The magnetic field strengths of accreting millisecond pulsars

TL;DR

This study estimates the magnetic field strengths of 14 accreting millisecond pulsars by analyzing RXTE data to determine flux levels corresponding to the inner edge of their accretion disks, providing bounds on their magnetic dipole moments.

Contribution

It introduces a method to estimate magnetic field bounds of pulsars using flux variations and accretion theory, applied to all known RXTE-observed accreting millisecond pulsars.

Findings

Estimated magnetic field strength bounds for 14 pulsars.

Identified flux levels corresponding to disk inner edge positions.

Discussed potential improvements with future data.

Abstract

In this work we have estimated upper and lower limits to the strength of the magnetic dipole moment of all 14 accreting millisecond X-ray pulsars observed with the Rossi X-ray Timing Explorer (RXTE). For each source we searched the archival RXTE data for the highest and lowest flux levels with a significant detection of pulsations. We assume these flux levels to correspond to the closest and farthest location of the inner edge of the accretion disk at which channelled accretion takes place. By estimating the accretion rate from the observed luminosity at these two flux levels, we place upper and lower limits on the magnetic dipole moment of the neutron star, using assumptions from standard magnetospheric accretion theory. Finally, we discuss how our field strength estimates can be further improved as more information on these pulsars is obtained.