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[43.01] The Emission Spectrum of the Accretion Column on Her X-1

D.A. Leahy (University of Calgary)

Like many other X-ray pulsars, the pulse shape of Her X-1 is energy dependent. Since the pulse shape is caused by the varying line-of-sight to the emission region as the neutron star rotates, the energy dependence implies a spatially dependent emission spectrum. Some model for the spatial structure of the emission region is needed in order to separate the emission spectrum from different parts of the emission region.

For Her X-1 the geometry of the emission region has been well determined (Leahy, 2004, ApJ, 613, 517). This was possible due to the observed pulse shape evolution caused by the precessing accretion disk in the system (Scott, Leahy, Wilson, 2000, ApJ, 539, 392). Only a filled cone shaped emission fits the observed pulse shape. This model is described here and is applied to observations of the X-ray pulse shape at several different X-ray energies. The emission spectrum of the top surface and of the side surface of the accretion column are thus derived from observations. The resulting spectra are compared to some theoretical calculations of emission from a strongly magnetized plasma.

This work was funded by a grant from the Natural Sciences and Engineering Research Council of Canada.

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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.