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Blazars display strong variability in their intensity and spectra. For the study of EBL attenuation, blazar
variability is both a nuisance and an opportunity. Variability is a nuisance because measuring the spectral steepening of a source is more difficult when such spectrum is changing constantly. In the case of the LAT, or any
other space-based instrument, a precise measurement of the high energy spectrum of a source requires long integration times, and thus, the time-average steepening is what is actually measured. The impact of blazar variability has already been probed with the simulation and analysis described above, and as can be seen, it did not prevent a correct determination of the collective level of EBL attenuation experienced by blazars as
a function of redshift. It should be noted however, that blazar variability is not well understood (this is something that GLAST will measure), and that the variability model used in the simulation might differ significantly from reality. Blazar variability could also represent an advantage. The energy cut-off observed in a given blazar should be the same independently of the flaring state of the source, if due to EBL absorption. This would constitute a powerful check of the effectiveness of individual blazars as probe of the EBL.
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