Temporal Characteristics of SGR 1806-20 and SGR 1900+14 Bursts

We study the temporal properties of 268 bursts from SGR 1806$-$20 and 679 bursts from SGR 1900+14 all observed with the Rossi X-Ray Timing Explorer/Proportional Counter Array. Temporal parameters, such as T$_{90}$ durations and $\tau$$_{90}$ emission times are implemented. We find a lognormal distribution of burst durations, ranging over more than two orders of magnitude: T$_{90}$ $\sims$ 10$ {-2}$ to $\gtrsim$ 1 s, with a peak $\sim$ 0.1 s. The burst light curves tend to be asymmetrical, with more than half of all events showing rise times t$_{r}$ $<$ 0.2 T$_{90}$. We find that there exists a correlation between the duration and fluence of bursts from both sources. We also find a significant anti-correlation between hardness ratio and fluence of SGR bursts. Finally we discuss possible physical implications of these results within the framework of the magnetar theory.