arXiv 2203.014632022-03-03astro-ph.EP

用HST/WFC3确认热木星WASP-77 Ab热发射光谱中的水吸收

Confirmation of Water Absorption in the Thermal Emission Spectrum of the Hot Jupiter WASP-77Ab with HST/WFC3

Megan Mansfield, Lindsey Wiser, Kevin B. Stevenson, Peter Smith, Michael R. Line, Jacob L. Bean, Jonathan J. Fortney, Vivien Parmentier, Eliza M. -R. Kempton, J… 展开作者

Megan Mansfield, Lindsey Wiser, Kevin B. Stevenson, Peter Smith, Michael R. Line, Jacob L. Bean, Jonathan J. Fortney, Vivien Parmentier, Eliza M. -R. Kempton, Jacob Arcangeli, Jean-Michel Désert, Brian Kilpatrick, Laura Kreidberg, Matej Malik

备注：: 12 pages, 7 figures, submitted to The Astronomical Journal
DOI：: 10.3847/1538-3881/ac658f

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摘要：

热彗星的二次日食观测可以揭示它们的成分和热结构。先前的观测已经显示了热木星日食光谱的多样性，包括吸收特征，发射特征和无特征的黑体光谱。本文给出了用哈勃太空望远镜（HST）和斯皮策太空望远镜在$1-5$ $μ$ m之间观测到的热木星WASP-77 Ab的二次食谱。HST观测显示出吸水迹象，表明非倒置热结构。我们适合的数据与一维自由检索和网格的一维自洽的前向模型，以确认这种非倒置的结构。自由反演对$\log(n_\mathrm{H_2O})>-4.78$的大气水丰度设置了$3σ$下限，不能约束CO丰度。网格拟合产生了轻微的超恒星金属丰度，并将碳氧比限制在小于或等于太阳值。我们还将我们的数据与Gemini-South/IGRINS光谱仪最近对WASP-77 Ab的高分辨率观测进行了比较，发现我们的观测结果与高分辨率数据的最佳拟合模型一致。然而，来自IGRINS数据的金属丰度显着低于来自我们的自洽模型拟合。我们发现，这种差异可能是由于不平衡的化学，和不同的结果之间的模型在这里应用表明，仅用低分辨率，低波长覆盖数据约束不平衡化学的困难。未来结合IGRINS，HST和JWST的观测工作将改善我们对WASP-77 Ab大气成分的估计。

英文摘要：

Secondary eclipse observations of hot Jupiters can reveal both their compositions and thermal structures. Previous observations have shown a diversity of hot Jupiter eclipse spectra, including absorption features, emission features, and featureless blackbody-like spectra. We present a secondary eclipse spectrum of the hot Jupiter WASP-77Ab observed between $1-5$ $μ$m with the Hubble Space Telescope (HST) and the Spitzer Space Telescope. The HST observations show signs of water absorption indicative of a non-inverted thermal structure. We fit the data with both a one-dimensional free retrieval and a grid of one-dimensional self-consistent forward models to confirm this non-inverted structure. The free retrieval places a $3σ$ lower limit on the atmospheric water abundance of $\log(n_\mathrm{H_2O})>-4.78$ and can not constrain the CO abundance. The grid fit produces a slightly super-stellar metallicity and constrains the carbon-to-oxygen ratio to less than or equal to the solar value. We also compare our data to recent high-resolution observations of WASP-77Ab taken with the Gemini-South/IGRINS spectrograph and find that our observations are consistent with the best-fit model to the high-resolution data. However, the metallicity derived from the IGRINS data is significantly lower than that derived from our self-consistent model fit. We find that this difference may be due to disequilibrium chemistry, and the varying results between the models applied here demonstrate the difficulty of constraining disequilibrium chemistry with low-resolution, low wavelength coverage data alone. Future work to combine observations from IGRINS, HST, and JWST will improve our estimate of the atmospheric composition of WASP-77Ab.

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