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Application of a two dipole model to PSR J1640-4631, a pulsar with an anomalous braking index
- Publication Year :
- 2019
-
Abstract
- Recent timing observation provides an intriguing result for the braking index of the X-ray pulsar PSR J1640-4631, which has a measured braking index $n=3.15\pm0.03$. The decrease of the inclination angle between between the spin axis and the magnetic axis can be responsible for such a high braking index. However, the physical mechanisms causing the change of the magnetic inclination angle have not been fully understood. In this Letter, we apply a two-dipole model given by Hamil et al (2016) to explain the decrease of the magnetic inclination angle of PSR J1640-4631. The rotation effect of a charged sphere and the magnetization of ferromagnetically ordered material produce magnetic moments $M_{1}$ and $M_{2}$, respectively. There exist a minimum of the potential energy for the magnetic moment $M_{2}$ in the magnetic field of $M_{1}$, hence the $M_{2}$ will freely rotate around the minimum energy position (i. e equilibrium position), similar to a simple pendulum. Our calculation indicate the magnetic moment $M_{2}$ would evolve towards alignment with the spin axis for PSR J1640-4631, and cause the magnetic inclination angle to decrease. The single peak in the pulse profile favors a relatively low change rate of the magnetic inclination angle.<br />Comment: 5 pages, 2 figures, PASJ in press
- Subjects :
- Astrophysics - High Energy Astrophysical Phenomena
Subjects
Details
- Database :
- arXiv
- Publication Type :
- Report
- Accession number :
- edsarx.1909.01699
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.1093/pasj/psz109