RADIO OBSERVATIONS OF THE GAMMA-RAY BLAZAR Q-0528+134

In this paper we report the insights on the nature on the gamma-ray qu asar 0528+134, which we obtained from a multifrequency radio monitorin g program. The radio observations were made with the Effelsberg 100-m telescope and the IRAM 30-m telescope between 1992 and 1996, and with the Green Bank Interferometer between 1992 and 1993. In this paper we also summarize the findings from VLBI observations up to now. The VLBI structure of 0528+134 typically shows a one-sided core jet structure of similar to 5 mas length. At least one component shows apparent supe rluminal motion with beta(app) = 4.4+/-1.7 (H-0 = 100 km s(-1) Mpc(-1) , q(0) = 0.5). Superluminal motion is expected since strong Doppler bo osting in this source is required in view of the gamma-ray luminosity and the variability timescale, which violate the compactness limit. In summer 1993 we observed a major outburst at all frequencies above a f ew GHz, which peaked a few months after a strong outburst in high ener gy gamma-rays and showed the canonical time evolution of a cooling and /or expanding electron distribution. In late 1995 the strongest ever o bserved radio outburst occurred, reaching the highest flux level of S = 11.9 +/- 0.15 Jy at 32 GHz on 12/8/95. Though 0528+134 has been repe atedly observed by EGRET during 1995, no similar chart-breaking gamma- ray outburst has been reported. Our data indicate that there is no one -to-one relation between the gamma-ray brightness and the radio flux l evel a short time later.