Spectral analysis accepts as input data set a count rate spectrum, which has to be properly rebinned with regard to count statistic. Such a spectrum cannot be directly projected out of an event file. It has to be prepared carefully by consideration of timing and spatial information, especially, if background subtraction is applied. This data set is produced by prepare/spectrum as a table with up to nine columns. Descriptor file type should be SPE. The first three columns are mandatory. They describe how the spectrum is binned and which channels are considered in a fitting procedure. At least two other columns are necessary which contain the observed count rate spectrum of the source, or the background, or the total spectrum. Of course, any combination of these spectra is also possible. The column labels of this table and their units are described in Table 6.1.
Table 6.1:
Table Column labels of a count rate spectrum
Beside the general EXSAS header there are several special descriptors associated to this table. They contain the result of the history how the observed spectrum was extracted from the original photon event file. This special header is collected in Table 6.2 Until now the spectral analysis is taking no usage from this information. Details about this header can be found in C.
Table 6.2:
Special descriptors of an observed count rate spectrum