Abstract Details

Name: Ritaban Chatterjee
Affiliation: Presidency University
Conference ID: ASI2020_357
Title : Multi-Band X-ray Variability of the Blazar Mrk 421 Using AstroSat
Authors and Co-Authors : Ritaban Chatterjee (Presidency University, Kolkata), Agniva Roychowdhury (University of Maryland Baltimore County), Sunil Chandra (North-West University, Potchefstroom), Atreyee Sinha (AstroParticule et Cosmologie, Universite Paris Diderot, Paris).
Abstract Type : Oral
Abstract Category : Extragalactic Astronomy
Abstract : We present the results of our analysis of the 500 ks X-ray light curves of Mrk 421 from the Soft X-ray Imaging Telescope (SXT) and the Large Area X-Ray Proportional Counter (LAXPC) instrument onboard the Indian space telescope AstroSat. We cross-correlate the light curves at various energy bands in the range 0.3--50 keV. We find both soft and hard lags of a few hours, i.e., the variations at some of the harder bands lead those at the softer bands and vice versa. Given that the X-ray emission in Mrk 421 is predominantly due to synchrotron radiation hard lags may be due to gradual acceleration of emitting particles while the soft lags may be caused by the relative radiation cooling timescales of higher and lower energy particles. Contribution of the synchrotron self-Compton process at the hard X-ray band may cause changes in the nature of the multi-band time lag as well. We calculate the phase spectrum, i.e., the average value of the time lag between the components with the same Fourier frequency in the light curves. Calculation of such a detailed phase spectrum was possible due to the very well-sampled data that could be obtained from AstroSat. It shows that the time lag remains approximately constant at the lower frequency range and then undergoes a change in sign above a certain frequency. This general behavior is consistent with some recent models of jet emission variability. It may be explained if the rise of an outburst is rapid and occurs at the harder channel first following which the emission decays at a slower rate, which takes place at the softer channel first. We discuss more detailed implications of the above variability analyses.