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Abstract: Using pulsewidth data for 872 isolated radio pulsars we test the hypothesisthat pulsars evolve through a progressive narrowing of the emission conecombined with progressive alignment of the spin and magnetic axes. The new dataprovide strong evidence for the alignment over a time-scale of about 1 Myr witha log standard deviation of around 0.8 across the observed population. Thistime-scale is shorter than the time-scale of about 10 Myr found by previousauthors, but the log standard deviation is larger. The results are inconsistentwith models based on magnetic field decay alone or monotonic counter-alignmentto orthogonal rotation. The best fits are obtained for a braking indexparameter n gamma approximately equal to 2.3, consistent the mean of the sixmeasured values, but based on a much larger sample of young pulsars. Theleast-squares fitted models are used to predict the mean inclination anglebetween the spin and magnetic axes as a function of log characteristic age.Comparing these predictions to existing estimates it is found that the model inwhich pulsars are born with a random angle of inclination gives the best fit tothe data. Plots of the mean beaming fraction as a function of characteristicage are presented using the best-fitting model parameters.



Autor: Matthew D. T. Young, Lee S. Chan, Ron R. Burman, David G. Blair

Fuente: https://arxiv.org/



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