发表机构
University of Bern; ETH Zurich; Space Telescope Science Institute; University of Southampton; University of Oxford; Macquarie University（伯尔尼大学; 苏黎世联邦理工学院; 太空望远镜科学研究所; 南安普顿大学; 牛津大学; 麦考瑞大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过 JWST 观测发现岩石行星 GJ 357 b 的昼侧亮温异常高，超出无大气参考温度，排除多种大气模型，可能源于表面发射率或局部热区，需后续光谱验证。
AI 中文摘要
作为 JWST 热岩石巡天的一部分，我们分析了 GJ 357 b 的 JWST/MIRI F1500W 二次掩星观测，GJ 357 b 是一颗围绕附近 M 矮星运行的岩石系外行星。我们还对 GJ 357 系统进行了新的全球分析，结合 TESS 测光、JWST/NIRSpec 凌星观测、MIRI 二次掩星、径向速度和 Gaia 视差测量，以获得一套自洽的恒星和行星参数。我们测得掩星深度为 $200.5 \pm 12.7\\,\mathrm{ppm}$，对应 $15\\,\mu\mathrm{m}$ 处的昼侧亮温 $T_{\mathrm{b},15\\,\mu\mathrm{m}}=923^{+39}_{-38}\\,\mathrm{K}$。推断的亮温显著超过零邦德反照率、无再分布、盘积分热辐射昼侧参考温度 $686 \pm 14\\,\mathrm{K}$。实测掩星深度与所测试的零反照率、灰色无大气表面模型相差 $5.2\sigma$，并且也与本文考虑的高平均分子量大气模型不一致，包括纯 CO$_2$、纯 H$_2$O 以及含 100 ppm CO$_2$ 的 N$_2$。MIRI/F1500W 波段过量发射的可能解释包括波长相关的表面发射率、局部热区，或所测试模型中未包含的大气温度结构和不透明度来源。后续中红外掩星光谱观测将约束昼侧发射光谱的形状，并有助于检验所提出的表面和大气解释。
英文摘要
As part of the JWST Hot Rocks Survey, we analyzed a JWST/MIRI F1500W secondary-eclipse observation of GJ 357 b, a rocky exoplanet orbiting a nearby M dwarf. We also performed a new global analysis of the GJ 357 system, combining TESS photometry, a JWST/NIRSpec transit observation, the MIRI secondary eclipse, radial velocities, and Gaia parallax measurements to obtain a self-consistent set of stellar and planetary parameters. We measure an occultation depth of $200.5 \pm 12.7,\mathrm{ppm}$, corresponding to a dayside brightness temperature at $15,μ\mathrm{m}$ of $T_{\mathrm{b},15,μ\mathrm{m}}=923^{+39}_{-38},\mathrm{K}$. The inferred brightness temperature substantially exceeds the zero-Bond-albedo, no-redistribution, disk-integrated bolometric dayside reference temperature of $686 \pm 14,\mathrm{K}$. The measured eclipse depth differs from the tested zero-albedo, grey airless-surface model by $5.2σ$ and is also inconsistent with the high-mean-molecular-weight atmospheric models considered here, including pure CO$_2$, pure H$_2$O, and N$_2$ with 100 ppm CO$_2$. Possible explanations for the excess emission in the MIRI/F1500W band include wavelength-dependent surface emissivity, localized hot regions, or atmospheric temperature structures and opacity sources not included in the tested models. Follow-up mid-infrared eclipse spectroscopy would constrain the shape of the dayside emission spectrum and help test the proposed surface and atmospheric explanations.
Comments19 pages, 15 figures. To be submitted to Astronomy & Astrophysics
