In the compact GRB model the e - e + pair is produced by two photons with energies E 1 and E 2, which in sum are above the threshold energy (E 1 + E 2 > 2 E th, E th = √ E 1 E 2 ) and where product E 1 E 2 is E 1 E 2 ≥ 2 (m e c 2 ) 2 /(1 – cos θ), 2(m e c 2 ) 2 = 2(511 кэВ) 2, and θ is an angle between directions of the two photons/rays.
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