  Type I X-ray bursts are thermonuclear flashes observed from the surfaces of
accreting neutron stars (NSs) in Low Mass X-ray Binaries. Oscillations have
been observed during the rise and/or decay of some of these X-ray bursts. Those
seen during the rise can be well explained by a spreading hot spot model, but
large amplitude oscillations in the decay phase remain mysterious because of
the absence of a clear-cut source of asymmetry. To date there have not been any
quantitative studies that consistently track the oscillation amplitude both
during the rise and decay (cooling tail) of bursts. Here we compute the light
curves and amplitudes of oscillations in X-ray burst models that realistically
account for both flame spreading and subsequent cooling. We present results for
several such "cooling wake" models, a "canonical" cooling model where each
patch on the NS surface heats and cools identically, or with a
latitude-dependent cooling timescale set by the local effective gravity, and an
"asymmetric" model where parts of the star cool at significantly different
rates. We show that while the canonical cooling models can generate
oscillations in the tails of bursts, they cannot easily produce the highest
observed modulation amplitudes. Alternatively, a simple phenomenological model
with asymmetric cooling can achieve higher amplitudes consistent with the
observations.
