论文标题
太阳状磁性周期对超球星大气逃生的影响
Influence of the Sun-like magnetic cycle on exoplanetary atmospheric escape
论文作者
论文摘要
恒星高能辐射（X射线和极端紫外线，XUV）驱动大气中的近距离球星逃逸。鉴于恒星照射取决于恒星磁性并且恒星具有磁性周期，我们研究了循环如何影响超球星大气逃生的演变。首先，我们考虑一个假设的HD209458B状的行星，绕太阳为此，我们在HD209458B的一维水动力逃逸模型中实施了在一个半太阳能周期上可用的太阳XUV辐射。我们发现大气逃生率显示了循环变化（从7.6到18.5 $ \ times $ 10 $^{10} $ g s $^{ - 1} $），几乎与事件恒星辐射成正比。为了将其与观测值进行比较，我们在两条氢管中计算光谱传播。我们发现$α$ Transits中的不可检测的循环变化。鉴于H $α$线的温度敏感性，其当量宽度在整个周期中的幅度为1.9 mA变化，可以在HD209458B等系外行星中检测到。我们证明XUV通量在太阳周期内与磁通量成正比。其次，我们将此关系应用于HD189733的XUV通量的循环演化，使用近十年来Zeeman多普勒成像的恒星的可用磁通量观测值。然后，使用XUV通量来模拟HD189733B中的逃生，该逃逸率从2.8到6.5 $ \ times $ 10 $^{10} $ g s $^s $^{ - 1} $不等。像HD209458B情况下一样，这引入了LY $α$和H $α$ transits的变化，H $α$变化的可能性更高。最后，我们表明，强烈的恒星耀斑将显着增强$α$和H $α$ transit深度。
Stellar high-energy radiation (X-ray and extreme ultraviolet, XUV) drives atmospheric escape in close-in exoplanets. Given that stellar irradiation depends on the stellar magnetism and that stars have magnetic cycles, we investigate how cycles affect the evolution of exoplanetary atmospheric escape. Firstly, we consider a hypothetical HD209458b-like planet orbiting the Sun. For that, we implement the observed solar XUV radiation available over one and a half solar cycles in a 1D hydrodynamic escape model of HD209458b. We find that atmospheric escape rates show a cyclic variation (from 7.6 to 18.5 $\times$ 10$^{10}$ g s$^{-1}$), almost proportional to the incident stellar radiation. To compare this with observations, we compute spectroscopic transits in two hydrogen lines. We find non-detectable cyclic variations in Ly$α$ transits. Given the temperature sensitiveness of the H$α$ line, its equivalent width has an amplitude of 1.9 mA variation over the cycle, which could be detectable in exoplanets such as HD209458b. We demonstrate that the XUV flux is linearly proportional to the magnetic flux during the solar cycle. Secondly, we apply this relation to derive the cyclic evolution of the XUV flux of HD189733 using the available magnetic flux observations of the star from Zeeman Doppler Imaging over nearly a decade. The XUV fluxes are then used to model escape in HD189733b, which shows escape rate varying from 2.8 to 6.5 $\times$ 10$^{10}$ g s$^{-1}$. Like in the HD209458b case, this introduces variations in Ly$α$ and H$α$ transits, with H$α$ variations more likely to be observable. Finally, we show that a strong stellar flare would enhance significantly Ly$α$ and H$α$ transit depths.
