论文标题
巨人吃巨人：大规模损失和巨型行星改变了巨型分支的尖端的光度
Giants eating giants: Mass loss and giant planets modifying the luminosity of the Tip of the Giant Branch
论文作者
论文摘要
在红色巨型阶段，恒星以自出生以来的最高速度散开质量。质量损失的速率不是固定的，而是从恒星到明星的变化，最多可达5 \％，从而导致恒星在红色巨型分支（TRGB）尖端的光度变化。同样，在此阶段，大多数恒星都吞噬了行星系统的一部分，包括其气体巨型行星和可能的棕色矮人。气体巨型行星质量在宿主星质量的0.1至2 \％之间。吞没他们的天然气巨人行星可以改变其在TRGB处的发光度，即去除He-Core退化的点。我们表明，通过吞没气体巨星行星的恒星质量增加只会使TRGB处的星星的光度修改小于0.1 \％，而金属性可以将恒星在TRGB处的光度调整高达0.5 \％。然而，恒星对流包膜的湍流增加对恒星的光度产生了更大的作用，我们估计，这可能大至5 \％。效果始终朝着增加湍流的方向，因此混合长度变成了TRGB处恒星光度的系统降低。我们发现，质量损失率的星到明星变化将主导TRGB的光度的变化，并在5 \％水平上贡献。如果星际明星的变化是由环境效应驱动的，那么相同的效应可能会产生环境驱动的平均效果，对银河系红色巨型分支的尖端的光度。吞噬棕色矮人将产生更加戏剧性的效果。最后，我们探讨了如何通过高分辨率光谱法推断出低金属性RGB恒星中系外行星的席位，以及如何从水平分支的形态中量化质量损失率分布。
During the red giant phase, stars loose mass at the highest rate since birth. The mass-loss rate is not fixed, but varies from star-to-star by up to 5\%, resulting in variations of the star's luminosity at the tip of the red giant branch (TRGB). Also, most stars, during this phase, engulf part of their planetary system, including their gas giant planets and possibly brown dwarfs. Gas giant planet masses range between 0.1 to 2\% of the host star mass. The engulfing of their gas giants planets can modify their luminosity at the TRGB, i.e. the point at which the He-core degeneracy is removed. We show that the increase in mass of the star by the engulfing of the gas giant planets only modifies the luminosity of a star at the TRGB by less than 0.1\%, while metallicity can modify the luminosity of a star at the TRGB by up to 0.5\%. However, the increase in turbulence of the convective envelope of the star, has a more dramatic effect, on the star's luminosity, which we estimate could be as large as 5\%. The effect is always in the direction to increase the turbulence and thus the mixing length which turns into a systematic decrease of the luminosity of the star at the TRGB. We find that the star-to-star variation of the mass-loss rate will dominate the variations in the luminosity of the TRGB with a contribution at the 5\% level. If the star-to-star variation is driven by environmental effects, the same effects can potentially create an environmentally-driven mean effect on the luminosity of the tip of the red giant branch of a galaxy. Engulfment of a brown dwarf will have a more dramatic effect. Finally, we touch upon how to infer the frequency, and identify the engulfment, of exoplanets in low-metallicity RGB stars through high resolution spectroscopy as well as how to quantify mass loss rate distributions from the morphology of the horizontal branch.
