Input Data Formats

   

There are two main data format that can be input to the timing analysis commands: Binned Data Tables (BDT) and Photon Event Tables (PET).   

1. A BDT is a two-column MIDAS table: the first column (R*8) contains the starting time of the current bin (measured starting from the value reported in the BIN_START descriptor), and the second (R*4) contains the number of counts in that bin. The gaps in the light curve correspond to time jumps in the first column. The EXSAS descriptor FILE_TYPE is BIN. Besides the EXSAS main header, few special descriptors are associated to a BDT, namely:
   • BIN_SIZE (R*8) Bin size (in the units of the input dataset). It specifies the distance between two consecutive bins in absence of gaps.
   • BIN_START (R*8) Is the starting time (in the units of the input dataset) of the first bin. The times reported in the first table column are offset from this value.
   • BIN_END (R*8) Is the starting time (in units of the input dataset) of the last bin in the table.
2. A PET is a MIDAS table with a number of columns between 1 and 7. One of the columns must contain the arrival times of the photons (R*8), and the table must be explicitly sorted in time. This means that, even though the arrival times are actually in increasing order, the table must be sorted with the command SORT/TIME. The EXSAS descriptor FILE_TYPE is either PET or PETC (photon arrival times are barycentric corrected). Besides the main EXSAS header there are some custom descriptors important for timing analysis:
   • NR_DATASET (I*4) Is the number of datasets contained in the file. This number must be 1 in order for the file to be accepted by the timing commands.