  Accreting neutron stars (NS) can exhibit high-frequency modulations, known as
burst oscillations, in their lightcurves during thermonuclear X-ray bursts.
Their frequencies can be offset from the spin frequency of the NS (known
independently) by several Hz, and can drift by 1-3 Hz. One plausible
explanation for this phenomenon is that a wave is present in the bursting ocean
that decreases in frequency (in the rotating frame) as the burst cools. The
strongest candidate is the buoyant $r$-mode; however, models for the burning
ocean background used in previous studies over-predict frequency drifts by
several Hz. Using new background models (which include shallow heating, and
burning in the tail of the burst) the evolution of the buoyant $r$-mode is
calculated. The resulting frequency drifts are smaller, in line with
observations. This illustrates the importance of accounting for the detailed
nuclear physics in these bursts.
