Neutron star's initial spin period distribution

We analyse different possibilities to explain the wide initial spin period distribution of radio pulsars presented by Noutsos et al. With a population synthesis modelling, we demonstrate that magnetic field decay can be used to interpret the difference between the recent results by Noutsos et al and those by Popov and Turolla, where a much younger population of neutron stars associated with supernova remnants with known ages has been studied. In particular, an exponential field decay with τmag = 5 Myr can produce a ‘tail’ in the reconstructed initial spin period distribution up to P0 > 1 s starting with a standard Gaussian with 〈P0〉 = 0.3 s and σP = 0.15 s. Another option to explain the difference between initial spin period distributions from Noutsos et al. and Popov and Turolla – the emerging magnetic field – is also briefly discussed.