Vol 15, No 4

Understanding the X-ray spectrum of anomalous X-ray pulsars and soft gamma-ray repeaters

Yan-Jun Guo, Shi Dai, Zhao-Sheng Li, Yuan Liu, Hao Tong, Ren-Xin Xu


Abstract Hard X-rays above 10 keV are detected from several anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs), and different models have been proposed to explain the physical origin within the frame of either a magnetar model or a fallback disk system. Using data from Suzaku and INTEGRAL, we study the soft and hard X-ray spectra of four AXPs/SGRs: 1RXS J170849–400910, 1E 1547.0–5408, SGR 1806–20 and SGR 0501+4516. It is found that the spectra could be well reproduced by the bulk-motion Comptonization (BMC) process as was first suggested by Tr ̈umper et al., showing that the accretion scenario could be compatible with X-ray emission from AXPs/SGRs. Simulated results from the Hard X-ray Modulation Telescope using the BMC model show that the spectra would have discrepancies from the power-law, especially the cutoff at ~200 keV. Thus future observations will allow researchers to distinguish different models of the hard X-ray emission and will help us understand the nature of AXPs/SGRs.


Keywords stars: neutron — pulsars: individual (1E 1547.0–5408, 1RXS J170849– 400910, SGR 0501+4516, SGR 1806–20) — X-rays: stars

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