A 2.1 Solar Mass Pulsar Measured by Relativistic Orbital Decay

摘要

PSR J0751+1807 is a millisecond pulsar in a circular 6 hr binary system witha helium white dwarf secondary. Through high precision pulse timingmeasurements with the Arecibo and Effelsberg radio telescopes, we have detectedthe decay of its orbit due to emission of gravitational radiation. This is thefirst detection of the relativistic orbital decay of a low-mass, circularbinary pulsar system. The measured rate of change in orbital period, correctedfor acceleration biases, is dP_b/dt=(-6.4+-0.9)x10^-14. Interpreted in thecontext of general relativity, and combined with measurement of Shapiro delay,it implies a pulsar mass of 2.1+-0.2 solar masses, the most massive pulsarmeasured. This adds to the emerging trend toward relatively high neutron starmasses in neutron star--white dwarf binaries. Additionally, there is someevidence for an inverse correlation between pulsar mass and orbital period inthese systems. We consider alternatives to the general relativistic analysis ofthe data, and we use the pulsar timing data to place limits on violations ofthe strong equivalence principle.