  We report high-precision transit photometry for the recently detected planet
HD 17156b. 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 M_p = 3.09 (+0.22-0.17)
M_Jup and radius R_p = 1.23 (+0.17-0.20) R_Jup for the planet places it at the
outer edge of the density distribution of known transiting planets with rho_p =
1.66 (+1.37-0.60) rho_Jup. The obtained transit ephemeris is T_tr =
2454438.48271 (+0.00077-0.00057) + N x 21.21747 (+0.00070-0.00067) BJD. The
derived plausible tidal circularization time scales for HD 17156b are larger
than the age of the host star. The measured high orbital eccentricity e =
0.6719 (+0.0052-0.0063) can thus not be interpreted as the clear sign of the
presence of another body in the system.
