VLBI polarization observations of intraday variability

Abstract

Global λ6 cm VLBI polarization observations of the intraday variable sources 0716+714, 0917+624, and 0954+658 are analyzed. Integrated VLA measurements during the VLBI observations suggest that although there were no substantial total intensity variations, the polarization for all three sources varied significantly during the 24 h VLBI experiment. The VLBI data were divided into 2–3 h segments in order to identify corresponding rapid variability in the VLBI structure. There is evidence that the polarization variability indicated by the VLA measurements of 0917+624 is present in the VLBI data (i.e. it occurred on mas scales), but this is not the case for the other two sources.