Flaring activity of Mrk 421 in 2012 and 2013: orphan flare and multiwavelength analysis

TL;DR

This study analyzes the 2012 and 2013 flaring activity of Mrk 421 across multiple wavelengths, revealing an orphan gamma-ray flare and correlated optical and X-ray activity, providing insights into blazar emission mechanisms.

Contribution

It presents a detailed multiwavelength analysis of Mrk 421's flares, highlighting the first orphan gamma-ray flare and correlated optical and X-ray activity, advancing understanding of blazar variability.

Findings

2012 gamma-ray flare was an orphan flare with no X-ray counterpart

2013 bright optical states correlated with soft and hard X-ray activity

Strong correlation between GeV gamma-rays and optical/hard-X rays in 2013

Abstract

The first one started in 2012 July 16 (MJD 56124) and the second one in 2013 April 9 (MJD 56391). The multiwavelength data analysis shows that the $\gamma$-ray flare observed in 2012 was not detected in the hard-X ray bands. This result is usually interpreted as an "orphan" flare. In 2013, the analysis of the multiwavelength light curves shows that there are two very bright states detected in the optical R-band. The first one in 2013 April 9 (R =11.74 $\pm$ 0.04) and the second one in May 12 (R =11.62 $\pm$ 0.04). Also, high activity states were detected in the soft and hard X-rays. A discrete correlation function analysis of this last flare shows a strong correlation between the GeV $\gamma$-rays and the optical/hard-X ray emission. These results are discussed in terms of the more adequate standard scenarios that could explain the multiwavelength variations displayed by this blazar.