HRC-S Quantum Efficiencey Verification
using White Dwarf HZ 43
Deron Pease, Hank Donnelly, Jeremy Drake
For this study we employed the hot white dwarf HZ 43 (ObsID 59) to perform HRC-S on-axis QE calibration/confirmation over the low energy range 0.065 - 0.20 keV.
Martin Barstow (MB - Leicester University, UK) and
David Finley (DF - Eureka Scientific)
each provided source models for HZ 43 (see models below).
Using IDL to convolve the source models with the current state of
the HRC-S QE model (version 1.1), we were to generate predicted HRC-S counts.
The predicted counts with total model uncertainties are:
377336   ±   15.0%       - MB
321097   ±   15.0%       - DF
The HRC-S observation of HZ 43 was conducted with the LETG inserted.
To compare with the no-grating HRC-S on-axis QE,
we extracted the observed counts from a circle around 0th order,
and accounted for attenuation by the LETG.
A very large HRC-S background region was defined as the active detector
minus the source region.
The background-subtracted observed counts are:    338624   ±   0.2%
The source models for HZ43 have uncertainties of ~15.0%.
The HRC-S QE over this range was not calibrated prior to flight.
An educated guess at the low energy HRC-S QE was made,
with the uncertainty stated to include all physically possible values.
Thus, we rely on the HZ 43 source models to constrain the HRC-S QE
and provide the total model uncertainty of at least ~15%.
With the MB model the HRC-S sees 11.4% less (absolute difference) than predicted by the model. With the DF model the HRC-S sees 5.2% more than predicted by the model. For both models the observed matches the predicted within the 15.0% total model uncertainty.
Last modified: 09/25/12
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