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arXiv 1503.06669astro-ph.SR
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主序星上的恒星风I:风模型

Stellar Winds on the Main-Sequence I: Wind Model

C. P. Johnstone, M. Güdel, T. Lüftinger, G. Toth, I. Brott

摘要:

目的:我们开发了一种方法,用于估计低质量主序星的恒星风的性质之间的质量为0.4和1.1太阳质量的距离范围内的恒星。方法:我们使用一维热压驱动的水动力风模型运行的通用平流代码。使用现场测量的太阳风,我们产生的模型的缓慢和快速的组成部分的太阳风。我们考虑两种完全不同的方法来缩放风的基本温度到其他恒星:在模型A中,我们假设风的温度从根本上与日冕温度有关,在模型B中,我们假设风的底部的声速是逃逸速度的固定分数。在本系列的第二篇论文中,我们使用观测约束的旋转演化模型来推导风的质量损失率。结果如下:我们的模型为太阳风提供了一个很好的描述真正的太阳风远离太阳表面,但在太阳日冕是不现实的。我们运行了1200个风模型的网格,以推导出作为恒星质量、半径和风温度的函数的风特性的关系。利用这些结果,我们探讨风的性质如何依赖于恒星的质量和旋转。结论:基于我们的两个假设的风温度的缩放,我们认为,仍然有很大的不确定性,这些属性应该如何确定。解决这种不确定性可能需要将太阳风物理学应用于其他恒星,并对恒星风的性质进行详细的观测约束。在本文的最后一节中,我们给出了如何应用我们的结果来计算远离恒星表面的恒星风条件的一步一步的指导。

英文摘要:

Aims: We develop a method for estimating the properties of stellar winds for low-mass main-sequence stars between masses of 0.4 and 1.1 solar masses at a range of distances from the star. Methods: We use 1D thermal pressure driven hydrodynamic wind models run using the Versatile Advection Code. Using in situ measurements of the solar wind, we produce models for the slow and fast components of the solar wind. We consider two radically different methods for scaling the base temperature of the wind to other stars: in Model A, we assume that wind temperatures are fundamentally linked to coronal temperatures, and in Model B, we assume that the sound speed at the base of the wind is a fixed fraction of the escape velocity. In Paper II of this series, we use observationally constrained rotational evolution models to derive wind mass loss rates. Results: Our model for the solar wind provides an excellent description of the real solar wind far from the solar surface, but is unrealistic within the solar corona. We run a grid of 1200 wind models to derive relations for the wind properties as a function of stellar mass, radius, and wind temperature. Using these results, we explore how wind properties depend on stellar mass and rotation. Conclusions: Based on our two assumptions about the scaling of the wind temperature, we argue that there is still significant uncertainty in how these properties should be determined. Resolution of this uncertainty will probably require both the application of solar wind physics to other stars and detailed observational constraints on the properties of stellar winds. In the final section of this paper, we give step by step instructions for how to apply our results to calculate the stellar wind conditions far from the stellar surface.

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