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arXiv 0909.2510astro-ph.EPastro-ph.SR
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对HD 189733 b大气中分子的搜寻

A Search for molecules in the atmosphere of HD 189733b

J. R. Barnes, Travis S. Barman, H. R. A. Jones, R. J. Barber, Brad M. S. Hansen, L. Prato, E. L. Rice, C. J. Leigh, A. Collier Cameron, D. J. Pinfield

摘要:

我们使用信号增强技术和匹配滤波器分析,以寻找K波段光谱吸收签名的近轨道太阳系外巨行星,HD 189733 b。利用NIRSPEC在凯克II望远镜上进行的时间序列观测,我们研究了H2O和含碳分子的相对丰度,这些分子现在已经在HD 189733 b的昼侧光谱中被确定。我们发现了一个低水平的候选行星特征,接近HD 189733 b的~153 km/s速度幅度。然而,一些系统的变化,主要是由于不完善的大地线去除,仍然在剩余的光谱时间序列中,我们搜索的行星信号。我们的候选人签名的鲁棒性进行了评估,使我们能够得出结论,这是不可能确认的任何行星信号出现在Fp/F* 对比深于95.4%的置信水平的存在。我们的搜索并不能使我们在99.9%的置信度下以Fp/F* = 1/1920的对比度探测到这颗行星。我们还研究了模型的不确定性对我们可靠地恢复行星信号的能力的影响。使用不正确的温度,模型不透明度波长和模型的温度-压力分布的最小二乘反卷积程序,我们用来提高我们的光谱时间序列观测的S/N比有重要的后果。我们发现,经验和模型行星光谱之间的不匹配可能会削弱探测的重要性约30- 60%,从而可能会削弱我们以高置信度恢复行星信号的能力。

英文摘要:

We use signal enhancement techniques and a matched filter analysis to search for the K band spectroscopic absorption signature of the close orbiting extrasolar giant planet, HD 189733b. With timeseries observations taken with NIRSPEC at the Keck II telescope, we investigate the relative abundances of H2O and carbon bearing molecules, which have now been identified in the dayside spectrum of HD 189733b. We detect a candidate planet signature with a low level of significance, close to the ~153 km/s velocity amplitude of HD 189733b. However, some systematic variations, mainly due to imperfect telluric line removal, remain in the residual spectral timeseries in which we search for the planetary signal. The robustness of our candidate signature is assessed, enabling us to conclude that it is not possible to confirm the presence of any planetary signal which appears at Fp/F* contrasts deeper than the 95.4 per cent confidence level. Our search does not enable us to detect the planet at a contrast ratio of Fp/F* = 1/1920 with 99.9 per cent confidence. We also investigate the effect of model uncertainties on our ability to reliably recover a planetary signal. The use of incorrect temperature, model opacity wavelengths and model temperature-pressure profiles have important consequences for the least squares deconvolution procedure that we use to boost the S/N ratio in our spectral timeseries observations. We find that mismatches between the empirical and model planetary spectrum may weaken the significance of a detection by ~30-60 per cent, thereby potentially impairing our ability to recover a planetary signal with high confidence.

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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