Pair production in the millisecond pulsar J0030+0451

TL;DR

This paper investigates pair production mechanisms in the millisecond pulsar J0030+0451, focusing on electric field limits, radiation processes, and implications for radio emission and high-energy gamma-ray production.

Contribution

It analyzes the relative importance of radiation reaction and Breit-Wheeler pair production in millisecond pulsars, highlighting the potential dominance of Breit-Wheeler process in J0030+0451.

Findings

Breit-Wheeler process likely dominates pair production in J0030+0451.

High polar-cap temperature favors gamma-ray production over pair creation.

Absence of phase-aligned gamma-ray emission suggests lack of ultra-high energy electrons.

Abstract

The electric field accelerating electrons in the Timokhin-Arons polar-cap model as applied to millisecond pulsars is so high that the electron Lorentz factors are limited either by radiation reaction or by the Breit-Wheeler process. In the former case, it is possible to obtain an upper limit for curvature radiation momentum components perpendicular to the local magnetic field which is independent of the flux-line radius of curvature. The threshold value for single-photon conversion to pairs is high but is possibly reached in J0030+0451. However, owing to the high polar-cap temperature reported, direct pair production by the Breit-Wheeler process is probably more important. If the existence of coherent radio emission in millisecond pulsars is assumed to need a high-multiplicity pair plasma, then it follows that the primary electrons also produce gamma-rays in the Fermi-LAT energy band for which the magnetosphere is completely transparent. The absence of these, in phase with the radio emission, would be an immediate indication that ultra-high energy electrons and an active Timokhin-Arons polar cap are not present in J0030+0451.