| The Energetic X-ray Imaging Telescope Experiment (EXITE) is a balloon-borne hard x-ray telescope with sensitivity in the 20-300 keV energy range. EXITE uses a 34.5 cm diameter NaI scintillation crystal bonded to the photocathode of a large image intensifier tube. Imaging is accomplished through a graded uniformly redundant array coded-aperture mask to give 22 arcminute resolution over a 3.3{dollar}spcirc{dollar} FWHM field-of-view. We describe detector and gondola systems design, assembly, and testing, including techniques for detector calibration before and during flight. We also describe gondola pointing and ground-based command and data acquisition systems.; Observations were obtained during two flights: one in October 1989 from Ft. Sumner, NM, and one in May 1989 from Alice Springs, Australia. Detector and gondola system performance during these flights is evaluated. We discuss the methods for image processing and spectral analysis with emphasis on calibration results and the impact of non-uniform background on image reconstruction. We present observations of the Crab x-ray source to verify the overall performance of the instrument.; Observations are discussed in terms of power-law spectral signatures for black holes and constraints on inverse Compton models. We present observations of black hole candidates Cygnus X-1 and GX339-04, which we have detected. We also present observations of the galactic center region, including a detection of the black hole candidate 1E1740-2942 and a possible new transient source. Finally we present upper limits to hard x-ray emission from the black hole candidate A0620-00 with constraints on quiescent accretion for models of soft x-ray transients. |
