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

TL;DR

This study analyzes the spectral and timing data of the Compton Thick Seyfert 2 galaxy NGC 1068 using NuSTAR and XMM-Newton, determining coronal temperature and its stability over multiple epochs.

Contribution

First calculation of the coronal temperature ($ m{kT_{e}}$) in NGC 1068 and assessment of its variation across different observation epochs.

Findings

Coronal temperature $ m{kT_{e}}$ ranges between 8.46 and 9.13 keV.

No significant variation in $ m{kT_{e}}$ over time.

Flux variations observed at energies beyond 20 keV in certain epochs.

Abstract

We present the timing and spectral analysis of the Compton Thick Seyfert 2 active galactic nuclei NGC 1068 observed using {\it NuSTAR} and {\it 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 {\it NuSTAR} carried out during the period December 2012 to November 2017, and, (b) six epochs of observations with {\it XMM-Newton} carried out during July 2000 to February 2015. From timing analysis of the {\it NuSTAR} observations, we found the source not to show any variations in the soft band. However, on examination of the flux at energies beyond 20 keV, during August 2014 and August 2017 the source was brighter by about 20\% and 30\% respectively compared to the mean flux of the three 2012 {\it NuSTAR} observations as in agreement with earlier results in literature. From an analysis of {\it 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$^{+0.39}_{-0.66}$ keV 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.