  Non-photospheric-radius-expansion (non-PRE) double-peaked bursts may be
explained in terms of spreading (and temporary stalling) of thermonuclear
flames on the neutron star surface, as we argued in a previous study of a burst
assuming polar ignition. Here we analyze Rossi X-ray Timing Explorer (RXTE)
Proportional Counter Array (PCA) data of such a burst (but with a considerably
different intensity profile from the previous one) from the low mass X-ray
binary (LMXB) system 4U 1636-536, and show that this model can qualitatively
explain the observed burst profile and spectral evolution, if we assume an
off-polar, but high-latitude ignition, and burning front stalling at a higher
latitude compared to that for the previous burst. The off-polar ignition can
account for the millisecond period brightness oscillations detected from this
burst. This is the first time oscillations have been seen from such a burst.
Our model can qualitatively explain the oscillation amplitude measured during
the first (weaker) peak, and the absence of oscillations during the second
peak. The higher latitude front stalling facilitates the first clear detection
of a signature of this stalling, which is the primary result of this work, and
may be useful for understanding thermonuclear flame spreading on neutron stars.
