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1999 September 08 (M1.4)

A GOES M1.4 solar flare occurred on 1999 September 8 at an H-alpha location of N12E53 (heliographic coordinates). The soft X-ray flux began at 12:08 (43680 s), peaked at 12:17 (44220 s), and ended at 12:27 (44820 s) UT (GOES Geophysical Data Web Site). OSSE received a BATSE solar-flare trigger at 44010 s and all the OSSE detectors slewed to the scan-angle position of the Sun and detectors one and two remained pointed at the sun while detectors three and four initiated standard on-source-off-source viewing strategies. Solar observations began at 44045 s UT.

Significant gamma-ray emission to ~600 keV was observed lasting until about 44290 s UT with two peaks of emission at ~44100 s and ~ 44150 s. Two additional weaker emmision episodes occurred at ~44470 s and ~44960 s. 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 44053-44307 s UT (254 seconds), which corresponds to the first emission episode. The electron bremsstrahlung component was well-fit with a simple power law having a spectral index of ~3.11. There was no evidence for nuclear lines.

Figure 1

Figure 2

Last revised: 11 Dec 1997