Improved parameters for the transiting planet HD 17156b: a high-density giant planet with a very eccentric orbit

TL;DR

This study refines the parameters of HD 17156b, revealing it as a high-density giant planet with a notably eccentric orbit, based on combined high-precision photometry and radial velocity data analyzed through MCMC methods.

Contribution

The paper provides improved measurements of HD 17156b's mass, radius, and orbit, highlighting its high density and eccentricity with a comprehensive combined analysis approach.

Findings

Mass of 3.09 M_Jup with uncertainties

Radius of 1.23 R_Jup with uncertainties

High orbital eccentricity of 0.6719

Abstract

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.