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1999 July 29 (M5.3)

A GOES M5.3 solar flare occurred on July 29 1999 at an H-alpha location of N25E51 (heliographic coordinates). The soft X-ray flux began at 19:31 (70260 s), peaked at 19:36 (70560 s), and ended at 19:40 (70800 s) UT (GOES Geophysical Data Web Site). OSSE received a BATSE solar-flare trigger at 70432 s. The four OSSE detectors were already aimed towards the sun. Two remained in the same position while the other two initiated standard on-source-off-source viewing strategies.

Significant gamma-ray emission to ~200 keV was observed lasting until about 70600 s UT with one peak of emission at ~70470 s. Weaker gamma-ray emission followed, lasting until ~70700. Count rate time profiles in various energy windows at a temporal resolution of ~8 s are shown in Figure 1. Figure 2 shows a representative count spectrum obtained from one Sun-pointed detector integrated over the time period 70393-70606 s UT (213 seconds). The electron bremsstrahlung component was well-fit with a simple power law having a spectral index of ~5.32. There was no evidence for nuclear lines.

Figure 1

Figure 2

Last revised: 13 July 2000