The Burst and Transient Source Experiment

Abstract

The Burst and Transient Source Experiment (BATSE) is one of four experiments 011 the Compton Gamma Ray Observatory (GRO), which was launclied into a 450-!a orbit on April 5, 1991. BATSE was designed primarily for the study of gamma-ray bursts, unexplained flashes of celestial g a m m a r ys tliat last from a fraction of a second to over 100 secouds and have not been detected at any otlicr wavelength. BATSE consists of eight detector modules situated at the corners of the GRO spacecraft. Each module contaius a I.arge-Area Detector (LAD), optimized for sensitivity, and a Spectroscopy Detector (SD), optimized for spectral resolution. Signals from the detectors are sent to the Ceutral Electronics Unit (CEU), which detects gamma-ray bursts and constructs data types with a range of spectral and temporal resolutions. The unpreccdentcd sensitivity of Uie LAD’S has resulted in the detection of over 500 bursts, more than have been detected by all other instruments combined since the discovery of bursts two decades ago. By comparing the relative count rates among tbc eight detectors, the direction to a burst can be dctennincd. The most interesting result obtained so far is that the spatial distribution of the burst sources is riot consistent with my known galactic component. BATSE also continuously monitors the intensity of hard x rays from several celestial sources, using the h U i as ai occulting disk. In this way, several flaring episodes of known sources have been detected, and a new transient source, GRO 50422+32, was discovered. BATSE also can construct pulsar light curves by onboard folding of data at known pulsar periods.