论文标题
在超热木星黄蜂中检测氢Balmer线
Detection of the hydrogen Balmer lines in the ultra-hot Jupiter WASP-33b
论文作者
论文摘要
超热木星（UHJS）是高度辐照的巨型系外行星，日间温度极高，导致大多数分子物种的热解离。预计中性氢原子是超热木星上层大气中的主要物种之一。通过观察其Balmer系列的吸收，已经在几个UHJ中检测到中性氢。在这里，我们报告了使用carmenes和harps-north光谱仪进行的超热木星黄蜂的四个过境观察结果，以及在行星传输频谱中检测H $α$，H $β$和H $γ$线的检测。四个转运的组合H $α$传输谱的吸收深度为0.99 $ \ pm $ 0.05％，这对应于有效半径为1.31 $ \ pm $ 0.01 rp。强H $α$吸收表明该线探测高空热圈。假设大气是流体动力和LTE，我们进一步拟合了三个Balmer系列。我们检索了热层温度$ 12200^{+1300} _ { - 1000} $ k和质量损失率$ {\ rm \ dot {m}} = 10^{11.8^{+0.6} _ { - 0.6} _ { - 0.5}}} $ g/s。检索到的大质量损失率与“ Balmer驱动的”大气逃生方案兼容，在该方案中，近乎硫酸盐中的恒星Balmer Continua辐射基本上被行星热层的激发氢原子所吸收。
Ultra-hot Jupiters (UHJs) are highly irradiated giant exoplanets with extremely high day-side temperatures, which lead to thermal dissociation of most of the molecular species. It is expected that the neutral hydrogen atom is one of the main species in the upper atmospheres of ultra-hot Jupiters. Neutral hydrogen has been detected in several UHJs by observing its Balmer line absorption. Here, we report four transit observations of the ultra-hot Jupiter WASP-33b, performed with the CARMENES and HARPS-North spectrographs, and the detection of the H$α$, H$β$, and H$γ$ lines in the planetary transmission spectrum. The combined H$α$ transmission spectrum of the four transits has an absorption depth of 0.99$\pm$0.05 %, which corresponds to an effective radius of 1.31$\pm$0.01 Rp . The strong H$α$ absorption indicates that the line probes the high-altitude thermosphere. We further fitted the three Balmer lines using the PAWN model, assuming that the atmosphere is hydrodynamic and in LTE. We retrieved a thermosphere temperature $12200^{+1300}_{-1000}$ K and a mass-loss rate ${\rm \dot{M}}=10^{11.8^{+0.6}_{-0.5}}$ g/s. The retrieved large mass-loss rate is compatible with the "Balmer-driven" atmospheric escape scenario, in which the stellar Balmer continua radiation in the near-ultraviolet is substantially absorbed by the excited hydrogen atoms in the planetary thermosphere.
