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Detection of a westward hotspot offset in the atmosphere of hot gas giant CoRoT-2b

Nature Astronomy volume 2, pages 220–227 (2018)Cite this article

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Abstract

Short-period planets exhibit day–night temperature contrasts of hundreds to thousands of kelvin. They also exhibit eastward hotspot offsets whereby the hottest region on the planet is east of the substellar point1; this has been widely interpreted as advection of heat due to eastward winds2. We present thermal phase observations of the hot Jupiter CoRoT-2b obtained with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. These measurements show the most robust detection to date of a westward hotspot offset of 23 ± 4°, in contrast with the nine other planets with equivalent measurements3,4,5,6,7,8,9,10. The peculiar infrared flux map of CoRoT-2b may result from westward winds due to non-synchronous rotation11 or magnetic effects12,13, or partial cloud coverage, that obscure the emergent flux from the planet’s eastern hemisphere14,15,16,17. Non-synchronous rotation and magnetic effects may also explain the planet’s anomalously large radius12,18. On the other hand, partial cloud coverage could explain the featureless dayside emission spectrum of the planet19,20. If CoRoT-2b is not tidally locked, then it means that our understanding of star–planet tidal interaction is incomplete. If the westward offset is due to magnetic effects, our result represents an opportunity to study an exoplanet’s magnetic field. If it has eastern clouds, then it means that a greater understanding of large-scale circulation on tidally locked planets is required.

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Fig. 1: Fit model to Spitzer phase observation of CoRoT-2b.
Fig. 2: Surface brightness map of CoRoT-2b.
Fig. 3: Energy budget of CoRoT-2b and other hot Jupiters.
Fig. 4: Dayside emission spectrum of CoRoT-2b.

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References

  1. Knutson, H. A. et al. A map of the day-night contrast of the extrasolar planet HD 189733b. Nature 447, 183–186 (2007).

    Article  ADS  Google Scholar 

  2. Showman, A. P. & Guillot, T. Atmospheric circulation and tides of “51 Pegasus b-like” planets. Astron. Astrophys. 385, 166–180 (2002).

    Article  ADS  Google Scholar 

  3. Cowan, N. B. et al. Thermal phase variations of WASP-12b: defying predictions. Astrophys. J. 747, 82 (2012).

    Article  ADS  Google Scholar 

  4. Knutson, H. A. et al. 3.6 and 4.5 μm phase curves and evidence for non-equilibrium chemistry in the atmosphere of extrasolar planet HD 189733b. Astrophys. J. 754, 22 (2012).

    Article  ADS  Google Scholar 

  5. Maxted, P. F. L. et al. Spitzer 3.6 and 4.5 μm full-orbit light curves of WASP-18. Mon. Not. R. Astron. Soc. 428, 2645–2660 (2013).

    Article  ADS  Google Scholar 

  6. Zellem, R. T. et al. The 4.5 μm full-orbit phase curve of the hot Jupiter HD 209458b. Astrophys. J. 790, 53 (2014).

    Article  ADS  Google Scholar 

  7. Wong, I. et al. 3.6 and 4.5 μm phase curves of the highly irradiated eccentric hot Jupiter WASP-14b. Astrophys. J. 811, 122 (2015).

    Article  ADS  Google Scholar 

  8. Wong, I. et al. 3.6 and 4.5 μm Spitzer phase curves of the highly irradiated hot Jupiters WASP-19b and HAT-P-7b. Astrophys. J. 823, 122 (2016).

    Article  ADS  Google Scholar 

  9. Demory, B.-O., Gillon, M., Madhusudhan, N. & Queloz, D. Variability in the super-Earth 55 Cnc e. Mon. Not. R. Astron. Soc. 455, 2018–2027 (2016).

    Article  ADS  Google Scholar 

  10. Stevenson, K. B. et al. Spitzer phase curve constraints for WASP-43b at 3.6 and 4.5 μm. Astron. J. 153, 68 (2017).

    Article  ADS  Google Scholar 

  11. Rauscher, E. & Kempton, E. M. R. The atmospheric circulation and observable properties of non-synchronously rotating hot Jupiters. Astrophys. J. 790, 79 (2014).

    Article  ADS  Google Scholar 

  12. Rogers, T. M. & Komacek, T. D. Magnetic effects in hot Jupiter atmospheres. Astrophys. J. 794, 132 (2014).

    Article  ADS  Google Scholar 

  13. Rogers, T. M. Constraints on the magnetic field strength of HAT-P-7 b and other hot giant exoplanets. Nat. Astron. 1, 0131 (2017).

    Article  ADS  Google Scholar 

  14. Demory, B.-O. et al. Inference of inhomogeneous clouds in an exoplanet atmosphere. Astrophys. J. Lett. 776, L25 (2013).

    Article  ADS  Google Scholar 

  15. Parmentier, V., Fortney, J. J., Showman, A. P., Morley, C. & Marley, M. S. Transitions in the cloud composition of hot Jupiters. Astrophys. J. 828, 22 (2016).

    Article  ADS  Google Scholar 

  16. Lee, G., Dobbs-Dixon, I., Helling, C., Bognar, K. & Woitke, P. Dynamic mineral clouds on HD 189733b. I. 3D RHD with kinetic, non-equilibrium cloud formation. Astron. Astrophys. 594, A48 (2016).

    Article  ADS  Google Scholar 

  17. Roman, M. & Rauscher, E. Modeling the effects of inhomogeneous aerosols on the hot Jupiter Kepler-7b’s atmospheric circulation. Astrophys. J. 850, 17 (2017).

    Article  ADS  Google Scholar 

  18. Guillot, T. & Havel, M. An analysis of the CoRoT-2 system: a young spotted star and its inflated giant planet. Astron. Astrophys. 527, A20 (2011).

    Article  ADS  Google Scholar 

  19. Moses, J. I., Madhusudhan, N., Visscher, C. & Freedman, R. S. Chemical consequences of the C/O ratio on hot Jupiters: examples from WASP-12b, CoRoT-2b, XO-1b, and HD 189733b. Astrophys. J. 763, 25 (2013).

    Article  ADS  Google Scholar 

  20. Wilkins, A. N. et al. The emergent 1.1–1.7 μm spectrum of the exoplanet CoRoT-2b as measured using the hubble space telescope. Astrophys. J. 783, 113 (2014).

    Article  ADS  Google Scholar 

  21. Alonso, R. et al. The secondary eclipse of the transiting exoplanet CoRoT-2b. Astron. Astrophys. 501, L23–L26 (2009).

    Article  ADS  Google Scholar 

  22. Snellen, I. A. G., de Mooij, E. J. W. & Burrows, A. Bright optical day-side emission from extrasolar planet CoRoT-2b. Astron. Astrophys. 513, A76 (2010).

    Article  Google Scholar 

  23. Alonso, R., Deeg, H. J., Kabath, P. & Rabus, M. Ground-based near-infrared observations of the secondary eclipse of CoRoT-2b. Astron. J. 139, 1481–1485 (2010).

    Article  ADS  Google Scholar 

  24. Gillon, M. et al. The thermal emission of the young and massive planet CoRoT-2b at 4.5 and 8 μm. Astron. Astrophys. 511, A3 (2010).

    Article  Google Scholar 

  25. Deming, D. et al. Warm Spitzer photometry of the transiting exoplanets CoRoT-1 and CoRoT-2 at secondary eclipse. Astrophys. J. 726, 95 (2011).

    Article  ADS  Google Scholar 

  26. Schwartz, J. C. & Cowan, N. B. Balancing the energy budget of short-period giant planets: evidence for reflective clouds and optical absorbers. Mon. Not. R. Astron. Soc. 449, 4192–4203 (2015).

    Article  ADS  Google Scholar 

  27. Delorme, P. et al. In-depth study of moderately young but extremely red, very dusty substellar companion HD206893B. Astron. Astrophys. https://doi.org/10.1051/0004-6361/201731145 (2017).

  28. Rauscher, E. & Kempton, E. M. R. Erratum: “The atmospheric circulation and observable properties of non-synchronously rotating hot Jupiters”. Astrophys. J. 799, 241 (2015).

    Article  ADS  Google Scholar 

  29. Armstrong, D. J. et al. Variability in the atmosphere of the hot giant planet HAT-P-7 b. Nat. Astron. 1, 0004 (2016).

    Article  Google Scholar 

  30. Yadav, R. K. & Thorngren, D. P. Estimating the magnetic field strength in hot Jupiters. Astrophys. J. Lett. 849, L12 (2017).

    Article  ADS  Google Scholar 

  31. Menou, K. Magnetic scaling laws for the atmospheres of hot giant exoplanets. Astrophys. J. 745, 138 (2012).

    Article  ADS  Google Scholar 

  32. Kempton, E. M.-R., Bean, J. L. & Parmentier, V. An observational diagnostic for distinguishing between clouds and haze in hot exoplanet atmospheres. Astrophys. J. Lett. 845, L20 (2017).

    Article  ADS  Google Scholar 

  33. Feng, Y. K. et al. The impact of non-uniform thermal structure on the interpretation of exoplanet emission spectra. Astrophys. J. 829, 52 (2016).

    Article  ADS  Google Scholar 

  34. Arras, P. & Socrates, A. Thermal tides in fluid extrasolar planets. Astrophys. J. 714, 1–12 (2010).

    Article  ADS  Google Scholar 

  35. Alonso, R. et al. Transiting exoplanets from the CoRoT space mission. II. CoRoT-Exo-2b: a transiting planet around an active G star. Astron. Astrophys. 482, L21–L24 (2008).

    Article  ADS  Google Scholar 

  36. Fazio, G. G. et al. The infrared array camera (IRAC) for the Spitzer Space Telescope. Astrophys. J. Suppl. Ser. 154, 10–17 (2004).

    Article  ADS  Google Scholar 

  37. Werner, M. W. et al. The Spitzer Space Telescope mission. Astrophys. J. Suppl. Ser. 154, 1–9 (2004).

    Article  ADS  Google Scholar 

  38. Cabrera, J. et al. Planetary transit candidates in CoRoT-LRc01 field. Astron. Astrophys. 506, 501–517 (2009).

    Article  ADS  Google Scholar 

  39. Skrutskie, M. F., Cutri, R. M. et al. The Two Micron All Sky Survey (2MASS). Astron. J. 131, 1163–1183 (2006)

  40. Kreidberg, L. batman: BAsic Transit Model cAlculatioN in python. Publ. Astron. Soc. Pacific 127, 1161–1165 (2015).

    Article  ADS  Google Scholar 

  41. Mandel, K. & Agol, E. Analytic light curves for planetary transit searches. Astrophys. J. Lett. 580, L171–L175 (2002).

    Article  ADS  Google Scholar 

  42. Schröter, S. et al. The corona and companion of CoRoT-2a. Insights from X-rays and optical spectroscopy. Astron. Astrophys. 532, A3 (2011).

    Article  Google Scholar 

  43. Lanza, A. F. et al. Magnetic activity in the photosphere of CoRoT-Exo-2a. Active longitudes and short-term spot cycle in a young Sun-like star. Astron. Astrophys. 493, 193–200 (2009).

    Article  ADS  Google Scholar 

  44. Cowan, N. B. & Agol, E. Inverting phase functions to map exoplanets. Astrophys. J. Lett. 678, L129 (2008).

    Article  ADS  Google Scholar 

  45. Charbonneau, D. et al. Detection of thermal emission from an extrasolar planet. Astrophys. J. 626, 523–529 (2005).

    Article  ADS  Google Scholar 

  46. Stevenson, K. B. et al. Transit and eclipse analyses of the exoplanet HD 149026b using BLISS mapping. Astrophys. J. 754, 136 (2012).

    Article  ADS  Google Scholar 

  47. Ingalls, J. G. et al. Repeatability and accuracy of exoplanet eclipse depths measured with post-cryogenic spitzer. Astron. J. 152, 44 (2016).

    Article  ADS  Google Scholar 

  48. Schwartz, J. C. & Cowan, N. B. Knot a bad idea: testing BLISS mapping for Spitzer space telescope photometry. Publ. Astron. Soc. Pacific 129, 014001 (2017).

    Article  ADS  Google Scholar 

  49. Deming, D. et al. Spitzer Secondary Eclipses of the Dense, Modestly-irradiated, Giant Exoplanet HAT-P-20b Using Pixel-level Decorrelation. Astrophys. J. 805, 132 (2015).

  50. Benneke, B. et al. Spitzer observations confirm and rescue the habitable-zone super-earth K2-18b for future characterization. Astrophys. J. 834, 187 (2017).

    Article  ADS  Google Scholar 

  51. Foreman-Mackey, D., Hogg, D. W., Lang, D. & Goodman, J. emcee: the MCMC hammer. Publ. Astron. Soc. Pacific 125, 306 (2013).

    Article  ADS  Google Scholar 

  52. Espinoza, N. & Jordán, A. Limb darkening and exoplanets: testing stellar model atmospheres and identifying biases in transit parameters. Mon. Not. R. Astron. Soc. 450, 1879–1899 (2015).

    Article  ADS  Google Scholar 

  53. Kipping, D. M. Efficient, uninformative sampling of limb darkening coefficients for two-parameter laws. Mon. Not. R. Astron. Soc. 435, 2152–2160 (2013).

    Article  ADS  Google Scholar 

  54. Keating, D. & Cowan, N. B. Revisiting the energy budget of WASP-43b: enhanced day-night heat transport. Astrophys. J. Lett. 849, L5 (2017).

    Article  ADS  Google Scholar 

  55. Schwarz, G. et al. Estimating the dimension of a model. Ann. Statistics 6, 461–464 (1978).

    Article  ADS  MathSciNet  MATH  Google Scholar 

  56. Wit, E., Heuvel, E. & Romeijn, J. ‘All models are wrong…’: an introduction to model uncertainty. Stat. Neerl. 66, 217–236 (2012).

    Article  MathSciNet  Google Scholar 

  57. Kass, R. E. & Raftery, A. E. Bayes factors. J. Am. Statistical Assoc. 90, 773–795 (1995).

    Google Scholar 

  58. Zhang, M. et al. Phase curves of WASP-33b and HD 149026b and a new correlation between phase curve offset and irradiation temperature. Preprint at http://arxiv.org/abs/1710.07642 (2017).

  59. Cowan, N. B., Voigt, A. & Abbot, D. S. Thermal phases of Earth-like planets: estimating thermal inertia from eccentricity, obliquity, and diurnal forcing. Astrophys. J. 757, 80 (2012).

    Article  ADS  Google Scholar 

  60. Cowan, N. B. & Agol, E. The statistics of albedo and heat recirculation on hot exoplanets. Astrophys. J. 729, 54 (2011).

    Article  ADS  Google Scholar 

  61. Perez-Becker, D. & Showman, A. P. Atmospheric heat redistribution on hot Jupiters. Astrophys. J. 776, 134 (2013).

    Article  ADS  Google Scholar 

  62. Schwartz, J. C., Kashner, Z., Jovmir, D. & Cowan, N. B. Phase offsets and the energy budgets of hot Jupiters. Astrophys. J. 850, 154 (2017).

  63. STScI Development Team pysynphot Synthetic photometry software package (2013); http://ascl.net/1303.023

  64. Hansen, C. J., Schwartz, J. C. & Cowan, N. B. Features in the broad-band eclipse spectra of exoplanets: signal or noise? Mon. Not. R. Astron. Soc. 444, 3632–3640 (2014).

    Article  ADS  Google Scholar 

  65. Perna, R., Menou, K. & Rauscher, E. Magnetic drag on hot jupiter atmospheric winds. Astrophys. J. 719, 1421–1426 (2010).

    Article  ADS  Google Scholar 

  66. Van der Walt, S., Colbert, C. C. & Varoquaux, G. The NumPy array: a structure for efficient numerical computation. Comp. Sci. Eng. 13, 22–30 (2011).

    Article  Google Scholar 

  67. Astropy Collaboration. Astropy: a community python package for astronomy. Astron. Astrophys. 558, A33 (2013).

    Article  Google Scholar 

  68. Hunter, J. D. Matplotlib: a 2D graphics environment. Comp. Sci. Eng. 9, 90–95 (2007).

    Article  Google Scholar 

  69. Foreman-Mackey, D. corner.py: scatterplot matrices in python. J. Open Source Software 1, 24 (2016).

  70. Pérez, F. & Granger, B. E. IPython: a system for interactive scientific computing. Comp. Sci. Eng. 9, 21–29 (2007).

    Article  Google Scholar 

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Acknowledgements

L.D. thanks S. Carey, J. Ingalls and W. Glaccum from the Spitzer IRAC team for the helpful discussions that contributed to the reduction of the data. Funding for this work was provided in part by the Natural Sciences and Engineering Research Council of Canada (NSERC) discovery grant and the California Institute of Technology’s Infrared Processing and Analysis Center (Caltech/IPAC) Visiting Graduate Research Fellowship. Work by S.S. was funded by the Google Summer of Code programme. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech.

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Authors and Affiliations

  1. Department of Physics, McGill University, Montréal, Québec, Canada

    Lisa Dang, Nicolas B. Cowan & Joel C. Schwartz

  2. McGill Space Institute (MSI), McGill University, Montréal, Québec, Canada

    Lisa Dang, Nicolas B. Cowan & Joel C. Schwartz

  3. Institut de Recherche sur les Exoplanètes (iREx), Université de Montréal, Montréal, Québec, Canada

    Lisa Dang, Nicolas B. Cowan & Joel C. Schwartz

  4. Department of Earth and Planetary Sciences, McGill University, Montréal, Québec, Canada

    Nicolas B. Cowan & Joel C. Schwartz

  5. Department of Astronomy, University of Michigan, Ann Arbor, Michigan, USA

    Emily Rauscher

  6. Division of Physics, Mathematics & Astronomy, California Institute of Technology, Pasadena, California, USA

    Michael Zhang

  7. Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, California, USA

    Heather A. Knutson

  8. School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA

    Michael Line

  9. New York University Abu Dhabi, Abu Dhabi, UAE

    Ian Dobbs-Dixon

  10. Department of Astronomy, University of Maryland, College Park, Maryland, USA

    Drake Deming

  11. Department of Computer Science and Engineering, Amrita Vishwa Vidyapeetham, Amritapuri, Kerala, India

    Sudarsan Sundararajan

  12. Department of Astronomy and Astrophysics, University of California, Santa Cruz, California, USA

    Jonathan J. Fortney

  13. Department of Astronomy & Astrophysics, Pennsylvania State University, University Park, Pennsylvania, USA

    Ming Zhao

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Contributions

L.D. extracted the photometric measurements from the data, detrended the data, developed and fit the phase curve models, led the analysis and wrote the manuscript. N.B.C. is the prinicpal investigator of the successful Spitzer proposal from which we obtained the observations and contributed to the writing of the manuscript. J.C.S. contributed materials to the main text. E.R. contributed to the interpretation for the results and to the discussion. M.Z. and H.A.K. verified the robustness of the analysis and contributed to the interpretation of results. S.S. contributed to the photometric measurements pipeline. J.C.S., E.R., H.A.K., I.D.-D., M.L., D.D., J.J.F. and M.Z. are co-investigators of the successful Spitzer proposal from which we obtained the observations. All authors commented on the manuscript.

Corresponding author

Correspondence to Lisa Dang.

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Supplementary information

Supplementary Information

Supplementary Tables 1–6, Supplementary Figures 1–15, Supplementary text, Supplementary references.

Supplementary Dataset 1

Binned data supporting Supplementary Figure 1.

Supplementary Dataset 2

Full data supporting Supplementary Figure 1.

Supplementary Dataset 3

Data supporting top panel of Supplementary Figure 13.

Supplementary Dataset 4

Data supporting bottom panel of Supplementary Figure 13.

Supplementary Dataset 5

Data supporting Supplementary Figure 4.

Supplementary Dataset 6

Data supporting Supplementary Figure 14.

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Dang, L., Cowan, N.B., Schwartz, J.C. et al. Detection of a westward hotspot offset in the atmosphere of hot gas giant CoRoT-2b. Nat Astron 2, 220–227 (2018). https://doi.org/10.1038/s41550-017-0351-6

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