科研之友
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摘要
Blazar spectral models generally have numerous unconstrained parameters, leading to ambiguous values for physical properties like Doppler factor delta(D) or fluid magnetic field B'. To help remedy this problem, a few modifications of the standard leptonic blazar jet scenario are considered. First, a log-parabola function for the electron distribution is used. Second, analytic expressions relating energy loss and kinematics to blazar luminosity and variability, written in terms of equipartition parameters, imply delta(D), B', and the peak electron Lorentz factor gamma(pk)'. The external radiation field in a blazar is approximated by Ly alpha radiation from the broad-line region (BLR) and approximate to 0.1 eV infrared radiation from a dusty torus. When used to model 3C 279 spectral energy distributions from 2008 and 2009 reported by Hayashida et al., we derive delta(D) similar to 20-30, B' similar to few G, and total (IR + BLR) external radiation field energy densities u similar to 10(-2)-10(-3) erg cm(-3), implying an origin of the gamma-ray emission site in 3C 279 at the outer edges of the BLR. This is consistent with the gamma-ray emission site being located at a distance R less than or similar to Gamma(2)ct(var) similar to 0.1(Gamma/30)(2)(t(var)/10(4) s) pc from the black hole powering 3C 279's jets, where t(var) is the variability timescale of the radiation in the source frame, and at farther distances for narrow-jet and magnetic-reconnection models. Excess greater than or similar to 5GeV gamma-ray emission observed with Fermi LAT from 3C 279 challenges the model, opening the possibility of a second leptonic component or a hadronic origin of the emission. For low hadronic content, absolute jet powers of approximate to 10% of the Eddington luminosity are calculated.
- 出版日期2014-2-20
