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M. G. Baring (Rice University)
Quiescent, non-thermal X-ray emission of soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs) is observed at levels that are very intense for neutron stars. While dwarfed by the flare activity, this component nevertheless has important implications for our understanding of the magnetar environment. In quiescence, it is quite possible that SGRs and AXPs emit in a pulsar-like mode, even if the power is not of a rotational origin. The principal candidate for such emission is inverse Compton scattering in the strong fields of their magnetospheres, since it is believed to dominate over other primary emission mechanisms in high field pulsars. This paper outlines expectations for such emission spectra, formed from non-thermal electrons accelerated in a pulsar-like polar cap potential upscattering thermal X-rays from the hot stellar surface. It is found that a steep, non-thermal X-ray portion of the spectrum connects to a very flat soft gamma-ray continuum with spectral cutoffs that depend strongly on the observational perspective. The broadband spectra differ significantly from those produced in outer gap models. Observational flux constraints on the high energy component lead to the identification of diagnostics on the emission geometry.
This work was sponsored by the NASA Astrophysics Theory Program.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.