XMM-Newton SAS Home Page
XMM-Newton Science Analysis System


epreject (epreject-5.18.1) [xmmsas_20211130_0941-20.0.0]


Algorithm

  Energy scale correction:

  ** bin 20 adu and 30-40 adu images from input event file 

  ** determine chip mask area on which to perform offset correction  
       o remove offset columns (read from offset extension) from mask
       o remove 10 sigma excesses (3x3 pixel sliding box) in 30-40 adu image 
         due to soft sources or optical loading from mask   

  ** inside mask area, 

       if offset map is available and -withoffsetmask=true  

         o create residual offset map by subtracting median
           from each column and row 

       else

         o subtract 20 adu calibration reference image from 20 adu image
         o if statistically significant excesses are found on 4x1 pixel grid
           look up offset correction value corresponding to the 
             observed excess in each pixel

       end if

  ** loop over input event file and
       
       o apply offset correction value to PHA value of each event           
       o copy correction value into newly created OFF\_COR column   

  Suppression of detector noise:

  ** create averaged low energy spectra for each chip row

  ** determine median spectrum for each +/- 10 rows range

  ** for each row and each spectral bin determine the ratio of the
       calibration noise spectra divided by the accumulated median spectra

  ** apply cutoff value and chip specific correction factors to noise ratios

  ** loop over the event file and randomly flag the events according
       to the noise ratio of the corresponding chip row and energy channel



XMM-Newton SOC -- 2021-11-30