ABSORPTION OF VERY-HIGH-ENERGY GAMMA-RAYS BY INTERGALACTIC INFRARED RADIATION - A NEW DETERMINATION

We present a new calculation of the intergalactic gamma-ray pair-produ ction absorption coefficient as a function of both energy and redshift . In reexamining this problem, we make use of a new empirially based c alculation (as opposed to previous model calculations) of the intergal actic infrared radiation field (IIRF). We find smaller opacities than those given previously (Stecker & De Jager 1997). We apply our results to the new observations of the flaring gamma-ray spectra of Mrk 421 a nd Mrk 501, both at a redshift of similar to 0.03. Our new calculation s indicate that there should be no significant curvature in the spectr a of these sources for energies below 10 TeV, as indicated by recent o bservations. However, the intrinsic spectra of these sources should be harder by amounts of similar to 0.25 to 0.45 in the spectral index (i n the 1-10 TeV range), with an intergalactic absorption cutoff above s imilar to 20 TeV.