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arXiv 1712.03384astro-ph.EP
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来自WFC3数据的WASP-67 b和HAT-P-38 b的比较研究

A comparative study of WASP-67b and HAT-P-38b from WFC3 data

Giovanni Bruno, Nikole K. Lewis, Kevin B. Stevenson, Joseph Filippazzo, Matthew Hill, Jonathan D. Fraine, Hannah R. Wakeford, Drake Deming, Brian Kilpatrick, Mi… 展开作者

Giovanni Bruno, Nikole K. Lewis, Kevin B. Stevenson, Joseph Filippazzo, Matthew Hill, Jonathan D. Fraine, Hannah R. Wakeford, Drake Deming, Brian Kilpatrick, Michael R. Line, Caroline V. Morley, Karen A. Collins, Dennis M. Conti, Joseph Garlitz, Joseph E. Rodriguez

摘要:

大气温度和行星重力被认为是影响巨大系外行星大气中云形成的主要参数。最近试图了解云的形成探索了广泛的区域的平衡温度-重力参数空间。在这项研究中,我们比较了两个具有几乎相同的平衡温度($T_\mathrm{eq}$ $\sim 1050 \, \mathrm{K}$)和重力($g \sim 10 \, \mathrm{m \, s}^{-1})$)的巨行星的情况。在$HST$周期23期间,我们收集了WFC 3/G141对两颗行星WASP-67 b和HAT-P-38 b的观测。HAT-P-38 b的质量为0.42 M $_\mathrm{J}$,半径为1.4 $R_\mathrm{J}$,其大气相对清澈,并可清晰地探测到水。我们用新的观测资料修正了这颗行星的轨道周期,得到了$P = 4.6403294 \pm 0.0000055 \, \mathrm{d}$。WASP-67 b的质量为0.27 M $_\mathrm{J}$,半径为0.83 $R_\mathrm{J}$,比HAT-P-38 b显示出更柔和的吸水特征,表明大气中的云顶更高,或者更富含金属。光谱的差异支持了这样一种假设,即巨大的系外行星大气层携带着它们形成历史的痕迹。未来的观测需要在可见光和中红外探测气溶胶的属性和约束这些行星的演化情景。

英文摘要:

Atmospheric temperature and planetary gravity are thought to be the main parameters affecting cloud formation in giant exoplanet atmospheres. Recent attempts to understand cloud formation have explored wide regions of the equilibrium temperature-gravity parameter space. In this study, we instead compare the case of two giant planets with nearly identical equilibrium temperature ($T_\mathrm{eq}$ $\sim 1050 \, \mathrm{K}$) and gravity ($g \sim 10 \, \mathrm{m \, s}^{-1})$. During $HST$ Cycle 23, we collected WFC3/G141 observations of the two planets, WASP-67 b and HAT-P-38 b. HAT-P-38 b, with mass 0.42 M$_\mathrm{J}$ and radius 1.4 $R_\mathrm{J}$, exhibits a relatively clear atmosphere with a clear detection of water. We refine the orbital period of this planet with new observations, obtaining $P = 4.6403294 \pm 0.0000055 \, \mathrm{d}$. WASP-67 b, with mass 0.27 M$_\mathrm{J}$ and radius 0.83 $R_\mathrm{J}$, shows a more muted water absorption feature than that of HAT-P-38 b, indicating either a higher cloud deck in the atmosphere or a more metal-rich composition. The difference in the spectra supports the hypothesis that giant exoplanet atmospheres carry traces of their formation history. Future observations in the visible and mid-infrared are needed to probe the aerosol properties and constrain the evolutionary scenario of these planets.

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