The restoration of astronomical X-ray spectra.

The present limitations in the measurement of astronomical X-ray spectra are discussed with particular regard to the poor spectral resolution of gas proportional counters. The problem of inferring an incident photon spectrum from the data is considered. Current procedures and their drawbacks are outlined, and a direct method of solution is derived by presenting the data as a Fredholm integral equation of the first kind. This approach utilizes singular function decomposition of the resolution operator with appropriate filtering to stabilize the solution in the presence of noise. After illustrating the operation of this technique on computer simulated data, analysis of Ariel V data is presented. The general applicability of this method of analysis in X-ray astronomy is considered.