Replying to John's questions about pileup; The print_kernel gives me, e.g., (similar for psffrac~0.95 or for the other source) isis> print_kernel(1); 1: 0.211913 0.929297 2: 0.029725 0.0673295 3: 0.00277968 0.00325211 4: 0.000194952 0.000117811 5: 1.09384e-05 3.41426e-06 *** pileup fraction: 0.0707029 where 26 pileup<1>.nregions 0 1 1 1 10 27 pileup<1>.g0 0 1 1 0 1 28 pileup<1>.alpha 0 0 0.5165195 0 1 29 pileup<1>.psffrac 0 1 0.9 0.9 0.95 I expected a pileup fraction of ~9% based on PIMMS, so this is pretty close (not sure what to make of the other output). Alpha does change in the opposite direction to psffrac, but the source model parameters don't seem to change significantly (of order 1% or less). For one source, I get alpha=0.43 when psffrac=0.95, alpha=0.52 when psffrac=0.9. For the other, I get alpha=0.53 when psffrac=0.95, and alpha=0.62 when psffrac=0.9. The fits are about equally good for either set of values. Generally alpha seems to have (90%) errors of ~0.07 to 0.14 or so either way for any fixed psffrac value. -CraigReceived on Tue Apr 30 2002 - 18:58:06 EDT
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