DETECTION OF GAMMA-RAYS ABOVE 1.5 TEV FROM MKN-501

A detection of TeV gamma-rays from Mkn 501 is reported, based on obser vations made between March and August 1996 with the first HEGRA Cheren kov telescope (CT1). From the image analysis, 351 excess candidate gam ma-ray events are obtained from the 147 h dataset. The statistical sig nificance of the excess is 5.2 sigma. The average excess rate is 2.4 /- 0.5 h(-1) above the approximate to 1.5 TeV threshold of CT1. Under the assumption that the spectrum of Mkn 501 follows a power law we fin d a differential spectral index of 2.6 +/- 0.5 and obtain a time-avera ged integral flux above 1.5 TeV of 2.3(+/-0.4)(Stat)(+1.5 - 0.6)(Syst) x 10(-12) cm(-2) s(-1). Comparison with our near contemporary observa tions of the Crab Nebula, used as a standard candle to test CT1 after upgrading to a 127 pixel camera, indicates that Mkn 501 has a spectrum similar to that of the Crab Nebula above 1.5 TeV. The integral flux a bove 1.5 TeV from Mkn 501 is found to have been between 2.2 and 3.6 ti mes smaller than that from the Crab Nebula. HEGRA is the second experi ment to have detected Mkn 501 in the TeV range.