Transit spectrophotometry of the exoplanet HD 189733b - II. New Spitzer observations at 3.6 μm
Transit spectrophotometry of the exoplanet HD 189733b - II. New Spitzer observations at 3.6 μm
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系外行星 HD 189733b - II 的凌日分光光度测量 3.6 μm 处的新斯皮策观测结果
DOI：
10.1051/0004-6361/200913093
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发表时间：
2010
影响因子：
6.5
通讯作者：
Gregory W. Henry
中科院分区：
文献类型：
--
作者：
J. Désert;J. Désert;D. Sing;D. Sing;A. Vidal;G. Hébrard;D. Ehrenreich;A. D. Étangs;V. Parmentier;R. Ferlet;Gregory W. Henry
上下文。本文介绍了用斯皮策空间望远镜上的红外阵列相机在3.6μ米处对热木星HD189733b进行的新的初级凌日观测。以前3.6微米的测量具有很强的系统性，通过比较3.6微米和5.8微米的观测结果，很难得出对水探测有信心的结论。目标。我们的目标是限制地球的大气结构和组成，并改进以前得出的参数。方法：研究方法。为了提高卫星近红外半径在3.6μm的精度，我们使用了一条高分辨率的S/N斯皮策光度传递光曲线，并利用子阵模式下积分的高阶时间序列进行了观测。我们能够从凌日光线曲线的拟合中得到准确的系统参数，包括行星与恒星的半径比、撞击参数、系统的规模和凌日的中心时间。我们将结果与透射谱模型以及之前在相同波长下的观测结果进行了比较。结果。我们得到了以下系统参数：Rp/R�=0.15566+0.00011−0.00024，b=0.661+0.0053−0.0050，a nda/R�=8.925+0.0490−0.0523，在3.6μm处，这些测量比以前的研究精度高三倍，因为它们受益于更高的观测效率和更小的统计和系统误差。尽管如此，我们发现半径比必须根据恒星的活动进行修正，并提出了一种方法，使用V波段的地面长持续时间光度跟踪来实现这一点。由此得到的行星-恒星半径比修正了恒星的可变性，与我们之前在同一带通中获得的测量结果一致。我们还讨论了水汽不能通过比较在3.6μm和5.8μm测得的行星半径来探测到，因为在3.6μ-S测得的半径受其他物种的吸收的影响，可能是雾霾的瑞利散射。
Context. We present a new primary transit observation of the hot-jupiter HD 189733b, obtained at 3.6 μm with the Infrared Array Camera (IRAC) onboard the Spitzer Space Telescope. Previous measurements at 3.6 microns suffered from strong systematics, and conclusions could hardly be obtained with confidence on the water detection by comparison of the 3.6 and 5.8 microns observations. Aims. We aim at constraining the atmospheric structure and composition of the planet and improving previously derived parameters. Methods. We use a high-S /N Spitzer photometric transit light curve to improve the precision of the near infrared radius of the planet at 3.6 μm. The observation has been performed using high-cadence time series integrated in the subarray mode. We are able to derive accurate system parameters, including planet-to-star radius ratio, impact parameter, scale of the system, and central time of the transit from the fits of the transit light curve. We compare the results with transmission spectroscopic models and with results from previous observations at the same wavelength. Results. We obtained the following system parameters of Rp/R� = 0.15566 +0.00011 −0.00024 , b = 0.661 +0.0053 −0.0050 ,a nda/R� = 8.925 +0.0490 −0.0523 at 3.6 μm. These measurements are three times more accurate than previous studies at this wavelength because they benefit from greater observational efficiency and less statistic and systematic errors. Nonetheless, we find that the radius ratio has to be corrected for stellar activity and present a method to do so using ground-based long-duration photometric follow-up in the V-band. The resulting planet-to-star radius ratio corrected for the stellar variability agrees with our previous measurement obtained in the same bandpass. We also discuss that water vapour could not be detected by a comparison of the planetary radius measured at 3.6 and 5.8 μm, because the radius measured at 3.6 μ mi s affected by absorption by other species, possibly Rayleigh scattering by haze.
影响因子：
6.5
作者：
S. Czesla;K. Huber;U. Wolter;S. Schröter;J. Schmitt
通讯作者：
S. Czesla;K. Huber;U. Wolter;S. Schröter;J. Schmitt