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Astron. Astrophys. 351, 627-634 (1999)
Irregular variables of type Lb
Energy distributions and stellar parameters
F. Kerschbaum
Institut für Astronomie der Universität Wien, Türkenschanzstrasse 17, 1180 Wien, Austria
Received 18 August 1999 / Accepted 28 September 1999
Abstract
AGB variables of types Lb, SRa, SRb, and Mira are studied by
fitting combinations of blackbodies to visual, near infrared and IRAS
data. This paper supplements an earlier work dealing with a smaller
sample of SRa and SRb variables. The fitted parameters
![[FORMULA]](img1.gif)
, ![[FORMULA]](img2.gif)
and
![[FORMULA]](img3.gif)
are related to physically meaningful
quantities. Also, quantities derived from the fits like the ratio of
the luminosities of the two fitted blackbodies are confronted with
independent mass-loss estimators.
For the O-rich Lb variables all of the `blue' objects can be
reasonably well approximated by only one blackbody whereas the `red'
ones need two. Among the `blue' objects a significant fraction seem to
be not on the AGB at all but a kind of `RGB pollution'. The
values, reflecting mainly offseted
(-500 K) effective temperatures for objects with small to moderate
mass-loss, are significantly higher in the `blue' cases.
Carbon-rich objects differ significantly from the O-rich ones in
their fit parameters. Sometimes `unphysically' low
are found - a result of circumstellar
reddening in the high mass-loss cases. Furthermore lower values of
, accompanied by normal
s and large shell radii are common and
can be related to the phenomenon of detached shells. S-stars populate
a similar region to the optically thin carbon stars in their fit
properties.
Key words: stars: AGB and
post-AGB 
stars: variables:
general
stars:
mass-loss
infrared: stars
Send offprint requests to: kerschbaum@astro.univie.ac.at
Contents
© European Southern Observatory (ESO) 1999
Online publication: November 3, 1999
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