X-ray intraday variability of the TeV blazar Mrk 421 with {\it XMM-Newton}

TL;DR

This study analyzes 17 years of X-ray observations of the blazar Mrk 421 to investigate its intraday flux and spectral variability, providing insights into particle acceleration and emission mechanisms in its jet.

Contribution

It offers a comprehensive analysis of long-term X-ray variability and spectral correlations in Mrk 421, constraining models of jet emission and particle acceleration.

Findings

Positive correlation between soft and hard X-ray bands suggests common electron populations.

Variability timescales and flux-spectral correlations provide constraints on emission models.

Evidence of turbulent behavior in jet emission processes.

Abstract

Highly variable Markarian 421 is a bright high synchrotron energy peaked blazar showing wide featureless non-thermal spectrum making it a good candidate for our study of intraday flux and spectral variations over time. We analyse its X-ray observations of over 17 years taken with the EPIC-PN instrument to probe into the intraday variability properties. The photon energy band of 0.3 - 10.0 keV, and its sub-bands, soft 0.3-2.0 keV and hard 2.0-10.0 keV. To examine flux variability, fractional variability amplitude and the minimum variability timescale have been calculated. We also probed into the spectral variability by studying hardness ratio for each observation and the correlation between the two energy bands using discrete correlation function and inspecting the normalized light curves. The parameters obtained from these methods have been studied for any correlation or non-random trends. From this work, we speculate on the constraints for possible particle acceleration and emission processes in the jet, for better understanding of the processes involving a turbulent behaviour except of shocks. A positive discrete correlation function between the two sub-bands indicates the role of the same electron population in the emission of photons in the two bands. The correlation between the parameters of flux variability and parameters of spectral variation and lags in sub-energy bands provide the constraints to be considered for any modelling of emission processes.