A search for hard X-rays from five strong extragalactic radio sources

Data from the University of California at San Diego (UCSD) hard X-ray instrument on OSO-7 have been used to search the regions containing 3C 390.3, M87, 3C 273, 3C 111, and 3C 129. We have a weak detection of 3C 390.3 and a possible detection of 3C 111. Sensitive upper limits on hard X-rays have been obtained for the other objects. The available observational data indicate a correlation between hard X-ray emission, self-absorbed gigahertz radio emission, and strong optical emission lines in extragalactic sources. Self-Compton X-ray models have been calculated for the sources observed in this paper, and the angular sizes, lifetimes, and B fields in these sources have been estimated. These model calculations agree with existing VLBI and time variability data.