Modeling the emission processes in blazars

Abstract

Blazars are the most violent steady/recurrent sources of high-energy gamma-ray emission in the known Universe. They are prominent emitters of electromagnetic radiation throughout the entire electromagnetic spectrum. The observable radiation most likely originates in a relativistic jet oriented at a small angle with respect to the line of sight. This review starts out with a general overview of the phenomenology of blazars, including results from a recent multiwavelength observing campaign on 3C279. Subsequently, issues of modeling broadband spectra will be discussed. Spectral information alone is not sufficient to distinguish between competing models and to constrain essential parameters, in particular related to the primary particle acceleration and radiation mechanisms in the jet. Short-term spectral variability information may help to break such model degeneracies, which will require snap-shot spectral information on intraday time scales, which may soon be achievable for many blazars even in the gamma-ray regime with the upcoming GLAST mission and current advances in Atmospheric Cherenkov Telescope technology. In addition to pure leptonic and hadronic models of gamma-ray emission from blazars, leptonic/hadronic hybrid models are reviewed, and the recently developed hadronic synchrotron mirror model for TeV γ-ray flares which are not accompanied by simultaneous X-ray flares ("orphan TeV flares") is revisited.

On the multiwavelength emission from gamma ray burst afterglows

“…The above picture carries certain analogies to the radiation models put forward during the last decade to explain the multiwavelength (MW) observations of blazar emission, and, especially, to the "one-zone" SSC models (for recent reviews see Böttcher 2007;and Mastichiadis 2009). These models are based on solving an equation for the electron distribution function including synchrotron and SSC losses and, at the same time, calculating the radiated photon spectrum.…”

Synchrotron Self‐Compton Analysis of TeV X‐Ray‐Selected BL Lacertae Objects

“…In the leptonic models (see, e.g., Böttcher 2007 for a review), the low-energy component is interpreted as synchrotron emission from leptons and the high-energy component as radiation from target photons Compton upscattered by relativistic jet leptons. The target photons can originate from the synchrotron radiation (synchrotron self-Compton [SSC]; Bloom & Marscher 1996), as well as external sources, e.g., the broadline region (Sikora et al 1994), a dusty torus ( Byażejowski et al 2000), and/or the accretion disk ( Dermer et al 1992;Dermer & Schlickeiser 1993).…”

Very high energy photons and neutrinos: Implications for UHECR

“…Such a flare may be suggestive of a hadronic origin for the TeV gamma-rays [12], in which case neutrinos would also be expected. In 2002 a large flare occurred for both the synchrotron X-ray peak and the high energy, presumably inverse Compton, peak.…”