Characterization of the HD 17156 planetary system
  AIMS : To improve the parameters of the HD 17156 system (peculiar due to the eccentric and long orbital period of its transiting planet) and constrain the presence of stellar companions.   METHODS : Photometric data were acquired for 4 transits, and high precision radial velocity measurements were simultaneously acquired with SARG@TNG for one transit. The template spectra of HD 17156 was used to derive effective temperature, gravity, and metallicity. A fit of the photometric and spectroscopic data was performed to measure the stellar and planetary radii, and the spin-orbit alignment. Planet orbital elements and ephemeris were derived from the fit. Near infrared adaptive optic images was acquired with ADOPT@TNG.   RESULTS: We have found that the star has a radius of R_S = 1.43+/-0.03 R_sun and the planet R_P =1.02+/-0.08 R_jup. The transit ephemeris is T_c = 2454\756.73134+/-0.00020+N*21.21663+/-0.00045 BJD. The analysis of the Rossiter-Mclaughlin effect shows that the system is spin orbit aligned with an angle lambda = 4.8 +/- 5.3 deg. The analysis of high resolution images has not revealed any stellar companion with projected separation between 150 and 1000 AU from HD 17156. 
M. Barbieri, R. Alonso, S. Desidera, A. Sozzetti, A.F. Martinez   Fiorenzano, J. M. Almenara, M. Cecconi, R.U. Claudi, D. Ch...