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Observing stellar surface structure with the ESO-VLT interferometer

Published online by Cambridge University Press:  25 May 2016

O. Von Der Lühe ,
S. Solanki  and
Th. Reinheimer
O. Von Der Lühe
Affiliation:
European Southern Observatory Karl-Schwarzschild-Str. 2, D - 85748 Garching
S. Solanki
Affiliation:
Institut für Astronomie ETH Zürich
Th. Reinheimer
Affiliation:
Max-Planck-Institut für Radioastronomie Auf dem Hügel 69, Bonn

Abstract

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The ESO Very Large Telescope (VLT) has the capability to coherently combine the light from four 8m telescopes and from smaller Auxiliary telescopes with baselines 4m and 200m (VLT Interferometer or VLTI). The resulting resolution approaches 0.5 milli-arcsec at visible wavelengths and 1 milli-arcsec in the near infra-red. We estimate that about 2000 nearby bright stars can be resolved with these baselines. The surface of about 400 stars, mainly K and M giants, can be mapped with a resolution of a dozen pixels or better across the stellar surface. This resolution permits detailed studies of the structure of stellar atmospheres, their hydrodynamics and magneto-hydrodynamics. VLTI can easily resolve starspots and very likely also convection cells on an active K-type giant at 10pc distance. A marginal detection of the largest starspots on a very active solar-type star at the same distance may be possible, but it appears very unlikely that the surface structure on an inactive solar-type star can be imaged.

We present computer simulations of stellar surfaces to study in detail the response of the interferometer to an extended, complex source. First results which simulate the end-to-end process in a simplified manner indicate that useful maps can be produced provided that a sufficient number of baselines are combined in Earth-rotation synthesis mode. We also give arguments that high spectral resolution will prove essential to constrain reconstructed maps.

Type
Session II: “Direct Mapping: The Last Frontier”
Information
Symposium - International Astronomical Union , Volume 176: Stellar Surface Structure , 1996 , pp. 147 - 164
Copyright
Copyright © Kluwer 1996 

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