Evidence for a minimum ellipticity in millisecond pulsars

G. Woan, M. D. Pitkin, B. Haskell, D. I. Jones, P. D. Lasky

Published 2018-06-07Version 1

Neutron stars spin down over time due to a number of energy-loss processes. We provide tantalising population-based evidence that millisecond pulsars have a minimum ellipticity of $\epsilon\approx10^{-9}$ around their spin axis and that consequently some spin down mostly through gravitational-wave emission. We discuss the implications of such a minimum ellipticity in terms of the internal magnetic field strengths and nuclear matter composition of neutron stars and show it would result in the Advanced LIGO and Virgo gravitational-wave detectors, or their upgrades, detecting gravitational waves from some known millisecond pulsars in the near future.