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The 2009 Fermi Symposium

On the Location of the Blazar Zone in Fermi Blazars

Luigi Costamante


The location of the SED-peaks and Gamma-ray emitting region in blazars (so-called "blazar zone") is still uncertain. Some scenarios locate it inside the Broad Line Region (BLR), so to produce Gamma-rays through Comptonization of UV photons, while others locate it at large distances, where Comptonization of dust IR photons dominate. BLR photons however should typically imprint an absorption feature in the Gamma-ray spectra above 10 GeV (due to gamma-gamma absorption), and the different distances could yield different variability properties. Fermi-LAT is now detecting several FSRQ above 10 GeV, allowing for the first .me a test of the different scenarios. We will discuss the insights on the blazar-zone location that the Fermi spectra and lightcurves are providing.