  The quasar 1156+295 (4C +29.45) is one of the targets in the Urumqi
monitoring program which aimed to search for evidence of annual modulation in
the timescales of intra-day variable (IDV) sources. The IDV observations of
1156+295 were carried out nearly monthly from October 2007 to October 2009,
with the Urumqi 25m radio telescope at 4.8 GHz. The source has shown prominent
IDV of total flux density in most observing sessions with variability
timescales of <= 1 day at 4.8 GHz. The estimated IDV timescales seem to follow
an annual cycle that can be fitted with an anisotropic interstellar
scintillation (ISS) model suggesting that a significant part of the flux
density variations is due to ISS. The source underwent a dramatic flare in
2008. We studied the possible consequences of the flare on the IDV of 1156+295
by comparing the changes in its IDV characteristics with the evolution of the
43 GHz Very Long Baseline Array (VLBA) core size of the source. Conclusions:
The quasar 1156+295 shows evidence for an annual modulation of its IDV
timescales at 4.8 GHz, the ISS-induced IDV timescales and variability strength
might be affected by the overall activity state of the source core. More
frequent IDV and VLBI measurements are required to confirm the relation between
the IDV appearance and the core-size evolution of the source.
