Ulysses GRB Integral 0.5-Second Omnidirectional Counting Rates

This data set contains data and software for integral 0.5-second omnidirectional counting rates from the Ulysses Gamma Ray Burst
(GRB) experiment. It consists of count rates from the sum of two hemispherical detectors convering 4 pi steradians and operating continuously. The detectors
are 3 mm thick CsI scintillators coupled to photomultiplier tubes. The nominal energy range is 25-150 keV, but Table 1 (see below) should be consulted to find
the accurate thresholds for any day of the mission. A more complete description of the instrument may be found in Hurley et al. (1992) and Cotin et al. (1983).
Althoughthe prime objectives of this investigation are the study of solar and cosmic x- and gamma-ray bursts, it should be noted that the experiment is also
sensitive to solar protons and electrons. The former deposit energy directly in the scintillator if they are energetic enough, while the latter may produce x-
radiation locally by bremsstrahlung. Thus although the counting rates are generally stable at about 500 c/s over the long term, there are periods of
weeks to a month or so when the rates increase considerably due to particles. Examples may be found in March 1991 (solar protons) and February 1992
(particles in the Jovian magnetosphere).

The time resolution of the data takes on one of four values depending on the telemetry rate and instrument operating mode: 0.25, 0.5, 1, or 2 seconds. Data
rate changes produce short spikes in the count rates due to a processing artefact. These can in principle be corrected if the data are scanned and the
rate changes are identified; the count rate spikes can then be adjusted to their correct values. There are also short (one sample long) count rate
dropouts, due to an artefact of the onboard software. These may be seen in the sample plots; they cannot be corrected for.

Two figures give examples of solar and cosmic events in the data. The upper panel gives the count rates for day 142, 1993, around 8.24 hours UT. The solar event is evident as a 300 second long increase. Note the count rate dropouts. The bottom panel includes a 20 second long cosmic gamma-ray burst from day 237, 1993 around 8.79 hours UT.