XMM-Newton Science Analysis System


arfgen (arfgen-1.104) [xmmsas_20230412_1735-21.0.0]

Out of time event correction

For EPIC-PN, in particular, there is a mode-dependent loss of photons due to the readout cycle. This can result in a 6% dead-time effect for full frame mode. This has been taken into account in the exposure time in the spectrum header for files created with pipeline versions greater than 20010618 but wasn't catered for in earlier pipeline runs. arfgen checks the PPSVERS keyword in the file header and applies the correction to the output ARF if the pipeline version is older than 18 June 2001 and if the parameter modelootcorr is set to true (the default). The PPSVERS keyword is written by pipeline modules and not by the SAS $\ast$proc routines; this means that if the data is reprocessed to create new event files then this keyword will not be present. If arfgen does not find the keyword it issues a warning. This should be ignored if the event file has been created with SAS 5.3 or any SAS version not older than 18 June 2001.

A PN ARF would be decreased by the following amount:

Mode	Factor (%)
PRIME_FULL_WINDOW	6.2
PRIME_FULL_WINDOW_EXTENDED	2.3
PRIME_SMALL_WINDOW	1.1