arXiv:1403.6244v1 [astro-ph.HE] 25 Mar 2014 Analysis of short bursts in SGR 1806-20, 1E 1048-5937 and SGR 0501+4516 Zhijie Qu 1 , Zhaosheng Li 1 , Yupeng Chen 2 , Shi Dai 1 , Long Ji 2 , Renxin Xu 1,3 , Shu Zhang 2 ABSTRACT We analyzed the temporal and spectral properties, especially the short bursts, for three anomalous X-ray pulsars (AXPs) and soft gamma repeaters (SGRs), in- cluding SGR 1806-20, 1E 1048-5937 and SGR 0501+4516. Using the data from XMM-Newton, we located the short bursts through Bayesian blocks algorithm. The short bursts duration distributions for three sources were fitted by two log- normal functions, however, the spectra of shorter bursts (< 0.2 s) and longer bursts (≥ 0.2 s) can be well fitted by two black body components with differ- ent emission areas for SGR 0501+4516. We studied the flux evolution of the persistent and the burst emission, and found a similar tendency of flux during outburst. We also found that there is a positive correlation between the burst luminosity and the persistent luminosity with a power law index γ =1.22 ± 0.19. The ratio of this persistent emission to the time averaged short bursts is in the range of 10 ∼ 10 3 , similar to the case in Type I X-ray burst. In the end, we discussed our results in the accretion model and magnetar model for AXPs and SGRs. Subject headings: pulsars: individual (SGR 1806-20, 1E 1048-5937, SGR 0501+4516) - stars: neutron - X-rays: bursts 1. Introduction Anomalous X-ray pulsars (AXPs) and soft gamma repeaters (SGRs) are isolated neu- tron stars. They have long rotation periods (2 ∼ 10 s) and rapid spin-down rates (10 -13 ∼ 1 School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, P. R. China 2 Institute of High Energy Physics & Theoretical Physics Center for Science Facilities, Chinese Academy of Sciences, Beijing 100049, China 3 Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, P. R. China