  We report here the results of a 90 ks BeppoSAX observation of the low mass
X-ray binary and atoll source KS 1731-260 during a quiescent phase. From this
observation we derive a source X-ray luminosity of \sim 10^{33} ergs/s (for a
source distance of 7 kpc). If the neutron star is spinning at a period of a few
milliseconds, as inferred from the nearly-coherent oscillations observed during
type-I X-ray bursts, the quiescent X-ray luminosity constrains the neutron star
magnetic field strength to less than \sim 10^9 G. If the quiescent emission
originates from the release of thermal energy accumulated through deep crust
heating in the previous accretion phase, then the measured quiescent luminosity
requires a neutron star mass of more than 1.7 M_\odot or a very long outbust
recurrence time (\sim 10^3 yr). The former possibility would be in agreement
with the expectation of the recycling scenario, namely that the neutron star
has accreted a significant amount of mass, enough to spin it up to millisecond
periods.
