  Runaway thermonuclear burning of a layer of accumulated fuel on the surface
of a compact star provides a brief but intense display of stellar nuclear
processes. For neutron stars accreting from a binary companion, these events
manifest as thermonuclear (type-I) X-ray bursts, and recur on typical
timescales of hours to days. We measured the burst rate as a function of
accretion rate, from seven neutron stars with known spin rates, using a burst
sample accumulated over several decades. At the highest accretion rates, the
burst rate is lower for faster spinning stars. The observations imply that fast
(> 400 Hz) rotation encourages stabilization of nuclear burning, suggesting a
dynamical dependence of nuclear ignition on the spin rate. This dependence is
unexpected, because faster rotation entails less shear between the surrounding
accretion disk and the star. Large-scale circulation in the fuel layer, leading
to enhanced mixing of the burst ashes into the fuel layer, may explain this
behavior; further numerical simulations are required to confirm.
