  Observations with RXTE have revealed kilohertz quasi-periodic brightness
oscillations (QPOs) from nearly twenty different neutron-star low-mass X-ray
binaries (LMXBs). These frequencies often appear as a pair of kilohertz QPOs in
a given power density spectrum. In many models the higher-frequency of these
QPOs is a beaming oscillation at the frequency of a nearly circular orbit at
some radius near the neutron star. In such models it is expected that there
will also be beaming oscillations at the stellar spin frequency and at
overtones of the orbital frequency, but no strong QPOs have been detected at
these frequencies. We therefore examine the processes that can attenuate
beaming oscillations near neutron stars, and in doing so extend the work on
this subject that was initiated by the discovery of lower-frequency QPOs from
LMXBs. Among our main results are (1)in a spherical scattering cloud, all
overtones of rotationally modulated beaming oscillations are attenuated
strongly, not just the even harmonics, and (2)it is possible to have a
relatively high-amplitude modulation near the star at, e.g., the stellar spin
frequency, even if no peak at that frequency is detectable in a power density
spectrum taken at infinity. We discuss the application of these results to
modeling of kilohertz QPOs.
