A search for 10 TeV γ-ray emission from 15 active galactic nuclei (AGNs) which were detected by EGRET was made with the Tibet air shower array installed at an elevation of 4300 m above sea level. The data set, taken in the period from 1990 June 18 through 1992 September 29 has been used to search for continuous emission as well as emission on the timescale of 1 day. No evidence for emission from any of the AGNs on any of the time scales examined was found. The 95% confidence level upper limit to the continuous flux is presented on each source, and in particular the result for Markarian 421 is compared with other experiments. Further observation of γ-rays at energies around 10 TeV from nearby AGNs will provide reliable information on the strength of the intergalactic background photon field.
|出版ステータス||Published - 1994 7月 10|
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