A BeppoSAX Observation of KS 1731-260 in its Quiescent State: Constraints on the NS Magnetic Field

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 ~1033 ergs s-1 (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. We consider all the mechanisms that have been proposed to explain the quiescent X-ray emission of neutron sta... Mehr ...