Extreme HBL-like behavior of Markarian 421 and its two-zone photohadronic interpretation

TL;DR

This paper analyzes the extreme high-energy behavior of blazar Markarian 421 during a 2010 outburst, demonstrating that a two-zone photohadronic model effectively explains its multiwavelength flaring spectra, unlike the standard model.

Contribution

It introduces a two-zone photohadronic model that successfully explains the extreme HBL-like behavior of Markarian 421 during a high activity period, surpassing the standard model's explanations.

Findings

Two-zone photohadronic model fits the observed spectra well.

Standard photohadronic model is inadequate for extreme HBL behavior.

Estimated minimum bulk Lorentz factor from highest energy gamma-ray event.

Abstract

Markarian 421 is the nearest high-energy peaked blazar and also is the first extragalactic source to be detected in multi-TeV $\gamma$-rays. It has been observed in multiwavelength for exceptionally long period of time with dense monitoring and several major outbursts have been detected from this source. In March 2010, the source was in a high state of activity and was observed in multiwavelength by various telescopes for 13 consecutive days. During this period the position of the synchrotron peak was found to be above $10^{17}$ Hz and also the position of the second peak was shifted towards higher energy, a signature of extreme HBL-like behavior. We observed that the standard photohadronic model is inadequate to explain the observed spectra. However, a recently proposed two-zone photohadronic model explains very well the GeV-TeV flaring events observed by both MAGIC and VERITAS telescopes. From the observation of the highest energy $\gamma$-ray event on MJD 55266 we also estimated the minimum bulk Lorentz factor.