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Session 113 - Old Worn-Out Stars.
Oral session, Thursday, January 16
Piers 2/3,

[113.08] Spin-Down of an Oblique Rotator

A. Melatos (Caltech)

A phenomenological model of rotation-powered pulsars is presented that accounts for the observed spin-down behavior of all three pulsars with braking indices measured from absolute pulse numbering (the Crab, PSR B0540-69, and PSR B1509-58). The model assumes that the magnetosphere is current-starved and that energy transport is Poynting-flux-dominated at the light cylinder. Under these conditions, the stellar braking torque can be calculated in terms of just three observable parameters: the rotation period, the period derivative, and the angle between the rotation and magnetic axes. With no free parameters, the theory yields braking index values that agree with timing data to 4 per cent for the above three pulsars, although there is disagreement with a recent braking index measurement for Vela. The implications of the theory for the surface magnetic fields of pulsars and their evolutionary tracks on the P-Pdot diagram are discussed, and further observational tests of the theory (e.g. based on the second deceleration parameter) are proposed.

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