- Conference date: 20–22 July 2011
- Location: Palo Alto, California, USA
Magnetars are a fascinating subclass of neutrons stars, mainly emerging in the X-ray frequency, with evidence of ultra-strong magnetic field exceeding the critical value, Bc = 4:4×1013 G. So far, soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are believed to be magnetars, based on their slow rotations, high spin-down rates, and burst activities. From its launch, Suzaku has been observed 11 magnetars, and also performed some successful ToO observations of transient sources. Becoming new promising targets in the Suzaku era, the AO-4 Magnetar Key Project has been performed since 2009. Using a best combination of the XIS and the HXD, the hard X-ray tail above 10 keV was clearly detected from 7 of them, including at least two activated sources, together with the soft thermal component from all of them. These Suzaku investigations revealed that a broad-band (0.8-70 keV) spectra of known magnetars systematically change depending on their characteristic age and/or magnetic field. The hard X-rays of magnetars become weaker but harder for older and weak-field objects. In addition, we have been monitoring broad-band persistent X-ray spectra of transient magnetars, together with spectral diagnostics of their weak short bursts. Here we summarize latest Suzaku results on magnetars. Although the emission mechanism of the hard X-rays has not yet been explained by conventional interpretations, the future ASTRO-H mission is expected to provide a more unified understanding of magnetars.
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