VHE $\gamma$-ray/X-ray correlation studies in Mrk 421 down to the quiescent state

TL;DR

This study investigates the correlation between VHE gamma-ray and X-ray emissions in Mrk 421 across various activity levels, emphasizing the correlation's robustness even during the quiescent state.

Contribution

It provides a comprehensive analysis of the VHE gamma-ray/X-ray correlation in Mrk 421, especially during low activity states, using multi-instrument data over different time scales.

Findings

Correlation persists even at low flux levels

Robustness of correlation confirmed during quiescent states

Multi-instrument data supports consistent correlation

Abstract

The blazar Mrk 421 is one of the closest, brightest and fastest varying source in the extragalactic X-ray/TeV sky. In the last years, many multi-wavelength campaigns have been carried out to study the correlation between the very high energy (VHE) $\gamma$-ray and X-ray fluxes of this source and, although the activity in these two energy ranges seems to be correlated in many observations, no conclusive results have been achieved yet. In this work we present a robust study of the VHE $\gamma$-ray/X-ray correlation of Mrk 421 with data taken with different VHE experiments on different time scales and for different levels of activity of the source, with special focus on the low activity states. In particular, we discuss the robustness of the correlation at the lowest fluxes corresponding to the quiescent state of Mrk 421.