omlcbuild (step13). The task omlcbuild generates
coincidence loss and dead-time corrected source time series using the source and
background rates produced by evselect. The background rates are
subtracted and the photometry corrections are applied. If the source is offset
from the centre, the knowledge of the PSF is used to account for possible
missing photons. Time dependent sensitivity degradation is corrected as for
image data. A light-curve is obtained as final result for each of the sources
in the fast mode windows in the exposure.
The parameter bkgfromimage=yes can be used to measure the background in
the associated image mode data. This is the default option in SAS version 14.
(See section § 6.3.4.)