WINERED 探测到亚海王星 GJ 3090b 上的强烈大气外流
WINERED Detects a Strong Atmospheric Outflow on the Sub-Neptune GJ 3090b
- Carnegie Science Observatories（卡内基科学观测站）
- Massachusetts Institute of Technology（麻省理工学院）
- Washington University, St. Louis（圣路易斯华盛顿大学）
- Space Telescope Science Institute（太空望远镜科学研究所）
- University of Chicago（芝加哥大学）
- Arizona State University（亚利桑那州立大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究利用 WINERED 高分辨率光谱在亚海王星 GJ 3090b 上探测到强烈的氦吸收，表明其正经历快速光致蒸发，大气寿命仅约 3 亿年。
AI中文摘要：
亚海王星是已知的最常见的短周期（P<100天）行星。该领域的一个主要目标是全面了解它们的成分和演化历史，而实现这一目标的重要工具是亚稳态氦（He*）透射光谱，它追踪大气逃逸。在本文中，我们报告了在高光谱分辨率下在亚海王星 GJ 3090b 的大气中探测到 He*。我们用麦哲伦二号/WINERED 观测了该行星的两次连续凌星，在凌星期间分别探测到峰值 He* 吸收为 2.033±0.086%（23.6σ）和 1.619±0.122%（13.3σ）。第一次凌星在出凌附近受到恒星耀斑的影响，而第二次凌星未受影响。信号振幅可变，且比 Ahrer 等人（2025）的 JWST/NIRISS 观测所预期的更深。我们未观测到显著的多普勒位移，信号的半高全宽为 25 km/s，表明存在光致蒸发。我们的外流模型表明 Z_atm≲100倍太阳丰度，因为观测到的 He* 振幅在富金属大气中难以实现。为了匹配 JWST 和 VLT/CRIRES+ 的减弱透射光谱，GJ 3090b 的低层大气可能被气溶胶覆盖。最后，我们发现 GJ 3090b 的大气寿命约为 300 Myr，远短于先前报道的值。这颗青春期（约 1 Gyr）亚海王星目前正处于光致蒸发演化的变革阶段。
英文摘要：
Sub-Neptunes are the most common short-period ($P<100$ d) planets known. A major goal for the field is to build a comprehensive understanding of their compositions and evolutionary histories, and an important tool for achieving this goal is metastable helium (He$^*$) transmission spectroscopy, which traces atmospheric escape. In this paper, we report the detection of He$^*$ in the atmosphere of the sub-Neptune GJ 3090b at high spectral resolution. We observed two consecutive transits of this planet with Magellan II/WINERED, and detected peak He$^*$ absorptions during transit of $2.033\pm0.086\%$ (23.6$σ$) and $1.619\pm0.122\%$ (13.3$σ$), respectively. The first transit was affected by a stellar flare near egress while the second transit was unaffected. The signal is variable in amplitude and deeper than anticipated by the JWST/NIRISS observations of Ahrer et al. (2025). We do not observe a significant Doppler shift, and the signal has a FWHM of $25$ km s$^{-1}$, implicating photoevaporation. Our outflow modeling suggests that $Z_\mathrm{atm}\lesssim100\times$ solar, as the observed He$^*$ amplitudes are challenging to achieve in a metal-rich atmosphere. To match the muted transmission spectra from JWST and VLT/CRIRES+, GJ 3090b's lower atmosphere is likely covered by aerosols. Finally, we found that GJ 3090b has an atmospheric lifetime of $\sim300$ Myr, much shorter than previously reported. This adolescent ($\sim1$ Gyr) sub-Neptune is currently in a transformative phase of photoevaporative evolution.
