  Recent studies have shown that runaway thermonuclear burning of material
accreted onto neutron stars, i.e. Type I X-ray bursts, may affect the accretion
disk. We investigate this by performing a detailed time-resolved spectral
analysis of the superburst from 4U 1636-536 observed in 2001 with the Rossi
X-ray Timing Explorer. Superbursts are attributed to the thermonuclear burning
of carbon, and are approximately 1000 times more energetic than the regular
short Type I bursts. This allows us to study detailed spectra for over 11 ks,
compared to at most 100 s for regular bursts. A feature is present in the
superburst spectra around 6.4 keV that is well fit with an emission line and an
absorption edge, suggestive of reflection of the superburst off the accretion
disk. The line and edge parameters evolve over time: the edge energy decreases
from 9.4 keV at the peak to 8.1 keV in the tail, and both features become
weaker in the tail. This is only the second superburst for which this has been
detected, and shows that this behavior is present even without strong radius
expansion. Furthermore, we find the persistent flux to almost double during the
superburst, and return to the pre-superburst level in the tail. The combination
of reflection features and increased persistent emission indicates that the
superburst had a strong impact on the inner accretion disk, and it emphasizes
that X-ray bursts provide a unique probe of accretion physics.
