arXiv 1911.033582019-11-11astro-ph.EP

ACCESS：热木星WASP-43 b的可见近红外光谱，有$\rm H_2O$的证据，但没有Na或K的证据

ACCESS: A Visual to Near-infrared Spectrum of the Hot Jupiter WASP-43b with Evidence of $\rm H_2O$, but no evidence of Na or K

Ian C. Weaver, Mercedes López-Morales, Néstor Espinoza, Benjamin V. Rackham, David J. Osip, Dániel Apai, Andrés Jordán, Alex Bixel, Nikole K. Lewis, Munazza K. … 展开作者

Ian C. Weaver, Mercedes López-Morales, Néstor Espinoza, Benjamin V. Rackham, David J. Osip, Dániel Apai, Andrés Jordán, Alex Bixel, Nikole K. Lewis, Munazza K. Alam, James Kirk, Chima McGruder, Florian Rodler, Jennifer Fienco

备注：: 27 pages, 18 figures, 7 tables. Accepted for publication in AJ. Updated affiliations
DOI：: 10.3847/1538-3881/ab55da

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摘要：

我们提出了一个新的基于地面的热木星WASP-43 b的可见光透射光谱，作为ACCESS调查的一部分。该光谱来源于2015年至2018年期间观察到的四次凌日，组合波长覆盖范围在5，300 nm-9，000 nm之间，230个波段的平均光度精度为708 ppm。我们结合文献HST/WFC 3观测对我们的透射光谱进行大气反演，以在5，318 nm-16，420 nm的组合光谱范围内搜索云/薄雾以及Na，K，H $α$和$\rm H_2O$行星吸收和恒星斑点污染的存在。在WASP-43 b的大气中，我们没有检测到Na I或K I碱性线或H $α$的统计学显著存在。我们发现，所观察到的透射光谱可以最好地解释由主机恒星的光球和一个明确的行星大气层与$\rm H_2O$的不均匀性的组合。该模型产生的$8.26\pm0.42$对数证据高于平坦（无特征）光谱。特别是，在平均覆盖分数$f_\text{het} = 0.27^{+0.42}_{-0.16}$和温度对比度$ΔT = 132\text{ K} \pm 132\text{ K}$的四个ACCESS过境时期，观察结果略微有利于大的低对比度斑点的存在。在行星的大气层中，我们恢复了$-2.78^{+1.38}_{-1.47}$，这是与以前的$\rm H_2O$丰度测定这颗行星的$\rm H_2O$体积混合比的日志。

英文摘要：

We present a new ground-based visual transmission spectrum of the hot Jupiter WASP-43b, obtained as part of the ACCESS Survey. The spectrum was derived from four transits observed between 2015 and 2018, with combined wavelength coverage between 5,300 Å-9,000 Å and an average photometric precision of 708 ppm in 230 Å bins. We perform an atmospheric retrieval of our transmission spectrum combined with literature HST/WFC3 observations to search for the presence of clouds/hazes as well as Na, K, H$α$, and $\rm H_2O$ planetary absorption and stellar spot contamination over a combined spectral range of 5,318 Å-16,420 Å. We do not detect a statistically significant presence of Na I or K I alkali lines, or H$α$ in the atmosphere of WASP-43b. We find that the observed transmission spectrum can be best explained by a combination of heterogeneities on the photosphere of the host star and a clear planetary atmosphere with $\rm H_2O$. This model yields a log-evidence of $8.26\pm0.42$ higher than a flat (featureless) spectrum. In particular, the observations marginally favor the presence of large, low-contrast spots over the four ACCESS transit epochs with an average covering fraction $f_\text{het} = 0.27^{+0.42}_{-0.16}$ and temperature contrast $ΔT = 132\text{ K} \pm 132\text{ K}$. Within the planet's atmosphere, we recover a log $\rm H_2O$ volume mixing ratio of $-2.78^{+1.38}_{-1.47}$, which is consistent with previous $\rm H_2O$ abundance determinations for this planet.

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