Modeling the production of flares in $γ$-ray quasars

M. Sikora; M. Blazejowski; M. C. Begelman; R. Moderski

doi:10.1086/321329

paper

Modeling the production of flares in $γ$ -ray quasars

arXiv:astro-ph/0102091 · doi:10.1086/321329

Abstract

Theories of high energy radiation production in quasar jets can be verified by studies of both time-averaged spectra and variability patterns. While the former has been explored extensively, the latter is in its infancy. In this paper, we study the production of short-term flares in the shock-in-jet model. We examine how the flares' profiles depend on such parameters as shock/dissipation lifetime, electron-injection time profile, adiabaticity, and half-opening angle of the jet. In particular, we demonstrate the large difference between flare profiles produced in the radiative and adiabatic regimes. We apply our model to the $\sim$ day timescale flares observed in optically violently variable (OVV) quasars, checking whether the external-radiation-Compton (ERC) model for $γ$ -ray flares at energies $> 30$ MeV (EGRET range) can be reconciled with the flares observed at lower energies. Specifically, we show that the strict correlation between X-ray and $γ$ -ray flares strongly supports the dominance of the synchrotron self-Compton mechanism in the X-ray band. We also derive conditions that must be satisfied by the ERC model in order to explain a lag of the $γ$ -ray peak behind the optical one, as claimed to be observed in PKS 1406-076. Finally, we predict that in ERC models where the MeV peak is related to the break in electron distribution due to inefficient cooling of electrons below a certain energy, the flares should decay significantly more slowly in the soft $γ$ -ray band than at energies greater than 30 MeV.

accepted to ApJ

Modeling the production of flares in γ-ray quasars

Abstract

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Modeling the production of flares in $γ$ -ray quasars