XMM-Newton Science Analysis System


epiclccorr (epiclccorr-1.23.1) [xmmsas_20230412_1735-21.0.0]

Description

The aim of this task (epiclccorr) is to correct EPIC source TS produced by eveselect for the following effects:

• Absolute Corrections: Corrections due to events lost through inefficiencies of various sorts in the mirror-detector system. We will consider these corrections as energy dependent:
  • Vignetting
  • Bad pixels
  • Chip gaps
  • PSF
  • Quantum Efficiency
  This will give the Count Rate which would have been detected by this camera with this filter, if it had been observed on-axis with an infinity extraction radius. As such the final Count Rates may be converted to fluxes using tools such as PIMMS.
• Relative Corrections: Corrections which vary with time:
  • Dead Time.
  • GTIs.
  • Exposure.
  • background counts.
• Background Substraction:

Optionally, an EPIC background TS can be supplied and in this case the initial source TS will be also background corrected (backscale correction included ). The first version of epiclccorr will only accept background TS with exactly the same start and stop time and bin size as in the source TS. The background TS will be corrected for relative effects related to the geometrical area of the source TS. The results of the background corrected rates and errors are stored in columns BACKV and BACKE in the output file. Bear in mind that a big background area will slow down epiclccorr run.

epiclccorr also needs as input the event file used to create both source and background time series.

epiclccorr will perform the Absolute corrections making use of the arfgen and evselect SAS tasks. A broad energy spectrum (50 eV energy bin) will be created using the Data SubSpace (DSS) expressions and it will be passed to arfgen SAS task. This task takes calibration information provided by the CAL, performs the necessary corrections for instrumental factors, such us, Vignetting, Bad Pixels, Chip Gaps, PSF, filter transmission, Quantum Efficiency, to get the corresponding Absolute Correction for the source TS. If the extraction region is too complex, arfgen can fail trying to calculate the source position from the DSS. In this case, the withsourcepos parameter must be used, and the user must introduce the source coordinates.

epiclccorr output also contains the following extensions:

• SRC_GTIS. This extension contains GTIs which cover all the non-null RATE values.

• BKG_GTIS. This extension (only present if withbkgset=`yes') contains GTIs which cover all the non-null BACKV values.

epiclccorr is also compatible with the output of barycen task.

The following corrections will not be included in the first version:

• source spectrum time variability.
• Out of Time Events.
• pileup.

The relative corrections will be performed by designing and coding specific algorithms for each instrument EPICMOS and EPICPN and each mode. A detailed description can be found in section .