Computer Science
Scientific paper
May 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997aipc..410..307h&link_type=abstract
The fourth compton symposium. AIP Conference Proceedings, Volume 410, pp. 307-327 (1997).
Computer Science
15
Active And Peculiar Galaxies And Related Systems, Gamma-Ray Sources, Gamma-Ray Bursts, Gamma-Ray, Quasars
Scientific paper
Roughly 60 blazars have been identified with >100 MeV EGRET γ-ray sources, and show inferred isotropic luminosities as large as 3×1049 ergs s-1. The two most remarkable characteristics about the EGRET observations are that the γ-ray luminosity often dominates the bolometric power, and that variability on time-scales of one day or less is seen from several sources. Gamma-ray blazars have been detected with redshifts ranging from ≅0.03 to ≅2.3. The distribution of redshifts is similar to that of flat spectrum radio quasars. The distribution of >100 MeV photon spectral indices for strong detections is well described by a Gaussian function peaking near 2.16 with a standard deviation of 0.31. In some cases, flare spectra at >100 MeV energies are harder than spectra in quiescence. Blazar spectra at hard X-ray and soft γ-ray energies have harder spectra and, from analyses of contemporaneous data sets, the change in spectral index clearly exceeds 0.5 for 3C 273 and marginally exceeds 0.5 for PKS 0528+134. An index change of 0.5 is predicted by incomplete Compton cooling models. COMPTEL observations reveal a separate class of 2 identified blazars and 3 unidentified candidates with narrow peaks at MeV energies. The combined luminosity and variability data strengthen arguments for relativistic beaming or bulk outflow from the active nucleus. Gamma-ray transparency arguments are based on the pair-production attenuation of γ rays in a stationary region defined by the variability time-scale, and many violations are indicated. The Elliot-Shapiro relation compares the minimum black hole mass implied by the Eddington limit with the maximum black hole mass implied by the variability time-scale related to the black hole Schwarzschild radius; weak violations have been observed for PKS 0528+134 and PKS 1622-297. Most models adopt a beaming paradigm. In models considering leptons as the directly accelerated and radiating particles, Compton scattering is favored to make the γ-ray emission, though opinions differ on whether the soft photons are primarily internal synchrotron photons or accretion disk photons which enter the jet either directly or after scattering off clouds. Hadronic models involve secondary production or photomeson production followed by pair cascades, and predict associated neutrino production.
Collmar Werner
Dermer Carles D.
Hartman Robert C.
von Montigny C.
No associations
LandOfFree
Gamma-ray blazars 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 Gamma-ray blazars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gamma-ray blazars will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-833081