Modified pulsar current analysis: probing magnetic field evolution

TL;DR

This paper introduces a modified pulsar current analysis method that studies magnetic field decay in radio pulsars by analyzing flow along the characteristic age, revealing a roughly twofold decay over 400,000 years.

Contribution

The study presents a new approach analyzing pulsar flow along characteristic age, improving the detection of magnetic field decay in neutron stars.

Findings

Magnetic field decays by about a factor of two in 8×10^4 to 10^6 years.

Decay timescale estimated at approximately 4×10^5 years.

Method can potentially become a powerful tool with better data.

Abstract

We use a modified pulsar current analysis to study magnetic field decay in radio pulsars. In our approach we analyse the flow, not along the spin period axis as has been performed in previous studies, but study the flow along the direction of growing characteristic age, $\tau=P/(2\dot P)$. We perform extensive tests of the method and find that in most of the cases it is able to uncover non-negligible magnetic field decay (more than a few tens of per cent during the studied range of ages) in normal radio pulsars for realistic initial properties of neutron stars. However, precise determination of the magnetic field decay timescale is not possible at present. The estimated timescale may differ by a factor of few for different sets of initial distributions of neutron star parameters. In addition, some combinations of initial distributions and/or selection effects can also mimic enhanced field decay. We apply our method to the observed sample of radio pulsars at distances $<10$ kpc in the range of characteristic ages $8 \times 10^4 < \tau < 10^6$ years where, according to our study, selection effects are minimized. By analysing pulsars in the Parkes Multibeam and Swinburne surveys we find that, in this range, the field decays roughly by a factor of two. With an exponential fit this corresponds to the decay time scale $\sim 4 \times 10^5$ yrs. With larger statistics and better knowledge of the initial distribution of spin periods and magnetic field strength, this method can be a powerful tool to probe magnetic field decay in neutron stars.