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XRTBCKBOX*

This is an ICL procedure which allows the user to interactively select a source box and a background box, within which to sort XRT data.

Optionally an optimisation algorithm may be used to select the radius of the source box such that the signal to noise ratio of the source is maximised (default is no optimisation). This optimisation is turned on by specifying :

  ICL> XRTBCKBOX OPT

YOU SHOULD NOT OPTIMISE WHEN PRODUCING A SPECTRUM OF AN ON-AXIS SOURCE CONTAINING SIGNIFICANT SOFT (0.25 KEV) COUNTS. THIS IS BECAUSE THE PSF CORRECTION IN XRTCORR CANNOT COPE WITH THE 'ELECTRONIC GHOST IMAGE' EFFECT IN LOW ENERGY DATA. The algorithm uses a default energy of 0.5 keV. For sources which may have considerably harder or softer spectra than this, the energy may be set on the command line e.g. to set the energy to 0.2 keV.

  ICL> XRTBCKBOX 0.2

The optimisation should only be used on point sources.

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Next: Method Up: XRT ROSAT Prev: Wrapups