Be objects are defined as stars of spectral type B, and luminosity classes
III to V, whose
spectra show, or have shown at some time, Balmer (and sometimes other) lines
in
emission. The origin of this emission is atomic transitions in a circumstellar
envelope,
relatively cool (
K) and relatively dense (
)
with a composition similar to that of the
stellar photosphere. The contribution of the circumstellar envelope has
dramatic effects upon the observables: the slope of the continuum is
distorted, the photospheric absorption lines are filled-in with an unknown
amount of circumstellar emission in such a way that it is very difficult to
deduce either the spectral type
of the underlying star or the actual amount of the emitting material, the line
profiles themselves are distorted and the photometric indices contaminated.
As a consequence we cannot apply the usual photometric and spectroscopic
techniques to derive the astrophysical parameters of the underlying star.
Our goal is to elaborate a method to determine the intrinsic parameters of Be
stars from 
photometry and Balmer line spectroscopy. A first
attempt to develop such a method was the work of Fabregat &
Reglero (1990) based on published studies of emission properties of
circumstellar
disks around Be stars. However the photometry and the spectroscopy were not
simultaneous. Since Be stars are known to be highly variable some
uncertainty is expected in the derived relationships. Thus, the latter authors
consider their calibration to be preliminary.
With this in mind we planned to build a set of stars with high quality
photometry and spectroscopy, as simultaneous as possible and with
accurate values of reddening and distance modulus. This latter requirement
was fulfilled by observing Be stars with well established membership of open
clusters so that both interstellar reddening and distance modulus can be
inferred from that of the cluster
(Mermilliod 1982; Slettebak 1985).
In Fabregat et al. (1996), hereafter
called Paper I, we presented the photometric measurements along with a careful
analysis of the data. One of the main results obtained was the observation of
a clearly different photometric behavior between Be stars earlier than B5V
and later ones. This fact, of course, is expected to contribute to the
uncertainty of the above mentioned calibration.
In the present paper we present the spectroscopy and analyze the data as far as the available resolution makes it possible, mainly in order to guarantee the homogeneity of the sample. Further work will include the elaboration of a calibration valid for Be type stars, the determination of astrophysical parameters for circumstellar envelopes and their modeling.