Constraints on Metastable Helium in the Atmospheres of WASP-69b and WASP-52b with Ultranarrowband Photometry
Constraints on Metastable Helium in the Atmospheres of WASP-69b and WASP-52b with Ultranarrowband Photometry
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DOI：
10.3847/1538-3881/ab8e34
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发表时间：
2020-04
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通讯作者：
S. Vissapragada;H. Knutson;N. Jovanovic;C. Harada;A. Oklopčić;J. Eriksen;D. Mawet;M. Millar-Blanchaer;S. Tinyanont;G. Vasisht
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作者：
S. Vissapragada;H. Knutson;N. Jovanovic;C. Harada;A. Oklopčić;J. Eriksen;D. Mawet;M. Millar-Blanchaer;S. Tinyanont;G. Vasisht
利用地面和空间光谱学对亚稳态 23S 氦吸收的红外观测正在迅速成熟，因为该物种是系外行星大气的独特探测器。具体来说，三重态特征中的凌日深度（真空波长接近 1083.3 nm）可用于约束系外行星高层大气的温度和质量损失率。在这里，我们提出了一种新的光度测量技术，使用超窄带滤光片（半高宽 0.635 nm）与安装在帕洛马天文台 200 英寸黑尔望远镜广视场红外相机中的光束整形扩散器耦合来测量亚稳态 23S 氦吸收。我们使用大地 OH 线和氦弧灯来表征滤光片的折射效应，并确认我们对滤光片传输曲线的理解。我们通过观察 WASP-69b 的凌日来对我们的新技术进行基准测试，并检测到 0.498% ± 0.045% (11.1σ) 的过量吸收，这与考虑我们的带通后的先前测量结果一致。然后，我们使用这种方法来研究膨胀的气体巨星 WASP-52b，并将氦带通中的过量吸收上限设置为 95%，上限为 0.47%。使用大气逃逸模型，我们将 WASP-69b 在 7000 K (12,000 K) 时的质量损失率限制为 ( )。此外，我们还为 WASP-52b 在这些温度 ( ) 下的质量损失率设定了上限。这些结果表明，超窄带光度测定可以可靠地量化亚稳态氦特征的吸收。
Infrared observations of metastable 23S helium absorption with ground- and space-based spectroscopy are rapidly maturing, as this species is a unique probe of exoplanet atmospheres. Specifically, the transit depth in the triplet feature (with vacuum wavelengths near 1083.3 nm) can be used to constrain the temperature and mass-loss rate of an exoplanet’s upper atmosphere. Here, we present a new photometric technique to measure metastable 23S helium absorption using an ultranarrowband filter (FWHM 0.635 nm) coupled to a beam-shaping diffuser installed in the Wide-field Infrared Camera on the 200 inch Hale Telescope at Palomar Observatory. We use telluric OH lines and a helium arc lamp to characterize refractive effects through the filter and to confirm our understanding of the filter transmission profile. We benchmark our new technique by observing a transit of WASP-69b and detect an excess absorption of 0.498% ± 0.045% (11.1σ), consistent with previous measurements after considering our bandpass. We then use this method to study the inflated gas giant WASP-52b and place a 95th percentile upper limit on excess absorption in our helium bandpass of 0.47%. Using an atmospheric escape model, we constrain the mass-loss rate for WASP-69b to be ( ) at 7000 K (12,000 K). Additionally, we set an upper limit on the mass-loss rate of WASP-52b at these temperatures of ( ). These results show that ultranarrowband photometry can reliably quantify absorption in the metastable helium feature.