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Astron. Astrophys. 361, 795-802 (2000)

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Centrifugal buoyancy as a mechanism for neutron star glitches

B. Carter 1, D. Langlois 1 and D.M. Sedrakian 1,2

1 Département d'Astrophysique Relativiste et de Cosmologie, C.N.R.S., Observatoire de Paris, 92195 Meudon, France
2 Erevan State University, Erevan, Republic of Armenia

Received 23 April 1999 / Accepted 20 March 2000

Abstract

The frequent glitches (sudden increases of the apparent angular velocity) observed in certain pulsars are generally believed to be attributable to discontinuous angular momentum transfer to the outer neutron star crust from a differentially rotating superfluid layer, but the precise mechanism is not quite elucidated. Most explanations invoke vortex pinning as the essential mechanism responsible for the build up of strain in the crust that is relaxed, either by fracture of the solid structure or by discontinous unpinning, during the glitch. It is shown here that there is another mechanism that could give rise to strain, and subsequent fracture, of the solid crust, even if vortex pinning is ineffective: this is the effective force arising from the deficit of centrifugal buoyancy that will be present whenever there is differential rotation. This centrifugal buoyancy deficit force will be comparable in order of magnitude, but opposite in direction, to the force that would arise from vortex pinning if it were effective.

Key words: stars: neutron – stars: pulsars: general – stars: rotation – hydrodynamics

Send offprint requests to: D. Langlois (langlois@obspm.fr)

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© European Southern Observatory (ESO) 2000

Online publication: October 2, 2000
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