Cookbook for HXD Simulations
2012 October, HXD Team
Note added on 2014 December 22: Note that proposals that require HXD data are not allowed in AO-10; however, proposers may discuss additional scientific objectives that could be achieved if the HXD data are available. In preparing such proposals, these files, originally provided for Cycle 7 propers, can be used.
1: Introduction
The HXD covers the highest energy range of the Suzaku band-pass, from 10 to 600 keV. The detector is a collimated well-type phoswich array designed to achieve the lowest background, and therefore the highest sensitivity ever achieved, in this band.
In spite of the low detector background, the sensitivity of the HXD is dominated by the systematic error of the instrumental background estimates. We suggest you fully take into account this error in all simulations.
To restate: only objects brighter than the systematic error of the background estimate at the energy band in question are detectable.
The background systematic error will have an energy dependence as well as a time dependence. See Technical Description for details. For example, with 100 ks exposure, the systematic errors are +/-3% for PIN in the 15-40 keV band and 1.5% for GSO in the 50-100 keV band.
2: Responses and Background Files
Files can be obtained individually following the links below, or collectively by downloading this gzipped tar file containing all 4 (note, however, that the response files are identical to those found in the Suzaku CALDB).
For the PIN
- ae_hxd_pinxinome9_20100731.rsp: PIN response file for a source observed at the "XIS nominal" pointing position
- ae_hxd_pinbkg_20101012.pha: PIN background file (exposure: 3 Msec)
For the GSO
- ae_hxd_gsoxinom_20100524.rsp: GSO response file for a source observed at the "XIS nominal" pointing position
- ae_hxd_gsobkg_20101012.pha: GSO background file (exposure: 3 Msec)
Notes
- The background files are generated based on the Lockman hole observation performed on 2009-06-12. The PIN threshold (and hence the response) of Epoch 9 is applied. Channels below E=15 keV should be ignored due to the uncertainties in the response and the background. As long as this is done, the simulations should be accurate for AO-7 observations.
- The PIN background includes CXB contribution, and simulated to have an exposure of 3 Msec. In the GSO case, CXB is negligible and is also simulated to have an exposure of 3 Msec.
- Please note that we do not have separate rmf and arf files for the HXD.
- Please also note that the background in the above files drop sharply above ~77 keV for the PIN, and ~750 keV for the GSO. These are outside the nominal bandpass of these detectors, and should not affect the feasibility studies.
3: Simulation procedure of HXD data
For an accurate feasibility study, systematic uncertainties in the background estimation must be taken into account. This can be done by reading the background files into xspec both as background and correction files, and then using the cornorm command. See Chapter 5 of Technical Description for details.
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