The executable ii_shadow_build creates shadowgrams of ISGRI events in the given time (Tbin) and energy (Ebin) ranges. For every shadowgram a corresponding efficiency shadowgram is created. For pixels active during the revolution (switch status ON), efficiency falls into two components and is null for the others: the first factor takes into account the dead time of the corresponding module MDU; the second factor reflects the efficiency energy dependence, extracted from ISGR-EFFC-MOD structure.
The position of the characteristic low threshold value is evolving with time as can be seen in the Fig. 32, with the ISGRI efficiency being lower than 50% below this energy. As an example, for revolutions later than Rev.1000, energies below 22 keV should be ignored, and after Rev. 1600 it is not possible to use ISGRI data below 30 keV for accurate spectral fitting.
Together with the NOMEX correction, applied in ii_skyimage, ii_spectra_extract and ii_lc_extract, the efficiency energy dependency model attempts to recover the equivalent ``true'' spectrum, independent of the time in the mission and source position in the FoV. It should be noted that interpretation of the count rates derived from the efficiency-corrected detector count rates, should be done with caution, owing to several limitations:
This executable also applies two different noisy pixel detection techniques. The first one is time-based; it discriminates every pixel for which the scientific SELECT_FLAG equals one (even only once over all the Science Window events). Note: this flag was filled by the executable ibis_isgr_evts_flag. The second method is spectral-based; it discriminates pixels by estimating their spectral deviation from the average ISGRI spectrum. This spectral method can be switched ON/OFF by parameter NoisyDetFlag.
|(in the main script)||(executable)|
|IBIS_II_ChanNum||isgri_e_num||integer||Number of energy intervals for ISGRI.
possible values: 1 - 10
|IBIS_II_E_band_min||isgri_e_min||string||List of lower energy boundaries (keV).
default: "15 40 100 200 400 700 1200"
|IBIS_II_E_band_max||isgri_e_max||string||List of upper energy boundaries (keV).
default: "40 100 200 400 700 1200 2500"
|IBIS_NoisyDetMethod||NoisyDetFlag||integer|| Defines the way to deal with noisy pixels
possible values: 0 Time-based noisy detection;
1 Time-based + Spectral-based method.