Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e
Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e
复制标题
检索 HR 8799e 大气中的散射云和不平衡化学
DOI：
10.1051/0004-6361/202038325
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发表时间：
2020
影响因子：
6.5
通讯作者：
A. Zurlo
中科院分区：
文献类型：
--
作者：
P. Mollière;T. Stolker;S. Lacour;G. Otten;J. Shangguan;B. Charnay;T. Molyarova;M. Nowak;T. Henning;G. Marleau;D. Semenov;E. V. Dishoeck;F. Eisenhauer;P. Garcia;R. G. Lopez;Julien H. Girard;A. Greenbaum;S. Hinkley;P. Kervella;L. Kreidberg;A. Maire;E. Nasedkin;L. Pueyo;I. Snellen;A. Vigan;J. Wang;P. D. Zeeuw;A. Zurlo
上下文云在系外行星大气中无处不在，它们代表了对其光谱的模型解释的挑战。当生成大量的模型谱时，复杂的云模型通常证明在数值上太昂贵，而更有效的模型可能被过度简化。
目标。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。
方法.我们使用辐射转移代码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。
结果在模拟检索中，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。将我们的框架应用于使用GPI，SPHERE和GRAVITY对HR 8799 e的观测，我们发现了由不平衡化学控制的多云大气，证实了以前的分析。我们得到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，少云。用自洽的Exo-REM模型拟合观测结果导致可比的结果，而不约束C/O。
结论.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。这一C/O值与恒星一致，表明HR 8799 e可能形成于CO2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。
Context. Clouds are ubiquitous in exoplanet atmospheres and they represent a challenge for the model interpretation of their spectra. When generating a large number of model spectra, complex cloud models often prove too costly numerically, whereas more efficient models may be overly simplified.
Aims. We aim to constrain the atmospheric properties of the directly imaged planet HR 8799e with a free retrieval approach.
Methods. We used our radiative transfer code petitRADTRANS for generating the spectra, which we coupled 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.
Results. 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 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: either cloudy or more isothermal and less cloudy. Fitting the observations with the self-consistent Exo-REM model leads to comparable results, without constraining C/O.
Conclusions. 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 CO2 or CO iceline. As it is the innermost planet of the system, this constraint could apply to all HR 8799 planets.
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影响因子：
6.5
作者：
G. C. R. Abuter;M. Accardo;A. Amorim;N. Anugu;G. Ávila;N. Azouaoui;M. Benisty;J. Berger;N. Bl
通讯作者：
G. C. R. Abuter;M. Accardo;A. Amorim;N. Anugu;G. Ávila;N. Azouaoui;M. Benisty;J. Berger;N. Bl
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作者：
Arazi Pinhas;N. Madhusudhan;S. Gandhi;R. MacDonald
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DOI：
10.1016/j.jqsrt.2013.07.002
发表时间：
2013-11-01
影响因子：
2.3
作者：
Rothman, L. S.;Gordon, I. E.;Wagner, G.
通讯作者：
Wagner, G.
影响因子：
4.8
作者：
R. MacDonald;N. Madhusudhan
通讯作者：
R. MacDonald;N. Madhusudhan
影响因子：
6.5
作者：
Allard N
通讯作者：
Allard N