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

Abstract

We present seven light curves of the exoplanet systemHAT-P-3, taken as part of a transit timing programme using the rapid imager to search for exoplanets instrument on the Liverpool Telescope. The light curves are analysed using aMarkov chainMonte Carlo algorithm to update the parameters of the system. The inclination is found to be i = 86.75⁺°·²²₋₀.₂₁◦, the planet-star radius ratio to be Rp/R✴ = 0.1098⁺°·°°¹°₋₀.₀₀₁₂ and the stellar radius to be R✴ = 0.834⁺°·°¹⁸₋₀.₀₂₆ R , 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 is 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) = 245 4856.701 18 ± 0.000 18 HJD and P = 2.899 738 ± 0.000 007 d. 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 and 1.81M⊕ in the interior and exterior 2:1 resonances, respectively, assuming the planets are initially in circular orbits.