Title: Early Fermi Gamma-ray Space Telescope Observations of the Quasar 3C454.3

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 {approx} 3 x 10{sup -6} photons cm{sup -2} s{sup -1}, for energies > 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} {approx} 25). The observed {gamma}-ray spectrum is not consistent with a simple power-law, but instead steepens strongly above {approx} 2 GeV, and is well described by a broken power-law with photon indices of {approx} 2.3 and {approx} 3.5 below and above the break, respectively. This is the first direct observation of a break in the spectrum of a high luminosity blazar above 100 MeV, and it is likely directmore » evidence for an intrinsic break in the energy distribution of the radiating particles. Alternatively, the spectral softening above 2GeV could be due to -ray absorption via photonphoton pair production on the soft X-ray photon field of the host AGN, but such an interpretation would require the dissipation region to be located very close ({approx}< 100 gravitational radii) to the black hole, which would be inconsistent with the X-ray spectrum of the source.« less

Authors:

Abdo, A

Publication Date:

Thu May 07 00:00:00 EDT 2009

Research Org.:

SLAC National Accelerator Lab., Menlo Park, CA (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

952997

Report Number(s):

SLAC-PUB-13590
TRN: US0902645

DOE Contract Number:  

AC02-76SF00515

Resource Type:

Journal Article

Journal Name:

Submitted to Astrophysical Journal

Additional Journal Information:

Journal Name: Submitted to Astrophysical Journal

Country of Publication:

United States

Language:

English

Subject:

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORPTION; BLACK HOLES; ENERGY SPECTRA; LUMINOSITY; PAIR PRODUCTION; PHOTONS; QUASARS; TELESCOPES; ASTRO, GRQC