Monte Carlo Simulator and Ancillary Response Generator of Suzaku XRT/XIS System for Spatially Extended Source Analysis

Abstract

We have developed a framework for the Monte Carlo simulations of X-Ray Telescope (XRT) and X-ray Imaging Spectrometer (XIS) on board Suzaku, mainly for the scientific analysis of spatially and spectroscopically complex celestial sources. A photon-by-photon instrumental simulator is built on the ANL platform, which has been successfully used in ASCA data analysis. The simulator has a modular structure, in which the XRT simulation is based on a ray-tracing library, while the XIS simulation utilizes a spectral “Redistribution Matrix File” (RMF), generated separately by other tools. Instrumental characteristics and calibration results [e.g., XRT geometry, reflectivity, mutual alignments, thermal shield transmission, build-up of the contamination on the XIS optical blocking filters (OBF)] are incorporated as completely as possible. Most of this information is available in the form of FITS (Flexible Image Transport System) files in the standard calibration database (CALDB). This simulator can also be utilized to generate an “Ancillary Response File” (ARF), which describes the XRT response and the amount of OBF contamination. An ARF is dependent on the spatial distribution of the celestial target and the photon accumulation region on the detector, as well as the observing conditions, such as the observation date and satellite attitude. We describe the principles of the simulator and the ARF generator, and demonstrate their performance compared with in-flight data.