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B.2 Spectral

 

There is some temporal variation of the PSPC gain which is not included in the gain correction process currently applied to data in SASS.   

This effect showed up primarily as inconsistencies between calibration spectra of N132D taken at different epochs across the ROSAT mission. Another artifact of the problem is highly significant residuals in number of spectra compared to the expected model, these appear as large negative residuals below about 0.20 keV and large positive residuals between about 0.20 to 0.40 keV. An example of this effect is in

ftp://heasarc.gsfc.nasa.gov/rosat/problems/temporal_gain/spectral_problem.ps

for more detail see [Turner1993]. Initial analysis suggests the gain shift is energy dependent. Findings to date are summarized in TN-ROS-ME-ZA00/032 [Prieto et al.1994].