Improved parameters for the transiting planet HD17156b: A high-density giant planet with a very eccentric orbit

Abstract

We report high-precision transit photometry for the recently detected planet HD17156b. Using these new data with previously published transit photometry and radial velocity measurements, we perform a combined analysis based on a Markov Chain Monte Carlo approach. The resulting mass Mp = 3.09-0.17+0.22 MJup and radius Rp = 1.23-0.20+0.17 RJup for the planet places it at the outer edge of the density distribution of known transiting planets with ρp = 1.66-0.60+1.37 ρJup. The obtained transit ephemeris is TTr = 2 454 438.48271-0.00057+0.00077+N × 21.21747-0.00067+0.00070 BJD. The derived plausible tidal circularization time scales for HD17156b are larger than the age of the host star. The measured high orbital eccentricity e = 0.6719-0.0063+0.0052 can thus not be interpreted as the clear sign of the presence of another body in the system.