S/N in this sample is very low, and the significance level we demand (4$
\sigma $) is almost at the signal height (see sec. \[shorts\]). Hence, a pulse determined by the algorithm is almost always well separated (otherwise the minimum between the pulse and its neighbor would be insignificant). Specifically 61 pulses out of the 65 pulses found in our sample are well separated: the minimum between pulses, on both sides, is lower than half of the maximum of the pulse. Thus, pulse widths are almost never underestimated. The combination of the other effects causes pulse widening. Hence our estimate of $ \delta t_{min}/T $ , is only an upper limit.

Fig. \[dt/T in shorts\] shows $ \delta t_{min} $ and $
\delta t_{min}/T $ for both groups *’short’* and *’noisy long’*. In the *’short’* sample the median $ \delta t_{min}/T $ is 0.25 while 35% of bursts have $
\delta t_{min}/T\leq0.1 $ and 35% of the bursts show a smooth structure ($ \delta t_{min}/T=1 $). This result could mislead us to the conclusion that a significant fraction of the short bursts have a smooth time profile. But a look at the *’noisy long’* results show that also in this 