Calibration Access and Data Handbook

Description

The files provide the encircled energy function within the X-ray point spread function of each of the three mirror modules. The encircled energy functions are tabulated at discrete energies for an on-axis position of the source. The circular windows in which the encircled energy is calculated are assumed to be perfectly centered on the PSF.

• The table section provides the on-axis encircled energy fraction as a function of the radius of the circular window in mm. The tables are used by the CCF access layer to interpolate the on-axis encircled energy function of one mirror module to any energy.

• Scaling parameters (conv, cor1 and cor2) are provided in the headers of the XRT_XENCIREN CCF files. They are used to correct the on-axis encircled energy fraction for off-axis position of the extraction window. There units are arcsec/mm, arcsec$^{-1}$ and arcsec$^{-2}$, respectively.