Up: H observations of Be
Be stars are rapid rotating, early type stars
characterised by Balmer line emission and IR excess. They
exhibit irregular variability both, spectroscopically and
photometrically. They are surrounded by a gaseous envelope, which is
photoionized by the radiation from the central star. The subsequent
recombination process gives rise to the hydrogen line emission. The
emission line profiles of Be stars show a variety of shapes. One
of the earliest models to explain these profiles
was the rotational model by Struve (1931). Since then many
emission line spectroscopic studies have been made to understand the Be
phenomenon - particularly the process of envelope formation - and
the physical parameters of the disk like its shape, size and
kinematics.
Though great progress has been made in explaining the line profiles, by
invoking general physical mechanisms,
there are still certain aspects which are not well understood. Hummel
& Dachs (1992) and Hummel (1994) have proposed an
elegant mechanism
which largely explains as to how symmetric profiles of the winebottle
through the shell type, and their variations in between, can be
generated by the same optically thick Keplerian envelope when viewed
from different angles. One of the objectives of the present study is
to see how observational data agree with the scenario put forward by
Hummel (1994). Towards this end, we have acquired high resolution
H
profiles for a sample of 44 Be stars. Given the latitude of
our observatory (24.653
N), both, the northern and the mid-southern
declination sources are accessible in the sky, and this is reflected in
the choice of our sources.
The other objective behind this study was the idea of building up, or
filling in the gaps in, the database of the emission line profiles of Be
stars, particularly that for the temporal variability of the line
profiles. The atlas by Hanuschik et al. (1996) shows that significant
variations can occur in the profiles over protracted periods. Our data
is intended to make an additional input for any comprehensive model, that
may be constructed, for explaining the variability. Incidentally,
concurrent with this study and with a view to getting a more complete
picture, a near IR spectroscopic survey of about 30 Be stars was also
made at a medium resolution (R = 1000). Some of the preliminary
results on this may be found in Ashok & Banerjee (2000).
![\begin{figure}
\par\includegraphics[width=16.5cm,clip]{h2226f1.eps}\end{figure}](/articles/aas/full/2000/20/h2226/Timg8.gif) |
Figure 1:
Plots of the line profiles of different Be stars.
The intensity plotted on the Y axis is relative and
in units of the continuum level
|
![\begin{figure}
\par\includegraphics[width=16.5cm,clip]{h2226f2.eps} \end{figure}](/articles/aas/full/2000/20/h2226/Timg9.gif) |
Figure 2:
Plots of the line profiles of different Be stars.
The intensity plotted on the Y axis is relative and
in units of the continuum level
 |
![\begin{figure}
\par\includegraphics[width=16.5cm,clip]{h2226f3.eps}\end{figure}](/articles/aas/full/2000/20/h2226/Timg10.gif) |
Figure 3:
Plots of the line profiles of different Be stars.
The intensity plotted on the Y axis is relative and
in units of the continuum level
 |
![\begin{figure}
\par\includegraphics[width=16.5cm,clip]{h2226f4.eps}\end{figure}](/articles/aas/full/2000/20/h2226/Timg11.gif) |
Figure 4:
Plots of the line profiles of different Be stars.
The intensity plotted on the Y axis is relative and
in units of the continuum level
 |
![\begin{figure}
\par\includegraphics[width=16.5cm,clip]{h2226f5.eps}\end{figure}](/articles/aas/full/2000/20/h2226/Timg12.gif) |
Figure 5:
Plots of the line profiles of different Be stars.
The intensity plotted on the Y axis is relative and
in units of the continuum level
 |
![\begin{figure}
\par\includegraphics[width=16.5cm,clip]{h2226f6.eps}\end{figure}](/articles/aas/full/2000/20/h2226/Timg13.gif) |
Figure 6:
Plots of the line profiles of different Be stars.
The intensity plotted on the Y axis is relative and in
units of the continuum level
 |
![\begin{figure}
\par\includegraphics[width=16.5cm,clip]{h2226f7.eps}\end{figure}](/articles/aas/full/2000/20/h2226/Timg14.gif) |
Figure 7:
Plots of the line profiles of different Be stars.
The intensity plotted on the Y axis is relative and
in units of the continuum level
 |
![\begin{figure}
\par\includegraphics[width=16.5cm,clip]{h2226f8.eps} \end{figure}](/articles/aas/full/2000/20/h2226/Timg15.gif) |
Figure 8:
Plots of the line profiles of different Be stars.
The intensity plotted on the Y axis is relative and in
units of the continuum level
 |
Up: H observations of Be
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