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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.

Predicted Counts

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

Observed Counts

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%

Comparison with Error Analysis

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.

Source Models

MBmod Source Model       DFmod Source Model       Source Models Plotted (.ps)

Contact CXC Calibration (cxccal@cfa.harvard.edu) for further information

Last modified: 09/25/12

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