On the eccentricity of HD 209458b

.We report 85 high-precision Doppler radial velocity measurements taken between 1999.5 and 2005.0 of the parent star of the transiting planet HD 209458b. We obtain an orbital fit to the 68 radial velocities taken out of transit and derive planetary parameters,, and ( with e = 0.014 +/- 0.009 omega = 80 degrees +/- 80 degrees M-pl (0.69 +/- 0.06) M-Jup (with M-* = 1(.)14 +/- 0.10 M circle dot). We perform orbital fits to synthetic data sets based on known planetary parameters, and we find that our measured eccentricity is consistent with eccentricities estimated from synthetic e p 0.014 radial velocity data sets generated by planets fixed on circular orbits. The orbital model that we derive suggests that structurally significant tidal heating in the interior of the planet is probably not occurring. Furthermore, the current set of radial velocities shows no evidence for additional bodies in the system.