Radio observations of the first three-month Fermi-AGN at 4.8 GHz

Abstract

Using the Urumqi 25m radio telescope, sources from the first three-month Fermi-LAT detected AGN catalog with declination >0 were observed in 2009 at 4.8 GHz. The radio flux density appears to correlate with the gamma-ray intensity. Intra-day variability (IDV) observations were performed in March, April and May in 2009 for selected 42 gamma-ray bright blazars, and 60% of them show evident flux variability at 4.8 GHz during the IDV observations, the IDV detection rate is higher than that in previous flat-spectrum AGN samples. The IDV appears more often in the VLBI-core dominant blazars, and the non-IDV blazars show relatively `steeper' spectral indices than the IDV blazars. Pronounced inter-month variability has been found in two BL Lac objects: J0112+2244 and J0238+1636.Comment: 10 pages, 3 figures, accepted for publication in RA