XMM-Newton Science Analysis System: Users' Guide

4.6.1 Removing Out-of-Time events from pn images

The effect on images is shown in Fig. 14 (btw. note the arc-like structures due to single mirror reflections (stray light) at the top left of the FoV).

Figure 14: 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 above, 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 § 4.9) from the OoT and the ``normal'' event lists (named image_oot.fits and image.fits, respectively), the necessary image arithmetic can be performed with the FTOOL task farith:

1. The OoT image is multiplied by 0.063 creating the output file image_oot_scaled.fits:

   farith image_oot.fits 0.063 image_oot_scaled.fits MUL
   

2. The scaled OoT image is subtracted from the ``normal'' image:

   farith image.fits image_oot_scaled.fits image_clean.fits SUB
   

   The resulting image image_clean.fits is more or less cleared from OoT events.