Multi-TeV flaring in nearby high-energy blazars: A photohadronic scenario

Abstract

Blazars are a subclass of AGN and flaring in multi-TeV gamma-ray seems to be the major activity in high energy blazars a subgrup of blazars. Flaring is also unpredictable and switches between quiescent and active states involving different time scales and fluxes. While in some high energy blazars a strong temporal correlation between X-ray and multi-TeV gamma-ray has been observed, outbursts in some other have no low energy counterparts and explanation of such extreme activity needs to be addressed through different mechanisms as it is not understood well. The extragalactic background light (EBL) plays an important role in the observation of these high energy gamma-rays as it attenuates through pair production of electron-positron and also changes the spectral shape of the high energy photons. In the context of the photohadronic model and taking EBL correction into account, flaring can be explained very well. In a series of papers we have developed this model to explain multi-TeV flaring events form many blazars. Here in this review, the photohadronic model is discussed and applied to explain the multi-TeV flaring from nearby high energy blazars: Markarian 421, Markarian 501 and 1ES1959+650. * sarira@nucleares.unam.mx 1 arXiv:1907.01174v1 [astro-ph.HE]

Multi-TeV Flaring from High-energy Blazars: An Evidence of the Photohadronic Process

“…By assuming that the multi-TeV emission in the HBLs are due to the photohadronic interaction in the jet (Sahu 2019;Sahu et al 2017b), a simple relation between the observed VHE spectrum and the intrinsic spectrum is derived. We assume that during the VHE emission period, the Fermi accelerated protons having a power-law spectrum (Dermer & Schlickeiser 1993), dN/dE ∝ E −α (the power index α ≥ 2) , interact with the background seed photons in the jet to produce the ∆-resonance (pγ → ∆ + ), which subsequently decays to γ-rays via intermediate π 0 and to neutrinos through π + .…”

The VHE SED modelling of Markarian 501 in 2009

“…The photohadronic model of Sahu et al [15,16,21,22] can explain the flaring events from HBLs very well and it relies on the standard interpretation of the leptonic model discussed above to explain both low and high energy peaks by synchrotron and SSC photons respectively as in the case of any other AGN.…”

“…Using the scaling condition of Eq. (1), the photon density in the inner region can be expressed in terms of the observed flux [15,16].…”

“…Also the highest energy protons emitted in the emission process should satisfy F p < F Edd /2 which will constrain the optical depth τ pγ for the pγ → ∆ process and consequently the n γ,f in the inner region. The hidden jet lies between R s (Schwarzschild radius) and R b so that photon density in the inner region is high [15,16].…”

“…[14]. In a recent paper Sahu et al, have explained the VHE flare of May 1 well using the photohadronic scenario by taking into account the EBL correction to the spectrum [15,16].…”