1999A&A...352L.107K

We observed the quasar 0917+624 at three epochs at a wavelength of 6cm in order to study its short-timescale variability. In December 1997 and February 1999, the source showed its usual characteristics: variations on a 10-15% level have been found on timescales ≤1.5days. In contrast, in September 1998 the source exhibited a monotonic increase of about 7% during a five-day-observing campaign. Assuming an intrinsic origin of the variations, this corresponds to a change in brightness temperature of at least two orders of magnitude. We discuss shortly several mechanisms which may cause the observed change of the variability properties of 0917+624.