詹姆斯·韦布空间望远镜近红外光谱仪（JWST/NIRSpec）相位曲线揭示熔岩行星TOI-561b存在高反射大气
A Highly Reflective Atmosphere on the Lava World TOI-561b Revealed by JWST/NIRSpec Phase Curve
- Université de Montréal（蒙特利尔大学）
- University of Waterloo（滑铁卢大学）
- University of Oxford（牛津大学）
- Carnegie Institution for Science（卡内基科学机构）
机构由 AI 辅助整理，请以论文原文为准。
中文总结 AI 辅助
本研究通过JWST/NIRSpec相位曲线观测，证实超短周期岩质行星TOI-561b存在高反射大气，其反照率可由昼侧近晨昏线处形成的硅酸盐云解释。
中文摘要 AI 辅助
超短周期（USP）岩质行星因受主星强烈辐射，预计会失去大量气态包层，因此近期发现TOI-561b周围存在大气的结果尤为令人惊讶。该发现基于行星的整体密度和昼侧发射光谱，而全轨道相位曲线观测为约束行星大气的存在及特性提供了更全面的方法。本文利用JWST/NIRSpec多轨道光谱相位曲线测绘TOI-561b的3-5μm发射，明确考虑了非食基线的曲率和可能的热点偏移。通过简单的能量平衡论证并与环流模型对比，发现相位曲线观测结果最适合用高邦德反照率和适度的全球热传递来解释。我们的37小时连续观测提供了长基线，可同时对恒星 granulation（ granulation 译为“米粒组织”）、行星相位曲线和昼侧发射进行建模，有效分离这些信号，得到的昼侧发射光谱对恒星变异性更具鲁棒性，且与仅基于食的拟合结果一致。利用环流模型输出，我们约束了云的可能形成位置并测试了候选成分，发现二氧化硅（SiO₂）和硅酸镁（MgSiO₃）等硅酸盐云可在昼侧近晨昏线处形成，并能解释观测到的反照率。我们的发现证实TOI-561b似乎拥有全球反射大气，这表明其内部与挥发性物质存在交换以维持该大气。
英文摘要
Ultra-short period (USP) rocky planets are expected to be depleted of any substantial gaseous envelope due to the intense irradiation they receive from their host star, making the recent detection of an atmosphere around TOI-561~b particularly surprising. That finding was based on the planet's bulk density and dayside emission spectrum, but full-orbit phase curve observations offer a more comprehensive way to constrain the presence and characteristics of a planet's atmosphere. In this paper, we map TOI-561~b's 3-5~$μ$m emission using JWST/NIRSpec multi-orbit spectroscopic phase curves, explicitly accounting for the curvature of the out-of-eclipse baseline and possible hotspot offsets. From a simple energy balance argument as well as comparing to general circulation models, we find the phase curve observations are best explained with high Bond albedo and moderate global heat transfer. Our 37-hour continuous observation provides a long baseline that allows us to model stellar granulation, the planetary phase curve, and dayside emission simultaneously, effectively disentangling these signals and yielding a dayside emission spectrum that is more robust against stellar variability and consistent with previous eclipse-only fits. Using general circulation model outputs, we constrain where clouds can plausibly form and test candidate compositions, finding that silicate clouds, such as SiO$_2$ and MgSiO$_3$, can form on the dayside near the terminator and explain the observed albedo. Our findings confirm that TOI-561~b appears to have a global reflective atmosphere, suggesting exchange of volatiles with the interior to maintain it.
