  A number of neutron star low-mass X-ray binaries have recently been
discovered to show broad, asymmetric Fe K emission lines in their X-ray
spectra. These lines are generally thought to be the most prominent part of a
reflection spectrum, originating in the inner part of the accretion disk where
strong relativistic effects can broaden emission lines. We present a
comprehensive, systematic analysis of Suzaku and XMM-Newton spectra of 10
neutron star low-mass X-ray binaries, all of which display broad Fe K emission
lines. Of the 10 sources, 4 are Z sources, 4 are atolls and 2 are accreting
millisecond X-ray pulsars (also atolls). The Fe K lines are well fit by a
relativistic line model for a Schwarzschild metric, and imply a narrow range of
inner disk radii (6 - 15 GM/c^2) in most cases. This implies that the accretion
disk extends close to the neutron star surface over a range of luminosities.
Continuum modeling shows that for the majority of observations, a blackbody
component (plausibly associated with the boundary layer) dominates the X-ray
emission from 8 - 20 keV. Thus it appears likely that this spectral component
produces the majority of the ionizing flux that illuminates the accretion disk.
Therefore, we also fit the spectra with a blurred reflection model, wherein a
blackbody component illuminates the disk. This model fits well in most cases,
supporting the idea that the boundary layer is illuminating a geometrically
thin disk.
