Variation of the γγ opacity by the He II Lyman continuum constrains the location of the γ-ray emission region in the blazar 3C 454.3
Abstract
We study spectral properties of the brightest γ-ray blazar 3C 454.3 using 138 weeks of observations by the Fermi Gamma-ray Space Telescope (Fermi). We probe the behaviour of the source as a function of time at different brightness levels. The Fermi spectra in the GeV range can be well described by a wide underlying lognormal distribution with the photon-photon absorption breaks produced by the He II and H I Lyman recombination continua (LyC). We find a power-law dependence of the peak energy on flux and discover anticorrelation between the column density of the He II LyC and flux. This implies that the γ-ray emission zone lies close to the boundary of the high-ionization part of the broad-line region and moves away from the black hole when the flux increases. Identification of the γ-ray production with the relativistic jet implies that the jet is already accelerated at sub-parsec distances from the central black hole, which favours the Blandford-Znajek process as the jet launching mechanism.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 2011
- DOI:
- 10.1111/j.1745-3933.2011.01107.x
- arXiv:
- arXiv:1105.2762
- Bibcode:
- 2011MNRAS.417L..11S
- Keywords:
-
- black hole physics;
- galaxies: active;
- galaxies: jets;
- quasars: emission lines;
- quasars: individual: 3C 454.3;
- gamma-rays: general;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Cosmology and Extragalactic Astrophysics
- E-Print:
- 5 pages, 5 figures, MNRAS Letters, in press