论文标题
核心超冲程受到没有太阳对流芯和一些太阳样恒星的限制
Core overshoot constrained by the absence of a solar convective core and some solar-like stars
论文作者
论文摘要
对流核心的过冲混合是恒星进化的重要不确定性。由于数值模拟和湍流对流模型预测指数降低了径向RMS的湍流速度，因此对过冲混合的流行处理是应用扩散过程，指数降低扩散系数。重要的是研究扩散系数的参数，因为它们确定了混合区域中混合的效率。在本文中，我们研究了核心过冲混合对太阳模型中核心性质的影响，并通过使用热震的推断和观察太阳能8B中性漏物来限制了过冲模型的参数。对于太阳质量恒星，核心过冲的混合有助于延长ZAMS中对流芯的寿命。如果混合的强度足够高，那么太阳模型中的对流芯可以生存直到当今太阳时代，从而导致声速和密度曲线与Heliose震响的推断相比，声音速度和密度曲线很大。 8B中微子通量也有利于辐射太阳核心。这些限制了对流过冲混合的指数扩散模型的参数。对1.0 <m <1.5的13个开普勒低质量恒星的有限的强糖研究显示了过冲参数的质量依赖性范围。详细分析了不同元素的过冲混合过程。发现指数扩散过冲模型可为具有不同核衡时间尺度的元素提供不同的有效过冲混合长度。
Convective-core overshoot mixing is a significant uncertainty in stellar evolution. Because numerical simulations and turbulent convection models predict exponentially decreasing radial rms turbulent velocity, a popular treatment of the overshoot mixing is to apply a diffusion process with exponentially decreasing diffusion coefficient. It is important to investigate the parameters of the diffusion coefficient because they determine the efficiency of the mixing in the overshoot region. In this paper, we have investigated the effects of the core overshoot mixing on the properties of the core in solar models and have constrained the parameters of the overshoot model by using helioseismic inferences and the observation of the solar 8B neutrino flux. For solar-mass stars, the core overshoot mixing helps to prolong the lifetime of the convective core developed at the ZAMS. If the strength of the mixing is sufficiently high, the convective core in a solar model could survive till the present solar age, leading to large deviations of the sound-speed and density profiles comparing with the helioseismic inferences. The 8B neutrino flux also favours a radiative solar core. Those provide a constraint on the parameters of the exponential diffusion model of the convective overshoot mixing. A limited asteroseismic investigation of 13 Kepler low-mass stars with 1.0 < M < 1.5 shows a mass-dependent range of the overshoot parameter. The overshoot mixing processes for different elements are analyzed in detail. It is found that the exponential diffusion overshoot model leads to different effective overshoot mixing lengths for elements with different nuclear equilibrium timescale.
