SIMBAD references

We present near-simultaneous (within one week) high-resolution Hα spectra and near-infrared photometry of 69 B and Be stars. We confirm that, for the Be stars, the infrared excess and Hα emission are correlated, albeit with a rather large scatter. Given the near-simultaneity of our observations, this scatter probably is not related to intrinsic variability, but rather reflects a genuine star-to-star variation in physical conditions. In order to derive information about the density and velocity structure of Be star discs, we calculate theoretical infrared excesses, Hα equivalent widths and Hα line profiles for two different models. We find that the model used by Poeckert & Marlborough (1978a) to fit the spectrum of γ Cas, is not capable of reproducing the observed correlation between the infrared excess and the excess Hα equivalent width, producing - for given infrared excess - Hα emission lines that are weaker than observed. The model of Waters (1986), used successfully to fit the infrared excess continuum emission of Be stars, also fails, producing Hα emission lines that are too strong. We discuss these results in terms of the density structure of the wind.