There are several hundred Be stars in the ARAS Beam
database between mag 9 and 12 (the estimated lower limit for
obtaining high S/N spectra with the Star Analyser at Three Hills Observatory).
Most have either no data or only old data from over 5 years ago. This could
prove a fertile area for amateurs interested in checking the current status of
these stars.
The latest spectrum of HD216629 in the ARAS Beam database is
dated1997 so an update is overdue. At Mag 9.3 however it is outside the range of
most amateur medium resulution spectrographs. A low resolution spectrum can
easily be obtained however using the Star Analyser grating. While not
showing the detailed line profile, it should be possible to make
an estimate of the strength of any emission line to flag any
needing follow up measurements.
The Star Analyser spectrum was
reduced in the usual way and finally normalised using a fit to the
continuum so that the lines strengths relative to the continuum could be
compared. Spectra taken from the OHP ELODIE database from
1994-1997 are shown normalised in the same way for comparison.
(Note,
the ELODIE spectra are at much higher resolution than the Star
Analyser (~40000 compared with ~100) A Gaussian filter was applied to the
ELODIE results to simulate the Star Analyser resolution.
There is good
agreement between the features in the current spectrum taken with the Star
Analyser and those taken 1994-1997 using ELODIE. In particular, the H
alpha emission line is of similar strength with a perhaps 20% weakening
curently compared with the earlier spectra, though this may be within the error
of the technique. (The slight fine scale ripple in the Star Analyser spectrum is
though to have been produced by the algorithm used to rotate the image prior to
extracting the spectral data)
For completeness here is a high
resolution plot of the H alpha region from the 1997 spectrum in the ELODIE
Archive
