The discovery of quiescent X-ray emission from SAX J1808.4-3658, the transient 2.5ms pulsar

摘要

We report on a 20 ks BeppoSAX observation of the transient 2.5 ms X-raypulsar SAX J1808.4-3658 in its quiescent state. A source at a level of ~ 3 x10^-3 c/s was detected with the BeppoSAX/MECS at a position consistent withthat of SAX J1808.4-3658. The inferred 0.5-10 keV luminosity was to thatmeasured from other quiescent low mass X-ray transients hosting an old neutronstar. This result is discussed in the light of the propeller and radio pulsarshock emission models for the quiescent emission of these systems.