论文标题
从13个地面过境观测值的地面系外行星LHS 3844b的光学传输光谱
Optical Transmission Spectroscopy of the Terrestrial Exoplanet LHS 3844b from 13 Ground-Based Transit Observations
论文作者
论文摘要
对光谱镜的大气研究，可访问的陆地系外行星为这些世界与太阳系陆地行星之间的比较行星学奠定了基础。 LHS 3844b是一种高度辐射的陆地系外行星（r = 1.303 +/- 0.022r_earth），绕着Mid-M Dwarf 15 parsecs绕行。基于近红外Spitzer相曲线的工作排除了该星球上的表面压力>/= 10条的大气。我们提出了13个使用麦哲伦粘土望远镜进行的LHS 3844B的公交观测值，LDSS3C多对象光谱仪覆盖620-1020 nm。我们使用高斯过程回归分别分析了13个数据集中的每个数据集，并呈现白色和光谱光曲线。在联合白光曲线中，我们将RMS精度达到65 ppm时，将其归为10分钟。 （RP/RS）^2的平均白光曲线值为0.4170 +/- 0.0046％。要构建传输频谱，我们将白光曲线分成20个分光光度测量带，每个分光光度测量带跨越20 nm，并计算每个频段中（rp/rs）^2的平均值。我们将传输频谱与两组大气模型进行比较。我们不利于表面压力>/= 0.1 bar to 5.2 sigma置信度的清晰的太阳组成气氛（MU = 2.34）。我们不利于表面压力>/= 0.1 bar至置信度（2.9-Sigma）的清晰的H2O蒸汽气氛（MU = 18）。我们观察到的传输光谱有利于平坦线。对于具有表面压力>/= 1 bar的太阳能组成气氛，我们排除了云层的云层压力为0.1 bar（5.3-Sigma），但我们无法在下部压力下解决高空云。我们的结果进一步增加了证据，表明LHS 3844b没有大气。
Atmospheric studies of spectroscopically accessible terrestrial exoplanets lay the groundwork for comparative planetology between these worlds and the Solar System terrestrial planets. LHS 3844b is a highly-irradiated terrestrial exoplanet (R=1.303+/-0.022R_Earth) orbiting a mid-M dwarf 15 parsecs away. Work based on near-infrared Spitzer phase curves ruled out atmospheres with surface pressures >/=10 bars on this planet. We present 13 transit observations of LHS 3844b taken with the Magellan Clay telescope and the LDSS3C multi-object spectrograph covering 620-1020 nm. We analyze each of the 13 data sets individually using a Gaussian process regression, and present both white and spectroscopic light curves. In the combined white light curve we achieve an RMS precision of 65 ppm when binning to 10-minutes. The mean white light curve value of (Rp/Rs)^2 is 0.4170+/-0.0046%. To construct the transmission spectrum, we split the white light curves into 20 spectrophotometric bands, each spanning 20 nm, and compute the mean values of (Rp/Rs)^2 in each band. We compare the transmission spectrum to two sets of atmospheric models. We disfavor a clear, solar composition atmosphere (mu=2.34) with surface pressures >/=0.1 bar to 5.2-sigma confidence. We disfavor a clear, H2O steam atmosphere (mu=18) with surface pressures >/=0.1 bar to low confidence (2.9-sigma). Our observed transmission spectrum favors a flat line. For solar composition atmospheres with surface pressures >/=1 bar we rule out clouds with cloud-top pressures of 0.1 bar (5.3-sigma), but we cannot address high-altitude clouds at lower pressures. Our results add further evidence that LHS 3844b is devoid of an atmosphere.
