Flux and spectral variability of Mrk 421 during its moderate activity state using<i>NuSTAR</i>: Possible accretion disc contribution?

The X-ray emission in BL Lac objects is believed to be dominated by synchrotron from their relativistic jets. However, when the jet not strong, one could expect signatures of inverse Compton scattering accretion disc photons corona. Moreover, observed variability can also originate disc, and gets propagated amplified jet. Here, we present results on object Mrk 421 using NuSTAR data acquired during 2017 source was a moderate brightness state. For comparison with high activity, considered epoch April 2013 very Our aim explore possibility signature overall 421. spectral fitting two component advective flow model shows gives (a) size dynamic corona at base ~28 10 r$_s$, (b) mass rate 0.021 0.051 $\dot M_{\rm Edd}$, (c) halo 0.22 0.35 (d) viscosity parameter Keplerian 0.18 $-$ 0.25. In assumed model, total flux, flux correlate radio these epochs. We conclude that spectra all epochs are well described based model. estimated relations show contribute emission, (that covers small portion broad band energy distribution 421) isolation. models disfavoured respect considering conjunction other wavelengths.