The Hubble PanCET program: The near-ultraviolet transmission spectrum of WASP-79b
The Hubble PanCET program: The near-ultraviolet transmission spectrum of WASP-79b
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哈勃 PanCET 计划：WASP-79b 的近紫外透射光谱
DOI：
10.1051/0004-6361/202244429
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发表时间：
2023
影响因子：
6.5
通讯作者：
Gressier A
中科院分区：
文献类型：
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作者：
Gressier A
介绍了用空间望远镜成像光谱仪(STIS)在近紫外区(NUV)对热木星WASP-79b进行的哈勃太空望远镜(HST)凌日观测。两次凌日观测是PanCET计划的一部分，用来获得该行星在2280和3070ä之间的透射谱。我们使用抖动工程参数和多项式模型来拟合两次凌日的白光曲线，对原始数据中的系统效应进行了校正。我们在短波长观察到行星与恒星半径比的增加，但没有光谱分辨的吸收线。半径比在2400A和3000A之间的差达0.0191±0.0042(~4.5−σ)。尽管NUV透射谱没有显示出流体力学逃逸的证据，但强烈的大气特征很可能是由于非常高海拔的物种造成的。我们用Exo-REM对WASP-79b的温度和组成进行了一维模拟。温度压力分布与辐射活跃云，特别是MnS、Mg2SiO4、Fe和Al_2O_3云的凝聚曲线相交。尽管如此，这些物种都不会在短波长产生观测到的吸收水平，也不能解释观测到的行星半径的增加。WASP-79b的凌日深度达到23尺度高度，是在这个温度(~1700K)下观测到的系外行星上最大的光谱特征之一。WASP-79b与三个较热的热木星的透射谱的比较表明，在0.2-0.3微米范围内，WASP-178b和WASP-121b的吸收水平相似，而HAT-P-41b的光谱是平坦的。这些特征可以用SiO_2吸附来解释。
We presentHubbleSpace Telescope (HST) transit observations of the Hot-Jupiter WASP-79 b acquired with the Space Telescope Imaging Spectrograph (STIS) in the near ultraviolet (NUV). Two transit observations, part of the PanCET program, are used to obtain the transmission spectra of the planet between 2280 and 3070 Å. We correct for systematic effects in the raw data using the jitter engineering parameters and polynomial modelling to fit the white light curves of the two transits. We observe an increase in the planet-to-star radius ratio at short wavelengths, but no spectrally resolved absorption lines. The difference between the radius ratios at 2400 Å and 3000 Å reaches 0.0191 ± 0.0042 (~4.5−σ). Although the NUV transmission spectrum does not show evidence of hydrodynamical escape, the strong atmospheric features are likely due to species at very high altitudes. We performed a 1D simulation of the temperature and composition of WASP-79 b using Exo-REM. The temperature pressure profile crosses condensation curves of radiatively active clouds, particularly MnS, Mg2SiO4, Fe, and Al2O3. Still, none of these species produces the level of observed absorption at short wavelengths and can explain the observed increase in the planet’s radius. WASP-79 b’s transit depth reaches 23 scale height, making it one of the largest spectral features observed in an exoplanet at this temperature (~1700 K). The comparison of WASP-79 b’s transmission spectrum with three warmer hot Jupiters shows a similar level of absorption to WASP-178 b and WASP-121 b between 0.2 and 0.3 µm, while HAT-P-41 b’s spectrum is flat. The features could be explained by SiO absorption.