论文标题
在WASP-21b的下层和高层大气中检测Na
Detection of Na in WASP-21b's lower and upper atmosphere
论文作者
论文摘要
光传递光谱对热木星大气的参考压力水平和散射特性提供了至关重要的约束。对于某些在大气中检测到碱原子的行星，它们的线轮廓可以作为连接上层和下大气层的良好探针。 WASP-21b是一种土星质量的木星，绕着厚盘恒星绕，低密度和平衡温度为1333 K，这使其成为传输光谱法的良好目标。在这里，我们提出了一个基于Osiris光谱仪在10.4 m Gran望远镜的Canarias（GTC）观察到的WASP-21B的低分辨率传输频谱，以及一个基于Harps-N的三个过渡频谱，由harps-n tnazinale galileo（TNG）和hares harps和harps和harps和harps的三个高分辨率传输频谱。我们对GTC的低分辨率传输光谱进行了光谱检索分析，并以$ 3.5- $σ$的置信度水平报告了NA的检测。 NA线表现出宽线轮廓，可以归因于压力扩大，这表明大多数清晰的行星气氛。频谱显示在K D $ _1 $线路处的暂定多余的吸收。使用HARPS-N和HARP，我们在光谱上解决了Na Doublet传输频谱。在运输过程中检测到Na双线的过量吸收，并显示与行星轨道运动一致的径向速度移位。我们提出了一个指标，以定量地区分具有相对清晰的气氛与其他大气的热木星，而WASP-21b在所有特征性的热木星中具有最大的度量值。在WASP-21B的下层和高层大气中检测NA的检测表明，它是将来随访观察的理想目标，为在广泛的压力水平范围内了解其大气的性质提供了机会。
Optical transmission spectroscopy provides crucial constraints on the reference pressure levels and scattering properties for hot Jupiter atmospheres. For certain planets, where alkali atoms are detected in the atmosphere, their line profiles could serve as a good probe to link upper and lower atmospheric layers. WASP-21b is a Saturn-mass hot Jupiter orbiting a thick disc star, with a low density and an equilibrium temperature of 1333 K, which makes it a good target for transmission spectroscopy. Here, we present a low-resolution transmission spectrum for WASP-21b based in one transit observed by the OSIRIS spectrograph at the 10.4 m Gran Telescopio Canarias (GTC), and a high-resolution transmission spectrum based in three transits observed by HARPS-N at Telescopio Nazinale Galileo (TNG) and HARPS at the ESO 3.6 m telescope. We performed spectral retrieval analysis on GTC's low-resolution transmission spectrum and report the detection of Na at a confidence level of $>$3.5-$σ$. The Na line exhibits a broad line profile that can be attributed to pressure broadening, indicating a mostly clear planetary atmosphere. The spectrum shows a tentative excess absorption at the K D$_1$ line. Using HARPS-N and HARPS, we spectrally resolved the Na doublet transmission spectrum. An excess absorption at the Na doublet is detected during the transit, and shows a radial velocity shift consistent with the planet orbital motion. We proposed a metric to quantitatively distinguish hot Jupiters with relatively clear atmospheres from others, and WASP-21b has the largest metric value among all the characterized hot Jupiters. The detection of Na at both lower and upper atmosphere of WASP-21b reveals that it is an ideal target for future follow-up observations, providing the opportunity to understand the nature of its atmosphere across a wide range of pressure levels.
