论文标题
温带亚纽马TOI-270D的哈勃太空望远镜传输光谱：可能含有水蒸气的氢气大气
Hubble Space Telescope transmission spectroscopy for the temperate sub-Neptune TOI-270d: a possible hydrogen-rich atmosphere containing water vapour
论文作者
论文摘要
TOI-270D是通过透明的（j = 9.1mag）M3V宿主星的过渡系外行星调查卫星（TESS）发现的温带亚核。 TOI-270D大约半径为2RE，平衡温度为350K，是使用Transit Spectroscopicy进行大气表征的最有希望的小型系外行星之一。在这里，我们介绍了由Hubble太空望远镜（HST）广场相机3（WFC3）光谱仪制成的TOI-270D的主要过境观察，该观察量在1.126-1.644微米波长范围内，以及95％可信的上限，$ 8.2 \ $ 8.2 \ times 10^{ - 14} $ erg s $^$ erg s $^$^$^$^$^$} $^{ - 1} $ arcsec $^{ - 2} $用于使用太空望远镜成像光谱仪（STIS）获得的恒星Ly-Alpha排放。源自苔丝和WFC3数据的传输光谱提供了相对于无特征光谱的4-硅质意义的富含氢气的分子吸收的证据。对于H2O，获得了任何个体吸收器的最有力的证据，这是3-硅意义的有利的。当仅在WFC3数据上检索并允许具有异质性恒星亮度曲线的可能性时，H2O的检测显着性将降低至2.8-sigma。因此，需要进一步的观察结果来鲁棒地确定TOI-270D的大气组成并评估恒星异质性的影响。如果得到证实，我们的发现将使TOI-270D成为迄今为止具有检测到的大气光谱特征的最小，最酷的系外行星之一。
TOI-270d is a temperate sub-Neptune discovered by the Transiting Exoplanet Survey Satellite (TESS) around a bright (J=9.1mag) M3V host star. With an approximate radius of 2RE and equilibrium temperature of 350K, TOI-270d is one of the most promising small exoplanets for atmospheric characterisation using transit spectroscopy. Here we present a primary transit observation of TOI-270d made with the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) spectrograph across the 1.126-1.644 micron wavelength range, and a 95% credible upper limit of $8.2 \times 10^{-14}$ erg s$^{-1}$ cm$^{-2}$ A$^{-1}$ arcsec$^{-2}$ for the stellar Ly-alpha emission obtained using the Space Telescope Imaging Spectrograph (STIS). The transmission spectrum derived from the TESS and WFC3 data provides evidence for molecular absorption by a hydrogen-rich atmosphere at 4-sigma significance relative to a featureless spectrum. The strongest evidence for any individual absorber is obtained for H2O, which is favoured at 3-sigma significance. When retrieving on the WFC3 data alone and allowing for the possibility of a heterogeneous stellar brightness profile, the detection significance of H2O is reduced to 2.8-sigma. Further observations are therefore required to robustly determine the atmospheric composition of TOI-270d and assess the impact of stellar heterogeneity. If confirmed, our findings would make TOI-270d one of the smallest and coolest exoplanets to date with detected atmospheric spectral features.
