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Resonant Cyclotron Scattering and Comptonization in Neutron Star Magnetospheres
Maxim Lyutikov
UBC
Abstract:
Resonant cyclotron scattering of the surface radiation in magnetospheres
of neutron stars may considerably modify emergent spectra. Resonant
tranfer has a number of unusual characteristics: (i) in the limit of high
resonant optical depth, cyclotron resonant layer is half opaque, in a
sharp contrast to the case of non-resonant scattering; (ii) transmitted
flux is on average Compton up-scattered by 1+ 2 betaT, where betaT is
a typical thermal velocity in units of the velocity of light; reflected
flux has on average the initial frequency. (iii) for both transmitted and
reflected fluxes the dispersion of intensity decreases with increasing
optical depth; (iv) emerging spectrum is appreciably non-Plankian while
narrow spectral features produced at the surface are erased; (v) optical
optical photons are less affected by resonant Comptonization than X-rays
due to different polarization of normal modes in resonances. We discuss
applications to Anomaous X-ray Pulsars and thermally emitting Isolated Neutron Stars
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