Modeling and Reproducibility of Suzaku HXD PIN/GSO Background

TL;DR

This paper presents a detailed model of the Suzaku HXD background, demonstrating high reproducibility and low systematic errors, which enhances the sensitivity of hard X-ray observations despite the lack of imaging capability.

Contribution

The study develops a comprehensive background model for Suzaku HXD that accounts for temporal variations, improving reproducibility and reducing systematic errors in background estimation.

Findings

Background model achieves less than 3% systematic error for PIN in 10 ksec exposures.

Model reproduces GSO background with less than 1% systematic error.

Reproducibility depends on event selection criteria and integration time.

Abstract

Suzaku Hard X-ray Detector (HXD) achieved the lowest background level than any other previously or currently operational missions sensitive in the energy range of 10--600 keV, by utilizing PIN photodiodes and GSO scintillators mounted in the BGO active shields to reject particle background and Compton-scattered events as much as possible. Because it does not have imaging capability nor rocking mode for the background monitor, the sensitivity is limited by the reproducibility of the non X-ray background (NXB) model. We modeled the HXD NXB, which varies with time as well as other satellites with a low-earth orbit, by utilizing several parameters, including particle monitor counts and satellite orbital/attitude information. The model background is supplied as an event file in which the background events are generated by random numbers, and can be analyzed in the same way as the real data. The reproducibility of the NXB model depends on the event selection criteria (such as cut-off rigidity and energy band) and the integration time, and the 1sigma systematic error is estimated to be less than 3% (PIN 15--40 keV) and 1% (GSO 50--100 keV) for more than 10 ksec exposure.