论文标题
大气中的二分法
The dichotomy of atmospheric escape in AU Mic b
论文作者
论文摘要
在这里，我们研究了新发现的近距离球星au mic b。一方面，高EUV恒星通量有望在Au Mic b中引起强大的大气逃逸。另一方面，这位年轻恒星的风被认为非常强大，这可能会减少甚至抑制地球的大气逃生。据认为，AU MIC的风质量减少率高达$ 1000 $ $ 1000 $倍的倍（$ \ dot {m} _ \ odot $）。为了研究这种二分法，我们对AU MIC系统中的恒星风 - 星际大气相互作用进行了3D流体动力学模拟，并预测了Au Mic b的合成ly- $α$ transits。我们从系统地改变了恒星风质量的速率，从“无风”场景到最大的巨大风，其质量减少率为$ 1000〜 \ dot {m} _ \ odot $。我们发现，随着恒星风变得更强烈，行星蒸发率从$ 6.5 \ times 10^{10} $ g/s降至该值的一半。在恒星风中，大气被迫占据较小的体积，影响过境特征。我们预测的LY-$α$吸收从$ \ sim 20 \％$下降，在“无风”的情况下，在极端恒星风的情况下几乎没有任何LY-$α$吸收。因此，未来的ly- $α$过境不仅可以限制在AU MIC B的蒸发率上，还可以限制其宿主星的质量损失率。
Here, we study the dichotomy of the escaping atmosphere of the newly discovered close-in exoplanet AU Mic b. On one hand, the high EUV stellar flux is expected to cause a strong atmospheric escape in AU Mic b. On the other hand, the wind of this young star is believed to be very strong, which could reduce or even inhibit the planet's atmospheric escape. AU Mic is thought to have a wind mass-loss rate that is up to $1000$ times larger than the solar wind mass-loss rate ($\dot{M}_\odot$). To investigate this dichotomy, we perform 3D hydrodynamics simulations of the stellar wind--planetary atmosphere interactions in the AU Mic system and predict the synthetic Ly-$α$ transits of AU Mic b. We systematically vary the stellar wind mass-loss rate from a `no wind' scenario to up to a stellar wind with a mass-loss rate of $1000~\dot{M}_\odot$. We find that, as the stellar wind becomes stronger, the planetary evaporation rate decreases from $6.5\times 10^{10}$ g/s to half this value. With a stronger stellar wind, the atmosphere is forced to occupy a smaller volume, affecting transit signatures. Our predicted Ly-$α$ absorption drops from $\sim 20\%$, in the case of `no wind' to barely any Ly-$α$ absorption in the extreme stellar wind scenario. Future Ly-$α$ transits could therefore place constraints not only on the evaporation rate of AU Mic b, but also on the mass-loss rate of its host star.
