Effect of a magnetic field on massive star winds I: mass-loss and velocity for a dipole field
| Autor: | Bard, Christopher, Townsend, Richard H. D. |
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| Rok vydání: | 2016 |
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| Druh dokumentu: | Working Paper |
| DOI: | 10.1093/mnras/stw1901 |
| Popis: | We generalize the Rigid-Field Hydrodynamic equations to accommodate arbitrary magnetic field topologies, resulting in a new Arbitrary Rigid-Field hydrodynamic (ARFHD) formalism. We undertake a critical point calculation of the steady-state ARFHD equations with a CAK-type radiative acceleration and determine the effects of a dipole magnetic field on the usual CAK mass-loss rate and velocity structure. Enforcing the proper optically-thin limit for the radiative line-acceleration is found to decrease both the mass-loss and wind acceleration, while rotation boosts both properties. We define optically-thin-correction and rotation parameters to quantify these effects on the global mass-loss rate and develop scaling laws for the surface mass-flux as a function of surface colatitude. These scaling laws are found to agree with previous laws derived from magnetohydrodynamic simulations of magnetospheres. The dipole magnetosphere velocity structure is found to differ from a global beta-velocity law, which contradicts a central assumption of the previously-developed XADM model of X-ray emission from magnetospheres. Comment: 18 pages, 12 figures. Accepted for publication in MNRAS |
| Databáze: | arXiv |
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