Journal Article

Pulsar magnetic alignment and the pulsewidth–age relation

M. D. T. Young, L. S. Chan, R. R. Burman and D. G. Blair

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 402, issue 2, pages 1317-1329
Published in print February 2010 | ISSN: 0035-8711
Published online February 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.15972.x
Pulsar magnetic alignment and the pulsewidth–age relation

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Using pulsewidth data for 872 isolated radio pulsars, we test the hypothesis that pulsars evolve through a progressive narrowing of the emission cone combined with progressive alignment of the spin and magnetic axes. The new data provide strong evidence for the alignment over a time-scale of about 1 Myr with a log standard deviation of around 0.8 across the observed population. This time-scale is shorter than the time-scale of about 10 Myr found by previous authors, but the log standard deviation is larger. The results are inconsistent with models based on magnetic field decay alone or monotonic counter-alignment to orthogonal rotation. The best fits are obtained for a braking index parameter, nγ≈ 2.3, consistent with the mean of the six measured values, but based on a much larger sample of young pulsars. The least-squares fitted models are used to predict the mean inclination angle between the spin and magnetic axes as a function of log characteristic age. Comparing these predictions to existing estimates, it is found that the model in which pulsars are born with a random angle of inclination gives the best fit to the data. Plots of the mean beaming fraction as a function of characteristic age are presented using the best-fitting model parameters.

Keywords: stars: evolution; stars: magnetic fields; stars: neutron; pulsars: general

Journal Article.  9021 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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