| We have known since the 1970's that the gamma-ray sky is variable. Only since Compton have we realized the tremendous richness of the high-energy sky. Supernovae, x-ray novae, active galaxies, the Sun, bursts - the sky is constantly changing. The flux from an individual source can often change by an order of magnitude or more. | 
Localization of the Superbowl Burst. Since it was detected by all four Compton instruments as well as another spacecraft, this location is particularly good. This type of multi-satellite positioning has led contributed to the eventual identification of a number of GRB counterparts. |
| No other sources, however, match gamma-ray bursts for their extraordinary behavior. For example, while millions of TV viewers watched the Superbowl on January 31, 1993, the wavefront of a very intense gamma-ray burst passed across the Earth and was detected by all four instruments on Compton. This burst was briefly more than 1000 times brighter than the rest of the gamma-ray sky. As seen by BATSE at low gamma-ray energies, 10 keV to a few MeV, the intense part of the burst consisted of a few short, closely spaced pulses lasting only about one second. EGRET also detected this initial phase of the burst, but quite unexpectedly, emission was seen to persist almost one minute later at high gamma-ray energies, 100 MeV to several GeV, where EGRET is most sensitive. | This "Superbowl Burst" was also seen by a detector on the Ulysses spacecraft, allowing the location to be refined well beyond the positional uncertainty of most gamma-ray bursts. |
Lightcurve of the "Superbowl Burst" showing complex structure
at different timescales. Understanding the wide variety of burst time profiles
and durations are part of the mystery of gamma-ray burst astrophysics.
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