Multiband photometry of the blazar PKS 0537-441: a major active state in December 2004–March 2005

Abstract

Multiband VRIJHK photometry of the Blazar PKS 0537-441 obtained with the REM telescope from December 2004 to March 2005 is presented. A major period of activity is found with more than four magnitudes variability in the V filter in 50 days and of 2.5 in 10 days. In intensity and duration the activity is similar to that of 1972 reported by Eggen (1973, ApJ, 186, 1), but it is much better documented. No clear evidence of variability on time-scale of minutes is found. The spectral energy distribution is roughly described by a power-law, with the weaker state being the softer.