rgssources creates the source list and adds to it the SRCLIST table. The extraction region extensions are added in the fourth stage (“spectra”) by rgsregions. The SRCLIST table is initialized with a variety of known or supposed source positions for which off-axis angles are calculated with respect to a particular reference pointing. One of these is selected to be the primary source (PRIMESRC), which is the nominal target source used later for the aspect-drift corrections and for fluxing in the final stage. If a user-defined source position is provided (parameter withsrc) it automatically becomes the primary source; otherwise rgssources selects the primary source on its own (see primestyle=auto in the task description). Selected sources are also imported from the EPIC source catalog, if provided (parameter withepicset). The default reference pointing is the one computed earlier by attfilter (parameter attstyle=expmedian), and it is not recommended to override this setting. Currently the aspect-drift corrections are computed using an approximate formula that assumes only small excursions from the reference pointing.
Do not restart rgsproc at this stage (“events”) for the purpose of adding more user-defined sources to the SRCLIST table. Running the pipeline over from scratch is not necessary and besides the new source will be added to a fresh source list rather than the existing one. Instead, invoke rgssources directly to update the existing source list and then restart rgsproc at the second stage (“angles”) after a change of primary source or at the fourth stage (“spectra”) after adding new spectrum sources or changing the background region.
