Context. Accurate parameters of the host stars of exoplanetsare needed for interpreting the new planetary systems. The CoRoTsatellite recently discovered a transiting rocky planet with a densitysimilar to the inner planets in our solar system, a so-called superEarth. The mass was determined using ground-based follow-upspectroscopy, which also revealed a second, non-transiting super Earth.Aims. These planets are orbiting a relatively faint (mV=11.7)G9V star called CoRoT-7. We wish to refine the determination of thephysical properties of the host star, which are important for theinterpretation of the properties of the planetary system. Methods. We used high-quality spectra from HARPS at theESO3.6m and UVES at the VLT8.2m. We usedvarious methods to analyse the spectra using 1DLTE atmosphericmodels. From the analysis of Fe I and Fe IIlines we determined the effective temperature, surface gravity andmicroturbulence. We used the Balmer lines to constrain the effectivetemperature and pressure-sensitive Mg1b and Ca lines to constrainthe surface gravity. We analysed both single spectra and co-add spectrato identify systematic errors. We determine the projected rotationalvelocity and macroturbulence by fitting the line shapes of isolatedlines. We finally determined an approximate absolute magnitude from theWilson-Bappu effect. Results. From the analysis of the three best spectra, we find K, ,,and kms-1.The chemical composition of 20 analysed elements is consistent withuniform scaling by the metallicity +0.12dex. From the analysis ofspectra of stars with well-known parameters with similar parameters toCoRoT-7 (the Sun and CenB) we demonstrate that our methods are robust within the claimed uncertainties. We compared the L/Mratio with isochrones to constrain the evolutionary status. Using theage estimate of 1.2-2.3Gyr based on stellar activity, wedetermine the mass and radius and .With these updated constraints we fitted the CoRoT transit light curvefor CoRoT-7b. The revised planet radius is slightly smaller, ,and the density becomes slightly higher, .Key words: stars: abundances - stars: late-type - stars: fundamental parameters
展开▼
