A representative sample of Be stars IV: Infrared Photometry and the Continuum Excess

Abstract

We present infra-red (JHK) photometry of 52 isolated Be stars of spectral types O9--B9 and luminosity classes III--V. We describe a new method of reduction, enabling separation of interstellar reddening and circumstellar excess. Using this technique we find that the disc emission makes a maximum contribution to the optical (B-V) colour of a few tenths of a magnitude. We find strong correlations between a range of emission lines (H\alpha, Br\gamma, Br11, and Br18) from the Be stars' discs, and the circumstellar continuum excesses. We also find that stellar rotation and disc excess are correlated.