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More Evidence for Variable Helium Absorption from HD 189733b

Zhang, Michael and Cauley, P. Wilson and Knutson, Heather A. and France, Kevin and Kreidberg, Laura and Oklopčić, Antonija and Redfield, Seth and Shkolnik, Evgenya L. (2022) More Evidence for Variable Helium Absorption from HD 189733b. . (Unpublished)

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We present a new Keck/NIRSPEC observation of metastable helium absorption from the upper atmosphere of HD 189733b, a hot Jupiter orbiting a nearby moderately active star. We measure an average helium transit depth of 0.420±0.013% integrated over the [-20, 20] km/s velocity range. Comparing this measurement to eight previously published transit observations with different instruments, we find that our depth is 32% (9σ) lower than the average of the three CARMENES transits, but only 16% (4.4σ) lower than the average of the five GIANO transits. We perform 1D hydrodynamical simulations of the outflow, and find that XUV variability on the order of 33%--common for this star--can change the helium absorption depth by 60%. We conclude that changes in stellar XUV flux can explain the observational variability in helium absorption. 3D models are necessary to explore other sources of variability, such as shear instability and changing stellar wind conditions.

Item Type:Report or Paper (Discussion Paper)
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URLURL TypeDescription Paper ItemJournal Article
Zhang, Michael0000-0002-0659-1783
Knutson, Heather A.0000-0002-0822-3095
France, Kevin0000-0002-1002-3674
Kreidberg, Laura0000-0003-0514-1147
Oklopčić, Antonija0000-0002-9584-6476
Redfield, Seth0000-0003-3786-3486
Shkolnik, Evgenya L.0000-0002-7260-5821
Additional Information:Attribution 4.0 International (CC BY 4.0). 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.
Group:Division of Geological and Planetary Sciences
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Record Number:CaltechAUTHORS:20220712-193852445
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115503
Deposited By: George Porter
Deposited On:13 Jul 2022 21:09
Last Modified:02 Jun 2023 01:25

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