用CAMAL监测大地吸收
Monitoring Telluric Absorption with CAMAL
摘要：
地面天文观测可能会受到大地水汽吸收的限制，这种吸收随时间变化很大，使近红外光谱学和光度学都变得非常复杂。为了达到在近红外中探测地球大小的系外行星所需的灵敏度，有必要同时监测可降水量（PWV），以减轻可变大地线对径向速度测量和过境光变曲线的影响。为了解决这个问题，我们提出了相机的自动监测大气线（CAMAL），一个独立的，廉价的6英寸孔径望远镜，专门用于测量PWV在弗雷德劳伦斯惠普尔天文台霍普金斯山。CAMAL利用三个窄带近红外滤波器来追踪影响微型系外行星径向速度阵列（MINERVA）和MINERVA-Red望远镜同时观测的大气水蒸气量。在这里，我们目前的设计CAMAL，讨论我们的数据分析方法，并显示从11个晚上的PWV测量结果与CAMAL。对于七个晚上的数据，我们有独立的PWV测量提取的高分辨率恒星光谱与Tillinghast反射器Echelle光谱仪（TRES）也位于霍普金斯山。我们使用TRES光谱校准CAMAL绝对PWV尺度。CAMAL和TRES PWV估计值之间的比较显示出良好的一致性，在PWV的10 mm范围内匹配到1 mm以内。CAMAL的光度精度分析传播到PWV测量精度优于0.5毫米在干燥条件下（PWV < 4毫米）。我们还发现，CAMAL派生的PWV高度相关的GPS为基础的水汽监测器位于约90公里以外的基特峰国家天文台，与均方根PWV的差异为0.8毫米。
英文摘要：
Ground-based astronomical observations may be limited by telluric water vapor absorption, which is highly variable in time and significantly complicates both spectroscopy and photometry in the near-infrared (NIR). To achieve the sensitivity required to detect Earth-sized exoplanets in the NIR, simultaneous monitoring of precipitable water vapor (PWV) becomes necessary to mitigate the impact of variable telluric lines on radial velocity measurements and transit light curves. To address this issue, we present the Camera for the Automatic Monitoring of Atmospheric Lines (CAMAL), a stand-alone, inexpensive six-inch aperture telescope dedicated to measuring PWV at the Fred Lawrence Whipple Observatory on Mount Hopkins. CAMAL utilizes three narrowband NIR filters to trace the amount of atmospheric water vapor affecting simultaneous observations with the MINiature Exoplanet Radial Velocity Array (MINERVA) and MINERVA-Red telescopes. Here we present the current design of CAMAL, discuss our data analysis methods, and show results from 11 nights of PWV measurements taken with CAMAL. For seven nights of data, we have independent PWV measurements extracted from high-resolution stellar spectra taken with the Tillinghast Reflector Echelle Spectrometer (TRES) also located on Mount Hopkins. We use the TRES spectra to calibrate the CAMAL absolute PWV scale. Comparisons between CAMAL and TRES PWV estimates show excellent agreement, matching to within 1 mm over a 10 mm range in PWV. Analysis of CAMAL's photometric precision propagates to PWV measurements precise to better than 0.5 mm in dry (PWV < 4 mm) conditions. We also find that CAMAL-derived PWVs are highly correlated with those from a GPS-based water vapor monitor located approximately 90 km away at Kitt Peak National Observatory, with a root mean square PWV difference of 0.8 mm.
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