Regions and Source Parameters

This section will deal with obtaining photons within specified regions of an image. Available regions are:

   Annulus
   Box
   Circle
   Ellipse
   Field -- entire field
   Irregular region based on intensity of map...
             i.e. region defined by contour levels.
   Pie -- angular wedge
   Point
   Polygon
   Rotbox -- rotated box

for more details type:

  cl> help regions

The imcnts task in the xray-spatial package sums the source and background counts in specified regions, and subtracts one from the other properly normalized. The results are saved in a table file, which can be read, printed or converted into an ascii file using the ttools.

The sample data file, xdata$rp110590.qp, contains a point source whose position is at x = 6930, y = 9390. The counts will be taken within a circle of 240 pixel radius (2' in the ROSAT PSPC. This is the recommended circle size for a PSPC point source which is not too far off axis). The examples requiring an extended source will use the data file, xdata$snr.qp, containing Einstein IPC data. Counts will be obtained in a box of 208 $\times$ 266 pixels, with exclusion of the point source at 503,513.