Validating the Orbital Periods of the Coolest TESS Planet Candidates

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 seven 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 100 days. These long orbital periods, however, are not easy to confirm due to frequent lengthy data gaps. Here we show that while many of these long period candidates likely have periods much shorter than reported, there are some TESS candidates with long periods to be found in the data. 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 ( P > 100 days). Due to their long periods, these planets will also have relatively cool equilibrium temperatures. We present these TESS Objects of Interest, 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.