贫金属低质量主序星的振动不稳定性
Vibrational Instability of Metal-Poor Low-Mass Main-Sequence Stars
摘要：
我们发现，由于pp链的$\varepsilon$机制，在贫金属低质量恒星中，低阶g模变得不稳定。由于这些恒星的外对流区仅限于最外层，因此对流处理的不确定性不会对结果产生显著影响。金属丰度的降低导致恒星不透明度的降低，从而增加恒星的光度。这使得恒星变得致密，导致密度差减小，这有利于$\varepsilon$机制的不稳定性。我们还发现了对流阻塞机制对贫金属低质量恒星高阶g模的不稳定性。由于贫金属星的有效温度和光度明显高于Pop I星，因此表现出$γ$ Dor型脉动的恒星质量要比Pop I星小得多。我们证明，这些模式是不稳定的约$1\,M_\odot$星的金属贫乏的情况下。
英文摘要：
We find that low-degree low-order g-modes become unstable in metal-poor low-mass stars due to the $\varepsilon$-mechanism of the pp-chain. Since the outer convection zone of these stars is limited only to the very outer layers, the uncertainty in the treatment of convection does not affect the result significantly. The decrease in metallicity leads to decrease in opacity and hence increase in luminosity of a star. This makes the star compact and results in decrease in the density contrast, which is favorable to the $\varepsilon$-mechanism instability. We find also instability for high order g-modes of metal-poor low-mass stars by the convective blocking mechanism. Since the effective temperature and the luminosity of metal-poor stars are significantly higher than those of Pop I stars, the stars showing $γ$ Dor-type pulsation are substantially less massive than in the case of Pop I stars. We demonstrate that those modes are unstable for about $1\,M_\odot$ stars in the metal-poor case.
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