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arXiv 1503.06505astro-ph.EP
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海王星甲烷D/H比率的大气模拟-初步结果

Atmospheric Modelling for Neptune's Methane D/H Ratio - Preliminary Results

Daniel V. Cotton, Lucyna L. Kedziora-Chudczer, Kimberly Bott, Jeremy Bailey

摘要:

太阳系天体的氘氢比(D/H比)是揭示其形成历史的重要线索。本文将海王星大气模型与双子座近红外光谱仪(GNIRS)高光谱分辨率观测数据进行拟合,确定了甲烷在红外H波段($\sim$ 1.6 μm)吸收的D/H比。该模型是使用我们的辐射转移软件VSTAR(Versatile Software for the Transfer of Atmospheric Radiation)和大气拟合软件ATMOF(Atmospheric Fitting)导出的。这项工作所使用的甲烷线清单是在过去几年中才得到的,因此可以对以前的估计进行改进。我们确定了行星盘上的一个明亮区域,并发现它对应于一个光学厚的低云。我们初步确定CH $_{\rm 3}$ D/CH $_{\rm 4}$为3.0 $\times10^{-4}$,这与Irwin等人(2014)最近使用相同模型参数和线列表但不同观测数据确定的3.0 $^{+1.0}_{-0.9}\sim\times10^{-4}$一致。这支持了海王星的原太阳冰D/H比远小于彗星的证据,并表明海王星在其目前的轨道内形成。

英文摘要:

The ratio of deuterium to hydrogen (D/H ratio) of Solar System bodies is an important clue to their formation histories. Here we fit a Neptunian atmospheric model to Gemini Near Infrared Spectrograph (GNIRS) high spectral resolution observations and determine the D/H ratio in methane absorption in the infrared H-band ($\sim$ 1.6 μm). The model was derived using our radiative transfer software VSTAR (Versatile Software for the Transfer of Atmospheric Radiation) and atmospheric fitting software ATMOF (ATMOspheric Fitting). The methane line list used for this work has only become available in the last few years, enabling a refinement of earlier estimates. We identify a bright region on the planetary disc and find it to correspond to an optically thick lower cloud. Our preliminary determination of CH$_{\rm 3}$D/CH$_{\rm 4}$ is 3.0$\times10^{-4}$, which is in line with the recent determination of Irwin et al. (2014) of 3.0$^{+1.0}_{-0.9}\sim\times10^{-4}$, made using the same model parameters and line list but different observational data. This supports evidence that the proto-solar ice D/H ratio of Neptune is much less than that of the comets, and suggests Neptune formed inside its present orbit.

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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