On the precession of the isolated pulsar PSR B1828-11 A time-varying magnetic field

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 167 d (Stairs et al. 2000). The only description based on a free precession of star’s rigid crust coupled to the magnetic dipole torque, explains the 500component, as the fundamental Fourier frequency, with its harmonic 250-component (Link & Epstein 2001). 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 (≃ 1000 d) 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 250 d are dominant for small wobble angle ≃ 3◦ and large field’s inclination angle ≥ 89◦.