2011A&A...525A..54B

We report the discovery of WASP-38b, a long period transiting planet in an eccentric 6.871815 day orbit. The transit epoch is 2455335.92050±0.00074 (HJD) and the transit duration is 4.663h. WASP-38b's discovery was enabled due to an upgrade to the SuperWASP-North cameras. We performed a spectral analysis of the host star HD 146389/BD+10 2980 that yielded T_eff=6150±80K, logg=4.3±0.1, vsini=8.6±0.4km/s, M_*=1.16±0.04M_☉ and R_*=1.33±0.03R_☉, consistent with a dwarf of spectral type F8. Assuming a main-sequence mass-radius relation for the star, we fitted simultaneously the radial velocity variations and the transit light curves to estimate the orbital and planetary parameters. The planet has a mass of 2.69±0.06M_Jup and a radius of 1.09±0.03R_Jup giving a density, ρ_p=2.1±0.1ρ_J. The high precision of the eccentricity e=0.0314±0.0044 is due to the relative transit timing from the light curves and the RV shape. The planet equilibrium temperature is estimated at 1292±33K. WASP-38b is the longest period planet found by SuperWASP-North and with a bright host star (V=9.4mag), is a good candidate for followup atmospheric studies.