Processing sequence

1. Create an image of the whole field using XSORT

        ICL> XSORT SRCFILE=CYGX1_IMAGE
        

2. Display the image using the 'I' routines.

        ICL> ILOAD  CYGX1_IMAGE
        ICL> IDISPLAY
        

3. Choose source and background box centres and sizes

        ICL> XRTBCKBOX
        

   This will allow you to use a cursor on the image to select the position and radius of a source and background box. It then sorts events from within these boxes into a source and background time series.
4. Background subtract the source file

        ICL> XRTSUB
        

   This corrects the background time series to that which would have been seen had this background been at the position of the source box. It then subtracts it from the source time series.
5. Correct the subtracted time series

        ICL> XRTCORR
        

   This will correct the time series for dead time, vignetting, scattering and some overall wire correction. It will not, however, attempt to remove the features imposed onto the time series by the window structure of the PSPC.
6. Analyse the result, for example,

        ICL> POWER
        

   Performs an FFT on the subtracted time series.