Publications of the MPIfR
Optical & Infrared
Interferometry Group
Wittkowski, M., Boboltz, D.A., Driebe,
T., Ohnaka, K.
Multi-wavelength interferometry of evolved
stars using VLTI and VLBA
"ESO Astrophysics Symposia"
Proceedings of the ESO Workshop: "The power of
optical/IR interferometry: recent scientific results and 2nd generation
VLTI instrumentation"
April 4-8, 2005 in Garching, Germany
pg.61-70 (2008)
Abstract
We report on our project of coordinated VLTI/VLBA observations of the
atmospheres and circumstellar environments of evolved stars. We
illustrate in general the potential of interferometric measurements to
study stellar atmospheres and envelopes, and demonstrate in particular
the advantages of a coordinated multi-wavelength approach including
near/mid-infrared as well as radio interferometry. We have so far made
use of VLTI observations of the near- and mid-infrared stellar sizes
and of concurrent VLBA observations of the SiO maser emission. To date,
this project includes studies of the Mira stars S Ori and RR Aql as
well as of the supergiant AH Sco. These sources all show strong
silicate emission features in their mid-infrared spectra. In addition,
they each have relatively strong SiO maser emission. The results from
our first epochs of S Ori measurements have recently been published and
the main results are reviewed here. The S Ori maser ring is found to
lie at a mean distance of about 2 stellar radii, a result that is
virtually free of the usual uncertainty inherent in comparing
observations of variable stars widely separated in time and stellar
phase. We discuss the status of our more recent S Ori, RR Aql, and AH
Sco observations, and present an outlook on the continuation of our
project.
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