confirms that the dip and second peak seen in the light curve are indeed astrophysical in origin rather than a passband effect.

Finally, we note a peculiar feature in the spectroscopic results: the temperature evolution of the photosphere shows two peaks, marking the start and end of the PRE phase. These start and end times coincide with the pause and the dip, respectively. Furthermore, both the pause and the dip have the same bolometric flux level of $(1.43\pm0.09){\ensuremath{\times 10^{-7}} }$[[erg[s$^{-1}$]{}[cm$^{-2}$]{}]{}]{}.

![ Time-resolved spectroscopy of the X-ray burst using a double blackbody model. The top panel shows the estimated bolometric flux, the middle four panels show the time evolution of the spectral parameters describing the burst emission (radii were calculated using a distance of 3.5kpc), and the bottom panel gives the reduced $\chi^2$ fit statistic. The grey band indicates the time interval where burst oscillations were detected. See text for further details. []{data-label="fig:time resolved"}](time-resolved-spectroscopy.pdf){width="\linewidth"}

Burst oscillations {#sec:oscillations}
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To search for burst oscillations, we constructed a $1/8192{{\rm\,s}\xspace}$ time-resolution light curve in the $0.3-10$ keV energy band. We then searched for coherent oscillations in a [10]{}Hz region centered on the known 401Hz pulsar spin frequency by applying a sliding window search method 