*5.1. T*<sup>100</sup> *vs. T*<sup>1</sup> *Analysis*

For *Swift*/BAT, two groups are identified using both the T<sup>100</sup> and T<sup>1</sup> intervals. Table 2 provides the classification results obtained with each interval. The sample sizes of the two groups are shown in Table 3, separated into long- (T<sup>90</sup> > 2 s) and short- (T<sup>90</sup> < 2 s) duration bursts.

**Table 3.** Sample sizes of short-duration (T<sup>90</sup> < 2 s) and long-duration (T<sup>90</sup> > 2 s) bursts in the *Swift*/BAT sample, and Groups 1 and 2, based on the analysis of the T<sup>1</sup> and the T<sup>100</sup> intervals.


A total of 95% (1185 of the 1251 bursts) of the classifications of *Swift*/BAT bursts determined using the T<sup>1</sup> interval at 4 ms resolution are consistent with those derived using the T<sup>100</sup> intervals at 64 ms resolution. There are 21 short-duration bursts, which are classified as Group 2 bursts when the T<sup>1</sup> interval is considered, but move to Group 1 when the T<sup>100</sup> interval is used for the analysis. There are 28 long-duration bursts, which move from Group 1 in the T<sup>1</sup> analysis to Group 2 when the T<sup>100</sup> interval is considered. These include five bursts in the list of *Swift*/BAT bursts with extended emission episodes compiled by Gibson et al. [100]. The long-duration supernova-accompanied burst GRB 101219B moves to Group 2 in the T<sup>100</sup> analysis, correctly placing it amongst the other bursts with associated supernovae. The inclusion of the full light-curve data in these cases is important for correct classification. The classification of bursts with associated supernovae is further discussed in Section 6. Some of the movement between groups may reflect the different temporal resolutions used for the T<sup>1</sup> (4 ms) and T<sup>100</sup> (64 ms) analyses. The minimum variability timescale with short GRBs of order 10 ms would not necessarily be captured by the T<sup>100</sup> analysis. There may also be cases where there are pre-trigger emissions that are not captured in the current approach, which starts at the trigger time.
