X-ray sky background estimation in the region surrounding S4436. The best fitting three-component model was extracted from XMM-Newton EPIC/pn (green), EPIC/MOS1 (black) and EPIC/MOS2 (red) data within an annulus located [12−15] arcmin away from NGC 3298. The data were jointly fitted with the ROSAT all-sky survey data (blue) extracted [1−1.5] degrees away from the core of the group. The bottom panel shows the ratio between the data and the best-fitting joint model.