Early Fermi Gamma-ray Space Telescope Observations of the Quasar 3C 454.3
Fermi/LAT Collaboration: A. A. Abdo, et al

TL;DR
Fermi Telescope observations of quasar 3C 454.3 reveal highly variable gamma-ray emission with spectral breaks, providing insights into relativistic jet physics and particle energy distributions in blazars.
Contribution
First direct detection of a spectral break in a high luminosity blazar above 100 MeV, indicating intrinsic particle energy distribution features.
Findings
Gamma-ray flux varies by factors of several over days.
Spectrum shows a significant break above 2 GeV, best described by a broken power-law.
Relativistic beaming with Doppler factor >8 is consistent with observations.
Abstract
This is the first report of Fermi Gamma-ray Space Telescope observations of the quasar 3C 454.3, which has been undergoing pronounced long-term outbursts since 2000. The data from the Large Area Telescope (LAT), covering 2008 July 7 - October 6, indicate strong, highly variable gamma-ray emission with an average flux of ~3 x 10^{-6} photons cm^{-2} s^{-1}, for energies above 100 MeV. The gamma-ray flux is variable, with strong, distinct, symmetrically-shaped flares for which the flux increases by a factor of several on a time scale of about three days. This variability indicates a compact emission region, and the requirement that the source is optically thin to pair-production implies relativistic beaming with Doppler factor delta > 8, consistent with the values inferred from VLBI observations of superluminal expansion (delta ~ 25). The observed gamma-ray spectrum is not consistent with…
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