Issue |
Astron. Astrophys. Suppl. Ser.
Volume 131, Number 2, August 1998
|
|
---|---|---|
Page(s) | 361 - 369 | |
DOI | https://doi.org/10.1051/aas:1998273 | |
Published online | 15 August 1998 |
Can interfero-polarimetry constrain extended atmospheres' models?
Observatoire de Haute-Provence, F-04870 Saint-Michel l'Observatoire, France
Send offprint request to: K. Rousselet-Perraut
Received:
24
April
1997
Accepted:
9
February
1998
Adding a polarimetric mode to a stellar interferometer enables to extend its
exploration capacities for extended circumstellar environments in which intrinsic polarization
becomes a non negligible observable. A general formalism is developed to map intensities and
corresponding visibilities in polarized light for any extended atmosphere. To constrain matter
distributions in scattering hot envelopes, an instrumental accuracy of 1% on the visibility is
required, which is compatible with the performances of existing instruments. This implies an
envelope flux contribution of 10 - 15% and limiting visual magnitudes Mv of 4 in a monospeckle
mode and of 8 - 10 in multispeckle modes, which allows to contemplate studying several hot
stars by this interfero-polarimetric technique. Finally, a specific instrumentation and an adapted
methodology are mandatory: observations at small spatial
frequencies () where
R* is the stellar radius), simultaneous recordings of the polarized interferograms and an
accurate calibration of the instrumental polarization. This technique can be applied to arrays of
few telescopes (such as the Very Large Telescope Interferometer - VLTI) as well as to
aperture synthesis arrays. Besides, such a polarimetric equipment must be advocated for the
future instruments since it greatly reduces the instrumental bias.
Key words: techniques: interferometric; polarimetric / stars: atmospheres; imaging
© European Southern Observatory (ESO), 1998