CHEOPS geometric albedo of the hot Jupiter HD 209458b

Journal
Date Issued
2022
Author(s)
•
K. Heng
•
M. Lendl
•
J. A. Patel
•
B. M. Morris
•
C. Broeg
•
P. Guterman
•
M. Beck
•
P. F. L. Maxted
•
O. Demangeon
•
L. Delrez
•
B. -O. Demory
•
D. Kitzmann
•
N. C. Santos
•
•
Y. Alibert
•
R. Alonso
•
G. Anglada
•
T. Bárczy
•
D. Barrado y Navascues
•
S. C. C. Barros
•
W. Baumjohann
•
T. Beck
•
W. Benz
•
N. Billot
•
X. Bonfils
•
•
J. Cabrera
•
S. Charnoz
•
A. Collier Cameron
•
C. Corral van Damme
•
Sz. Csizmadia
•
M. B. Davies
•
M. Deleuil
•
A. Deline
•
D. Ehrenreich
•
A. Erikson
•
•
A. Fortier
•
L. Fossati
•
M. Fridlund
•
D. Gandolfi
•
M. Gillon
•
M. Güdel
•
S. Hoyer
•
K. G. Isaak
•
L. Kiss
•
J. Laskar
•
A. Lecavelier des Etangs
•
C. Lovis
•
A. Luntzer
•
•
•
G. Olofsson
•
R. Ottensamer
•
•
E. Pallé
•
G. Peter
•
G. Piotto
•
D. Pollacco
•
D. Queloz
•
•
N. Rando
•
H. Rauer
•
I. Ribas
•
•
D. Ségransan
•
A. E. Simon
•
A. M. S. Smith
•
S. G. Sousa
•
M. Steller
•
Gy. M. Szabó
•
N. Thomas
•
S. Udry
•
V. Van Grootel
•
N. Walton
•
D. Wolter
DOI
Abstract
We report the detection of the secondary eclipse of the hot Jupiter HD 209458b in optical/visible light using the CHEOPS space telescope. Our measurement of 20.4 +/- 3.3 ppm translates into a geometric albedo of A_g = 0.096 +/- 0.016. The previously estimated dayside temperature of about 1500 K implies that our geometric albedo measurement consists predominantly of reflected starlight and is largely uncontaminated by thermal emission. This makes the present result one of the most robust measurements of A_g for any exoplanet. Our calculations of the bandpass-integrated geometric albedo demonstrate that the measured value of A_g is consistent with a cloud-free atmosphere, where starlight is reflected via Rayleigh scattering by hydrogen molecules, and the water and sodium abundances are consistent with stellar metallicity. We predict that the bandpass-integrated TESS geometric albedo is too faint to detect and that a phase curve of HD 209458b observed by CHEOPS would have a distinct shape associated with Rayleigh scattering if the atmosphere is indeed cloud free.
Volume
659
Start page
L4
Uri
Url
Issn Identifier
0004-6361
Rights
open.access
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