On the upper right frame of the GUI (Fig.), the functionality for simultaneous fitting of diffuse emission and point sources is provided, but we encourage the reader to consult the specific handbook of spimodfit to understand how this is handled. We suggest the general user not to exploit this functionality, unless he/she knows well the instrument and the program.
The bottom frame regards the background settings. The entry for the background file can be left empty to allow the internal handling, this is our suggested choice, or can assume the value back_model_idx.fits to use the background computed in the background step. The following entry regards this case, so that the user can allow for multiple background components, this is an advanced feature that should be used with a deep knowledge of spimodfit . The entry with the fitted detector ID range allows the user to select different ranges of the detectors to fit the background, the choice 00-18 is suggested so that the background at this stage is handled as a constant. The entry time variability definition allows the user to define time variability nodes and intervals. The default values regard the SPI annealing times and the detector failures plus a variability on science window time scale (0.084 days).
The button on background multipliers opens a window (Fig ) through which the user can make the program to compute a given background pattern. The relevant parameters are the detector ranges and the variability coefficients. The former is by default the list of all detectors so that each detector can be treated separately. The latter covers by default the SPI annealing times and a monthly variability. This is the best choice for point sources. We suggest not to touch the other parameters of the window, unless a specific analysis is pursued.