IDV Observations & Study of the Quasar 0917+624
  We carried out intra-day variability (IDV) observations from August 2005 to
January 2010 with the Urumqi 25m radio telescope for a dozen IDV sources
including the quasar 0917+624. This target exhibited pronounced
centimeter-band, intra-day variability during the 1980s--1990s, but its strong
IDV phase ceased in 2000. The source showed no IDV in the majority of the
Urumqi observing sessions, although weak IDV activity was detected in some.
Multifrequency UMRAO data for 0917+624 show that the spectral index is steeper
during the weak and non-IDV phases than during the strong IDV phase, supporting
the idea that the size of the scintillating component may be enlarged in the
weak/non IDV phases.
