Specific GRBM data analysis software

Except for the preliminary analysis software, the software for the analysis of GRBM ratemeters and spectra has been developed in the frame of this Thesis work. This software has been mainly developed with the IDL packages ver. 4.1 and 5.0; in the 240 channels spectra fitting procedures, the IDL programs have been interfaced with the CERN/MINUIT minimization software.

IDL is a licensed software particularly oriented to scientific data analysis; its main features and advantages are:

• an high level FORTRAN-like programming language, which is easy to be learned by people experienced in FORTRAN and allows to reduce substantially the length of programs with respect to FORTRAN and to perform operations directly on vectors and matrices;
• it permits to write events-driven programs with window graphic user interface (as the XASPLOT procedure described below);
• it contains instructions that allows excellent and flexible 2D and 3D plotting, surface//shade plotting, contour plotting, image plotting, etc.
• the standard distributions library is very rich of statistics, scientific and general data analysis purposes subroutines and functions; in addition, specific physics and astronomy libraries (e.g. the astrolib library) are available on the net.

The preliminary analysis of GRBM data is performed using XASPLOT, a graphic user interface interactive program developed by the PDS/GRBM hardware group in the IDL environment as a XAS contributed software. XASPLOT allows the user to perform many tasks, between which the most commonly used for GRBM data analysis are: preliminary data checks and plotting, rough background subtraction and conversion from XAS to ASCII formats.

Subsequent GRBM data analysis steps described in the previous sections of this chapter like background interpolation and subtraction, dead time corrections, introduction of systematics, flux and spectral evolution derivation from the 1 s ratemeters with the technique described in section 4.3, are performed by means of flexible programs and routines specifically written in IDL. Due to the capabilities of IDL, these programs do not only perform data analysis, but they perform also the plotting on video or postscript files and the creation of reports containing the results.

Although, as discussed in chapter 3 and in next subsection, the spectral fitting of the GRBM 240 channels energy spectra can be performed using standard public software, we have developed a specific fitting procedure composed by IDL routines interfaced via FORTRAN routines to the CERN/MINUIT software. The IDL part of the procedure perform data reading, pre-processing and final plotting and reporting. The MINUIT routines perform the $\chi^{2}$ minimization. In this way we take advantage both of the IDL package data handling and plotting capabilities and of the MINUIT software very powerful function minimization capabilities. The MINUIT algorithms allow for easier local minimum identification and new minimum search and better and more flexible error analysis with respect to e.g. XSPEC. The interface between IDL routines and MINUIT routines can be realized in two ways, depending on the machine operating system. One way is to create a specific module, written in C language, which has to be compiled with the MINUIT routines creating a share library, and use specific IDL call instruction to the C routine. With this method the data are transferred dynamically from the IDL routine to the MINUIT routines via the C module. Because this IDL instruction doesn't work in all operative systems, we have developed another interfacing method, which makes use of temporary files to transfer data.