Rotational and thermal dynamics of neutron stars

Abstract

This thesis explores the rotational and thermal dynamics of neutron stars. All neutron stars exhibit irregularities in their spin rates, which may be evidence of coupling between the solid crust and liquid components in the interior. We study short-time scale correlations in the stochastic variations in spin rate, timing noise, in 32 pulsars. Upon subtraction of low frequency wander, we find that in two stars a fluctuation in rotational phase at a given time is correlated with past fluctuations over a correlation time of ~̃ 10-40 d; over longer times, the fluctuations are uncorrelated. We interpret this result as the signature of a damped rotational mode in the star, excited by the noise process, and likely due to friction between the crust and interior liquid. In the second part of this thesis, we investigate the thermal and magnetic evolution of highly magnetized neutron stars, magnetars. We explore a thermo-resistive instability in the outer crusts of magnetars wherein a perturbation in temperature increases ohmic heating. We show that magnetars of characteristic age T age ~ 10 4 yr are unstable over timescales as short as days if strong current sheets are present in the outer crust. This instability could play an important role in the thermal and magnetic field evolution of highly magnetized neutron stars, and may be related to bursting activity in magnetars.