AI 中文总结
研究热木星中三维效应如何影响氦传输特征，更新三维大气蒸发模型自洽求解流体动力学方程及氢和氦原子数，生成合成氦传输，分析不同恒星风强度和XUV通量下的模型结果，揭示了氦传输特征变化及原因。
AI 中文摘要
氦I三重线（1083纳米）与流体动力学模型可用于表征系外行星的大气逃逸。但多数现有模型无法捕捉逃逸大气的三维物理过程，如潮汐力和与恒星风的相互作用。为研究三维效应如何影响氦传输特征，更新三维大气蒸发模型以自洽求解流体动力学方程及氢和氦原子数。还生成了合成氦传输。大气逃逸模型假设热木星与不同质量损失率和两种XUV通量的恒星风相互作用。考虑老年恒星的模型显示，随着恒星风强度增加，氦三重线密度降低，原因一是更强风减少逃逸大气体积，降低大气凌星遮挡；二是大气伸展性降低使光学深度减小，影响光电离和加热，进而影响行星物质气体温度，降低氦三重线密度。假设年轻恒星的模型显示出扩展外流，逃逸率高25倍。相同恒星风强度下，氦传输比假设老年恒星的XUV时深3.3倍。较弱恒星风和/或强XUV通量会导致凌星前氦吸收，所有情况都显示出（不同程度的）凌星后吸收，表现为彗星状尾巴。
英文摘要
The HeI triplet line (1083 nm), together with hydrodynamic models, can be used to characterize atmospheric escape of exoplanets. However, most of the available models cannot capture the three dimensional (3D) physics of escaping atmospheres, such as tidal forces and the interaction with stellar winds. To investigate how 3D effects affect the helium transit signature, we update our 3D atmospheric evaporation model to self-consistently solve the hydrodynamic equations together with the atomic hydrogen and helium populations. We also produce synthetic helium transits. Our atmospheric escape models assume a Hot Jupiter interacting with stellar wind of ranging mass-loss rates and two XUV fluxes, representative of an old and a young star. Models considering an old star show a decrease of helium triplet density with increasing stellar wind strength, which occurs for two reasons. First, stronger winds reduce the volume of the escaping atmosphere, which decreases obscuration of atmospheric transits. Secondly, as a consequence of a less extended atmosphere, optical depth is reduced, impacting both photoionization and heating, which in turn affect the gas temperature of planetary material, reducing the density of helium triplet. The model assuming a younger star shows an extended outflow, with escape rates 25 times higher. For the same stellar wind strength, the helium transit is 3.3 times deeper than when assuming the XUV of an older star. Weaker stellar winds and/or strong XUV flux allow for pre-transit helium absorption, while all scenarios show (different levels of) post-transit absorptions, described by the presence of a comet-like tail.
Comments25 pages, 16 figures, accepted for publication in MNRAS. Animations can be downloaded from this link: https://zenodo.org/records/21455405
