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J.E. Davis (MIT/CXC)
The problem of pileup in CCD cameras is discussed and a possible solution to the problem is proposed. The resulting pileup equation is quite general, including the effects of grade migration, and presents itself as a modification to the standard \verb|xspec| style equation used by spectral fitting programs. It is found that the computation time for handling pileup scales linearly with the number of piling photons. For these reasons, the model may be readily incorporated into spectral fitting programs.
The effectiveness of the model is demonstrated by its application to the heavily piled zeroth order data obtained by the Chandra X-Ray Observatory for II Pegasi, a highly active RS CVn binary star. II Pegasi was observed on 17-18 October 1999 using the Advanced CCD Imaging Spectrometer (ACIS) in conjunction with the High Energy Grating Spectrometer (HETGS). The predictions of the pileup model are shown to agree quite well with the observed zeroth order CCD spectrum.
This work was supported under Chandra X-Ray Center contract SV1-61010 from the Smithsonian Astrophysical Observatory.
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