PoS - Proceedings of Science
Volume 395 - 37th International Cosmic Ray Conference (ICRC2021) - MM - Multi-Messenger
A lepto-hadronic model of gamma-ray signal from extreme blazars
S. Das*, N. Gupta and S. Razzaque
Full text: pdf
Pre-published on: June 28, 2021
Published on: March 18, 2022
Abstract
The unattenuated TeV $\gamma$-ray spectrum observed in some blazars is inconsistent with the $\gamma\gamma$ absorption by seed photons in the relativistic jet or the extragalactic background light (EBL) during extragalactic propagation. In addition, the efficiency of inverse-Compton emission is suppressed at such high energies. Ultrahigh-energy cosmic rays (UHECRs; $E\gtrsim10^{17}$ eV) accelerated in blazar jets can escape from their sources and interact with the cosmic background photons. The resultant $\mathrm{e^\pm}$ and $\gamma$-rays can induce electromagnetic cascade resulting in a photon spectrum peaking at $\sim1$ TeV energies. We propose that the line-of-sight component can be observed as coming from their respective sources. We consider a random turbulent extragalactic magnetic field to constrain the survival fraction of UHECRs along the observer's line of sight. A one-zone leptonic model is used to fit the synchrotron spectrum of the blazars. The higher-energy peak is explained by a combination of synchrotron self-Compton spectrum produced by the same relativistic electrons and the $\gamma$-rays from line-of-sight UHECR interactions. Overall, the lepto-hadronic model better explains the multiwavelength spectral energy distribution (SED). We also calculate the line-of-sight neutrino flux from these blazars corresponding to the luminosity required in $\gamma$-rays. We discuss the prospects of UHECR detection from these resolved sources.
DOI: https://doi.org/10.22323/1.395.1002
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