Measuring starspots on magnetically active stars with the VLTI

M. Wittkowski, M. Schöller, S. Hubrig, B. Posselt, O. Von Der Lühe

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17 Scopus citations


We present feasibility studies to directly image stellar surface features, which are caused by magnetic activity, with the Very Large Telescope Interferometer (VLTI). We concentrate on late type magnetically active stars, for which the distribution of starspots on the surface has been inferred from photometric and spectroscopic imaging analysis. The study of the surface spot evolution during consecutive rotation cycles will allow first direct measurements (apart from the Sun) of differential rotation which is the central ingredient of magnetic dynamo processes. The VLTI will provide baselines of up to 200 m, and two scientific instruments for interferometric studies at near- and mid-infrared wavelengths. Imaging capabilities will be made possible by closure-phase techniques. We conclude that a realistically modeled cool surface spot can be detected on stars with angular diameters exceeding ∼ 2 mas using the VLTI with the first generation instrument AMBER. The spot parameters can then be derived with reasonable accuracy. We discuss that the lack of knowledge of magnetically active stars of the required angular size, especially in the southern hemisphere, is a current limitation for VLTI observations of these surface features.

Original languageEnglish (US)
Pages (from-to)241-250
Number of pages10
JournalAstronomische Nachrichten
Issue number3-4
StatePublished - 2002

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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