Astronomy and Astrophysics – Astrophysics
Scientific paper
1998-06-26
Astrophys.J.508:601,1998
Astronomy and Astrophysics
Astrophysics
21 pages (Latex), 4 figures (ps), accepted for publication in ApJ
Scientific paper
10.1086/306458
EGRET (20 MeV to 30 GeV) on board the Compton GRO has observed high-energy emission from about 40-50 Active Galactic Nuclei. Theoretical models of this emission based on the upscattering of thermal disk photons by cooling, relativistic electrons can successfully account for the EGRET observations, but they predict a considerably greater X-ray flux than that actually observed in a majority of these sources. This inconsistency may be an indication that the particles are energized during the Compton scattering process, since the X-ray emission is produced by the lowest energy electrons, whose density may be relatively small due to the acceleration. Such a situation may arise as a result of resistive field generation in electromagnetic acceleration schemes, which we here explore. A key feature of this model is the assumed existence of a current associated with the azimuthal component B_phi of the underlying magnetic field by a slight imbalance in the energy distributions of outwardly moving, relativistic electrons and protons produced at the disk surface via shock acceleration. The generation of an electric field (via magnetic field line reconnection) is thus required to maintain the current in the presence of a resistivity induced by the radiative drag on the relativistic electrons. We show that the resulting spectrum can exhibit a significant deficit of X-rays compared with gamma-rays. In addition, due to the uni-directional flow of the current associated with B_phi, this model would predict that the electrons are energized relative to the protons in the outflow only on one side of the disk. They should be decelerated on the reverse side. As such, we would anticipate that any given blazar should have a ~50% probability of being gamma-bright, which appears to be consistent with the observed ratio.
Fatuzzo Marco
Melia Fulvio
No associations
LandOfFree
The Hard X-Ray to Gamma-ray Spectrum in the EGRET AGNs does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Hard X-Ray to Gamma-ray Spectrum in the EGRET AGNs, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Hard X-Ray to Gamma-ray Spectrum in the EGRET AGNs will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-259503