A nearby 37.9-ms radio pulsar in a relativistic binary system

WITH very few exceptions¹, high Galactic latitudes have not been surveyed with sufficient sensitivity to detect millisecond pulsars. Accordingly we have conducted a preliminary sensitive survey at Galactic latitudes b ≥30°using the Arecibo 305-m radiotelescope at a frequency of 430 MHz. Here I report the discovery of a 37.9-ms radio pulsar, PSR1534 + 12, in a 10.1-hour eccentric binary orbit². Timing analysis constrains the masses of the pulsar and its companion to be 1.32 ± 0.03 M _⊙ and 1.36 ± 0.03 M _⊙ (where M _⊙ is the mass of the Sun). This, together with the high eccentricity (e=0.274) and small orbital diameter (∼2 R⊙ ), indicates that the companion is probably another neutron star, and that the orbital evolution is strongly influenced by effects due to general relativity. The exceptionally high timing accuracy obtainable in PSR1534 + 12, because the pulse is so strong and narrow, will allow general relativity to be tested with unprecedented accuracy. The unique morphology of the pulsar's emission and polarization will make possible the measurement of a previously unconfirmed relativistic effect, the geodetic precession of the pulsar spin-axis.