Search for Exoplanetary Ring Systems with TESS

Planetary rings are ubiquitous in the Solar System, including gas giants, ice giants and asteroids. On the other hand, in the case of exoplanets, of which more than 5000 are currently known, one ringed planet candidate was identified in the past systematic survey using the Kepler, but it has not been confirmed due to the long orbital period and the difficulty of follow-up observations and has not yet been discovered. In this study, We analyzed the archive data of the Transiting Exoplanet Survey Satellite (TESS) to search for ringed planet candidates that can be follow-up observations. First, we calculated the statistical precision required to detect the rings, which are assumed to be predominantly rocky. We then selected 284 objects that satisfied the required statistical precision from the 2691 objects that had not been identified as binary systems or false positives. For each object, we performed the ringless and ringed transit model fitting and analyzed the detection of ring features. As a result, no ringed planet candidates were found. Combined with the results of the analysis of the past using Kepler, it is suggested that it is difficult to detect ringed planets using our method on current observational satellites. We assumed the obliquity of the ring and estimated upper limits for the outer diameters of nine of the 284 objects with relatively good statistical precision. In this study, We discussed the other method for detecting ringed planets, wherein the transit depth variation is attributed to changes in the ring angle caused by the precession of the planet’s rotation axis. We also listed the candidate objects that are assumed to be detectable by the method for the TESS and Kepler, respectively.