ISGRI

1. Systematic uncertainties of 1% should be added to ISGRI

2. When using OBS1_SearchMode=2, the position of sources detected in a single ScW and associated to catalog sources with ISGRI_FLAG=2 is assigned to the pixel centre, instead of being fixed to the catalog position as it should. Similarly, with OBS1_SearchMode=2 and OBS1_SouFit=1, the position of all sources (cataloged and new) is assigned to the pixel centre. Especially for bright sources, the displacement between the pixel centre and the true source position can produce important residuals in the science window images.
   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 (i.e. if ISGRI_FLAG=2 or OBS1_SouFit=1).

3. In the mosaic build with the option spread=1 the source flux is slightly reduced ( 10 %) compared to the weighted average of the fluxes measured in the Science Window.

4. The maximum number of sources handled by ii_spectra_extract is 200 but it is strongly recommended to only fit spectra of the sources that are effectively active (visible, detectable) during the Science Window.

5. With OSA10, new calibration files have been produced including a correction for the variation of gain across the entire mission, as observed in previous OSA versions. However, on single revolution time scale, a drift in counts is still observed. For the latest part of the mission, spectra extracted at the beginning and end of a same revolution can therefore show an artificial difference in counts. The secular drift observed in all bands over the mission life-time is known and due to the evolution of gain: this effect is accounted for by the set of ARFs available in the IC tree.

6. The position of the low-energy threshold is increasing with time (see Sect. 12.4.1). A safe lower limit for the response is 18 keV until revolution 848.
   Between revolutions 848-1090, we recommend to ignore data below 20 keV.
   From revolutions 1090 on, we recommend the user to ignore data below 22 keV.

7. A problem on-board IBIS causes event times to be shifted by 2 seconds under some circumstances (this is rare). The software tries to correct the data. The keyword TIMECORR found in the event files (*-*-ALL or *-*PRP extensions), indicates whether the correction was done. If you are doing an accurate timing analysis and your data contains TIMECORR 0 please take great care: If TIMECORR=1 or 2, the applied correction should be OK. If TIMECORR=3 you should better not use these data. If TIMECORR=4 contact ISDC.

8. The lightcurve extraction (ii_lc_extract) is performed by building shadowgrams for each time and energy bin. It potentially takes a large amount of CPU time and there is a minimum usable time bin. The time bin must be such that the total number of maps in the file isgr-corr-shad does not exceed 2 GB worth of disk space. The product of the number of time bins in a science window, and the number of energy bands must be less than about 9942.

9. ii_pif will crash if the input catalog inCat contains more than 500 sources.

10. At large off-axis angles the IBIS response is not well known and strongly energy dependent. Therefore, the user should be careful when analyzing observations performed at large off-axis angles, above 12 degrees, since systematic flux variations might be introduced. The systematic flux variations are energy dependent, and therefore the user should be careful both with photometric and spectral analysis of sources at large off- axis angles.