  Accretion disks around neutron stars regularly undergo sudden strong
irradiation by Type I X-ray bursts powered by unstable thermonuclear burning on
the stellar surface. We investigate the impact on the disk during one of the
first X-ray burst observations with the Neutron Star Interior Composition
Explorer (NICER) on the International Space Station. The burst is seen from Aql
X-1 during the hard spectral state. In addition to thermal emission from the
neutron star, the burst spectrum exhibits an excess of soft X-ray photons below
1 keV, where NICER's sensitivity peaks. We interpret the excess as a
combination of reprocessing by the strongly photoionized disk and enhancement
of the pre-burst persistent flux, possibly due to Poynting Robertson drag or
coronal reprocessing. This is the first such detection for a short
sub-Eddington burst. As these bursts are observed frequently, NICER will be
able to study how X-ray bursts affect the disk and corona for a range of
accreting neutron star systems and disk states.
