HIGH-PRECISION TIMING OF FIVE MILLISECOND PULSARS: SPACE VELOCITIES, BINARY EVOLUTION, AND EQUIVALENCE PRINCIPLES

Abstract

We present high-precision timing of five millisecond pulsars (MSPs) carried\nout for more than seven years; four pulsars are in binary systems and one is\nisolated. We are able to measure the pulsars' proper motions and derive an\nestimate for their space velocities. The measured two-dimensional velocities\nare in the range 70-210 km/s, consistent with those measured for other MSPs. We\nalso use all the available proper motion information for isolated and binary\nMSPs to update the known velocity distribution for these populations. As found\nby earlier works, we find that the velocity distribution of binary and isolated\nMSPs are indistinguishable with the current data. Four of the pulsars in our\nobserving program are highly recycled with low-mass white dwarf companions and\nwe are able to derive accurate binary parameters for these systems. For three\nof these binary systems we are able to place initial constraints on the pulsar\nmasses with best-fit values in the range 1.0-1.6 M_sun. The implications of the\nresults presented here to our understanding of binary pulsar evolution are\ndiscussed. The updated parameters for the binary systems studied here, together\nwith recently discovered similar systems, allowed us to update previous limits\non the the violation of the strong equivalence principle through the parameter\n|Delta| to 4.6x10^-3 (95% confidence) and the violation of\nLorentz-invariance/momentum-conservation through the parameter |hat{alpha}_3|\nto 5.5x10^-20 (95% confidence).\n