WATCH possesses an on-board algorithm of triggering on burst events. A burst is
detected if an increase in the count rate of more than 6 standard
deviations above the background level has been registered at one of 12 sampling
times evenly covering on the logarithmic scale a range from 16 ms to
32 s. If an event is detected on a time scale shorter than 2 s,
its time history will be recorded with a resolution of 1 s, whereas
for slower bursts the standard integration time of either 7 s
or 14 s will be used. The purpose of the ground data analysis is then
to separate events of cosmic and different nature. These latter
include solar flares which differ from GRBs in their
generally softer spectra. It is also usually possible to establish
with WATCH that their incident direction is coincident with the
direction to the solar disc. In many cases burst events were generated
by accelerated charged particles. The time histories of such events
are different from those of GRBs. Although most non-cosmic
events can be reliably identified by their characteristic features,
the origin of a number of bursts remains unsettled. In this catalogue,
only those events are presented that either have been
localized with WATCH or are designated as cosmic in the catalogues of
other GRB experiments. The significance of the detection
of 
% of the bursts included in the catalogue was not high
enough (
) to generate a trigger on board. These events,
discovered already in the course of the ground analysis as a
significant (
) increase in the count rate, are coincident
in time with GRBs observed by other experiments, mainly by
the BATSE instrument on the Compton Gamma-Ray Observatory
(Meegan et al. 1996).