In early January, 1996, a second satellite, the X-ray Timing Explorer, detected X-ray bursts coincident with the BATSE
Back in the 1990s the BATSE
instrument on NASA's Compton Gamma Ray Observatory made it clear that gamma-ray bursts come in at least two distinct types.
Instead, BATSE showed the GRB distribution to be isotropic (favoring no direction over another) and spatially limited (that is, the distribution has an outer edge).
Furthermore, BeppoSAX has been able to determine the positions of these X-ray afterglows with a precision of a few arcminutes - roughly 50 times more precise than BATSE.
Meanwhile, the BATSE
instrument remains the most sensitive detector of gamma-ray bursts in space, while the medium-energy OSSE and COMPTEL telescopes continue their studies of the galactic plane, quasars, and supernovae, and the EGRET high-energy detector monitors occasional solar flares.
Although its collecting area of 5,200 square centimeters is only half that of the BATSE
detectors on the Compton Gamma Ray Observatory, BAT will be five times more sensitive and offer a tenfold improvement in angular resolution.
The burst position was identified with data collected by spacecraft, including the BeppoSAX Wide Field Camera and the BATSE
and Ulysses detectors.
But BATSE has also detected more than a dozen gamma-ray flashes from the Earth.
At this point only circumstantial evidence -- the apparent association with thunderstorms -- links these colorful flashes to the gamma rays picked up by the BATSE detectors.
Could it be that the bursts were even weaker than we thought, and BATSE could not see past the solar neighborhood, let alone far enough for the galactic plane to show up?
BATSE has not been in operation long enough to collect a good sample of the rarer strong bursts, but the Pioneer Venus Orbiter (PVO) observed them for more than a decade before its demise in 1992.
As if to underscore the inconstancy of the gamma-ray sky, BATSE
also picked up a series of pulses from a mysterious object that had not been heard from for years.