possible to fit more complex models (e.g. a double $\beta$ model as used by @chhbbw05) to the data, our aim was just to characterise the density and pressure profiles in the inner regions and this simple model provides an adequate representation of the data here.

The surface brightness profile presented in Figure \[profile\] takes into account only the statistical uncertainty in surface brightness based on the count levels in the source and background annulus region. It is important also to consider any systematic uncertainty introduced by the use of the filter-wheel closed (FWC) background files in the double-subtraction process. The particle background scaling factors have a small associated uncertainty from the target observation and background file high-energy count rates used to determine the scaling; however, the dominant systematic uncertainty comes from spectral variation of the particle background between the 10-12 keV (MOS)/12-14 keV (pn) energy range used to determine the scaling, and the 0.3-8 keV energy range used in the profiles. @rp03 investigated the spectral properties of the particle background and report the variance in the background level in several energy bands for a large number of [*XMM-Newton*]{} observations. Based on their calculations we estimate that the systematic uncertainty on 