XMM-Newton Science Analysis System


specgroup (specgroup-1.7.1) [xmmsas_20230412_1735-21.0.0]

Minimum number of counts

With this option the spectrum is grouped such that each group contains a minimum number of (source+background) counts. This is the equivalent to the "group min 25" command available in the ftool GRPPHA. e.g.

which would produce a group for each set of bins which contained 50 or more counts. By default the grouping begins from the low energy end (usually the first channel). To reverse this and start from the high energy end use:

Note this grouping is based on the number of counts in the source spectrum, which may also contain background.