Measurement of Relativistic Orbital Decay in the PSR B1534+12 Binary System

We have made timing observations of binary pulsar PSR B1534+12 with radiotelescopes at Arecibo, Green Bank, and Jodrell Bank. By combining our newobservations with data collected up to seven years earlier, we obtain asignificantly improved solution for the astrometric, spin, and orbitalparameters of the system. For the first time in any binary pulsar system, nofewer than five relativistic or "post-Keplerian" orbital parameters aremeasurable with useful accuracies in a theory-independent way. We find theorbital period of the system to be decreasing at a rate close to that expectedfrom gravitational radiation damping, according to general relativity, althoughthe precision of this test is limited to about 15% by the otherwise poorlyknown distance to the pulsar. The remaining post-Keplerian parameters are allconsistent with one another and all but one of them have fractional accuraciesbetter than 1%. By assuming that general relativity is the correct theory ofgravity, at least to the accuracy demanded by this experiment, we find themasses of the pulsar and companion star each to be 1.339+-0.003 Msun and thesystem's distance to be d = 1.1+-0.2 kpc, marginally larger than the d ~ 0.7kpc estimated from the dispersion measure. The increased distance reducesestimates of the projected rate of coalescence of double neutron-star systemsin the universe, a quantity of considerable interest for experiments withterrestrial gravitational wave detectors such as LIGO.Comment: 17 pages, 4 figures, submitted to the Ap