2010MNRAS.401.1917G

We present seven light curves of the exoplanet system HAT-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 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°, the planet-star radius ratio to be R_p/R_*= 0.1098^+0.0010_–0.0012 and the stellar radius to be R_*= 0.834^+0.018_–0.026R_☉, 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) = 2454856.70118 ±0.00018 HJD and P = 2.899738±0.000007 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 1.81 M_⊕ in the interior and exterior 2:1 resonances, respectively, assuming the planets are initially in circular orbits.