DISCOVERY OF A VERY BRIGHT, NEARBY BINARY MILLISECOND PULSAR

DURING a survey of the southern sky for millisecond pulsars, we have discovered ne with by far the greatest flux density of any known millisecond pulsar, often exceeding 1 Jy at 430 MHz. The dispersion measure (integrated electron density along the line of sight) is the smallest for any known pulsar. This object, PSR J0437-4715, may be the closest known pulsar, and is several times closer than any other known millisecond pulsar. Its rotation period is 5.75 ms, and it is in a 5.7-day circular orbit with a low-mass companion. The spin-down energy flux density is the third highest known, after the Crab and Vela pulsars. These properties make possible studies of the pulsar at radio wavelengths with unprecedented detail, and indicate that it should be possible to detect both the pulsar and its companion at optical and perhaps shorter wavelengths.