The geometric albedo of the hot Jupiter HD 189733b measured with CHEOPS
Artikel i vetenskaplig tidskrift, 2023
Context. Measurements of the occultation of an exoplanet at visible wavelengths allow us to determine the reflective properties of a planetary atmosphere. The observed occultation depth can be translated into a geometric albedo. This in turn aids in characterising the structure and composition of an atmosphere by providing additional information on the wavelength-dependent reflective qualities of the aerosols in the atmosphere. Aims. Our aim is to provide a precise measurement of the geometric albedo of the gas giant HD 189733b by measuring the occultation depth in the broad optical bandpass of CHEOPS (350-1100 nm). Methods. We analysed 13 observations of the occultation of HD 189733b performed by CHEOPS utilising the Python package PyCHEOPS. The resulting occultation depth is then used to infer the geometric albedo accounting for the contribution of thermal emission from the planet. We also aid the analysis by refining the transit parameters combining observations made by the TESS and CHEOPS space telescopes. Results. We report the detection of an 24.7 ± 4.5 ppm occultation in the CHEOPS observations. This occultation depth corresponds to a geometric albedo of 0.076 ± 0.016. Our measurement is consistent with models assuming the atmosphere of the planet to be cloud-free at the scattering level and absorption in the CHEOPS band to be dominated by the resonant Na doublet. Taking into account previous optical-light occultation observations obtained with the Hubble Space Telescope, both measurements combined are consistent with a super-stellar Na elemental abundance in the dayside atmosphere of HD 189733b. We further constrain the planetary Bond albedo to between 0.013 and 0.42 at 3σconfidence. Conclusions. We find that the reflective properties of the HD 189733b dayside atmosphere are consistent with a cloud-free atmosphere having a super-stellar metal content. When compared to an analogous CHEOPS measurement for HD 209458b, our data hint at a slightly lower geometric albedo for HD 189733b (0.076 ± 0.016) than for HD 209458b (0.096 ± 0.016), or a higher atmospheric Na content in the same modelling framework. While our constraint on the Bond albedo is consistent with previously published values, we note that the higher-end values of ∼0.4, as derived previously from infrared phase curves, would also require peculiarly high reflectance in the infrared, which again would make it more difficult to disentangle reflected and emitted light in the total observed flux, and therefore to correctly account for reflected light in the interpretation of those phase curves. Lower reported values for the Bond albedos are less affected by this ambiguity.
Techniques: photometric
Planets and satellites: atmospheres
Planets and satellites: individual: HD 189733b
Författare
A. Krenn
Université de Genève
Institut fur Weltraumforschung
M. Lendl
Université de Genève
J. A. Patel
Stockholms universitet
L. Carone
Institut fur Weltraumforschung
M. Deleuil
Laboratoire d'Astrophysique de Marseille
S. Sulis
Laboratoire d'Astrophysique de Marseille
A. Collier Cameron
University of St Andrews
A. Deline
Université de Genève
P. Guterman
Laboratoire d'Astrophysique de Marseille
Institut National des Sciences de l'Univers
D. Queloz
Eidgenössische Technische Hochschule Zürich (ETH)
University of Cambridge
L. Fossati
Institut fur Weltraumforschung
A. Brandeker
Stockholms universitet
Kevin Heng
Universität Bern
Ludwig-Maximilians-Universität München (LMU)
The University of Warwick
B. Akinsanmi
Université de Genève
V. Adibekyan
Universidade do Porto
A. Bonfanti
Institut fur Weltraumforschung
O. Demangeon
Universidade do Porto
D. Kitzmann
Universität Bern
S. Salmon
Université de Genève
S. G. Sousa
Universidade do Porto
T. G. Wilson
University of St Andrews
Y. Alibert
Universität Bern
R. Alonso
Instituto de Astrofísica de Canarias
Universidad de la Laguna
G. Anglada
Consejo Superior de Investigaciones Científicas (CSIC)
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)
T. Bárczy
Admatis
D. Barrado Navascues
Centro de Astrobiologia (CAB)
S.C.C. Barros
Universidade do Porto
W. Baumjohann
Institut fur Weltraumforschung
M. Beck
Université de Genève
T. Beck
Universität Bern
W. Benz
Universität Bern
N. Billot
Université de Genève
L. Blecha
ALMATECH SA
X. Bonfils
Institut de Planétologie et d’Astrophysique de Grenoble (IPAG)
L. Borsato
Istituto nazionale di astrofisica (INAF)
C. Broeg
Universität Bern
J. Cabrera
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
S. Charnoz
Institut de Physique du Globe de Paris
C. Corral Van Damme
European Space Research and Technology Centre (ESA ESTEC)
Szilard Csizmadia
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
P. E. Cubillos
Istituto nazionale di astrofisica (INAF)
Institut fur Weltraumforschung
M. B. Davies
Lunds universitet
L. Delrez
Universite de Liège
B.O. Demory
Universität Bern
D. Ehrenreich
Université de Genève
Anders Erikson
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
J. Farinato
Istituto nazionale di astrofisica (INAF)
A. Fortier
Universität Bern
Malcolm Fridlund
Universiteit Leiden
Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik
D. Gandolfi
Universita degli Studi di Torino
Michaël Gillon
Universite de Liège
M. Gudel
Universität Wien
S. Hoyer
Laboratoire d'Astrophysique de Marseille
K. Isaak
European Space Research and Technology Centre (ESA ESTEC)
L.L. Kiss
Eötvös Loránd University (ELTE)
Magyar Tudomanyos Akademia
E. Kopp
Technische Universität Berlin
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
Freie Universität Berlin
J. Laskar
Observatoire de Paris
A. L. des Etangs
Institut d 'Astrophysique de Paris
C. Lovis
Université de Genève
D. Magrin
Istituto nazionale di astrofisica (INAF)
P. Maxted
Keele University
C. Mordasini
Universität Bern
Valerio Nascimbeni
Istituto nazionale di astrofisica (INAF)
G. Olofsson
Stockholms universitet
R. Ottensamer
Universität Wien
I. Pagano
Istituto nazionale di astrofisica (INAF)
E. Palle
Instituto de Astrofísica de Canarias
G. Peter
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
Giampaolo P. Piotto
Università di Padova
Istituto nazionale di astrofisica (INAF)
D. Pollacco
The University of Warwick
Roberto Ragazzoni
Università di Padova
Istituto nazionale di astrofisica (INAF)
N. Rando
European Space Research and Technology Centre (ESA ESTEC)
H. Rauer
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
Freie Universität Berlin
Technische Universität Berlin
I. Ribas
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)
Consejo Superior de Investigaciones Científicas (CSIC)
N. C. Santos
Universidade do Porto
Gaetano Scandariato
Istituto nazionale di astrofisica (INAF)
D. Segransan
Université de Genève
A.E. Simon
Universität Bern
A. M.S. Smith
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
Manfred B. Steller
Institut fur Weltraumforschung
Gy M. Szabó
Eötvös Loránd University (ELTE)
N. Thomas
Universität Bern
S. Udry
Université de Genève
B. Ulmer
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
Technische Universität Berlin
Freie Universität Berlin
V. Van Grootel
Universite de Liège
J. Venturini
Université de Genève
N. A. Walton
University of Cambridge
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 672 A24Ämneskategorier (SSIF 2011)
Astronomi, astrofysik och kosmologi
Atom- och molekylfysik och optik
Annan fysik
DOI
10.1051/0004-6361/202245016