Surveys for accreting black holes in binaries or active galactic nuclei, as well as high energy transients and Gamma-ray Bursts, are best carried out with wide-field hard X-ray (~5 – 600 keV) telescopes. Unlike focusing X-ray telescopes (e.g. Chandra) which image by grazing incidence optics over a small (~10arcmin) field of view, coded aperture telescopes (e.g. Swift/BAT) can image over a ~70 degree FoV, though with reduced sensitivity due to higher backgrounds. We have developed a series of ever more sophisticated telescopes and finely pixelated imaging detector arrays that are tested, and conduct science, on high altitude (~39km) balloon flights under our NASA grants. The Oct. 2009 ProtoEXIST1 flight (see below) was very successful and will be followed by a Sept. 2012 ProtoEXIST2 flight with the highest spatial/spectral resolution, ~4X finer than Swift/BAT. The telescope/detector is a prototype for 4 such telescopes that may be launched in 2016 on a Brazil satellite (MIRAX-HXI) for a full southern-sky Time Domain Astrophysics survey mission in the era of LSST and Advanced LIGO.
Branden Allen, Jonathan E. Grindlay, Jaesub Hong