The Short Bursts in SGR 1806-20, 1E 1048-5937, and SGR 0501+4516

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 the Bayesian blocks algorithm. The short bursts' duration distributions for three sources were fitted by two lognormal functions. The spectra of shorter bursts (<0.2s) and longer bursts (0.2s) can be well fitted in a 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 =1.23 +/- 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.Astronomy & AstrophysicsSCI(E)0ARTICLEquzhijie@pku.edu; lizhaosheng@pku.edu.cn; chenyp@ihep.ac.cn; dash41198@gmail.com; jilong@ihep.ac.cn; r.x.xu@pku.edu.cn; szhang@ihep.ac.cn949211-22212