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Variability in the atmosphere of the hot giant planet HAT-P-7 b

Nature Astronomy volume 1, Article number: 0004 (2017) Cite this article

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An exoplanet reflects and emits light as it orbits its host star, thus forming a distinctive phase curve1,2. By observing this light, we can study the atmosphere and surface of distant planets. The planets in our Solar System show a wide range of atmospheric phenomena, including stable wind patterns, changing storms and evolving anomalies. Brown dwarfs also exhibit atmospheric variability3,4. Such temporal variability in the atmosphere of a giant exoplanet has not yet been observed. HAT-P-7 b is an exoplanet with a known offset in the peak of its phase curve5,6. Here we present variations in the peak offset ranging between - 0.086 - 0.033 + 0.033 and 0.143 - 0.037 + 0.040 in phase, which implies that the peak brightness repeatedly shifts from one side of the planet’s substellar point to the other. The variability occurs on a timescale of tens to hundreds of days. These shifts in brightness are indicative of variability in the planet’s atmosphere, and result from a changing balance of thermal emission and reflected flux from the planet’s dayside. We suggest that variation in wind speed in the planetary atmosphere, leading to variable cloud coverage on the dayside and a changing energy balance, is capable of explaining the observed variation.

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Figure 1: Variation in peak offset of HAT-P-7 b phase curve with time.
Figure 2: Individual phase curves, with best-fitting model.
Figure 3: Model outputs giving positive and negative Θ values.
Figure 4: Contour map of Θ variations.

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Acknowledgements

D.J.A. acknowledges funding from the European Union Seventh Framework programme (FP7/2007–2013) under grant agreement No. 313014 (ETAEARTH). E.d.M. acknowledges support from the Michael West Fellowship. This paper includes data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission directorate. All of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts.

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Authors and Affiliations

  1. Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK

    D. J. Armstrong, H. P. Osborn, J. Blake & N. Fereshteh Saniee

  2. ARC, School of Mathematics & Physics, Queen’s University Belfast, University Road, Belfast, BT7 1NN, UK

    D. J. Armstrong & E. de Mooij

  3. Department of Physics and Astronomy, Astrophysics Group, University College London, London, NW1 2PS, UK

    J. Barstow

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Contributions

D.J.A. obtained and detrended the data, developed and fit the phase curve models, implemented the atmospheric model, produced the figures and wrote the manuscript. E.d.M. developed the discussion, contributed to the tests performed to check the results, and tested the results with his own models. H.P.O. contributed to the phase curve model, and produced visual interpretations of the results. J.Ba. developed the discussion of the atmospheric processes behind the peak offset variations. J.Bl. provided the initial development of the phase curve model. N.F.S. contributed to development of the figures. All authors commented on the manuscript.

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Correspondence to D. J. Armstrong.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Information Guide

Captions for Supplementary Table 1, Supplementary Figures 1–9, Supplementary Video 1 and Dataset 1. (PDF 127 kb)

Supplementary Information

Supplementary Table 1, Supplementary Figures 1–9 and description of phase curve model. (PDF 2248 kb)

Supplementary Video 1

HAT-P-7 b dayside visualization. (MP4 1400 kb)

Dataset 1

Table with individual fit values. (CSV 50 kb)

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Armstrong, D., de Mooij, E., Barstow, J. et al. Variability in the atmosphere of the hot giant planet HAT-P-7 b. Nat Astron 1, 0004 (2017). https://doi.org/10.1038/s41550-016-0004

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