  Using the Chandra/ACIS-I detector, we have identified an X-ray source (CXOU
132619.7-472910.8) in the globular cluster NGC 5139 with a thermal spectrum
identical to that observed from transiently accreting neutron stars in
quiescence. The absence of intensity variability on timescales as short as 4
seconds (< 25% rms variability) and as long as 5 years (<50% variability)
supports the identification of this source as a neutron star, most likely
maintained at a high effective temperature (approximately 1e6 K) by transient
accretion from a binary companion. The ability to spectrally identify quiescent
neutron stars in globular clusters (where the distance and interstellar column
densities are known) opens up new opportunities for precision neutron star
radius measurements.
