Astron. Astrophys. Suppl. Ser. 141, 65-77
J.S. Clark1 and I.A. Steele2
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1 - Astronomy Centre, CPES, University of Sussex, Brighton, BN1 9QH,
UK
2 - Astrophysics Research Institute, Liverpool John Moores
University, Liverpool, L41 1LD, UK
Received February 16; accepted September 29, 1999
m - 2.22 m) spectra of 66 isolated Be stars
of spectral types O9-B9 and luminosity classes III, IV & V.
We find that objects with
He I features either in emission or absorption are
B3 or earlier. Objects with Mg II emission but no He I are
B2 to B4, while objects with Br
emission but no evidence
of He I or Mg II are B5 or later.
Na I
emission in the spectra of 4 objects appears to indicate that regions
of the circumstellar envelopes of these stars must be shielded from
direct stellar radiation.
Systematic trends in the line strength
and profile of Br
are seen from early to late spectral types which
can be understood in terms of differences in the disc temperature
and density.
30 per-cent of the stars do not currently show evidence for line
emission. Compared to the emission line stars these objects have a
significantly lower mean rotational
velocity and a distribution
of spectral types that is significantly earlier.
This can be explained either as the
original misidentification of these objects as Be stars (i.e. they
never had line emission), or as evidence that stars with lower rotational
velocities may be more prone to changes between the Be and B phases.
Key words: stars: emission-line, Be -- infrared: stars
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