The GRBM & BATSE GRBs

The total number of GRBs detected by BATSE in common with the current GRBM archive ($\sim$80% of the data) is 283 out. This sample does not include those GRBs that have been detected also by experiments like WFC, IPN, ASM etc..., since they have been included in the well localized GRBs set. Among these 283 GRBs, only 4 did not trigger any SWTCs during the off-line quest, but, instead, did the on-board trigger logic (table ). On the other side, the on-board logic was triggered by 188 out of 283, corresponding to a fraction of ($66 \pm 5$)%, that fully agrees with the on-board efficiency estimated in eq.  ($64 \pm 3$%), and with the fraction found from the sample of well localized GRB ($68 \pm 9$%; see previous section).

In order to better show how the number of off-line detected bursts depends on the single rebin time (1 s, 2 s, 4 s, or 8 s), in table  the single number of GRBs so detected are reported; the numbers of GRBs that triggered the on-board logic are given as well.

Table: GRBM & BATSE GRBs.

Rebin Time (s)	#	# on-board	# only off-line
(kind of quest)	GRBs	trg GRBs (%)	GRBs
1	226	170 ($75 \pm 6$)	56
2	21	4 (19)	17
4	14	2 (14)	12
8	10	1 (10)	9
Early SWTCs	8	7	1
Off-line missed	4	4	0
Total	283	188 ($66 \pm 5$)	95

From table  it is apparent that, while at 1 s, a high fraction ($75 \pm 6$)% of GRBs triggered the on-board logic as well, the same fraction falls down to 10-20% for higher rebin time searches; this clearly reflects the fact that the brightest common bursts are caught during the 1 s search, according to what one should expect, while the other searches allow the detection of fainter or slow-varying bursts, for which the on-board trigger efficiency is definitely lower than its average value ($64 \pm 3$)%. Finally, it has to be pointed out that the bursts caught during the search with a given rebin time do not include those bursts, that had been detected also with lower rebin times; this means that, for example, the 21 bursts detected with integration time = 2 s, had not been previously caught during the 1 s rebin time quest.