Hard X-ray astronomy using high sensitivity balloon-borne telescope

Abstract

Despite remarkable success in the low energy X-ray astronomy in the past two decades, the high energy regime is relatively unexplored. This is mainly due to fundamental limitations arising from the sensitivity of the detector systems. The study of X-ray sources above 10 keV is one of the scientifically promising areas, but the available data in this region are very small. A variety of X-ray sources like active galactic nuclei, clusters of galaxies, X-ray pulsars, and low mass X-ray binaries do emit preferentially in the hard X-ray region. More generally the entire non-thermal X-ray universe is better revealed in the hard X-ray band. Recent developments in the large area multi-wire proportional counters for use in the hard X-ray region have provided very large areas, low detector background, and fairly narrow field of view. Since 1984, a successful programme of hard X-ray observations using high sensitivity, large area (0.5 m²) proportional counter telescope, for the spectral and the temporal study of the cosmic X-ray sources is being pursued at the Tata Institute of Fundamental Research, Bombay. Brief details of the payload, its flight performance, and some of the results obtained during various balloon-flights are described.