A two-zone photohadronic interpretation of the EHBL-like behavior of the 2016 multi-TeV flares of 1ES 1959+650

TL;DR

This paper introduces a two-zone photohadronic model to explain the extreme multi-TeV flaring behavior of blazar 1ES 1959+650 observed in 2016, which could not be explained by the standard model.

Contribution

The paper develops and applies a novel two-zone photohadronic model to successfully explain the extreme high-energy flaring spectra of 1ES 1959+650 in 2016.

Findings

The standard photohadronic model fails to explain the 2016 flaring spectra.

The two-zone model accurately fits the observed multi-TeV spectra.

Different spectral regimes correspond to standard and extreme flaring events.

Abstract

The high-energy-peaked blazar 1ES 1959+650 is a well-known and well studied nearby blazar that has undergone several episodes of multi-TeV flaring. In 2002 for the first time an orphan TeV flare was observed from this blazar. During a multiwavelength campaign between 29th April to 21st November 2016, MAGIC telescopes observed multi-TeV flarings during the nights of 13th, 14th June and 1st July 2016 when the position of the synchrotron peak was found to be above $10^{17}$ Hz. Also observed was that the second peak of the spectral energy distribution shifted towards higher energy, and exhibiting extreme HBL-like behavior. The photohadronic model which is very successful in explaning the multi-TeV flaring from many high energy blazars including 1ES 1959+650 is applied to study the flaring events of 2016. It is observed that the photohadronic model is unable to explain the observed spectra. Here, we use a two-zone photohadronic model to explain the observed spectra. We clearly demonstrate that the low energy regime (zone-1) of the spectra corresponds to the standard flaring events of the high energy blazar and the high energy regime (zone-2) of the spectra are solely due to the extreme nature of the flaring events. Our two-zone photohadronic model explains very well the multi-TeV flaring events observed by MAGIC telescopes.