  CONTEXT: High-resolution spectroscopy across spatially resolved stellar
surfaces aims at obtaining spectral-line profiles that are free from rotational
broadening; the gradual changes of these profiles from disk center toward the
stellar limb reveal properties of atmospheric fine structure, which are
possible to model with 3-D hydrodynamics. AIMS: Previous such studies have only
been carried out for the Sun but are now extended to other stars. In this work,
profiles of photospheric spectral lines are retrieved across the disk of the
planet-hosting star HD209458 (G0V). METHODS: During exoplanet transit, stellar
surface portions successively become hidden and differential spectroscopy
provides spectra of small surface segments temporarily hidden behind the
planet. The method was elaborated in Paper I, with observable signatures
quantitatively predicted from hydrodynamic simulations. RESULTS: From
observations of HD209458 with spectral resolution R=80,000, photospheric FeI
line profiles are obtained at several center-to-limb positions, reaching
adequately high S/N after averaging over numerous similar lines CONCLUSIONS:
Retrieved line profiles are compared to synthetic line profiles. Hydrodynamic
3-D models predict, and current observations confirm, that photospheric
absorption lines become broader and shallower toward the stellar limb,
reflecting that horizontal velocities in stellar granulation are greater than
vertical velocities. Additional types of 3-D signatures will become observable
with the highest resolution spectrometers at large telescopes.
