X-RAY Spectral Study of MKN 421 Using Astrosat Observation

Abstract

We present a detailed X-ray spectral study of the high energy peaked blazar MKN421 using the simultaneous broadband observations from the LAXPC and SXT instruments on-board the AstroSat satellite. In order to investigate the spectral properties of the source, we used the method of time resolved spectral analysis by dividing the total observation time into time-segments of 10 ksecs and then by fitting each segment with synchrotron emission of particle density from logparabola model. In each time-segment, we fitted the observed broadband X-ray spectrum. The X-ray spectrum of Mkn 421 showing significant spectral curvature is usually described by log-parabola model, however, the model fails to give the information of underlying physical parameters as the exact relationship of model parameters with the underlying physical quantities is not clear. Therefore in order to obtain the information of underlying physical parameters, we reproduce the X-ray spectrum with a analytical models viz. energy-dependent acceleration( EDA) model. On comparing the goodness of the fit of synchrotron convolved logparabola model with the EDA model, we noted that both the models provided nearly equally good fit to the broadband spectrum, though EDA model is comparatively better. Moreover, we studied the correlation between EDA model parameters (norm, , ) and the observed quantities using the Spearman rank correlation method. A significant anti-correlation is observed between and with rs = 􀀀0:82(Prs = 1:69 10􀀀9) and similar anti correlation is also obtained for the case of and norm rs = 􀀀0:86 (Prs = 3:5 10􀀀11). The above obtained correlation results between fit parameters for the case of EDA model are consistent with the definition. Which refer that the model is more appropriate for reproducing the X-ray spectrum of Mkn 421.