COMPTEL Observation of the Flaring Quasar

With a direct demodulation method, we have reanalyzed the data from the COMPTEL observation of PKS0528+134 during the 1993 March flare in γ-rays. Our results show that during the flare γ-rays were detected at a level approximately 2.4-3.8 times higher than the observed intensity in two earlier COMPTEL observations VP 0 and VP 1 in the energy range 3 MeV to 30 MeV. The 3-30 MeV time variability of the flux follows well the trend as observed by EGRET at higher energies. No convincing excess can be found around the position of PKS0528+134 in the energy range 0.75 MeV to 3 MeV, which indicates a spectral break around 3 MeV. The detections and non-detections in the four standard COMPTEL energy bands are consistent with the earlier reports given by Collmar et al., while the feature that γ-rays of the quasar still kept on flaring at energies down to 3 MeV is clearly found.