Neutron star's initial spin period distribution

Abstract

We analyze different possibilities to explain the wide initial spin period distribution of radio pulsars presented by Noutsos et al. (2013). With a population synthesis modeling we demonstrate that magnetic field decay can be used to interpret the difference between the recent results by Noutsos et al. (2013) and those by Popov & Turolla (2012), where a much younger population of NSs associated with supernova remnants with known ages has been studied. In particular, an exponential field decay with tau_mag = 5Myrs can produce a "tail" in the reconstructed initial spin period distribution (as obtained by Noutsos et al. 2013) up to P_0 > 1 s starting with a standard gaussian with P_0 = 0.3 s and sigma_P = 0.15 s. Another option to explain the difference between initial spin period distributions from Noutsos et al. (2013) and Popov & Turolla (2012) -- the emerging magnetic field -- is also briefly discussed.