PSR J1829+2456: a relativistic binary pulsar

We report the discovery of a new binary pulsar, PSR J1829+2456, found during a mid-latitude drift-scan survey with the Arecibo telescope. Our initial timing observations show the 41-ms pulsar to be in a 28-h, slightly eccentric, binary orbit. The advance of periastron (omega) over dot = 0.degrees28 +/- 0.degrees01 yr(-1) is derived from our timing observations spanning 200 d. Assuming that the advance of periastron is purely relativistic and a reasonable range of neutron star masses for PSR J1829+2456, we constrain the companion mass to be between 1.22 and 1.38 M., making it likely to be another neutron star. We also place a firm upper limit on the pulsar mass of 1.38 M.. The expected coalescence time due to gravitational wave emission is long (similar to60 Gyr), and this system will not significantly impact upon calculations of merger rates that are relevant to upcoming instruments such as LIGO.