Resonant Compton Upscattering in High Field Pulsars and Magnetars

Faculty Mentor(s)

Dr. Peter Gonthier, Hope College

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The extremely efficient process of resonant Compton scattering (RCS) in strong magnetic fields is believed to be a leading emission mechanism in high field pulsars and magnetars. New analytic developments for resonant Compton scattering, specifically spin-dependent cross sections devised using Sokolov & Ternov electron states, are the focus of this effort. These physically -correct forms display significant numerical departures from the older Johnson & Lippmann formalism for the cross sections in the resonance, thereby motivating the astrophysical deployment of this updated resonant Compton formulation. Useful approximate analytic forms for the cross section near and at the cyclotron resonance are presented. We highlight the application of these physics calculations in an inner magnetospheric model of the hard X-ray spectral tails in Anomalous X-ray Pulsars (AXPs), recently detected by RXTE and INTEGRAL. Relativistic electrons cool rapidly near the stellar surface, in the presence of intense baths of thermal X-ray photons, where the kinematics dominate and allow thermal photons to easily access the resonance. We present improved RCS electron cooling rates for magnetic fields above the quantum critical value, as functions of the magnetospheric colatitude and altitude. The kinematics provide the framework for an efficient scattering mechanism producing the characteristically flat spectral tails observed in AXPs.


This material is based upon work generously supported by the National Science Foundation under NSF-REU Grant No. PHY/DMR-1004811, and by Physics Department endowed funds (specifically the Guess Fund).

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