We analyse a sample of bright short bursts from the BATSE 4B-catalog and find that many short bursts are highly variable (δtmin/T ≪ 1, where δtmin is the shortest pulse duration and T is the burst duration). This indicates that it is unlikely that short bursts are produced by external shocks. We also analyse the available (first 1-2 s) high-resolution Time Tagged Events (TTE) data of some of the long bursts. We find that variability on a 10-ms time-scale is common in long bursts. This result shows that some long bursts are even more variable than it was thought before (δtmin/T ≈ 10-4-10-3).
- Gamma-rays: bursts