Neutron stars initial spin period distribution

TL;DR

This paper investigates the wide initial spin period distribution of radio pulsars by modeling magnetic field decay and its impact on observed pulsar properties, reconciling different observational results.

Contribution

It demonstrates that magnetic field decay, especially exponential decay with a 5 Myr timescale, can explain the observed distribution differences in pulsar initial spin periods.

Findings

Magnetic field decay can produce a tail in the initial spin period distribution.

An exponential decay with tau_mag = 5 Myrs fits the observed data.

Emerging magnetic field is also a potential explanation.

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.