Cool Stars 14 - Submitted Abstract # 92
This version created on 05 October 2006

Near-infrared H and K band Spectroscopy of a Selection of AGB Stars


Boddapati Anandarao, Physical Research Laboratory, Ahmedabad, India
Venkat Raman, Physical Research Laboratory, Ahmedabad, India

During their asymptotic giant branch (AGB) stage, intermediate mass
stars undergo substantial mass loss triggered by pulsational shocks
and radiation pressure.  Near-infrared spectroscopy is one of the
recognised tools to study the mass loss process.  We have carried out
H and K band spectroscopy at Mt Abu observatory (in Western India)
using the NICMOS camera/spectrograph at R = 1000  on a sample of more
than 60  AGB stars of different types:  M types, S types, SR types and
a few post-AGB stars or transition objects.  We present here results
on equivalent widths of various spectral lines and discuss these in
the light of the intrinsic properties of these stars like the
pulsation period and near and far infrared colours.  We also present
modelling of circumstellar matter in a number of these stars in order
to determine the mass loss rate and dust optical depths.  A clear
difference is seen in these parameters in different types of AGB
stars.  Implications of these results will be discussed in terms of
evolution of these stars.

----------------------------------