Be stars in open clusters .1. uvby beta photometry

We present uvby beta photometry for Be stars in eight open clusters and two OB associations. It is shown that Be stars occupy anomalous positions in the photometric diagrams, which can be explained in terms of the circumstellar continuum radiation contribution to the photometric indices. In the (b - y)(0) - M(V) plane Be stars appear redder than the non emission B stars, due to the additional reddening caused by the hydrogen free-bound and free-free recombination in the circumstellar envelope. In the c(0)- M(V) plane the earlier Be stars present lower c(0) values than absorption-line B stars, which is caused by emission in the Balmer discontinuity, while the later Be stars deviate towards higher co values, indicating absorption in the Balmer discontinuity of circumstellar origin.