  Some neutron star low-mass X-ray binaries have very long outbursts (lasting
several years) which can generate a significant amount of heat in the neutron
star crust. After the system has returned to quiescence, the crust then
thermally relaxes. This provides a rare opportunity to study the thermal
properties of neutron star crusts, putting constraints on the thermal
conductivity and hence the structure and composition of the crust. KS 1731-260
is one of only four systems where this crustal cooling has been observed. Here,
we present a new Chandra observation of this source approximately 8 years after
the end of the last outburst, and 4 years since the last observation. We find
that the source has continued to cool, with the cooling curve displaying a
simple power-law decay. This suggests that the crust has not fully thermally
relaxed yet, and may continue to cool further. A simple power law decay is in
contrast to theoretical cooling models of the crust, which predict that the
crust should now have cooled to the same temperature as the neutron star core.
