Converting data files from Chandra

In order to be a general-purpose tool we programmed Cora to require ASCII input which can be produced from any type of other format, which is much more difficult the other way around. The output of the Chandra software CIAO is in fits format with two layers representing the plus and minus order spectra. We provide an IDL script read_letg.pro that reads in the CIAO output and creates a co-added spectrum in CORA format. In IDL this script is called with
IDL> read_letg,/all
The output can be found in a file leg.dat and the keyword /all includes the effective areas as a sixth column in this file (see previous Section). . The script requires mrdfits (part of the astrolib) and interp_header (part of the atomdb package). The IDL script read_rgs.pro contains the function interp_header and can be used by compiling this script
IDL> .compile read_rgs
before starting read_letg. Another script is available for HETG data, read_hetg.pro, which works in the same way and produces two output files, meg.dat and heg.dat for the MEG and HEG spectra, respectively. Note that co-added spectra are produced, i.e., the two opositive dispersion orders are co-added and the respective effective areas are co-added. Individual spectra can be produced by adding the keywords /plus or /minus to read_hetg.