Particle acceleration and high-energy emission in the EGRET AGNs

Evonne Marietta, Fulvio Melia

Research output: Contribution to journalArticlepeer-review


Prior to the EGRET observations, jet formation models generally treated the acceleration and radiation mechanisms separately, since very little was known of the physical environment where the particles are initially energized. Because the high-energy emission from these sources presumably originates close to the central engine, the EGRET spectral measurements offer us the first opportunity to seriously model the early jet formation phase within ∼ 10 - 100 Schwarzschild radii of the nucleus. A viable mechanism for producing the high-energy gamma-rays is the Compton upscattering of ambient low-energy photons (e.g., from a disk) by relativistically moving particles. However, it is well known that the resulting Compton drag on the particles can significantly retard their progress, which results in a particle-photon-induced resistivity. Thus, if the energizing force on the particles is associated with an AGN magnetospheric phenomenon, as many have hypothesized, the electromagnetic acceleration is fully dependent on the magnitude of the photon drag and hence is connected directly to the radiative emission itself. These two processes, i.e., the particle acceleration and the associated Compton upscattering, eventually need to be treated self-consistently. Our primary goal in this preliminary set of calculations is to establish the range of blackhole masses, the spin rate, and the permissible magnetic field configurations that produce spectra and fluxes consistent with the EGRET observations. This analysis also predicts the degree of beaming and inclination effects, both of which should bear directly on theories that attempt to unify the radio-loud AGNs into a single class. As an illustration, we apply our model to QSO CTA 102 and obtain a reasonable agreement with the observed flux and spectral index. Published by Elsevier Science on behalf of COSPAR.

Original languageEnglish (US)
Pages (from-to)109-112
Number of pages4
JournalAdvances in Space Research
Issue number1
StatePublished - 1997

ASJC Scopus subject areas

  • Aerospace Engineering
  • Astronomy and Astrophysics
  • Geophysics
  • Atmospheric Science
  • Space and Planetary Science
  • General Earth and Planetary Sciences


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