The High Energy Telescope on EXIST

TL;DR

EXIST's High Energy Telescope aims to conduct the deepest all-sky survey for gamma-ray bursts, black holes, and transients, enabling rapid localization and follow-up observations across multiple wavelengths.

Contribution

This paper presents the design and recent engineering studies of the HET, a novel coded aperture telescope with a large CZT detector array for high-energy astrophysics.

Findings

HET will locate GRBs within 10-30 seconds with <20" accuracy.

The telescope's broad energy band (5-600 keV) and wide field of view enable detection of diverse high-energy phenomena.

Continuous sky scanning every 3 hours will provide detailed variability data for X-ray sources.

Abstract

The Energetic X-ray Imaging Survey Telescope (EXIST) is a proposed next generation multi-wavelength survey mission. The primary instrument is a High Energy telescope (HET) that conducts the deepest survey for Gamma-ray Bursts (GRBs), obscured-accreting and dormant Supermassive Black Holes and Transients of all varieties for immediate followup studies by the two secondary instruments: a Soft X-ray Imager (SXI) and an Optical/Infrared Telescope (IRT). EXIST will explore the early Universe using high redshift GRBs as cosmic probes and survey black holes on all scales. The HET is a coded aperture telescope employing a large array of imaging CZT detectors (4.5 m^2, 0.6 mm pixel) and a hybrid Tungsten mask. We review the current HET concept which follows an intensive design revision by the HET imaging working group and the recent engineering studies in the Instrument and Mission Design Lab at the Goddard Space Flight Center. The HET will locate GRBs and transients quickly (<10-30 sec) and accurately (< 20") for rapid (< 1-3 min) onboard followup soft X-ray and optical/IR (0.3-2.2 micron) imaging and spectroscopy. The broad energy band (5-600 keV) and the wide field of view (~90 deg x 70 deg at 10% coding fraction) are optimal for capturing GRBs, obscured AGNs and rare transients. The continuous scan of the entire sky every 3 hours will establish a finely-sampled long-term history of many X-ray sources, opening up new possibilities for variability studies.