A NEW BINARY MILLISECOND PULSAR

A 4.57 ms pulsar, PSR J1713 + 0747, in a 67.8 day binary orbit with a low-mass (>0.28 M.) companion has been detected in a systematic search of the sky at high Galactic latitudes with the Arecibo radio telescop e. The new pulsar is characterized by a weak magnetic field of 1.9 x 1 0(8) G and a spin-down age of 8.9 +/- 1.0 Gyr, making it probably one of the oldest neutron stars currently observed. The distance to the pu lsar is approximately 0.8 kpc as indicated by its dispersion measure. Small timing residuals (approximately 1 mus), a relatively large flux density at GHz frequencies (S1400 approximately 3 mJy), and a narrow, sharply peaked pulse morphology, make PSR J1713 + 0747 a new celestial clock of extraordinary precision and a rare target for VLBI frame-tie experiments.