ON THE ROTATION PROPERTIES OF BE STARS AND THEIR ENVELOPES

We present the results of low resolution spectroscopy (4 angstrom) obtained at CTIO for a sample of 42 Be, 4 B and 3 O stars covering the lambda 3700-7000 angstrom spectral range. Equivalent widths of the Balmer lines were measured up to H10. We also give the V/R state of the Halpha emission line. In addition, the peak separation and the width at the base of the Hbeta and Hgamma emission lines are tabulated for a total of 243 medium resolution (1 angstrom) spectra of 51 southern Be stars taken at the Manuel Foster Observatory, Chile. We analyzed our Halpha equivalent widths (Walpha) together with published data for a total of 122 Be and 2 Oe stars. An upper limit of Walpha incrasing with the projected rotational velocity v sin i is shown by the data. The Walpha values depend strongly on spectral type, being lower for later-type Be stars. This could indicate that the maximum strength of emission depends mainly on the spectral type and rotation velocity. The relation between Walpha (max) and v sin i, together with the observed excess in number of low v sin i Be stars and the reported anti-correlation between photometric period and v sin i give evidence for a considerable range of the true rotation velocities of Be stars: definitely there are intrinsically slow rotators among them. However, our results could also be interpreted in terms of anisotropic Halpha emission coming from the disk. The analysis of the net equivalent widths and peak separations of Halpha double emission line profiles strongly favor a disk type emitting envelope with a r(-j) rotation law with j = 1.4 +/- 0.2 which do not depend on the spectral subtype. This result is interpreted as evidence of radial motions in the envelopes of Be stars. The mean radial extensions of the regions which emit Balmer lines were determined to range between 30% (H10) and 60% (Hbeta) of the Halpha emitting envelope in the case j = 1. The mean electron density within the envelope has been found to vary only by a factor of 4. We compare our results with earlier investigations.