Multi-Epoch Photometric Survey of Exoplanet Atmospheric Variability Using TESS and K2 Archival Data

The analysis within this study utilized archival Transiting Exoplanet Survey Satellite (TESS) data combined with K2 photometric time-series for 595 "hot Jupiter" planets. Three independent measurements were made from these sources: per-sector transit depth, secondary eclipse depth, and per-epoch transit timing. The transit depth was then analyzed for variability relative to its own stellar noise floor; where the noise floor was derived from generating synthetic constant depth transits added into each star's photometry and processed with the same techniques used to extract the transit parameters.

A total of 17,770 transit times for 435 exoplanets were analyzed and no evidence of orbital decay was found. A lower bound for the reduced stellar tidal quality factor (Q′) at 95% confidence was determined to be >5.7 × 106. A stacked value of Q′ = 5.66 × 106 was also determined. An independent measurement of Q′ for WASP-12b produced values (2.0 × 105) consistent with those previously reported (1.8 × 105). Thus, the number of planets with calculated decay timescales < their host star's age was decreased from 191 "paradoxical" systems to 70. This result favours the interpretation that stars dissipate tidal energy inefficiently, rather than the alternative that many hot Jupiters have migrated inward comparatively recently.

Variable dayside emissions were detected for 21/42 secondary eclipses. In addition, seven out of nine planets observed with both secondary eclipse and transit-depth techniques exhibited variability in both measurements.