Comparison between GRBM and BATSE results

Given that BATSE gives for each detected GRB a 'rough' direction, peak fluxes values and fluences in 4 bands (from which some spectral information can be derived) and that it is expected to be a well calibrated experiment, we can use the GRBM+BATSE detected GRB sample to perform an in-flight verification of the calibration of the GRBM.
We performed a power-law fit to the BATSE fluences in the 25-50, 50-100 and 100-300 energy bands, to obtain a spectral model for each event. Then, given the source direction reported by BATSE or the high accuracy position given by the WFC for the BATSE/GRBM/WFC detected events, we calculated the expected counts in the GRBM and AC ratemeters bands by convolving the photon spectrum derived from BATSE fluences with LS1 or LS3 efficiency at the source direction.
We find that for those events with directions at an angular distance from LS1 or LS3 axis of $\pm$30$\rm ^{\circ}$ the agreement between expected and measured counts is good. The consistency between expected and measured data increases with the brightness of the event, indicating that for weak events there can be differences in BATSE and GRBM fluences estimations due to the different sensitivity of the two experiments.

In Tab. 4.11.2 we report results of this analysis for some of the GRBs also detected in the WFC. The expected count fluences refer to the GRBM band. The expected count fluences error computation accounts for errors of the power-law parameters and GRBM response systematics.

 

$$\theta \phi$$ GRB LS Expected Measured

$$\pm \pm$$ 960720 LS1 11.2 0.4

$$\pm \pm$$ 970111 LS3 12.4 7.6

$$\pm \pm$$ 970228 LS1 7.6 15

$$\pm \pm$$ 971214 LS1 -15.3 6.3

$$\pm \pm$$ 980109 LS3 12.0 -0.4

$$\pm \pm$$ 980329 LS3 11.0 0.4