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1991 June 10 (M4.5)

A GOES M4.5 solar flare occurred on 1991 June 10 at an H-alpha location of N31W10 (heliographic coordinates). The soft X-ray flux began at 02:22 (8520 s), peaked at 02:30 (9000 s) and ended at 02:38 (9480 s) UT (GOES Geophysical Data Web Site). OSSE received a BATSE transient trigger at 8866 s and the four OSSE detectors slewed to the scan-angle position of the Sun. Two of the four detectors then initiated +/- 4.5 degree on-source-off-source viewing strategies while the other two detectors remained pointed at the Sun.

Significant emmission of up to about 400 keV was observed during a ~110 s time interval (8900-9010 s). Count rate time profiles in various energy windows at a temporal resolution of ~8 s are shown in Figure 1. A representative count spectrum is shown in Figure 2. A broken power law which steepened from an index of about -4.0 below a break energy of ~105 keV to about -5.3 above the break energy fit the data better than a single power law. The total fluence above 50 keV was 761.5 +/- 3.8 photons cm-2.

Figure 1

Figure 2

Last revised: 19 Jul 1999