A transit timing analysis of seven RISE light curves of the exoplanet system HAT-P-3

TL;DR

This study analyzes seven transit light curves of exoplanet HAT-P-3 to refine system parameters, confirm orbital stability, and place limits on potential additional planets using transit timing variations.

Contribution

It provides improved measurements of HAT-P-3's parameters and establishes upper mass limits for hypothetical perturbing planets based on transit timing analysis.

Findings

Transit times are consistent with a linear ephemeris.

Refined stellar and planetary parameters with higher precision.

Upper mass limits for additional planets are as low as 0.33 and 1.81 Earth masses.

Abstract

We present seven light curves of the exoplanet system HAT-P-3, taken as part of a transit timing program using the RISE instrument on the Liverpool Telescope. The light curves are analysed using a Markov-Chain Monte-Carlo algorithm to update the parameters of the system. The inclination is found to be i = 86.75^{+0.22}_{-0.21} deg, the planet-star radius ratio to be R_p/R_star = 0.1098^{+0.0010}_{-0.0012}, and the stellar radius to be R_star = 0.834^{+0.018}_{-0.026} R_sun, consistent with previous results but with a significant improvement in the precision. Central transit times and uncertainties for each light curve are also determined, and a residual permutation algorithm used as an independent check on the errors. The transit times are found to be consistent with a linear ephemeris, and a new ephemeris is calculated as T_c(0) = 2454856.70118 +- 0.00018 HJD and P = 2.899738 +- 0.000007 days. Model timing residuals are fitted to the measured timing residuals to place upper mass limits for a hypothetical perturbing planet as a function of the period ratio. These show that we have probed for planets with masses as low as 0.33 M_earth and 1.81 M_earth in the interior and exterior 2:1 resonances, respectively, assuming the planets are initially in circular orbits.