Variability in the Nucleus of NGC 1068

The near-infrared output of the nucleus of NGC 1068 increased by a factor of two over the 18 years between 1976 and 1994 and has recently started to decline. It is not clear whether this event has been the response of an extended dusty region to a single outburst in the central engine or is the result of a continuous change in its XUV output. The integrated energy of the event amounts to well over 1052 erg and thus cannot be due to a single supernova. The variable part of the infrared flux from NGC 1068, observed through an aperture of constant diameter, is found to have a constant spectral shape. Comparison with similar data from other Seyfert galaxies shows that the variable infrared component in NGC 1068 is reddened by about 20 mag in Av if the emission mechanism is similar in all cases. This revised version was published online in July 2006 with corrections to the Cover Date.