PSPC

The following is a brief overview of the basic reduction sequence, the details are shown in the later subsections.

ROSAT data may be obtained from a datatape or from the Leicester data archive (LEDAS). In either case the raw data should be copied into a single directory. It is important that this directory does not contain any raw datafiles from another observation as this can cause problems with the pre-processing.

• Users of ASTERIX earlier than version 2-3-0 will need to apply xrtconv to the raw dataset to convert it into ASTERIX format.
• showxrt will produce a summary of the observation, listing information such as target name, pointing direction and exposure time.
• The program xrthk may be used to "clean" the data by producing a file of times when the background was low.
• xrtsort can now be used to sort the data directly into an ASTERIX data file. Example 1 shows xrtsort being used to create an image. If a file of time slots has been created with xrthk this can be used in xrtsort when sorting the data (see Example 2).
• The data can be background subtracted with the program xrtsub. A background file should first be sorted from a blank area of sky with xrtsort.
• xrtcorr is used to exposure correct a dataset. This includes corrections for instrumental effects, such as vignetting, dead time as well as normalisation to on-axis counts/sec.
• A detector matrix needs to be produced with xrtresp before spectral fitting can be performed. To use xspec convert the files using ast2xsp.