摘要：High-dispersion spectroscopy of brown dwarfs and exoplanets enables exciting science cases, e.g., mapping surface inhomogeneity and measuring spin rate. Here, we present L-band observations of HR 8799c using Keck NIRSPEC (R=15,000) in adaptive optics (AO) mode (NIRSPAO). We search for molecular species (H 2 O and CH 4 ) in the atmosphere of HR 8799c with a template-matching method, which involves cross-correlation between reduced spectra and a template spectrum. We detect H 2 O but not CH 4 , which suggests disequilibrium chemistry in the atmosphere of HR 8799c, and this is consistent with previous findings. We conduct planet signal injection simulations to estimate the sensitivity of our AO-aided high-dispersion spectroscopy observations. We conclude that 10 −4 contrast can be reached in the L band. The sensitivity is mainly limited by the accuracy of line list used in modeling spectra and detector noise. The latter will be alleviated by the NIRSPEC upgrade.
关键词：methods: observational;planetary systems;planets and satellites: atmospheres;planets and satellites: composition;techniques: high angular resolution;techniques: spectroscopic
