The short bursts in SGR 1806-20, 1E 1048-5937 and SGR 0501+4516

Abstract

We analyzed temporal and spectral properties, focusing on the short bursts, for three anomalous X-ray pulsars (AXPs) and soft gamma repeaters (SGRs), including SGR 1806-20, 1E 1048-5937 and SGR 0501+4516. Using the data from XMM-Newton, we located the short bursts by Bayesian blocks algorithm. The short bursts' duration distributions for three sources were fitted by two lognormal functions. The spectra of shorter bursts ($<0.2\mathrm{s}$) and longer bursts ($\ge 0.2\mathrm{s}$) can be well fitted in two blackbody components model or optically thin thermal bremsstrahlung model for SGR 0501+4516. We also found that there is a positive correlation between the burst luminosity and the persistent luminosity with a power law index ${\hat{I}}^3=1.23\pm 0.18$. The energy ratio of this persistent emission to the time averaged short bursts is in the range of $10-10^3$, being comparable to the case in Type I X-ray burst.

Accepted by PASP