PSR J1829+2456: a relativistic binary pulsar

We report the discovery of a new binary pulsar, PSR J1829+2456, found during a midlatitude 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 ˙ ω = 0. ◦ 28 ± 0. ◦ 01 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 (∼60 Gyr), and this system will not significantly impact upon calculations of merger rates that are relevant to upcoming instruments such as LIGO.