XMM-Newton Science Analysis System: User Guide

4.9.1 Removing Out-of-Time events from pn images

The effect on images is shown in figure 29 (note the arc-like structures due to single mirror reflections (stray light) at the top left of the FoV).

Figure 29: Effect of OoT events on images: The upper left panel contains a 2-10 keV band image of a pn observation of a bright source in full frame mode with the OoT events visible as a strip running along the length of the CCD. The upper right panel depicts the modeled OoT event distribution whereas in the lower left panel these are subtracted from the original image. The lower right panel shows the distribution of cleaned events in the soft (0.2-2 keV) energy band for comparison.

As mentioned in the previous section, 6.3 % of all events in a full-frame mode event file are OoT events. Because the OoT event list contains the same number of events as the original event list, the OoT image needs to be multiplied by 0.063 before subtracting it from the original image. Assuming that the user has created two images (see § 4.7), one from the OoT and the other from the "normal" event lists (named image_oot.fits and image.fits, respectively), simple image arithmetics, using for example FTOOL tasks, can be used to scale and subtract one image from the other (details in the corresponding pages of the SAS Analysis Threads). This process will remove from the image the strip associated with the OoT events.