On the optical--infra-red continuum emission
from equatorial discs of supergiant B[e] stars
John M. Porter
Astrophysics Research Institute, Liverpool John Moores
University, Twelve Quays House, Egerton Wharf, Birkenhead, CH41 1LD,
United Kingdom
Two models of the circumstellar disc around supergiant B[e] stars are
discussed: an equatorial wind model produced by wind bi-stability, and
a Keplerian viscous disc model. Both models are successful in
providing a site for dust formation once they have cooled
sufficiently. However, the optical--infra-red continuum is calculated
and it is found that both models have significant trouble in
accounting for observations. In particular the optical--near-IR
emission is accounted for, but the dust emission is underestimated by
at least an order of magnitude. Variations in the structure of the
models (the temperature variation with radius, the density structure
and the dust opacity) are investigated to assess how (in)appropriate
the standard models are for supergiant B[e] star discs. Changing the
temperature structure, and making simple dust opacity changes within
the disc has little effect on the resultant continuum emission. By
altering the density structure of the discs, the continuum may be
accounted for by both models: the equatorial wind model requires a
very flat density profile which is impossible to explain with any
accelerating wind, and the viscous disc model's density structure is
required to fall off less steeply with radius than would have been
expected, although this may be explained from consideration of viscous
processes in the disc. It is recognised that both theoretical
interpretations have difficulties and unsolved problems.
Accepted by A&A
Preprints from
jmp@astro.livjm.ac.uk
or on the web at
http://arXiv.org/abs/astro-ph/0211449
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