HARPS
• 37 New Validated Planets in Overlapping K2 Campaigns
• Validation of small Kepler transiting planet candidates in or near the habitable zone
• Ondr}ejov echelle spectrograph, ground based support facility for exoplanet missions
• The K2-OjOS Project: New and revisited planets and candidates in K2 campaigns 5, 16, & 18
• TOI-519 b: a short-period substellar object around an M dwarf validated using multicolour photometry and phase curve analysis
• Two super-Earths at the edge of the habitable zone of the nearby M dwarf TOI-2095
• TOI-3288 b and TOI-4666 b: two gas giants transiting low-mass stars characterised by NIRPS
• K2-399 b is not a planet. The Saturn that wandered through the Neptune desert is actually a hierarchical eclipsing binary
• Scaling K2. V. Statistical Validation of 60 New Exoplanets From K2 Campaigns 2-18
• Detecting false positives with PLATO using double-aperture photometry and centroid shifts