Imaging Hard X-ray Sky by EXIST
JaeSub Hong
Harvard University
jaesub@head.cfa.harvard.edu
Additional authors: Gerry Skinner, and EXIST imaging TWG
The proposed black hole finder concept, EXIST consists of a cluster of wide-field hard X-ray code-aperture imaging telescopes, with a total of 8 m^2 CZT detector arrays. The survey sensitivity of EXIST is ambitious - 50 uCrab after 1 year (<150 keV), which is 100 times more sensitive than the HEAO-A4 survey - the most extensive existing survey in this band. Preliminary analysis indicates that this high sensitivity goal is well within a reach, despite the expected low signal-to-background ratio (S/B ~ 10^-3 or 10^-4) for sources at the sensitivity limit. Successful operation at such a low signal-to noise ratio is has never yet been achieved with the coded-aperture technique. However, our analysis shows that the continuous scanning mode of telescope operation provides a crucial advantage in achieving such an unprecedented sensitivity by canceling out noises commonly arising from unknown systematics. The EXIST imaging technical working group has been formed to optimize all imaging aspects of the Exist mission and to ensure its success. First, we will focus on validating the proposed means for achieving the sensitivity goal under very realistic situations, considering a wide variety of possible systematics. Second, we will investigate various alternative design concepts to find the optimal telescope configuration for the given science - the black hole survey. In this contribution, we overview the reference design of EXIST and the current status of EXIST-related imaging studies, and we outline the plan for future studies.
