Significant Transit Timing Offsets of 31 Hot Jupiters

A precise transit ephemeris serves as the premise for follow-up exoplanet observations. The transit timing variation (TTV) as an important scientific output potentially reveals planetary orbital evolution. We compare transit timings of 262 hot Jupiters from TESS with the archival ephemeris and find 31 of them having significant TESS timing offsets, among which WASP-161b shows the most significant offset of -203.7$\pm$4.1 minutes. The median value of these offsets is 17.8 minutes, equivalent to 3.4 $\sigma$. We evaluate the timing precision of TESS Objects of Interest (TOI) which provides the TESS timings in this work. The evaluation is applied by deriving TESS transit timing from a self-generated pipeline. We refine and update the previous ephemeris, based on precise timing (uncertainty within 1 minute) and a long timing baseline ($\sim 10$ years). Our refined ephemeris gives the transit timing at a median precision of 1.11 minutes until 2025 and 1.86 minutes until 2030. All the targets with timing offset larger than 10$\sigma$ present earlier timings than the prediction, which cannot be due to underestimated ephemeris uncertainty, apsidal precision, or R$\o$mer effect as those effects should be unsigned. We regard the timing offsets mainly originating from the underestimated ephemeris uncertainty. For some particular targets, timing offsets are due to tidal dissipation. We find a tentative TTV of XO-3b (timing offset $>$ 10 $\sigma$) yielding a period derivative of 5.8$\pm$0.9$\times$10$^{-9}$. The TTV may be explained by tidal dissipation. Our result provides direct observational support for the tidal dissipation of XO-3b, reported in previous work.