2003A&A...399..653R

Analysis of both pulse timing and pulse shape variations of the isolated pulsar PSR B1828-11 shows highly correlated and strong Fourier power at periods ≃1000, 500, 250, and 167d (Stairs et al., 2000Natur.406..484S). The only description based on a free precession of the star's rigid crust coupled to the magnetic dipole torque, explains the 500d-component, as the fundamental Fourier frequency, with its harmonic 250d-component (Link & Epstein, 2001ApJ...556..392L). In this paper, we study a time-varying magnetic field model and show that if the dipole moment vector rotates with a period nearly equal to the longest (assumed fundamental) observed period (≃1000d) relative to the star's body axes, the resulting magnetic torque may produce the whole Fourier spectrum consistently. We also find the second and fourth harmonics at periods ≃500 and 250d are dominant for small wobble angle ≃3° and large field's inclination angle ≥89°. We note that, although our model simply explains the observed pulse timing and pulse shape variations of PSR B1828-11, it also evokes some serious problems with our currently understanding from the physics of the neutron star structure.