Hot pixels and columns are a routine feature of CCD detectors and
rgsproc takes action to exclude them from the spectra it
generates. The accumulation of nearly 1 million seconds data on the
bright blazar Mkn421 over the course of the mission has allowed a
class of cool pixels to be identified. These are single columns that
give signals a few percent below the values expected from their
immediately neighbours and are only likely to be relevant when
studying weak absorption features in spectra with high statistics. By
default, rgsproc does not discard these data but they can be
excluded using the keepcool
switch as in the following example:
rgsproc withsrc=yes srclabel=Mkn421 \ srcstyle=radec srcra=166.113808 srcdec=+38.208833 \ keepcool=no