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arXiv 1002.2434astro-ph.EP
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热木星XO-1b终端区大气的透射光谱探测

Probing the terminator region atmosphere of the Hot-Jupiter XO-1b with transmission spectroscopy

G. Tinetti, P. Deroo, M. R. Swain, C. A. Griffith, G. Vasisht, L. R. Brown, C. Burke, P. McCullough

摘要:

我们在这里报告了热木星XO-1b的第一个红外光谱。这些观测是在XO-1系统的一次日食期间用哈勃太空望远镜上的NICMOS仪器获得的。在1.2和1.8微米之间的近光子噪声限制光谱学使我们能够以良好的精度确定这个热木星的行星大气的主要成分。这是第三个在近红外光谱数据中可以获得的热木星大气层。光谱显示存在水蒸气(H2O)、甲烷(CH 4)和二氧化碳(CO 2),并暗示可能存在一氧化碳(CO)。我们表明,公布的IRAC二次过境发射光度数据是兼容的大气成分在终止器确定的NICMOS光谱,与一系列可能的混合比和热配置文件;需要额外的发射光谱数据,以减少可能的解决方案的简并性。最后,我们注意到XO-1b和HD 209458 b的1.2-1.8微米透射光谱之间的相似性,这表明这两个系统除了具有相似的恒星/轨道和行星参数外,还可能具有相似的系外行星大气成分。

英文摘要:

We report here the first infrared spectrum of the hot-Jupiter XO-1b. The observations were obtained with NICMOS instrument onboard the Hubble Space Telescope during a primary eclipse of the XO-1 system. Near photon-noise-limited spectroscopy between 1.2 and 1.8 micron allows us to determine the main composition of this hot-Jupiter's planetary atmosphere with good precision. This is the third hot-Jupiter's atmosphere for which spectroscopic data are available in the near IR. The spectrum shows the presence of water vapor (H2O), methane (CH4) and carbon dioxide (CO2), and suggests the possible presence of carbon monoxide (CO). We show that the published IRAC secondary transit emission photometric data are compatible with the atmospheric composition at the terminator determined from the NICMOS spectrum, with a range of possible mixing-ratios and thermal profiles; additional emission spectroscopy data are needed to reduce the degeneracy of the possible solutions. Finally, we note the similarity between the 1.2-1.8 micron transmission spectra of XO-1b and HD 209458b, suggesting that in addition to having similar stellar/orbital and planetary parameters the two systems may also have a similar exoplanetary atmospheric composition.

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