2020AJ....160..249R

From previous ground-based observations, the hot Jupiter exoplanet XO-6b was reported to exhibit apparently periodic transit timing variations (TTVs), with a semi-amplitude of 14 minutes and a period of about 450 days. These variations were interpreted as being due to a resonant perturbation between XO-6b and a hitherto unknown low-mass planet orbiting the same star. To understand this enigmatic planetary system better, we analyzed three sectors of data, spanning over seven months, from the Transiting Exoplanet Survey Satellite (TESS), which produces high-quality light curves that are well suited to characterizing exoplanets and searching for TTVs. Here we present an updated orbital period of 3.7649893 ± 0.0000037 days and a transit epoch of 2456652.7157 ± 0.0022 BJD_TDB. The planetary parameters we report, while consistent with their discovery values, have greatly improved precision. Notably, we find no evidence for TTVs: we can rule out TTVs >=2.5 minutes at the 3σ level. Therefore, the TESS data have sufficient precision and time baseline to readily reveal the previously reported TTVs of approximately 10 minutes. Our findings highlight the capability of TESS for robust follow-up, and confirm that TTVs are rarely seen in hot Jupiters, unlike is the case with small planets.