The X-ray continuum of accreting pulsars observed with Suzaku

The hard X-ray continuum emission observed from accreting pulsars like LMC X-4 or Cen X-3 is thought to be produced in accretion columns, i.e., by the accreted plasma falling towards the magnetic poles of the neutron star at relativistic speeds. We are entering an era where properties of the neutron star and the plasma flow can be studied by applying new physical models to describe the observed X-ray continuum emission.We present an analysis of Suzaku data of a sample of accreting pulsars. We first model the spectra using commonly applied empirical continuum models based on power-law shapes with a roll-over at high energies. This allows us to constrain the parameter space for additional components of the spectra like absorption, iron lines of different ionization stages, cyclotron lines (and thus the magnetic field strengths), and the often required broad ``10 keV bumps''. We compare the results to a previously published sample study based on RXTE data by Coburn et al. (2002). Among other things the results confirm the presence of a correlation between the energy and width of the cyclotron lines, suggesting that the width is dominated by thermal broadening.We then apply the accretion column model published by Becker and Wolff (2007) that describes the continuum as the sum of Comptonized contributions from three different seed photon sources, bremsstrahlung, blackbody radiation, and cyclotron emission, We find that the observed continuum emission is well described by this model, with the exception of in the case of the lower B-field source 4U 0115+63. We determine parameters like the accretion column radius and the plasma temperature. Providing a consistency check for the underlying physical picture we find a clear correlation between the accretion column temperature of the physical fits and spectral curvature, i.e., the folding energy of the empirical fits.