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POLAR model

The POLAR option permits a polar model of the specified psf to be constructed. The syntax is, POLAR(psf,rbin[,abin]) where psf is the name of an instrument psf (eg. XRT_PSPC).

The value rbin tells the psf system how to construct the radial bins. A single value simply specifies a bin width. The psf system auto- matically finds the number of radial bins in the dataset. An alternative specification is to supply radial bin boundaries separated by colons. In both methods of specifying rbin the values should be in the datasets axis units.

Optionally abin can be used to specify the number of azimuthal bins. If omitted, the default is one. Some examples are,

Radial bins every 10 arcmin starting from zero. Only one azimuthal bin.

  POLAR(PWFC,10.0)

5 arcmin radial bins, and 5 azimuthal bins,

  POLAR(PWFC,5.0,5)

Defines radial bins 0->5, 5->10, 10->30, 30->60 and 60->infinity.

  POLAR(PWFC,5:10:30:60)

Note that regardless of the number of azimuthal bins selected, the psf system only creates one bin from on-axis to the first radial bin boundary. This is done to eliminate any chance of discontinuities in the psf data precisely on-axis, where there is greatest likelihood of there being an interesting source.

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