Implications of the birth period - magnetic field relationship in the for the origin of magnetic fields in pulsars.

Lilia Ferrario

Australian National University


We model the recent results from the 1374 MHZ Parkes Multibeam Survey to investigate the magnetic field distribution and the birth period distribution of pulsars as a function of magnetic field. Using population synthesis calculations we relate these to the magnetic properties of their progenitor stars on the main sequence exploring the hypothesis that the fields in neutron stars are of fossil origin. We show that the observations of radio pulsars can be explained by the fossil hypothesis if the mean field of their progenitors is of about 15 Gauss.The required distribution implies that the vast majority of main sequence stars will have fields well below the current detectability limit, while the implied high field extrapolation of the distribution naturally explains the magnetars. We also show that as with the magnetic white dwarfs, there is evidence from the radio pulsars that there is a tendency for the stronger field pulsars to be born as slower rotators, and argue that this may be a characteristic that can be used to distinguish between the fossil and dynamo models for the origin of fields in compact stars.


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