On the precession of the isolated pulsar PSR B1828-11

A time-varying magnetic field

Institute for Advanced Studies in Basic Sciences, Gava Zang, Zanjan 45195, Iran

Corresponding author: vrezania@phys.ualberta.ca

Received: 10 September 2002
Accepted: 27 November 2002

Abstract

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. [CITE]). The only description based on a free precession of the star's rigid crust coupled to the magnetic dipole torque, explains the 500 d-component, as the fundamental Fourier frequency, with its harmonic 250 d-component (Link & Epstein [CITE]). 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 and large field's inclination angle ≥ . 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.