XMM-Newton Science Analysis System: User Guide

4.9.2 Removing Out-of-Time events from pn spectra

The handling of Out-of-Time events in spectra relies on dealing with FITS tables. As in the case of image cleaning of OoT events (see § 4.9.1), the necessary table manipulation and arithmetics can be performed with FTOOL tasks. Again, details of the procedure on how to correct a given spectrum from OoT events are given in the correspondent pages of the SAS Analysis Threads. As an example, the result of correcting for OoT events a given spectrum is shown in figure 30.

Figure 30: Effect of Out-of-Time events on a source spectrum (in this case the internal calibration source): the black data points display the source spectrum which is still contaminated by OoT events, the red points mark the source spectrum being cleared from OoT events. The energy range displayed is 5-8.5 keV.

The effect of OoT events is reduced to the broadening of the shoulders of a line and can cause a blending of lines. OoT events do not change the Full-width-at-half-maximum. The red spectrum shows that the lines in a spectrum cleared from OoT events are much easier to separate than in an untreated spectrum (black data points). Please keep in mind that the spectrum is displayed in a double logarithmic scale and restricted to a small energy band so as to emphasize the effect. Furthermore, the example shown here is data from the internal calibration source, which is very bright. For most targets a correction for OoT events in a spectrum should not be necessary. In any case, a correction is only necessary if OoT events overlap with the source under investigation.