Timing the Eccentric Binary Millisecond Pulsar in NGC 1851

We have used the Green Bank Telescope to observe the millisecond pulsar PSRJ0514-4002A on 43 occasions spread over 2 years. This 5-ms pulsar is located inthe globular cluster NGC 1851; it belongs to a binary system and has a highlyeccentric (e = 0.888) orbit. We have obtained a phase-coherent timing solutionfor this object, including very precise position, spin and orbital parameters.The pulsar is located 4.6" (about 1.3 core radii) from the center of thecluster, and is likely to lie on its more distant half. The non-detection ofeclipses at superior conjunction can be used, given the peculiar geometry ofthis system, to rule out the possibility of an extended companion. We havemeasured the rate of advance of periastron for this binary system to be$\dot{\omega}$ = 0.01289(4) degrees per year, which if due completely togeneral relativity, implies a total system mass of 2.453(14) solar masses.Given the known mass function, the pulsar mass has to be < 1.5 solar masses,and the mass of the companion has to be > 0.96 solar masses, implying that itis a heavy white dwarf. The 350-MHz flux density of this pulsar varies between0.2 and 1.4 mJy; the origin of these variations is not known.Comment: Accepted for publication in the Astrophysical Journa