The X/Gamma-ray Imaging Spectrometer (XGIS) for THESEUS and other mission opportunities

Abstract

We describe the science case, design and expected performances of the X/Gamma-ray Imaging Spectrometer (XGIS), a GRB and transients monitor developed and studied for the THESEUS mission project, capable of covering an exceptionally wide energy band (2 keV -10 MeV), with imaging capabilities and location accuracy <15 arcmin up to 150 keV over a Field of View of 2sr, a few hundreds eV energy resolution in the X-ray band (<30 keV) and few micro seconds time resolution over the whole energy band. Thanks to a design based on a modular approach, the XGIS can be easily re-scaled and adapted for fitting the available resources and specific scientific objectives of future high-energy astrophysics missions, and especially those aimed at fully exploiting GRBs and high-energy transients for multimessenger astrophysics and fundamental physics.

Imaging performance above 150 keV of the wide field monitor on board the ASTENA concept mission

“…Exploiting the fact that Gamma-rays will trigger both the top and bottom SDDs, while X-ray trigger only the top SDDs, in addition to the differences in the charges pulses shapes for the two kind of events (direct detection in the SDDs and detection of scintillation light), we are able to distinguish between the two type of events. This configuration has been proposed for the instrument XGIS (X/Gamma-ray Imaging Spectrometer) aboard the space mission THESEUS, 3 selected by ESA for Phase 0 study for the M7 program. In this paper we study a possible evolution of the XGIS concept: the Wide Field Monitor -Imager and Spectrometer (WFM-IS), proposed as part of the payload for the concept mission ASTENA (Advanced Surveyor for Transient Events and Nuclear Astrophysics).…”