High-precision timing of five millisecond pulsars: Space velocities, binary evolution, and equivalence principles

M. E. Gonzalez, I. H. Stairs, R. D. Ferdman, P. C. C. Freire, D. J. Nice, P. B. Demorest, S. M. Ransom, M. Kramer, F. Camilo, G. Hobbs, R. N. Manchester, A. G. Lyne

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We present high-precision timing of five millisecond pulsars (MSPs) carried out for more than seven years; four pulsars are in binary systems and one is isolated. We are able to measure the pulsars' proper motions and derive an estimate for their space velocities. The measured two-dimensional velocities are in the range 70-210 km s(-1), consistent with those measured for other MSPs. We also use all the available proper motion information for isolated and binary MSPs to update the known velocity distribution for these populations. As found by earlier works, we find that the velocity distribution of binary and isolated MSPs are indistinguishable with the current data. Four of the pulsars in our observing program are highly recycled with low-mass white dwarf companions and we are able to derive accurate binary parameters for these systems. For three of these binary systems, we are able to place initial constraints on the pulsar masses with best-fit values in the range 1.0-1.6 M(circle dot). The implications of the results presented here to our understanding of binary pulsar evolution are discussed. The updated parameters for the binary systems studied here, together with recently discovered similar systems, allowed us to update previous limits on the violation of the strong equivalence principle through the parameter vertical bar Delta vertical bar to 4.6 x 10(-3) (95% confidence) and the violation of Lorentz invariance/momentum conservation through the parameter vertical bar(alpha) over cap (3)vertical bar to 5.5 x 10(-20) (95% confidence).

Original languageEnglish
Article number102
Number of pages12
JournalAstrophysical Journal
Issue number2
Early online date28 Nov 2011
Publication statusPublished - 20 Dec 2011
Externally publishedYes


  • close binaries
  • proper motions
  • general pulsars
  • relativistic processes
  • neutron stars

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