WASP-39b中红外透射光谱中的二氧化硫
Sulphur dioxide in the mid-infrared transmission spectrum of WASP-39b
AI总结：
本研究利用JWST/MIRI LRS观测到WASP-39b中红外透射光谱中7.7和8.5μm处的SO₂特征，验证了此前的SO₂探测，推导其金属丰度约为太阳的7.1-8.0倍，证实光化学对该行星宽波段光谱的塑造作用。
摘要：
近期通过近红外JWST观测推断出，热（约1100K）土星质量系外行星WASP-39b的大气中存在二氧化硫（SO₂），这表明光化学是高温系外行星大气中的关键过程。这是因为与H₂O和H₂S的光化学作用产生的SO₂丰度（1-10ppm）相比，热化学平衡下的SO₂丰度很低（<1ppb）。然而，SO₂的推断是基于WASP-39b透射光谱中4.05μm处的单个小分子特征，因此需要在不同波长处检测其他SO₂吸收带，以更好地约束SO₂丰度。本文中，我们报告了利用JWST中红外仪器（MIRI）低分辨率光谱仪（LRS）测量的WASP-39b 5-12μm透射光谱中，检测到7.7μm和8.5μm处的SO₂光谱特征。我们的观测表明SO₂丰度为0.5-25ppm（1σ范围），与之前的研究结果一致。除了SO₂，我们还发现了宽的水蒸气吸收特征，以及在波长大于10μm时凌星深度出现无法解释的下降。通过用大气正演模型网格拟合光谱，我们得出WASP-39b的大气重元素含量（金属丰度）约为太阳的7.1-8.0倍，并证明光化学在很宽的波长范围内塑造了WASP-39b的光谱。
英文摘要：
The recent inference of sulphur dioxide (SO$_2$) in the atmosphere of the hot ($\sim$1100 K), Saturn-mass exoplanet WASP-39b from near-infrared JWST observations suggests that photochemistry is a key process in high temperature exoplanet atmospheres. This is due to the low ($<$1 ppb) abundance of SO$_2$ under thermochemical equilibrium, compared to that produced from the photochemistry of H$_2$O and H$_2$S (1-10 ppm). However, the SO$_2$ inference was made from a single, small molecular feature in the transmission spectrum of WASP-39b at 4.05 $μ$m, and therefore the detection of other SO$_2$ absorption bands at different wavelengths is needed to better constrain the SO$_2$ abundance. Here we report the detection of SO$_2$ spectral features at 7.7 and 8.5 $μ$m in the 5-12 $μ$m transmission spectrum of WASP-39b measured by the JWST Mid-Infrared Instrument (MIRI) Low Resolution Spectrometer (LRS). Our observations suggest an abundance of SO$_2$ of 0.5-25 ppm (1$σ$ range), consistent with previous findings. In addition to SO$_2$, we find broad water vapour absorption features, as well as an unexplained decrease in the transit depth at wavelengths longer than 10 $μ$m. Fitting the spectrum with a grid of atmospheric forward models, we derive an atmospheric heavy element content (metallicity) for WASP-39b of $\sim$7.1-8.0 $\times$ solar and demonstrate that photochemistry shapes the spectra of WASP-39b across a broad wavelength range.
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