Search for Exoplanetary Ring Systems with TESS

TL;DR

This study systematically searches for exoplanetary rings in TESS data, setting upper limits on ring sizes and occurrence rates, and proposes alternative detection methods like transit depth variations.

Contribution

Developed a pipeline for detecting rings in TESS data, established upper limits on ring sizes and occurrence rates, and explored new detection techniques such as ring precession signals.

Findings

No conclusive ring detections in the analyzed systems.

Upper limits on ring occurrence rate are below 2% for rings larger than 1.8 planetary radii.

Transit depth variation method could detect rings in 10-13 systems with current data.

Abstract

Photometric surveys for exoplanetary ring systems have not confirmed any object with Saturn-sized ring. We systematically analyse 308 TESS planet candidates, mainly comprised of giant short-period planets orbiting nearby bright stars. These targets are selected based on the optimistic detectability of rings, assuming a favourable ring orientation. We develop a pipeline with a two-step noise reduction and compare the fitting results of both ringless and ringed transit models to the resulting phase-folded light curves. Although we identify six systems where ringed models are statistically favoured, visual inspection of the signals suggests that none of them is conclusively attributed to the presence of rings. Assuming the ring orientation favourable for detection, we determine the 3$\sigma$ upper limits on ring sizes for 125 objects. Using these ring size limits, we derive upper limits on the ring occurrence rate, such as rings with an outer radius larger than 1.8 times the planetary radii occurring at rates lower than 2%. However, these limits can be relaxed if tidal alignment between the spin and orbital axes holds. We explore an alternative detection method using transit depth variations by ring precession and estimate that 10 and 13 systems are likely detectable in TESS and Kepler data, respectively.