The GRBM & BATSE non-triggered GRBs

The BATSE non-triggered burst catalogs used for cross-checking are the following two: by Kommers et al. (hereafter, Kommers') and by Stern et al. (hereafter Stern's) (see section  and references therein). First of all, it must be pointed out that the Kommers' catalog covers the BATSE data till the end of 1997, while the Stern's till the end of the mission (end of May 2000); this is the main reason explaining the higher number of GRBs detected by the GRBM in common with the Stern's catalog than with Kommers'.

Table: GRBM & BATSE non-triggered GRBs.

Kind of	#	# on-b	# only	#	# on-b	# only	#	# on-b	# only
Quest		trg	off-		trg	off-		trg	off-
	K	K	K	S	S	S	KS	KS	KS
1 s	7	4	3	34	26	8	41	30	11
2 s	5	1	4	8	0	8	13	1	12
4 s	1	0	1	13	0	13	14	0	14
8 s	5	0	5	6	0	6	11	0	11
Early SWTCs	0	0	0	0	0	0	0	0	0
Total	18	5	13	61	26	35	79	31	48

In table  the results of the cross-check with both catalogs are reported; the nine columns refer to the following classes: the first number (#) is the total number of GRBs of the corresponding catalog (K=Kommers, S=Stern, KS=Kommers+Stern); the ``on-b trg'' column reports the number of on-board triggered bursts, among those reported in the previous column; eventually, the ``only off-'' column reports the number of events, that did not trigger the on-board logic, thus corresponding to the difference between the numbers of the two previous columns. All the bursts that have been detected in common with the Kommers' catalog have not been considered any more in the Stern's catalog, sharing several GRBs with the Kommers' catalog. On the whole, 18 GRBs are found in common with Kommers' and 61 with Stern's, thus yielding 79 non-triggered bursts from BATSE data, also detected with the GRBM. In addition to the 283 BATSE common bursts from the 4B catalog of triggered GRBs, the total number of GRBM & BATSE GRBs raises to 362 GRBs (those also detected by the WFCs, or located by the IPN, etc...have not been taken into account here).

Furthermore, once again it is worth noting the fraction of GRBM on-board triggered GRBs out of the total number, i.e. 31 out of 79 GRBs, that is ($39 \pm 7$)%. This fraction is significantly lower than the on-board efficiency found in the preceeding cases, also than the BATSE catalog; the worse on-board trigger efficiency found for this sample, reflects the fact that, on average, these GRBs are fainter than the mean brightness of the overall GRBM catalog. This property also suggests that several bursts as bright as these GRBs and with similar features, on average, among those that triggered the off-line quest, might have been rejected or simply classified as Likely GRBs or Suspected GRBs, only because no other experiment could confirm them as true GRBs.

Eventually, the same fraction, i.e. the ratio of the number of on-board triggered GRBs over the total number of off-line detected GRBs, computed only for the 1 s rebin time quest, comes out to be $30/41 \simeq (73 \pm 13)$%, consistent with the corresponding value obtained in the case of the BATSE catalog, i.e. ($75 \pm 6$)% (sec. ).