Measurement of the multi-TeV gamma-ray flare spectra of Markarian 421 and Markarian 501

The energy spectrum of Markarian 421 in flaring states has been measured fr om 0.3 to 10 TeV using both small and large zenith angle observations with the Whipple Observatory 10 m imaging telescope. The large zenith angle tech nique is useful for extending spectra to high energies, and the extraction of spectra with this technique is discussed. The resulting spectrum of Mark arian 421 is fitted reasonably well by a simple power law: J(E)= E-2.54+/-0 .03+/-0.10 photons m(-1) s(-1) TeV-1, where the first set of errors is stat istical and the second set is systematic. This is in contrast to our recent ly reported spectrum of Markarian 501, which over a similar energy range ha s substantial curvature. The differences in TeV energy spectra of gamma-ray blazars reflect both the physics of the gamma-ray production mechanism and possibly differential absorption effects at the source or in the intergala ctic medium. Since Markarian 421 and Markarian 501 have almost the same red shift (0.031 and 0.033, respectively), the difference in their energy spect ra must be intrinsic to the sources and not due to intergalactic absorption , assuming the intergalactic infrared background is uniform.