arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2006.09394astro-ph.EP
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反演HR 8799 e大气中的散射云和不平衡化学

Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e

P. Mollière, T. Stolker, S. Lacour, G. P. P. L. Otten, J. Shangguan, B. Charnay, T. Molyarova, M. Nowak, Th. Henning, G. -D. Marleau, D. A. Semenov, E. van Dish… 展开作者

P. Mollière, T. Stolker, S. Lacour, G. P. P. L. Otten, J. Shangguan, B. Charnay, T. Molyarova, M. Nowak, Th. Henning, G. -D. Marleau, D. A. Semenov, E. van Dishoeck, F. Eisenhauer, P. Garcia, R. Garcia Lopez, J. H. Girard, A. Z. Greenbaum, S. Hinkley, P. Kervella, L. Kreidberg, A. -L. Maire, E. Nasedkin, L. Pueyo, I. A. G. Snellen, A. Vigan, J. Wang, P. T. de Zeeuw, A. Zurlo

摘要:

云在系外行星大气中无处不在,对它们光谱的模型解释提出了挑战。复杂的云模型对于生成大量的光谱来说在数值上代价太高,而更有效的模型可能过于简化。我们的目标是约束直接成像的行星HR 8799 e的大气特性与免费检索方法。我们使用我们的辐射转移代码petitRADTRANS来生成光谱,并将其耦合到PyMultiNest工具。我们增加了多重散射的效果,这对处理云很重要。两个云模型参数化进行了测试:第一个采用了冷凝物的混合和沉淀,第二个简单的参数化的功能形式的不透明度。在模拟检索中,使用不适当的云模型可能会导致大气比输入的更等温和更少多云。应用我们的框架对HR 8799 e进行GPI,SPHERE和重力观测,我们发现了一个由不平衡化学控制的多云大气,证实了以前的分析。我们取回那个${\rm C/O}=0.60_{-0.08}^{+0.07}$。其他模型还没有为这颗行星提供一个很好的约束C/O值。两种云模式反演的C/O值是一致的,但导致不同的大气结构:多云,或更等温和少多云。用自洽的Exo-REM模型拟合观察结果导致可比较的结果,同时不限制C/O。利用最灵敏仪器的数据,可以对直接成像的行星进行检索分析。HR 8799 e的推断C/O比与云模型无关,因此似乎是一个稳健的模型。这个C/O值与恒星一致,这可能表明HR 8799 e形成于CO $_2$或CO冰线之外。由于它是系统最里面的行星,这个限制可能适用于所有HR 8799行星。

英文摘要:

Clouds are ubiquitous in exoplanet atmospheres and represent a challenge for the model interpretation of their spectra. Complex cloud models are too numerically costly for generating a large number of spectra, while more efficient models may be too strongly simplified. We aim to constrain the atmospheric properties of the directly imaged planet HR 8799e with a free retrieval approach. We use our radiative transfer code petitRADTRANS for generating spectra, which we couple to the PyMultiNest tool. We added the effect of multiple scattering which is important for treating clouds. Two cloud model parameterizations are tested: the first incorporates the mixing and settling of condensates, the second simply parameterizes the functional form of the opacity. In mock retrievals, using an inadequate cloud model may result in atmospheres that are more isothermal and less cloudy than the input. Applying our framework on observations of HR 8799e made with the GPI, SPHERE and GRAVITY, we find a cloudy atmosphere governed by disequilibrium chemistry, confirming previous analyses. We retrieve that ${\rm C/O}=0.60_{-0.08}^{+0.07}$. Other models have not yet produced a well constrained C/O value for this planet. The retrieved C/O values of both cloud models are consistent, while leading to different atmospheric structures: cloudy, or more isothermal and less cloudy. Fitting the observations with the self-consistent Exo-REM model leads to comparable results, while not constraining C/O. With data from the most sensitive instruments, retrieval analyses of directly imaged planets are possible. The inferred C/O ratio of HR 8799e is independent of the cloud model and thus appears to be a robust. This C/O is consistent with stellar, which could indicate that the HR 8799e formed outside the CO$_2$ or CO iceline. As it is the innermost planet of the system, this constraint could apply to all HR 8799 planets.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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