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P.A. Becker (George Mason University), M.T. Wolff (Naval Research Laboratory)
Bright X-ray pulsars are among the most luminous celestial X-ray sources. Despite decades of theoretical and observational work since their discovery, no satisfactory model for the formation of the observed X-ray spectra has emerged. The pressure in the column is dominated by the radiation field, and therefore the equations describing the coupled radiative-dynamical structure must be solved simultaneously. Hence spectral formation in these sources is a complex, nonlinear process. One of the fundamental characteristics of the flow is the presence of a radiation-dominated accretion shock, which plays a critical role in the formation of the X-ray spectrum. In this paper, we present a self-consistent model for the dynamics and the radiative transfer occurring in bright X-ray pulsar accretion columns. The model describes the reprocessing of soft photons emitted from the thermal mound at the base of the column. These photons diffuse through the column and are upscattered during repeated crossings of the shock, before they escape out the sides of the column. We show that the X-ray spectrum resulting from this process has a power-law shape at high energies, in agreement with many observations of X-ray pulsars.
The author(s) of this abstract have provided an email address for comments about the abstract: pbecker@gmu.edu
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.