  We report an increase of more than 0.2 mag in the optical brightness of the
leading image (A) of the gravitational lens Q0957+561, detected during the
09/2000 -- 06/2001 monitoring campaign (2001 observing season). The brightening
is similar to or even greater than the largest change ever detected during the
20 years of monitoring of this system. We discuss two different provisional
explanations to this event: intrinsic source variability or microlensing
(either short timescale microlensing or cessation of the historical
microlensing). An exhaustive photometric monitoring of Q0957+561 is needed
until summer of 2002 and during 2003 to discriminate between these
possibilities.

Astrophysics