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. We estimate the current error to be +/-3% for PIN, and +/-5% for GSO.

The HXD team is continuously studying the background behavior to improve the systematic error. Details on our understanding and the current status will be posted in the future on the Suzaku web site.

2: Responses and Background Files

• ae_hxd_pinxinom_20051104.rsp: PIN response file for a source observed at the "XIS nominal" pointing position
• ae_hxd_pinhxnom_20051104.rsp: PIN response file for a source observed at the "HXD nominal" pointing position
• ae_hxd_pinbkg_20051105.pha: PIN background file
• ae_hxd_gso_20051019.rsp: GSO response file
• ae_hxd_gsobkg_20051105.pha: GSO background file

Please note that we do not have separate rmf and arf files for the HXD.

The PIN response is roughly 10% higher when a point source is observed at the "HXD nominal" pointing position, compared with the default ("XIS nominal") position.

3: Simulation procedure of HXD data for Cycle 1

For an accurate feasibility study, systematic uncertainties in the bacground 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 4 of Technical Description for details.