TESS Observations of the Hot Jupiter Exoplanet XO-6b: No Evidence of Transit Timing Variations

TL;DR

This study used TESS data to analyze the hot Jupiter XO-6b, finding no evidence of previously reported transit timing variations and providing more precise planetary parameters.

Contribution

We provided an updated orbital period and transit epoch for XO-6b, and demonstrated the absence of TTVs, challenging earlier ground-based claims.

Findings

No TTVs detected above 2.5 minutes at 3σ level.

Updated planetary parameters with improved precision.

Confirmed TESS's effectiveness for exoplanet follow-up.

Abstract

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 analysed 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 $\pm$ 0.0000037 days and a transit epoch of 2456652.7157 $\pm$ 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 $\gtrsim$ 2.5 minutes at the 3$\sigma$ level. Therefore, the TESS data have sufficient precision and time baseline to reveal readily the previously reported TTVs of approximately 10 minutes. Our findings highlight TESS's capabilities for robust follow-up, and confirm that TTVs are rarely seen in hot Jupiters, unlike is the case with small planets.