Multi-frequency, Multi-Epoch Study of Mrk 501: Hints for a two-component nature of the emission

TL;DR

This study analyzes multiwavelength data of Mrk 501, revealing evidence for a two-component emission model and challenging single-zone theories, supported by spectral modeling across different flux states.

Contribution

It introduces a two-component emission scenario for Mrk 501 based on multiwavelength observations and spectral analysis, moving beyond traditional single-zone models.

Findings

Evidence for two separate gamma-ray components in Mrk 501.

Detection of very hard intrinsic gamma-ray spectra from Fermi-LAT.

Successful modeling of broadband spectra with a multi-zone leptonic SSC model.

Abstract

Since the detection of very high energy (VHE) $\gamma$-rays from Mrk 501, its broad band emission of radiation was mostly and quite effectively modeled using one zone emission scenario. However, broadband spectral and flux variability studies enabled by the multiwavelength campaigns carried out during the recent years have revealed rather complex behavior of Mrk 501. The observed emission from Mrk 501 could be due to a complex superposition of multiple emission zones. Moreover new evidences of detection of very hard intrinsic $\gamma$-ray spectra obtained from {\it Fermi}--LAT observations have challenged the theories about origin of VHE $\gamma$-rays. Our studies based on {\it Fermi}--LAT data indicate the existence of two separate components in the spectrum, one for low energy $\gamma$-rays and the other for high energy $\gamma$-rays. Using multiwaveband data from several ground and space based instruments, in addition to HAGAR data, the spectral energy distribution of Mrk~501 is obtained for various flux states observed during 2011. In the present work, this observed broadband spectral energy distribution is reproduced with a leptonic, multi-zone Synchrotron Self-Compton model.