Miscellaneous on Imaging

• With the parameter OBS1_ExtenType (to find it on the GUI pages press the hidden button, and go to the IMA page) you can choose whether to keep the Residual and/or the true Exposure image in the isgri_sky_ima.fits file. With OBS1_ExtenType=``0'', 4 maps will be created per energy range (Intensity, Variance, Significance and Residuals). With OBS1_ExtenType = 1 true exposure maps will be written instead of residual images at the 4*n-th extension of isgri_sky_ima.fits. The new default value, ``2'' (instead of ``0'' before OSA 10), will add the true Exposure maps in an additional extension. OBS1_ExtenType = 3 will add single true Exposure map as the last extension. Please note that the change of default value (from ``0'' to ``2'') affects also the mosaic images as instead of an on-time map in the image mosaic file (isgri_mosa_ima.fits) one now gets an effective exposure map which has much lower values, because of the half-opening of the coded-mask and various vignetting effects that are here taken into account.

• If you are interested in running the analysis in more than 10 energy bands please see Section 9.5.

• You can decide if you want to let the software find the best fit position of a source (in the vicinity of the one in the catalog, default OBS1_SouFit=0), or if you would prefer the catalog position (for all sources from the input catalog!) to be used for the flux determination (OBS1_SouFit=1). If OBS1_SouFit=1, then the position of a new source is always attributed to the pixel center, and for catalog sources the catalog position is used for SearchMode=1,3, or the pixel center for SearchMode=2. Note that OBS1_SouFit=1 fixes all the source positions only in the individual Science Window analysis. In the mosaic, all source positions are always fitted regardless of the value of OBS1_SouFit. These fitted values are written to RA_FIN and DEC_FIN columns of isgri-srcl-res.fits, and are later used in spectral and lightcurve extraction steps as a source position. To fix the positions of only several sources, set for them ISGRI_FLAG=2 in the input catalog. For the weak sources with well-known positions it is recommended to use the catalog position (ISGRI_FLAG=2), whereas for bright sources, whose position is determined by the software with an accuracy better than , it is recommended to let the software to fit the position of the sources (ISGRI_FLAG=1).

  WARNING:

  When using OBS1_SouFit=1 with OBS1_SearchMode=2, not only the position of new sources but also that of cataloged ones is assigned to the pixel centre, instead of being fixed to the catalog position. It is therefore strongly recommended to avoid this combination of parameters. This problem is not present with OBS1_SearchMode=1 or 3, since in this case the catalog position is used when no fitting is requested (see also Sect.11).

• For OBS1_SearchMode = 1 or 3 (where you are forcing a catalog extraction) ghosts can be cleaned even from the known sources that happen to have a negative peak. This is done using OBS1_NegModels = 1 while with OBS1_NegModels empty or equal to ``0'' (the default) the deconvolved images will be cleaned from positive source ghosts only.