Precession Interpretation of the Isolated Pulsar PSR B1828−11

Pulse timing of the isolated pulsar PSR B1882-11 shows strong Fourier powerat periods ~1000, 500 and 250 d, correlated with changes in the pulse profile(Stairs, Lyne & Shemar 2000). We study the extent to which these data can beexplained by precession of the star's rigid crust coupled to the magneticdipole torque. We find that the correlated changes in the pulse duration andspin period derivative can be explained as precession at a period of ~500 dwith a wobble angle of ~3 deg if the star's dipole moment is nearly orthogonalto its symmetry axis. The dipole torque produces a harmonic at ~250 d.Comparison of the predicted spin dynamics with the observed pulse durationsrequires the radio beam to have a non-standard ``hour-glass'' shape. We makepredictions of variations in beam polarization and pulse profile with which totest this interpretation. The precession interpretation of PSR B1828-11seriously challenges the current understanding of the liquid interior of theneutron star. In particular, if the internal liquid is in a superfluid state,its rotational vortices cannot be significantly pinned to the crust.Comment: 15 pages, 5 figure