On the Bimodal Spin-period Distribution of Be/X-Ray Pulsars
Abstract
It has been reported that there are two populations of Be/X-ray pulsars, with the pulse period distribution peaked at ∼10 s and ∼200 s, respectively. A possible explanation of this bimodal distribution is related to different accretion modes in Be/X-ray binaries. In this work, we investigate the spin evolution of Be/X-ray pulsars based on the magnetically threaded accretion disk model. Compared with previous works, we take into account several distinct and important factors of Be/X-ray binaries, including the transient accretion behavior and possible change of the accretion disk structure during quiescence. We demonstrate that current Be/X-ray pulsars are close to the spin equilibrium determined by the balance of spin-up during outbursts and spin down during quiescence, and that the observed bimodal distribution can be well reproduced by the equilibrium spin periods with reasonable input parameters.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 2019
- DOI:
- 10.3847/1538-4357/aafee0
- arXiv:
- arXiv:1901.04707
- Bibcode:
- 2019ApJ...872..102X
- Keywords:
-
- accretion;
- accretion disks;
- stars: emission-line;
- Be;
- X-rays: binaries;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 13 pages, 3 figures