Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
K.-H. Hofmann, M. Scholz and P.R. Wood:
Limb-darkening and radii of M-type Mira
models
Astronomy and Astrophysics 339, 846-857 (1998)
Abstract.
Monochromatic limb-darkening and monochromatic radii predicted by the
M-type Mira models of Bessell et al. (1996) and by new models described
in
Sect. 2 were computed for selected typical bandpasses used in
interferometric
and lunar occultation work. The new self-excited pulsation model series
have
periods and luminosities similar to $o$ Ceti and R Leonis and comprise
both
fundamental (1 Msun, 1.2 Msun) and first overtone (2 Msun)
pulsators. Fundamental problems of defining and measuring radii of Mira
variables caused by the large extension of their atmospheres are
discussed.
Effective temperatures defined in terms of Rosseland and continuum
radii are
generally well determinable with an inherent inaccuracy of a few
percent, but
special problems occur for very cool models or at phases when models
are very
cool, below about 2500 K.
Fits of simple uniform disk (UD), fully darkened disk (FDD) and
Gauss-shaped
limb-darkening curves to the model-predicted visibilities were
performed and
tabulated for a set of 26x12 model-filter-combinations covering a
large variety of typical brightness distributions. These fits show that
either
the FDD or the Gauss curve is often a good or even excellent
approximation.
Limb-darkening curves for specific bandpasses of observational programs
can be
provided upon request.
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