Eclipse Mapping with MIRI: 2D Map of HD 189733b from 8 μm JWST MIRI LRS Observations

Creators: Lally, Maura¹; Challener, Ryan C.¹; Lewis, Nikole K.¹; Inglis, Julie²; Kataria, Tiffany³; Knutson, Heather A.²; Kilpatrick, Brian M.⁴; Batalha, Natasha E.⁵; Bonney, Paul³; Crossfield, Ian J. M.⁶; Foote, Trevor¹; Henry, Gregory W.⁷; Sing, David K.⁸; Stevenson, Kevin B.⁹; Wakeford, Hannah R.¹⁰; Zellem, Robert T.¹¹

1. Cornell University
2. California Institute of Technology
3. Jet Propulsion Lab
4. National Nuclear Security Administration
5. Ames Research Center
6. University of Kansas
7. Tennessee State University
8. Johns Hopkins University
9. Johns Hopkins University Applied Physics Laboratory
10. University of Bristol
11. Goddard Space Flight Center

Abstract

Observations and models of transiting hot Jupiter exoplanets indicate that atmospheric circulation features may cause large spatial flux contrasts across their daysides. Previous studies have mapped these spatial flux variations through inversion of secondary eclipse data. Though eclipse mapping requires high signal-to-noise data, the first successful eclipse map—made for HD 189733b using 8 μm Spitzer IRAC data—showed the promise of the method. JWST eclipse observations provide the requisite data quality to access the unique advantages of eclipse mapping. Using two JWST MIRI low-resolution spectroscopy eclipse observations centered on 8 μm to mimic the Spitzer bandpass used in previous studies, combined with the Spitzer IRAC 8 μm eclipses and partial phase curve (necessitated to disentangle map and systematic signals), we present a two-dimensional dayside temperature map. Our best-fit model is a two-component fifth-degree harmonic model with an unprecedentedly constrained eastward hotspot offset of 33.0_(−0.9)^(+0.7) deg. We rule out a strong hemispheric latitudinal hotspot offset, as three + component maps providing latitudinal degrees of freedom are strongly disfavored. As in previous studies, we find some model dependence in longitudinal hotspot offset; when we explore and combine a range of proximal models to avoid an overly constrained confidence region, we find an eastward hotspot offset of 32.5_(−10.6)^(+3.0) deg, indicating the presence of a strong eastward zonal jet. Our map is consistent with some previous eclipse maps of HD 189733b, though it indicates a higher longitudinal offset from others. It is largely consistent with predictions from general circulation models at the 115 mbar level near the 8 μm photosphere.

Copyright and License

Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under grant No. DGE - 2139899. This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with the program JWST-GO-2021 (PI Kilpatrick). Support for program JWST-GO-2021 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127. This research has made use of NASA's Astrophysics Data System and the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. We thank E. Agol and N. Cowan for the Spitzer eclipse and phase curve data used in this paper. We thank the referee for their constructive feedback, which strengthened this paper. Data products from this paper will be available in this Zenodo repository doi:10.5281/zenodo.15103478.

Facilities

JWST (MIRI LRS) - , Spitzer (IRAC) - .

Software References

NumPy (T. E. Oliphant 2006), matplotlib (J. D. Hunter 2007), astropy (A. M. Price-Whelan et al. 2018), SciPy (P. Virtanen et al. 2020), ThERESA (R. C. Challener & E. Rauscher 2022), mc3 (P. Cubillos et al. 2017), starry (R. Luger et al. 2019).

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