X-ray spectral and timing analysis of the Compton Thick Seyfert 2 galaxy NGC 1068

Abstract

ABSTRACT We present the timing and spectral analysis of the Compton Thick Seyfert 2 active galactic nuclei NGC 1068 observed using NuSTAR and XMM–Newton. In this work for the first time we calculated the coronal temperature ($\rm {kT_{e}}$) of the source and checked for its variation between the epochs if any. The data analysed in this work comprised of (a) eight epochs of observations with NuSTAR carried out during the period 2012 December to 2017 November, and, (b) six epochs of observations with XMM–fNewton carried out during 2000 July to 2015 February. From timing analysis of the NuSTAR observations, we found tfhe source not to show any variations in the soft band. However, on examination of the flux at energies beyond 20 keV, during 2014 August and 2017 August the source was brighter by about 20 and 30 per cent, respectively, compared to the mean flux of the three 2012 NuSTAR observations as in agreement with earlier results in literature. From an analysis of XMM–Newton data we found no variation in the hard band (2–4 keV) between epochs as well as within epochs. In the soft band (0.2–2 keV), while the source was found to be not variable within epochs, it was found to be brighter in epoch B relative to epoch A. By fitting physical models we determined $\rm {kT_{e}}$ to range between 8.46$^{+0.39}_{-0.66}$ and 9.13$^{+0.63}_{-0.98}$ keV. From our analysis, we conclude that we found no variation of $\rm {kT_{e}}$ in the source.