Detecting Water In the atmosphere of HR 8799 c with L-band High Dispersion Spectroscopy Aided By Adaptive Optics
Abstract
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 8799 c using Keck NIRSPEC (R = 15,000) in adaptive optics (AO) mode (NIRSPAO). We search for molecular species (H_2O and CH_4) in the atmosphere of HR 8799 c with a template-matching method, which involves cross-correlation between reduced spectra and a template spectrum. We detect H_2O but not CH_4, which suggests disequilibrium chemistry in the atmosphere of HR 8799 c, 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.
Additional Information
© 2018 The American Astronomical Society. Received 2018 June 25; revised 2018 September 21; accepted 2018 September 24; published 2018 November 20. We thank the anonymous referee for constructive comments and suggestions that greatly improved the manuscript. We acknowledge Rowan Swain for carefully proofreading the manuscript. We thank Jason Wang and Olivier Wertz for providing precise astrometric predictions for HR 8799 c. We thank Roger Smith and the NIRSPEC team, especially Ian McLean, Mike Fitzgerald, and Emily Martin, for valuable input on the correlated noise of ALADDIN InSb detectors. We thank Geoff Blake and his group for offering advice for NIRSPEC L-band observation and sharing the PyNIRSPEC data reduction pipeline. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.Attached Files
Published - Wang_2018_AJ_156_272.pdf
Accepted Version - 1809.09080.pdf
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Additional details
- Eprint ID
- 91064
- Resolver ID
- CaltechAUTHORS:20181120-073429737
- W. M. Keck Foundation
- Created
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2018-11-20Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Astronomy Department