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JPL pulsar timing observations. V - MACRO and microjumps in the VELA pulsar 0833-45
Cordes, J. M.; Downs, G. S.; Krause-Polstorff, J.
AA(Cornell University, Ithaca, NY; California, University, Berkeley; California Institute of Technology, Pasadena), AB(California Institute of Technology, Jet Propulsion Laboratory, Pasadena), AC(California Institute of Technology, Jet Propulsion Laboratory, Pasadena)
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 330, July 15, 1988, p. 847-869. Research supported by the California Institute of Technology, Alfred P. Sloan Foundation, Cornell University, University of California, and Owens Valley Radio Observatory. (ApJ Homepage)
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NASA/STI Keywords:
Neutron Stars, Pulsars, Stellar Rotation, Astrometry, Random Walk, Spin, Stellar Interiors, Superfluidity, Time Dependence, Vortices
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In this paper, 14.5 yr of JPL timing data are analyzed to study the spindown of the Vela pulsar. Discontinuities in the spin frequency and its derivatives have bimodal amplitude distributions. Macrojumps are characterized by relative changes in spin rate of about 10 to the -6th with a derivative of 0.01, while microjumps have relative changes in spin rate of less than about 10 to the -9th with derivative of less than about 0.0001. Macrojumps display a (+,-) signature with a well-defined ratio of the amplitudes. Microjumps, however, show all possible signs of events and a larger range in signature. Six macrojumps and their associated transients are quantified using a 10-parameter model for each jump. Amplitude and decay time parameters vary by a factor of about five over the set of jumps. The results are discussed in terms of superfluid vortex models. The macrojumps are consistent with a model in which angular momentum is suddenly transferred to the crust from a more rapidly rotating superfluid core, followed by relaxation of the spin-down rate.

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