The rmfit software package was developed by members of the gamma-ray astronomy group at the University of Alabama in Huntsville. It uses a forward-folding technique to obtain the best-fit parameters for a chosen model given user-selected source and background time intervals from data files containing observed count rates and a corresponding detector response matrix. rmfit displays lightcurves and spectra using a graphical interface that enables user-defined integrated or time-resolved spectral fits and binning in either time or energy. Originally developed for the analysis of BATSE Gamma-Ray Burst (GRB) spectroscopy, rmfit is a tool for the spectroscopy of transient sources. It has evolved considerably to accommodate the Fermi GBM and LAT data. Limited support is available for data from other instruments such as the Swift BAT. More information is available in the installation notes and accompanying tutorial.
You can install the GBM rmfit tool using the precompiled binary. The system requirements are:
Mac OS X 10.6 (Snowleopard) or higher
a machine with Linux or a Linux derivative