  We have used the Green Bank Telescope to observe the millisecond pulsar PSR
J0514-4002A on 43 occasions spread over 2 years. This 5-ms pulsar is located in
the globular cluster NGC 1851; it belongs to a binary system and has a highly
eccentric (e = 0.888) orbit. We have obtained a phase-coherent timing solution
for 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 the
cluster, and is likely to lie on its more distant half. The non-detection of
eclipses at superior conjunction can be used, given the peculiar geometry of
this system, to rule out the possibility of an extended companion. We have
measured the rate of advance of periastron for this binary system to be
$\dot{\omega}$ = 0.01289(4) degrees per year, which if due completely to
general 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 it
is a heavy white dwarf. The 350-MHz flux density of this pulsar varies between
0.2 and 1.4 mJy; the origin of these variations is not known.

Astrophysics