, Volume 45, Issue 4, pp 249-254

BL Lac: A new ultrahigh-energy gamma-ray source

Abstract

The active galactic nucleus BL Lac was observed with the GT-48 atmospheric Cherenkov detector of the Crimean Astrophysical Observatory from July 23–September 1, 1998, in order to search for ultrahighenergy gamma-ray (>1 TeV) emission. The object was in the field of view of the detector for more than 24 hours. The source was detected with a high level of confidence (7.2 σ) with a flux equal to (2.1±0.4)×10−11 photons cm−2 s−1.

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Translated from Astronomicheski \(\overset{\lower0.5em\hbox{\(\smash{\scriptscriptstyle\smile}\)}}{l}\) Zhurnal, Vol. 78, No. 4, 2001, pp. 291–297.
Original Russian Text Copyright © 2001 by Neshpor, Chalenko, Stepanian, Kalekin, Jogolev, Fomin, Shitov.