Vol. 616
In section 8. Stellar atmospheres

Spatially resolved spectroscopy across stellar surfaces. III. Photospheric FeI lines across HD189733A (K1 V)

by D. Dravins, M. Gustavsson, and H.-G. Ludwig A&A 616, A144


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This paper presents spatially resolved, high spectral-resolution spectroscopy with the ESO HARPS, of photospheric Fe I lines over the stellar surface of the cool planet-hosting K1 V star, HD 189733A. This is possible during an exoplanet transit as successive portions of the stellar surface become hidden, and differential spectroscopy between these various transit phases provides spectra of small surface segments temporarily hidden behind the planet. This provides spectral line profiles that are free from rotational broadening, and so their gradual change from the center towards the stellar limb reflects the fine structure in the stellar atmosphere. These observations are compared to 3D hydrodynamic models to explore fine structure and 3D line formation in the atmosphere of this star. This detailed understanding is important to enable future searches for Earth-analogue exoplanets around K-type stars, where the more tranquilsurface granulation and lower ensuing micro-variability may allow suchdetections.