BROAD-BAND OPTICAL OBSERVATIONS OF BL LACERTAE DURING THE 1997 OUTBURST

We present BVRI observations of BL Lacertae during its recent outburst . These observations, made during a 3 month period, cover a significan t portion of the optical flare. The reduced data are displayed as ligh t curves and broadband spectra. Changes in the spectral index are anal yzed, and the results are compared with previous BL Lac observations. We find that the variations are simultaneous in the optical bands, but the higher frequency bands show a higher amplitude of variability. Th e spectral index is variable during the active period, and there is ma rginal evidence that the spectrum flattens as the source gets brighter .