Transit Timing Variation of XO-3b: Evidence for Tidal Evolution of Hot Jupiter with High Eccentricity

TL;DR

This study analyzes transit timing variations of XO-3b using TESS data, providing evidence for orbital decay likely caused by tidal interactions, and discusses implications for the planet's tidal quality factor and orbital evolution.

Contribution

It presents the first detailed analysis of XO-3b's TTVs with TESS data, indicating orbital decay and exploring tidal evolution models.

Findings

TTVs show an orbital decay timescale of 1.4 Myr.

Tidal interaction explains the observed period decay.

Different tidal quality factors are estimated for star and planet.

Abstract

Observed transit timing variation (TTV) potentially reveals the period decay caused by star-planet tidal interaction which can explain the orbital migration of hot Jupiters. We report the TTV of XO-3b, using TESS observed timings and archival timings. We generate a photometric pipeline to produce light curves from raw TESS images and find the difference between our pipeline and TESS PDC is negligible for timing analysis. TESS timing presents a shift of 17.6 minutes (80 $\sigma$), earlier than the prediction from the previous ephemeris. The best linear fit for all timings available gives a Bayesian Information Criterion (BIC) value of 439. A quadratic function is a better model with a BIC of 56. The period derivative obtained from a quadratic function is -6.2$\times$10$^{-9}$$\pm$2.9$\times$10$^{-10}$ per orbit, indicating an orbital decay timescale 1.4 Myr. We find that the orbital period decay can be well explained by tidal interaction. The `modified tidal quality factor' $Q_{p}'$ would be 1.8$\times$10$^{4}$$\pm$8$\times$10$^{2}$ if we assume the decay is due to the tide in the planet; whereas $Q_{*}'$ would be 1.5$\times$10$^{5}$$\pm$6$\times$10$^{3}$ if tidal dissipation is predominantly in the star. The precession model is another possible origin to explain the observed TTVs. We note that the follow-up observations of occultation timing and radial velocity monitoring are needed for fully discriminating the different models.