A Simple Method to Improve the Quality of RXTE PCA Spectra

We fitted at once all of the several hundred RXTE PCA spectra of the Crab to a simple power-law model; the total number of counts in the composite spectrum is >10^9. We then used the spectrum of fit residuals (data/model) to correct large samples of spectra of G 339-4, H1743-322, and XTE J1550-564. The correction improved the quality of all the fits, and the improvement was dramatic for spectra with >10^7 counts. The Crab residual spectrum is somewhat different for each of the five PCA detectors, but it was relatively stable during the course of the 16-year mission. We provide public software that automates the process of applying the correction to PCA data and recommend that the correction be applied to all spectra with >10^6 counts.