On the Hadronic Beam Model for Gamma‐Ray Production in Blazars

Abstract

We consider a model for c-ray production in blazars in which a relativistic, highly collimated electronproton beam interacts with a dense, compact cloud as the jet propagates through the broad-and perhaps narrow-line regions of active galactic nuclei. During the propagation of the beam through the cloud, the process of excitation of plasma waves becomes an important energy-loss mechanism, especially for mildly relativistic proton beams. We compute the expected spectra of c-rays from the decay of neutral pions produced in hadronic collisions of the beam with the cloud, taking into account collisionless losses of the electron-proton beam. This model may explain the X-ray and TeV c-ray (both low and high emission states) of Mrk 421 as a result of synchrotron emission of secondary pairs from the decay of charged pions and c-ray emission from the decay of neutral pions for the plausible cloud parameters. However, clouds cannot be too hot and too dense. Otherwise, the TeV c-rays can be attenuated by the bremsstrahlung radiation in the cloud and the secondary pairs are not able to efficiently produce synchrotron Ñares because of the dominant role of inverse Compton scattering. The nonvariable c-ray emission observed from Mrk 421 in the EGRET energy range cannot be described by the c-rays from decay of neutral pions provided that the spectrum of protons in the beam is well described by a simple power law. These c-rays might only be produced by secondary pairs scattering the soft nonvariable X-rays, which might originate in the inner part of the accretion disk.

An exploration of hadronic interactions in blazars using IceCube

“…The low energy component is generally attributed to synchrotron radiation from electrons and positrons in the knots moving at relativistic speed in the jet. The high energy component can have different origins depending on the model considered: inverse Compton emission via up-scattering of the synchrotron photons (synchrotron-self Compton model; Bloom & Marscher 1996), inverse Compton emission via upscattering of the external radiation photons (external Compton model, Ghisellini & Mandau 1996), emission from decays of neutral pions produced in proton-proton interactions (Nellen et al 1993;Bednarek & Protheroe 1997;Beall & Bednarek 1999;Neronov et al 2008;Neronov & Ribordy 2009;Barkov et al 2010), proton-photon interactions (Mannheim & Biermann 1992;Mannheim 1993;Bednariek & Protheroe 1999;Mücke & Protheroe 2001;Atoyan & Dermer 2001Neronov & Semikoz 2002) or proton synchrotron radiation (Mücke & Protheroe 2001;Aharonian 2000;Mücke et al 2003). The maximal attainable energy of γ-ray emission is limited either by the maximal energies of electrons or by the onset of γγ pair creation (Sikora et al 1987).…”

“…However, a direct test of the presence of high-energy protons in the source is difficult because of the absence of a clear signature of proton-generated emission in the electromagnetic component of blazar and radio galaxy spectra. The main energy loss channels for the high-energy protons in the AGN environment are pion production in interactions with the low-energy protons (Nellen et al 1993;Bednarek & Protheroe 1997;Beall & Bednarek 1999;Neronov et al 2008;Neronov & Ribordy 2009;Barkov et al 2010) or interactions with radiation fields (Mannheim & Biermann 1992;Mannheim 1993;Bednariek & Protheroe 1999;Mücke & Protheroe 2001;Atoyan & Dermer 2001Neronov & Semikoz 2002). An additional possibility is proton synchrotron radiation energy losses (Mücke & Protheroe 2001;Aharonian 2000;Mücke et al 2003).…”

MULTIWAVELENGTH VARIABILITY PROPERTIES OFFERMIBLAZAR S5 0716+714

“…The soft photons could be synchrotron photons (the synchrotron self-Compton (SSC) model; Maraschi et al 1992) or photons outside the jet (the external radiation Compton (ERC) models: the accretion disk radiation (Dermer & Schlickeiser 1993), UV emission from the broad-line region (BLR; Sikora et al 1994), and infrared (IR) emission from a dust torus (Błażejowski et al 2000). In hadronic scenarios, if relativistic protons in a strongly magnetized environment are sufficiently accelerated, the particle-photon interaction processes, the synchrotron radiation of protons, and the proton-proton interaction processes must be taken into account (Mücke & Protheroe 2001;Aharonian 2000;Beall & Bednarek 1999).…”

Very High Energy Gamma-Ray Observations of Strong Flaring Activity in M87 in 2008 February

“…In blazars without prominent disk or broad-line features, the VHE emission is explained by inverse Compton pro-cesses involving the synchrotron photons and their parent electron population (synchrotron self-Compton models; e.g., Maraschi et al 1992). Alternatively, in hadronic models, interactions of a highly relativistic jet outflow with ambient matter (Dar & Laor 1997;Beall & Bednarek 1999), proton-induced cascades (Mannheim 1993), or synchrotron proton radiation (Mücke & Protheroe 2001;Aharonian 2000) may produce VHE g-rays. In such a scenario, M87 might also account for parts of the observed ultrahigh-energy cosmic rays (Protheroe et al 2003).…”