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Proceedings Paper

Exoplanets with JWST: degeneracy, systematics and how to avoid them
Author(s): Joanna K. Barstow; Patrick G. J. Irwin; Sarah Kendrew; Suzanne Aigrain
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Paper Abstract

The high sensitivity and broad wavelength coverage of the James Webb Space Telescope will transform the field of exoplanet transit spectroscopy. Transit spectra are inferred from minute, wavelength-dependent variations in the depth of a transit or eclipse as the planet passes in front of or is obscured by its star, and the spectra contain information about the composition, structure and cloudiness of exoplanet atmospheres. Atmospheric retrieval is the preferred technique for extracting information from these spectra, but the process can be confused by astrophysical and instrumental systematic noise. We present results of retrieval tests based on synthetic, noisy JWST spectra, for clear and cloudy planets and active and inactive stars. We find that the ability to correct for stellar activity is likely to be a limiting factor for cloudy planets, as the effects of unocculted star spots may mimic the presence of a scattering slope due to clouds. We discuss the pros and cons of the available JWST instrument combinations for transit spectroscopy, and consider the effect of clouds and aerosols on the spectra. Aerosol high in a planet’s atmosphere obscures molecular absorption features in transmission, reducing the information content of spectra in wavelength regions where the cloud is optically thick. We discuss the usefulness of particular wavelength regions for identifying the presence of cloud, and suggest strategies for solving the highly-degenerate retrieval problem for these objects.

Paper Details

Date Published: 29 July 2016
PDF: 13 pages
Proc. SPIE 9904, Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave, 99043P (29 July 2016); doi: 10.1117/12.2232543
Show Author Affiliations
Joanna K. Barstow, Univ. College London (United Kingdom)
Univ. of Oxford (United Kingdom)
Patrick G. J. Irwin, Univ. of Oxford (United Kingdom)
Sarah Kendrew, European Space Agency (United States)
Suzanne Aigrain, Univ. of Oxford (United Kingdom)


Published in SPIE Proceedings Vol. 9904:
Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave
Howard A. MacEwen; Giovanni G. Fazio; Makenzie Lystrup; Natalie Batalha; Nicholas Siegler; Edward C. Tong, Editor(s)

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