Nonthermal electron-positron pair production and the ''universal'' X-ray spectrum of active galactic nuclei

Journal Article · Mon Jul 15 00:00:00 EDT 1985 · Astrophys. J., Lett. Ed.; (United States)

DOI:https://doi.org/10.1086/184513· OSTI ID:5189951

Zdziarski, A A; Lightman, A P

We consider a nonthermal model for power-law X-ray and ..gamma..-ray sources. An initial, primary distribution of relativistic electrons is injected and cooled via Compton scattering of soft photons (produced either externally or by the synchrotron mechanism). The scattered photons, constituting a primary ..gamma..-ray source, produce electron-positron pairs that act as a secondary electron injection, which in turn produce a secondary photon spectrum. In contrast to the treatment of this problem presented by Bonometto and Rees in 1971 and Kazanas in 1984, we take into account pairs formed by a part of the photon spectrum optically thin to pair production. We solve self-consistently for the distribution of particles and photons, and present numerical results as well as analytical solutions to certain special cases. For the case of a delta-function primary electron injection we find that the photon spectrum in the X-ray region is well approximated by a power law, with the energy spectral index ..cap alpha../sub X/ lying in the relatively narrow range 0.5--0.9 as the compactness parameter L/sub X//R (where L/sub X/ is the X-ray luminosity and R is the source radius) varies over many orders of magnitude. We propose this as a possible mechanism to explain the universal X-ray spectra observed from active galactic nuclei.

• Research Organization: Harvard-Smithsonian Center for Astrophysics
• OSTI ID: 5189951
• Journal Information: Astrophys. J., Lett. Ed.; (United States), Vol. 294:2
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC X-RAY SOURCES
PAIR PRODUCTION
GALAXY NUCLEI
RADIATION SOURCES
ASTROPHYSICS
COSMIC PHOTONS
NUMERICAL ANALYSIS
THOMSON SCATTERING
X-RAY SPECTRA
COSMIC RADIATION
COSMIC RAY SOURCES
ELEMENTARY PARTICLES
INELASTIC SCATTERING
INTERACTIONS
IONIZING RADIATIONS
MASSLESS PARTICLES
MATHEMATICS
PHOTONS
RADIATIONS
SCATTERING
SPECTRA
640103* - Astrophysics & Cosmology- Quasi-Stellar
Radio
& X-Ray Sources- (-1987)