ELODIE metallicity-biased search for transiting Hot Jupiters I. Two Hot Jupiters orbiting the slightly evolved stars HD 118203 and HD 149143

We report the discovery of a new planet candidate orbiting the subgiant star HD 118203 with a period of P = 6.1335 days. The best Keplerian solution yields an eccentricity e = 0.31 and a minimum mass m₂ sin i = 2.1 M_Jup for the planet. This star has been observed with the ELODIE fiber-fed spectrograph as one of the targets in our planet-search programme biased toward high-metallicity stars, on-going since March 2004 at the Haute-Provence Observatory. An analysis of the spectroscopic line profiles using line bisectors revealed no correlation between the radial velocities and the line-bisector orientations, indicating that the periodic radial-velocity signal is best explained by the presence of a planet-mass companion. A linear trend is observed in the residuals around the orbital solution that could be explained by the presence of a second companion in a longer-period orbit. We also present here our orbital solution for another slightly evolved star in our metal-rich sample, HD 149143, recently proposed to host a 4-d period Hot Jupiter by the N2K consortium. Our solution yields a period P = 4.09 days, a marginally significant eccentricity e = 0.08 and a planetary minimum mass of 1.36 M _Jup. We checked that the shape of the spectral lines does not vary for this star as well.