GRB Probes of the High‐z Universe with EXIST

The Energetic X‐ray Imaging Survey Telescope (EXIST) mission concept was selected for further study under the Astrophysics Strategic Mission Concept Study (ASMCS) program. The mission design is optimized for study of high‐z GRBs as probes of the early Universe. With a 4.5 m2 imaging 5–600 keV (CZT) detector imaging a 90°×70° (>10% coding fraction) field of view with 2’ resolution and 5σ sources, EXIST will perform rapid (<200 sec) slews onto GRBs and obtain prompt images and spectra with a co‐aligned soft X‐ray telescope 0.1–10 keV) and with a 1.1 m optical‐IR telescope (IRT) simultaneously in 4 bands (0.3–0.52 μm, 0.52–0.9 μm, 0.9–1.38 μm, and 1.38–2.3 μm) for prompt identification (by dropouts or variability) of the GRB within a 3.75×4.25’ FoV. An autonomous spacecraft re‐point (<2’) will then (at ∼300 sec after GRB trigger) put the GRB on a 0.2×10” slit for either R = 3000 (for AB <21) or R = 30 (for AB ∼21–25) prompt spectra over the 0.3–0.9 μm and 0.9–2.3 μm bands. Thi...