Towards consistent mapping of distant worlds: secondary-eclipse scanning of the exoplanet HD 189733b
Context. Mapping distant worlds is the next frontier for exoplanet infrared (IR) photometry studies. Ultimately, constraining spatial and temporal properties of an exoplanet atmosphere (e.g., its temperature) will provide further insight into its physics. For tidally-locked hot Jupiters that transit...
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| Format: | Article |
| Language: | en_US |
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EDP Sciences
2014
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| Online Access: | http://hdl.handle.net/1721.1/85855 https://orcid.org/0000-0002-6892-6948 https://orcid.org/0000-0003-2415-2191 |
| _version_ | 1826200134609797120 |
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| author | de Wit, Julien Gillon, M. Demory, Brice-Olivier Seager, Sara |
| author2 | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences |
| author_facet | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences de Wit, Julien Gillon, M. Demory, Brice-Olivier Seager, Sara |
| author_sort | de Wit, Julien |
| collection | MIT |
| description | Context. Mapping distant worlds is the next frontier for exoplanet infrared (IR) photometry studies. Ultimately, constraining spatial and temporal properties of an exoplanet atmosphere (e.g., its temperature) will provide further insight into its physics. For tidally-locked hot Jupiters that transit and are eclipsed by their host star, the first steps are now possible.
Aims. Our aim is to constrain an exoplanet’s (1) shape, (2) brightness distribution (BD) and (3) system parameters from its phase curve and eclipse measurements. In particular, we rely on the secondary-eclipse scanning which is obtained while an exoplanet is gradually masked by its host star.
Methods. We use archived Spitzer/IRAC 8-μm data of HD 189733 (six transits, eight secondary eclipses, and a phase curve) in a global Markov chain Monte Carlo (MCMC) procedure for mitigating systematics. We also include HD 189733’s out-of-transit radial velocity (RV) measurements to assess their incidence on the inferences obtained solely from the photometry.
Results. We find a 6σ deviation from the expected occultation of a uniformly-bright disk. This deviation emerges mainly from a large-scale hot spot in HD 189733b’s atmosphere, not from HD 189733b’s shape. We indicate that the correlation of the exoplanet orbital eccentricity, e, and BD (“uniform time offset”) does also depend on the stellar density, ρ⋆, and the exoplanet impact parameter, b (“e-b-ρ⋆-BD correlation”). For HD 189733b, we find that relaxing the eccentricity constraint and using more complex BDs lead to lower stellar/planetary densities and a more localized and latitudinally-shifted hot spot. We, therefore, show that the light curve of an exoplanet does not constrain uniquely its brightness peak localization. Finally, we obtain an improved constraint on the upper limit of HD 189733b’s orbital eccentricity, e ≤ 0.011 (95% confidence), when including HD 189733’s RV measurements.
Conclusions. Reanalysis of archived HD 189733’s data constrains HD 189733b’s shape and BD at 8 μm. Our study provides new insights into the analysis of exoplanet light curves and a proper framework for future eclipse-scanning observations. In particular, observations of the same exoplanet at different wavelengths could improve the constraints on HD 189733’s system parameters while ultimately yielding a large-scale time-dependent 3D map of HD 189733b’s atmosphere. Finally, we discuss the perspective of extending our method to observations in the visible (e.g., Kepler data), in particular to better understand exoplanet albedos. |
| first_indexed | 2024-09-23T11:31:43Z |
| format | Article |
| id | mit-1721.1/85855 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T11:31:43Z |
| publishDate | 2014 |
| publisher | EDP Sciences |
| record_format | dspace |
| spelling | mit-1721.1/858552022-09-27T20:07:10Z Towards consistent mapping of distant worlds: secondary-eclipse scanning of the exoplanet HD 189733b de Wit, Julien Gillon, M. Demory, Brice-Olivier Seager, Sara Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Massachusetts Institute of Technology. Department of Physics MIT Kavli Institute for Astrophysics and Space Research de Wit, Julien Demory, Brice-Olivier Seager, Sara Context. Mapping distant worlds is the next frontier for exoplanet infrared (IR) photometry studies. Ultimately, constraining spatial and temporal properties of an exoplanet atmosphere (e.g., its temperature) will provide further insight into its physics. For tidally-locked hot Jupiters that transit and are eclipsed by their host star, the first steps are now possible. Aims. Our aim is to constrain an exoplanet’s (1) shape, (2) brightness distribution (BD) and (3) system parameters from its phase curve and eclipse measurements. In particular, we rely on the secondary-eclipse scanning which is obtained while an exoplanet is gradually masked by its host star. Methods. We use archived Spitzer/IRAC 8-μm data of HD 189733 (six transits, eight secondary eclipses, and a phase curve) in a global Markov chain Monte Carlo (MCMC) procedure for mitigating systematics. We also include HD 189733’s out-of-transit radial velocity (RV) measurements to assess their incidence on the inferences obtained solely from the photometry. Results. We find a 6σ deviation from the expected occultation of a uniformly-bright disk. This deviation emerges mainly from a large-scale hot spot in HD 189733b’s atmosphere, not from HD 189733b’s shape. We indicate that the correlation of the exoplanet orbital eccentricity, e, and BD (“uniform time offset”) does also depend on the stellar density, ρ⋆, and the exoplanet impact parameter, b (“e-b-ρ⋆-BD correlation”). For HD 189733b, we find that relaxing the eccentricity constraint and using more complex BDs lead to lower stellar/planetary densities and a more localized and latitudinally-shifted hot spot. We, therefore, show that the light curve of an exoplanet does not constrain uniquely its brightness peak localization. Finally, we obtain an improved constraint on the upper limit of HD 189733b’s orbital eccentricity, e ≤ 0.011 (95% confidence), when including HD 189733’s RV measurements. Conclusions. Reanalysis of archived HD 189733’s data constrains HD 189733b’s shape and BD at 8 μm. Our study provides new insights into the analysis of exoplanet light curves and a proper framework for future eclipse-scanning observations. In particular, observations of the same exoplanet at different wavelengths could improve the constraints on HD 189733’s system parameters while ultimately yielding a large-scale time-dependent 3D map of HD 189733b’s atmosphere. Finally, we discuss the perspective of extending our method to observations in the visible (e.g., Kepler data), in particular to better understand exoplanet albedos. Massachusetts Institute of Technology (Grayce B. Kerr Fund, Inc., fellowship) Wallonie-Bruxelles International (Fellowship) Belgian Senate (ODISSEA Prize) 2014-03-20T19:48:23Z 2014-03-20T19:48:23Z 2012-12 2012-02 Article http://purl.org/eprint/type/JournalArticle 0004-6361 1432-0746 http://hdl.handle.net/1721.1/85855 De Wit, J., M. Gillon, B.-O. Demory, and S. Seager. “Towards Consistent Mapping of Distant Worlds: Secondary-Eclipse Scanning of the Exoplanet HD 189733b.” Astronomy & Astrophysics 548 (December 2012): A128. https://orcid.org/0000-0002-6892-6948 https://orcid.org/0000-0003-2415-2191 en_US http://dx.doi.org/10.1051/0004-6361/201219060 Astronomy & Astrophysics Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf EDP Sciences EDP Sciences |
| spellingShingle | de Wit, Julien Gillon, M. Demory, Brice-Olivier Seager, Sara Towards consistent mapping of distant worlds: secondary-eclipse scanning of the exoplanet HD 189733b |
| title | Towards consistent mapping of distant worlds: secondary-eclipse scanning of the exoplanet HD 189733b |
| title_full | Towards consistent mapping of distant worlds: secondary-eclipse scanning of the exoplanet HD 189733b |
| title_fullStr | Towards consistent mapping of distant worlds: secondary-eclipse scanning of the exoplanet HD 189733b |
| title_full_unstemmed | Towards consistent mapping of distant worlds: secondary-eclipse scanning of the exoplanet HD 189733b |
| title_short | Towards consistent mapping of distant worlds: secondary-eclipse scanning of the exoplanet HD 189733b |
| title_sort | towards consistent mapping of distant worlds secondary eclipse scanning of the exoplanet hd 189733b |
| url | http://hdl.handle.net/1721.1/85855 https://orcid.org/0000-0002-6892-6948 https://orcid.org/0000-0003-2415-2191 |
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