Binning of EPIC spectra

SAS, by default, generates spectra of pn and MOS observations which are highly oversampled with respect to the energy resolution of the EPIC cameras. This allows users to bin their spectra in an optimum way, considering the specific spectral characteristics of the source and the number of collected photons. However, using the originally not binned, highly oversampled spectra for model fits and statistical tests leads to wrong results, e.g. chi2 is significantly underestimated. This often erroneously mimics an acceptable fit of the model to the data.

Future SAS versions will support sophisticated binning of all XMM-Newton spectra, taking into account the energy resolution and the levels of source and background spectra.

Further details are given in the Minutes of the XMM-Newton UG Meeting#10 and in the SAS workshop talk on "Spectral Analysis and Statistics"