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specgroup (specgroup-1.6) [xmmsas_20160201_1833-15.0.0]

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Minimum resolution

If the number of counts in a spectrum is very high then a statistical grouping can dramatically oversample the instrument resolution. This can cause problems during spectral fitting because the bins are then not completely independent.

A minimum energy width of each group can be enforced by setting the parameter oversample. e.g.


\begin{code}{\em specgroup spectrumset=srcspec.ds mincounts=25 oversample=3 rmfset=myrmf.ds }\end{code}

would ensure that no group was narrower than 1/3 of the full width half maximum (FWHM) resolution at the central photon energy of the group.

$\Delta E >= FWHM(E)$

where the values of FWHM(E) are read for a given instrument from a calibration file (XMM_SPECQUAL_nnnn.CCF for XMM instruments).


XMM-Newton SOC/SSC -- 2016-02-01