Statistical Properties of X-Ray Flares from the Supergiant Fast X-Ray Transients

Supergiant fast X-ray transients are a sub-class of high mass X-ray binaries, in which the compact object is a neutron star and it is accreting materials from its non-degenerate companion star. The sample of supergiant fast X-ray transients from XMM-Newton public observations have been intensively studied, and hence the corresponding parameters for identifying X-ray flares have been obtained by Sidoli et al., such as the rise time, the decay time, the duration time, the waiting time, the peak luminosity, the isotropic energy and the mean luminosity. In order to investigate the origin of the X-ray flares from the supergiant fast X-ray transients, we apply the cumulative distribution method with the power-law index dN (x)/dx proportional to (x + x(0))(-alpha x) to the target sample. We then find that the relevant parameters can be well described by the cumulative distribution with indices 1.0-1.9 for IGR J16418-4532, IGR J16328-4726 and IGR J18450-0435, respectively. This finding indicates that the X-ray flares are likely to be produced by the self-organizing critical process, one possible scenario may be due to reconnection in magnetized stellar wind blobs approaching into the magnetosphere of magnetized neutron star. Therefore, we suggest that the high mass X-ray binaries with similar X-ray flares likely belong to the self-organized criticality systems.