AI 中文总结
本研究针对超热木星 WASP-12b，通过 MMT/Hectochelle 观测发现其存在不遵循行星轨道运动的持续过量 Hα 吸收，结合 Athena++ 三维外流模型，证明强外流需三维模拟解释。
AI 中文摘要
高分辨率 Hα 和 He 10830 埃凌星光谱可系外行星的延展高层大气，通常会揭示行星静止系中发生的过量凌星吸收。然而，流体动力学模拟预测，如果气体快速逃离行星洛希瓣并被剪切成潮汐尾，吸收不会严格遵循行星的轨道运动。超热木星 WASP-12b 占据其洛希瓣的比例异常大（R_p/R_Roche = 0.55），本文提供了这颗独特行星上存在潮汐调制外流运动学的证据。我们使用 MMT/Hectochelle 观测了 WASP-12b 的一次凌星，发现凌星期间存在过量 Hα 吸收，其值为 3.29+0.35 -0.36%（9.3σ），且至少持续到凌星结束后 30 分钟。该信号不遵循行星的轨道运动，而是主要出现在恒星静止系中，与 HAT-P-32b 和 HAT-P-67b 的延展氦外流类似，且略有红移（+5.4+1.5 -1.7 km s^-1）。我们证明，一旦考虑到非典型信号运动学和基线自扣除，2012 年以来的高灵敏度观测中也出现了类似信号。最后，我们提出了 WASP-12b 外流大气的三维 Athena++ 模型，该模型同时呈现了观测到的延展形态和无行星对齐速度梯度的特征。本研究强调，对于解释强外流中形成的吸收线，三维模拟是必要的，其中气体可能不会简单遵循行星的多普勒特征。
英文摘要
High-resolution H$α$ and He 10830 Å transit spectroscopy can trace the extended upper atmospheres of exoplanets, typically revealing excess in-transit absorption that occurs in the planet's rest frame. However, hydrodynamical simulations predict that absorption should not strictly follow the planet's orbital motion if gas quickly escapes the planetary Roche lobe and shears into tidal tails. The ultra-hot Jupiter WASP-12b fills an exceptionally large fraction of its Roche lobe ($R_p/R_\mathrm{Roche} = 0.55$), and in this paper we present evidence for tidally-modulated outflow kinematics on this unique planet. We observed a transit of WASP-12b with MMT/Hectochelle and found an excess H$α$ absorption of $3.29^{+0.35}_{-0.36}\%$ (9.3$σ$) during the transit and extending at least 30~min post-egress. The signal does not follow the planet's orbital motion and instead appears largely in the stellar rest frame, similar to the extended helium outflows in HAT-P-32b and HAT-P-67b, and is slightly redshifted ($+5.4_{-1.7}^{+1.5}$ km s$^{-1}$). We demonstrate that a similar signal appears across previous high-sensitivity observations dating back to 2012 once the atypical signal kinematics and baseline self-subtraction are taken into account. Finally, we present a three-dimensional Athena++ model of WASP-12b's outflowing atmosphere that simultaneously exhibits the observed extended morphology and lack of planet-aligned velocity gradient. Our study highlights the necessity of three-dimensional simulations for interpreting absorption lines formed in strong outflows, where gas may not simply follow the planet's Doppler signature.
Comments12 pages, 5 figures, submitted to AJ
