LRG-BEASTS：热木星HAT-P-44b中钠的检测及水吸收的证据
LRG-BEASTS: Detection of sodium and evidence for water absorption in the hot Saturn HAT-P-44b
AI总结：
LRG-BEASTS调查发现热木星HAT-P-44b中钠和水吸收的证据，揭示其大气特征与WASP-39b相似。
摘要：
我们呈现了热木星HAT-P-44b的低分辨率光学传输光谱。该行星在半径（1.24 R_jup）、温度（1100 K）和质量（0.35 M_jup）方面与高度表征的WASP-39b非常相似。使用威廉·赫歇尔望远镜（WHT）上的ACAM仪器，我们获得了波长范围为495-874 nm、分辨率20 nm的传输光谱，其亚尺度高度精度达到246 ppm，尽管宿主恒星相对较暗（Vmag=13.2）。我们以3.9σ置信度检测到钠的吸收。传输光谱的大气检索还揭示了水吸收和氢气的瑞利散射的证据，与一个约800 K的冷大气和超太阳金属度（7×太阳±16-5）一致。检索模型的比较不支持超瑞利散射斜率或高海拔云（<1 mbar）的存在，但对中等海拔云的存在持中立态度。HAT-P-44b的传输光谱与其姐妹WASP-39b的非常相似。这是LRG-BEASTS（利用传输光谱进行地面系外行星大气调查）调查的第十年行星。
英文摘要：
We present the low-resolution optical transmission spectrum of the inflated hot Saturn HAT-P-44b. The planet is a close sibling in radius (1.24 $\mathrm{R_{Jup}}$), temperature (1100 K), and mass (0.35 $\mathrm{M_{Jup}}$) to the exceedingly well-characterized WASP-39b. Using the ACAM instrument on the William Herschel Telescope (WHT), we obtain a transmission spectrum with sub-scale height precision of 246 ppm, with a wavelength range of 495 -- 874 nm and a 20 nm resolution, despite a relatively faint host star ($V\mathrm{_{mag} = 13.2}$). We detect absorption due to sodium with 3.9$σ$ confidence. Atmospheric retrieval of the transmission spectrum also reveals evidence for \ch{H2O} absorption and Rayleigh scattering from \ch{H2} gas consistent with a cool 800 K atmosphere and a super-solar metallicity of 7$\substack{+16 \\ -5}$$\times$solar. Comparison of retrieval models disfavour the inclusion of a super-Rayleigh scattering slope or high-altitude clouds (at $<1$ mbar) while being agnostic towards the presence of mid-altitude clouds. Our transmission spectrum of HAT-P-44b shows strong similarity to that of its sibling WASP-39b.} This is the tenth planet in the LRG-BEASTS (Low-Resolution Ground-Based Exoplanet Atmosphere Survey using Transmission Spectroscopy) survey.
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