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epevents (epevents-6.55) [xmmsas_20211130_0941-20.0.0]

Analysis of extended sources or in the vicinity of moderately bright sources

If withoutoftime=y the task does not create the “normal” events file but uses the input file instead to create an event file where all events are treated as out-of-time events. After the pattern recognition for the same TIME, PHA, and RAWX a new RAWY is simulated by randomly shifting the pattern along the RAWY axis and performing the gain and CTI correction afterwards.

This out-of-time events file has the same temporal variations and pattern distribution as the “normal” event file. All events have an energy correction corresponding to the (randomly distributed) RAWY column. You can apply the same selection on both the “normal” and “out-of-time” event file, scale with a mode-dependent factor and subtract the “out-of-time” contribution from the other. You can create “out-of-time”-corrected spectra and images for an arbitrary time and energy range by subtracting the scaled product derived from the out-of-time events file from the product created from the “normal” events file.

The current (experimental) implementation does not automatically detect the instrument and bad pixel setting. The RAWY range to distribute the out-of-time events is instead derived from the RAWY range of the actual events in the data. The mode-dependent conversion factor has thus to be applied manually and is about 95% of the out-of-time event fraction (e.g. 0.060 for full frame mode) due to setting the top 10 rows to “bad”. This will we improved in later versions.

For an example how to use the current implementation of out-of-time event handling in an event file processing, consult the documentation of epchain.

Note that this parameter is only meaningful for IMAGING modes. Moreover, in the Large Window and Small Window modes out-of-time events can be introduced by sources that are outside the readout-window. These cannot be accounted for. Similarly, for Full Frame and Extended Full Frame modes (currently) the 11 rows closest to the CAMEX are set bad onboard but sources in these rows may also cause unrecognized out-of-time events. Finally, if a source is highly affected by pile-up this feature is projected onto the distribution of out-of-time events as well, however, the actual recorded out-of-time events do not suffer from this and thus residual effects remain.

XMM-Newton SOC -- 2021-11-30