Here is a brief summary of pcarmf v7.01, tentatively slated for release with the next ftools
delivery.  The "tentatively" should only suggest that if further improvements in creating
agreement between the matrices can be obtained, I will release that.

jpg  figure with gamma vs time for 5 PCU
Figure 1 shows the power law index fit to the first layer of each PCU as a function of Mission Day. The fit includes energies from 3. - 25. keV. The individual PCU are allowed to find their own preferred indices. There is some structure, correlated form PCU to PCU, that is not modelled, but there is no long term trend, and the variations within each PCU are small. The best fit indices are still somewhat high compared to the canonical value, but these matrices should be good for those who seek trends across the duration of RXTE. The quality of individual matrices is shown with residuals to fits to the Crab on different dates: April 26, 1996 December 20, 1997 February 24, 1999 August 1, 1999 (Epoch 4) While you are the ultimate judge, the residuals are relatively good compared to most previous efforts, and comparable (in fact I think the same) to v2.2.1, (which some have referred to as the "pre-fab" matrices) for which there was a definite trend with power law index vs time. For the time between now (12-20-99) and the release of the next ftools, I will construct v7.01 matrices for anyone who requests them. (send requests to keith.jahoda@gsfc.nasa.gov with a copy to xtehelp@athena.gsfc.nasa.gov) (I will be out for just a day or two at Christmas, and GSFC will be closed with the power off over the New Year's weekend. Otherwise, the response should be timely)