Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e

P. Molliere; T. Stolker; S. Lacour; G. P.P.L. Otten; J. Shangguan; B. Charnay; T. Molyarova; M. Nowak; Th Henning; G. D. Marleau; D. A. Semenov; E. Van Dishoeck; F. Eisenhauer; P. Garcia; R. Garcia Lopez; J. H. Girard; A. Z. Greenbaum; S. Hinkley; P. Kervella; L. Kreidberg; A. L. Maire; E. Nasedkin; L. Pueyo; I. A.G. Snellen; A. Vigan; J. Wang; P. T. De Zeeuw; A. Zurlo

doi:10.1051/0004-6361/202038325

Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e

P. Molliere^*, T. Stolker, S. Lacour, G. P.P.L. Otten, J. Shangguan, B. Charnay, T. Molyarova, M. Nowak, Th Henning, G. D. Marleau, D. A. Semenov, E. Van Dishoeck, F. Eisenhauer, P. Garcia, R. Garcia Lopez, J. H. Girard, A. Z. Greenbaum, S. Hinkley, P. Kervella, L. KreidbergA. L. Maire, E. Nasedkin, L. Pueyo, I. A.G. Snellen, A. Vigan, J. Wang, P. T. De Zeeuw, A. Zurlo

^*Corresponding author for this work

Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

151 Scopus citations

Abstract

Context. Clouds are ubiquitous in exoplanet atmospheres and they represent a challenge for the model interpretation of their spectra. When generating a large number of model spectra, complex cloud models often prove too costly numerically, whereas more efficient models may be overly simplified. Aims. We aim to constrain the atmospheric properties of the directly imaged planet HR 8799e with a free retrieval approach. Methods. We used our radiative transfer code petitRADTRANS for generating the spectra, which we coupled to the PyMultiNest tool. We added the effect of multiple scattering which is important for treating clouds. Two cloud model parameterizations are tested: the first incorporates the mixing and settling of condensates, the second simply parameterizes the functional form of the opacity. Results. In mock retrievals, using an inadequate cloud model may result in atmospheres that are more isothermal and less cloudy than the input. Applying our framework on observations of HR 8799e made with the GPI, SPHERE, and GRAVITY, we find a cloudy atmosphere governed by disequilibrium chemistry, confirming previous analyses. We retrieve that C/O = 0.60-0.08+0.07. Other models have not yet produced a well constrained C/O value for this planet. The retrieved C/O values of both cloud models are consistent, while leading to different atmospheric structures: either cloudy or more isothermal and less cloudy. Fitting the observations with the self-consistent Exo-REM model leads to comparable results, without constraining C/O. Conclusions. With data from the most sensitive instruments, retrieval analyses of directly imaged planets are possible. The inferred C/O ratio of HR 8799e is independent of the cloud model and thus appears to be a robust. This C/O is consistent with stellar, which could indicate that the HR 8799e formed outside the CO2 or CO iceline. As it is the innermost planet of the system, this constraint could apply to all HR 8799 planets.

Original language	English (US)
Article number	A131
Journal	Astronomy and Astrophysics
Volume	640
DOIs	https://doi.org/10.1051/0004-6361/202038325
State	Published - Aug 1 2020

Funding

Acknowledgements. We would like to thank Joanna Barstow for a thorough referee report, which greatly improved the quality of this paper. We also thank the A&A editor, Emmanuel Lellouch, for additional comments. P.M. thanks M. Line, J. Zalesky, and M. Min for insightful discussions. P.M. acknowledges support from the European Research Council under the European Union\u2019s Horizon 2020 research and innovation program under grant agreement No. 832428. T.S. acknowledges the support from the ETH Zurich Postdoctoral Fellowship Program. G.-D.M. acknowledges the support of the DFG priority program SPP 1992 \u201CExploring the Diversity of Extrasolar Planets\u201D (KU 2849/7-1) and from the Swiss National Science Foundation under grant BSSGI0_155816 \u201CPlanetsIn-Time\u201D. Part of this work has been carried out within the framework of the National Centre of Competence in Research PlanetS supported by the Swiss National Science Foundation. A.V. and. G.O. acknowledge funding from the European Research Council (ERC) under the European Union\u2019s Horizon 2020 research and innovation programme (grant agreement No. 757561). I.S. acknowledges funding from the European Research Council (ERC) under the European Union\u2019s Horizon 2020 research and innovation program under grant agreement No 694513. P.G. was supported by Funda\u00E7\u00E3o para a Ci\u00EAncia e a Tecnologia, with grants reference UIDB/00099/2020 and SFRH/BSAB/142940/2018. T.M. acknowledges support by the grant from the Government of the Russian Federation 075-15-2019-1875, \u201CStudy of stars with exoplanets\u201D. D.S. acknowledges support by the Deutsche Forschungsgemeinschaft through SPP 1833: \u201CBuilding a Habitable Earth\u201D (SE 1962/6-1). A.Z. acknowledges support from the FONDE-CYT Iniciaci\u00F3n en investigaci\u00F3n project number 11190837. R.G.L. acknowledge support by Science Foundation Ireland under Grant No. 18/SIRG/559. This work benefited from the 2019 Exoplanet Summer Program in the Other Worlds Laboratory (OWL) at the University of California, Santa Cruz, a program funded by the Heising-Simons Foundation. We also thank the A&A editor, Emmanuel Lellouch, for additional comments. P.M. thanks M. Line, J. Zalesky, and M. Min for insightful discussions. P.M. acknowledges support from the European Research Council under the European Union?s Horizon 2020 research and innovation program under grant agreement No. 832428. T.S. acknowledges the support from the ETH Zurich Postdoctoral Fellowship Program. G.-D.M. acknowledges the support of the DFG priority program SPP 1992 ?Exploring the Diversity of Extrasolar Planets? (KU 2849/7-1) and from the Swiss National Science Foundation under grant BSSGI0_155816 ?PlanetsIn- Time?. Part of this work has been carried out within the framework of the National Centre of Competence in Research PlanetS supported by the Swiss National Science Foundation. A.V. and. G.O. acknowledge funding from the European Research Council (ERC) under the European Union?s Horizon 2020 research and innovation programme (grant agreement No. 757561). I.S. acknowledges funding from the European Research Council (ERC) under the European Union?s Horizon 2020 research and innovation program under grant agreement No 694513. P.G. was supported by Funda??o para a Ci?ncia e a Tecnologia, with grants reference UIDB/00099/2020 and SFRH/BSAB/142940/2018. T.M. acknowledges support by the grant from the Government of the Russian Federation 075-15-2019-1875, ?Study of stars with exoplanets?. D.S. acknowledges support by the Deutsche Forschungsgemeinschaft through SPP 1833: ?Building a Habitable Earth? (SE 1962/6-1). A.Z. acknowledges support from the FONDECYT Iniciaci?n en investigaci?n project number 11190837. R.G.L. acknowledge support by Science Foundation Ireland under Grant No. 18/SIRG/559. This work benefited from the 2019 Exoplanet Summer Program in the Other Worlds Laboratory (OWL) at the University of California, Santa Cruz, a program funded by the Heising-Simons Foundation.

Keywords

Instrumentation: spectrographs
Methods: numerical
Planets and satellites: atmospheres
Radiative transfer

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1051/0004-6361/202038325

Cite this

Molliere, P., Stolker, T., Lacour, S., Otten, G. P. P. L., Shangguan, J., Charnay, B., Molyarova, T., Nowak, M., Henning, T., Marleau, G. D., Semenov, D. A., Van Dishoeck, E., Eisenhauer, F., Garcia, P., Garcia Lopez, R., Girard, J. H., Greenbaum, A. Z., Hinkley, S., Kervella, P., ... Zurlo, A. (2020). Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e. Astronomy and Astrophysics, 640, Article A131. https://doi.org/10.1051/0004-6361/202038325

@article{b7b06517e55d413a87741f9a23e6cfe2,

title = "Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e",

abstract = "Context. Clouds are ubiquitous in exoplanet atmospheres and they represent a challenge for the model interpretation of their spectra. When generating a large number of model spectra, complex cloud models often prove too costly numerically, whereas more efficient models may be overly simplified. Aims. We aim to constrain the atmospheric properties of the directly imaged planet HR 8799e with a free retrieval approach. Methods. We used our radiative transfer code petitRADTRANS for generating the spectra, which we coupled to the PyMultiNest tool. We added the effect of multiple scattering which is important for treating clouds. Two cloud model parameterizations are tested: the first incorporates the mixing and settling of condensates, the second simply parameterizes the functional form of the opacity. Results. In mock retrievals, using an inadequate cloud model may result in atmospheres that are more isothermal and less cloudy than the input. Applying our framework on observations of HR 8799e made with the GPI, SPHERE, and GRAVITY, we find a cloudy atmosphere governed by disequilibrium chemistry, confirming previous analyses. We retrieve that C/O = 0.60-0.08+0.07. Other models have not yet produced a well constrained C/O value for this planet. The retrieved C/O values of both cloud models are consistent, while leading to different atmospheric structures: either cloudy or more isothermal and less cloudy. Fitting the observations with the self-consistent Exo-REM model leads to comparable results, without constraining C/O. Conclusions. With data from the most sensitive instruments, retrieval analyses of directly imaged planets are possible. The inferred C/O ratio of HR 8799e is independent of the cloud model and thus appears to be a robust. This C/O is consistent with stellar, which could indicate that the HR 8799e formed outside the CO2 or CO iceline. As it is the innermost planet of the system, this constraint could apply to all HR 8799 planets.",

keywords = "Instrumentation: spectrographs, Methods: numerical, Planets and satellites: atmospheres, Radiative transfer",

author = "P. Molliere and T. Stolker and S. Lacour and Otten, {G. P.P.L.} and J. Shangguan and B. Charnay and T. Molyarova and M. Nowak and Th Henning and Marleau, {G. D.} and Semenov, {D. A.} and {Van Dishoeck}, E. and F. Eisenhauer and P. Garcia and {Garcia Lopez}, R. and Girard, {J. H.} and Greenbaum, {A. Z.} and S. Hinkley and P. Kervella and L. Kreidberg and Maire, {A. L.} and E. Nasedkin and L. Pueyo and Snellen, {I. A.G.} and A. Vigan and J. Wang and {De Zeeuw}, {P. T.} and A. Zurlo",

note = "Publisher Copyright: {\textcopyright} P. Molli{\`e}re et al. 2020.",

year = "2020",

month = aug,

day = "1",

doi = "10.1051/0004-6361/202038325",

language = "English (US)",

volume = "640",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

}

Molliere, P, Stolker, T, Lacour, S, Otten, GPPL, Shangguan, J, Charnay, B, Molyarova, T, Nowak, M, Henning, T, Marleau, GD, Semenov, DA, Van Dishoeck, E, Eisenhauer, F, Garcia, P, Garcia Lopez, R, Girard, JH, Greenbaum, AZ, Hinkley, S, Kervella, P, Kreidberg, L, Maire, AL, Nasedkin, E, Pueyo, L, Snellen, IAG, Vigan, A, Wang, J, De Zeeuw, PT & Zurlo, A 2020, 'Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e', Astronomy and Astrophysics, vol. 640, A131. https://doi.org/10.1051/0004-6361/202038325

TY - JOUR

T1 - Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e

AU - Molliere, P.

AU - Stolker, T.

AU - Lacour, S.

AU - Otten, G. P.P.L.

AU - Shangguan, J.

AU - Charnay, B.

AU - Molyarova, T.

AU - Nowak, M.

AU - Henning, Th

AU - Marleau, G. D.

AU - Semenov, D. A.

AU - Van Dishoeck, E.

AU - Eisenhauer, F.

AU - Garcia, P.

AU - Garcia Lopez, R.

AU - Girard, J. H.

AU - Greenbaum, A. Z.

AU - Hinkley, S.

AU - Kervella, P.

AU - Kreidberg, L.

AU - Maire, A. L.

AU - Nasedkin, E.

AU - Pueyo, L.

AU - Snellen, I. A.G.

AU - Vigan, A.

AU - Wang, J.

AU - De Zeeuw, P. T.

AU - Zurlo, A.

PY - 2020/8/1

Y1 - 2020/8/1

N2 - Context. Clouds are ubiquitous in exoplanet atmospheres and they represent a challenge for the model interpretation of their spectra. When generating a large number of model spectra, complex cloud models often prove too costly numerically, whereas more efficient models may be overly simplified. Aims. We aim to constrain the atmospheric properties of the directly imaged planet HR 8799e with a free retrieval approach. Methods. We used our radiative transfer code petitRADTRANS for generating the spectra, which we coupled to the PyMultiNest tool. We added the effect of multiple scattering which is important for treating clouds. Two cloud model parameterizations are tested: the first incorporates the mixing and settling of condensates, the second simply parameterizes the functional form of the opacity. Results. In mock retrievals, using an inadequate cloud model may result in atmospheres that are more isothermal and less cloudy than the input. Applying our framework on observations of HR 8799e made with the GPI, SPHERE, and GRAVITY, we find a cloudy atmosphere governed by disequilibrium chemistry, confirming previous analyses. We retrieve that C/O = 0.60-0.08+0.07. Other models have not yet produced a well constrained C/O value for this planet. The retrieved C/O values of both cloud models are consistent, while leading to different atmospheric structures: either cloudy or more isothermal and less cloudy. Fitting the observations with the self-consistent Exo-REM model leads to comparable results, without constraining C/O. Conclusions. With data from the most sensitive instruments, retrieval analyses of directly imaged planets are possible. The inferred C/O ratio of HR 8799e is independent of the cloud model and thus appears to be a robust. This C/O is consistent with stellar, which could indicate that the HR 8799e formed outside the CO2 or CO iceline. As it is the innermost planet of the system, this constraint could apply to all HR 8799 planets.

AB - Context. Clouds are ubiquitous in exoplanet atmospheres and they represent a challenge for the model interpretation of their spectra. When generating a large number of model spectra, complex cloud models often prove too costly numerically, whereas more efficient models may be overly simplified. Aims. We aim to constrain the atmospheric properties of the directly imaged planet HR 8799e with a free retrieval approach. Methods. We used our radiative transfer code petitRADTRANS for generating the spectra, which we coupled to the PyMultiNest tool. We added the effect of multiple scattering which is important for treating clouds. Two cloud model parameterizations are tested: the first incorporates the mixing and settling of condensates, the second simply parameterizes the functional form of the opacity. Results. In mock retrievals, using an inadequate cloud model may result in atmospheres that are more isothermal and less cloudy than the input. Applying our framework on observations of HR 8799e made with the GPI, SPHERE, and GRAVITY, we find a cloudy atmosphere governed by disequilibrium chemistry, confirming previous analyses. We retrieve that C/O = 0.60-0.08+0.07. Other models have not yet produced a well constrained C/O value for this planet. The retrieved C/O values of both cloud models are consistent, while leading to different atmospheric structures: either cloudy or more isothermal and less cloudy. Fitting the observations with the self-consistent Exo-REM model leads to comparable results, without constraining C/O. Conclusions. With data from the most sensitive instruments, retrieval analyses of directly imaged planets are possible. The inferred C/O ratio of HR 8799e is independent of the cloud model and thus appears to be a robust. This C/O is consistent with stellar, which could indicate that the HR 8799e formed outside the CO2 or CO iceline. As it is the innermost planet of the system, this constraint could apply to all HR 8799 planets.

KW - Instrumentation: spectrographs

KW - Methods: numerical

KW - Planets and satellites: atmospheres

KW - Radiative transfer

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U2 - 10.1051/0004-6361/202038325

DO - 10.1051/0004-6361/202038325

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SN - 0004-6361

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JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

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ER -

Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e

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