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The quasar 1156+295 (4C +29.45) is one of the targets in the Urumqimonitoring program which aimed to search for evidence of annual modulation inthe timescales of intra-day variable (IDV) sources. The IDV observations of1156+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 prominentIDV of total flux density in most observing sessions with variabilitytimescales of <= 1 day at 4.8 GHz. The estimated IDV timescales seem to followan annual cycle that can be fitted with an anisotropic interstellarscintillation (ISS) model suggesting that a significant part of the fluxdensity variations is due to ISS. The source underwent a dramatic flare in2008. We studied the possible consequences of the flare on the IDV of 1156+295by comparing the changes in its IDV characteristics with the evolution of the43 GHz Very Long Baseline Array (VLBA) core size of the source. Conclusions:The quasar 1156+295 shows evidence for an annual modulation of its IDVtimescales at 4.8 GHz, the ISS-induced IDV timescales and variability strengthmight be affected by the overall activity state of the source core. Morefrequent IDV and VLBI measurements are required to confirm the relation betweenthe IDV appearance and the core-size evolution of the source.

Two-year monitoring of intra-day variability of quasar 1156+295 at 4.8 GHz