XMM-Newton Science Analysis System


arfgen (arfgen-1.104) [xmmsas_20230412_1735-21.0.0]

Timing and Burst modes

These modes are treated as a special case within arfgen. For the EPIC-pn camera, regardless of the spatial region used to extract the spectra the source is assumed to be located at a DETY position calculated from the SRCPOS keyword in the spectrum header (or RAWY=190 if this keyword isn't present). The vignetting and encircled energy corrections are applied assuming a point source at this position. Bad pixels, columns and chip gaps are corrected for in the same way as for imaging mode observations.

In Timing mode it is recommended to take the full range of RAW-Y when extracting an EPIC-pn spectrum (in MOS the RAW-Y information is not present). It can be useful to take a restricted RAW-Y range in Burst mode to exclude contamination from the on-axis source. In this case arfgen scales the ARF proportionately to the range selected. Such a scaling is not applied for Timing mode data.

If pile-up is suspected in a Timing mode observation then it can be convenient to exclude the inner columns, containing the highest count rate. In this case a selection such as

(RAWX in [30:34] || RAW in [37:41])

should be used. Here, the inner two columns, RAWX=35 and 36, have been excluded. The encircled energy calculation will correct for the missing columns.