COMPTEL DETECTION OF THE HIGH-ENERGY GAMMA-RAY SOURCE 2CG-135+01

We present an analysis of COMPTEL observations made between November 1 991 and May 1994 of 2CG 135+01, a bright gamma-ray source located near the Galactic plane. At energies above 1 MeV, an excess consistent wit h the position of 2CG 135+01 is detected in the sum of the observation s, at flux levels which are a factor of 10-100 below those published i n the past. The detection significance of this excess, when the possib le presence of underlying Galactic diffuse emission is neglected, is 6 .6 sigma for 3 degrees of freedom. The differential photon spectrum in the 1-30 MeV energy range can be described by a power law with a spec tral index of 1.95(-0.3)(+0.2). Due to the uncertainties involved in m odelling the Galactic-disk diffuse emission underneath the source, the absolute flux levels must be considered uncertain by a factor of two. They are consistent with the extrapolation of the time-averaged spect rum of 2CG 135+01 measured with EGRET, thereby strengthening the ident ification. No significant temporal correlation between the gamma-ray e mission and the monitored radio emission of the possible counterpart r adio source GT 0236+610 (showing a 26.5 day modulation) is found.