Validating the Orbital Periods of the Coolest TESS Exoplanet Candidates

TL;DR

This paper validates the long orbital periods of several TESS exoplanet candidates, refining their periods and highlighting the potential for discovering cooler, long-period planets that may host exomoons or rings.

Contribution

It confirms long orbital periods for nine TESS candidates and identifies five more likely to have long periods, improving the accuracy of TESS exoplanet data.

Findings

Confirmed long periods for nine exoplanets.

Identified five candidates likely to have long periods.

Refined TESS orbital period measurements.

Abstract

When an exoplanet passes in front of its host star, the resulting eclipse causes an observable decrease in stellar flux, and when multiple such transits are detected, the orbital period of the exoplanet can be determined. Over the past six years, NASA's Transiting Exoplanet Survey Satellite (TESS) has discovered thousands of potential planets by this method, mostly with short orbital periods, although some have longer reported values over one hundred days. These long orbital periods, however, are note easy to confirm due to frequent lengthy data gaps. Here we show that while the majority of these long period candidates likely have periods much shorter than reported, there are a sizable number of TESS candidates with true long periods. These candidates generally only have two reported transits, but the periods of duo-transits like this, and even candidates with three or more transits, can be confirmed if the data rules out all possible shorter period aliases. Using TESS data, we confirm long orbital periods for nine candidate planets, and present five others that are likely long period. Due to their long periods, these planets will have relatively cool equilibrium temperatures, and may be more likely to host exomoons or rings. We present these TOIs, along with a variety of small corrections to other TESS orbital periods and three planet candidates with possible transit timing variations, with the goal of refining the TESS data set and enabling future research with respect to cool transiting planets.