VLBA Monitoring of 3C 273 and 3C 279 During INTEGRAL Campaigns

The gamma-ray blazars 3C 273 and 3C 279 were ob- served with the Very Long Baseline Array (VLBA) over seven epochs during the year 2003 as a part of support- ing observations for two INTEGRAL campaigns targeted on these sources. The VLBA observations were carried out in a full multi-wavelength polarimetric mode yield- ing total and polarized intensity maps at six frequencies ranging from 5 to 86 GHz. The VLBA maps probe the emission of the parsec scale jets in the angular scales of 0.1 - 50 mas, providing information about the dynam- ical state of the jets close to the central engine. As the gamma-ray emission above 100 keV is likely to be jet related, the co-ordinated VLBA observations give a pos- sibility to correlate the gamma-ray flux variations with the structural changes in the jet and, furthermore, with the flux and spectral variations of the individual syn- chrotron emitting components. Possible correlations can help to pinpoint the region where the gamma-ray emis- sion originates, and also establish the source of seed pho- tons for the inverse Compton process. We describe here the VLBA observations and present the first fully cali- brated maps together with a preliminary analysis.