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Limits on the TeV flux of diffuse gamma rays as measured with the HEGRA air shower array

HEGRA Collaboration·F. A. Aharonian
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Abstract

Using data from the HEGRA air shower array, taken in the period from April 1998 to March 2000, upper limits on the ratio I_gamma /I_CR of the diffuse photon flux I_gamma to the hadronic cosmic ray flux I_CR are determined for the energy region 20 TeV to 100 TeV. The analysis uses a gamma-hadron discrimination which is based on differences in the development of photon- and hadron-induced air showers after the shower maximum. A method which is sensitive only to the non-isotropic component of the diffuse photon flux yields an upper limit of I_gamma /I_CR (at 54 TeV) < 2.0*10^-3 (at the 90% confidence level) for a sky region near the inner galaxy (20 degrees < galactic longitude <60 degrees and |galactic latitude|<5 degrees). A method which is sensitive to both the isotropic and the non-isotropic component yields global upper limits of I_gamma /I_CR (at 31 TeV) <1.2*10^-2 and I_gamma /I_CR (at 53 TeV) < 1.4*10^-2 (at the 90% confidence level).

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HEGRA Collaboration, F. A. Aharonian. 2001-09-10. Limits on the TeV flux of diffuse gamma rays as measured with the HEGRA air shower array. https://arxiv.org/abs/astro-ph/0109145

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