- Newton look at the most X - ray - luminous galaxy cluster RX J 1347 . 5 − 1145

We present the first results from an XMM-Newton observation of RX J1347.5−1145 (z=0.451), the most luminous X-ray cluster of galaxies currently known, with a luminosity LX = 6.0±0.1×10 45 erg s in the [2-10] keV energy band. The cluster has an overall temperature of kT = 10.0 ± 0.3 keV and is not isothermal: the temperature profile shows a decline in the outer regions and a drop in the centre, indicating the presence of a cooling core. The spectral analysis identifies a hot region at radii 50-200 kpc to south-east of the main X-ray peak, at a position consistent with the subclump seen in the X-ray image. Excluding the data of the south-east quadrant, the cluster appears relatively relaxed and we estimate a total mass within 1 Mpc of 1.0 ± 0.2× 10M⊙.