1996A&A...314...87M

The results of a photometric monitoring in the B, V, R_C, I_C bands of the BL Lac object PKS 0422+004 performed in the autumn-winter 1994/95 are presented. The source exhibited variations greater than 2 magnitudes and reached its historical brightness maximum. The light curve can be described by a superposition of a long term change with a time scale of 60-80days and a series of outbursts, with a typical duration of 9-12days; the time profiles of the outbursts are characterized by quite similar rising/decay times (typically 5-6days) and by a maximum brightness phase shorter than 1-2days. The spectral slopes, derived from the broad band energy distributions, are found to be correlated with the flux level and the changes are in the direction of a flattening when the source luminosity increases. Some considerations on homogeneous, one-zone models and inhomogeneous jet models, based on the outburst structure are developed.