Revisiting the Transit Timing Variations in the TrES-3 and Qatar-1 systems with TESS data

TL;DR

This study refines the orbital parameters of TrES-3b and Qatar-1b using extensive TESS and ground-based transit data, detects potential transit timing variations, and explores possible causes, suggesting line-of-sight acceleration for Qatar-1b.

Contribution

It provides improved ephemerides for both systems and investigates the nature of TTVs, proposing line-of-sight acceleration as a plausible explanation for Qatar-1b's TTVs, which is a novel insight.

Findings

Refined orbital ephemerides for TrES-3b and Qatar-1b.

Detection of potential TTVs in both systems.

Line-of-sight acceleration as a plausible cause for Qatar-1b's TTVs.

Abstract

We present and analyze 58 transit light curves of TrES-3b and 98 transit light curves of Qatar-1b observed by Transiting Exoplanet Survey Satellite (TESS), plus two transit light curves of Qatar-1b observed by us using a ground-based 1.23\,m telescope. These light curves are combined with the best-quality light curves taken from the Exoplanet Transit Database (ETD) and literature. The precisely determined mid-transit times from these light curves enable us to obtain the refined orbital ephemerides with improved precision for both hot Jupiters. From the timing analysis, we find an indication for the presence of transit timing variations (TTVs) in both systems. Since the observed TTVs are unlikely to be short-term and periodic, the possibility of additional planets in the orbits close to TrES-3b and Qatar-1b are ruled out. Possible causes of long-term TTVs such as orbital decay, apsidal precession, the Applegate mechanism and line-of-sight acceleration are also examined. However, none of these possibilities are found to explain the observed TTV of TrES-3b. In contrast to this, the line-of-sight acceleration appears to be a plausible explanation for the observed TTV of Qatar-1b. In order to confirm these findings, further high-precision transit and RV observations of both systems would be worthwhile.