Pulsar magnetic alignment and the pulsewidthage relation
Abstract
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 timescale of about 1Myr with a log standard deviation of around 0.8 across the observed population. This timescale is shorter than the timescale of about 10Myr 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 counteralignment to orthogonal rotation. The best fits are obtained for a braking index parameter, n_{γ} ~ 2.3, consistent with the mean of the six measured values, but based on a much larger sample of young pulsars. The leastsquares 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 bestfitting model parameters.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 February 2010
 DOI:
 10.1111/j.13652966.2009.15972.x
 arXiv:
 arXiv:0911.0502
 Bibcode:
 2010MNRAS.402.1317Y
 Keywords:

 stars: evolution;
 stars: magnetic fields;
 stars: neutron;
 pulsars: general;
 Astrophysics  High Energy Astrophysical Phenomena
 EPrint:
 13 pages, 11 figures, Accepted for publication in MNRAS