Probing Broadband Spectral Energy Distribution and Variability of Mrk\,501 in the low flux state

TL;DR

This study analyzes the low activity state of blazar Mrk 501 across multiple wavelengths, fitting spectral models and exploring jet physics, revealing correlations between jet power and Lorentz factors, and suggesting accretion fueling.

Contribution

It provides a detailed broadband spectral analysis of Mrk 501 in a low flux state using various particle distribution models, highlighting the physical processes and jet characteristics.

Findings

Logparabola and broken power-law models fit X-ray spectra better than simple power-law.

Jet power correlates positively with bulk Lorentz factor.

Jet power is about 10% of the Eddington luminosity, indicating possible accretion fueling.

Abstract

We conducted a multi-wavelength analysis of the blazar Mrk\,501, utilizing observations from \emph{Astro}Sat (SXT, LAXPC), \emph{Swift-UVOT}, and \emph{Fermi-LAT} during the period August 15, 2016 to March 27, 2022. The resulting multi-wavelength light curve revealed relatively low activity of the source across the electromagnetic spectrum. Notably, logparabola and broken power-law models provided a better fit to the joint X-ray spectra from \emph{Astro}Sat-SXT/LAXPC instruments compared to the power-law model. During the low activity state, the source showed the characteristic harder when brighter trend at the X-ray energies. To gain insights into underlying physical processes responsible for the broadband emission, we performed a detailed broadband spectral analysis using the convolved one-zone leptonic model with different forms of particle distributions such as logparabola (LP), broken power-law (BPL), power-law model with maximum energy ($\xi_{max}$), and energy-dependent acceleration (EDA) models. Our analysis revealed similar reduced-$\chi^2$ values for the four particle distributions. The LP and EDA models exhibited the lowest jet powers. The correlation analyses conducted for the LP and BPL models revealed that there is a positive correlation between jet power and bulk Lorentz factor. Specifically, in the LP model, jet power proved independent of $\gamma_{min}$, whereas in the broken power-law model, jet power decreased with an increase in $\gamma_{min}$. The jet power in the LP/EDA particle distribution is nearly 10 percent of the Eddington luminosity of a $10^7$ M$_\odot$ black hole. This result suggests that the jet could potentially be fueled by accretion processes.