An IRAF-based pipeline for reduction and analysis of archived ROSAT data

Here we describe how IRAF/PROS was used to compute source hardness ratios for the recently published Einstein Catalog of IPC X-ray Sources. This catalog was prepared from the Imaging Proportional Counter (IPC) data of the Einstein X-ray Observatory, which operated in low-earth orbit from 1978 Nov until 1981 May. Before the catalog went to press, it was discovered that a bug in the production processing system had rendered the hardness ratios unreliable. For this reason, it was necessary to generate corrected hardness ratios for inclusion in the catalog. Our corrected hardness ratios were generated for ~4000 tabulated sources using the PI-corrected 'qpoe' files from the IPC event list CDROMs. An IRAF script was written which, given a list of sources, performs spectral extraction and computes the source and background count values needed for the hardness ratio calculation. These values were used as input for a previously-developed maximum likelihood algorithm to compute hardness ratios and errors for the sources. Using existing IRAF commands and tasks, we were able to process a large amount of the data quickly and conveniently. For tasks such as detailed data formatting and file manipulation, however, it was convenient to invoke AWK and Unix scripts. This underscores the desirability of having heterogeneous analysis tools even more readily available to scientific users in a unified software environment.