Asymmetry in the atmosphere of the ultra-hot Jupiter WASP-76 b***
Artikel i vetenskaplig tidskrift, 2024
Context.
WASP-76 b has been a recurrent subject of study since the detection of a signature in high-resolution transit spectroscopy data indicating an asymmetry between the two limbs of the planet. The existence of this asymmetric signature has been confirmed by multiple studies, but its physical origin is still under debate. In addition, it contrasts with the absence of asymmetry reported in the infrared (IR) phase curve.
Aims.
We provide a more comprehensive dataset of WASP-76 b with the goal of drawing a complete view of the physical processes at work in this atmosphere. In particular, we attempt to reconcile visible high-resolution transit spectroscopy data and IR broadband phase curves. Methods. We gathered 3 phase curves, 20 occultations, and 6 transits for WASP-76 b in the visible with the CHEOPS space telescope. We also report the analysis of three unpublished sectors observed by the TESS space telescope (also in the visible), which represents 34 phase curves.
Results.
WASP-76 b displays an occultation of 260 ± 11 and 152 ± 10 ppm in TESS and CHEOPS bandpasses respectively. Depending on the composition assumed for the atmosphere and the data reduction used for the IR data, we derived geometric albedo estimates that range from 0.05 ± 0.023 to 0.146 ± 0.013 and from <0.13 to 0.189 ± 0.017 in the CHEOPS and TESS bandpasses, respectively. As expected from the IR phase curves, a low-order model of the phase curves does not yield any detectable asymmetry in the visible either. However, an empirical model allowing for sharper phase curve variations offers a hint of a flux excess before the occultation, with an amplitude of ∼40 ppm, an orbital offset of ∼−30◦, and a width of ∼20◦. We also constrained the orbital eccentricity of WASP-76 b to a value lower than 0.0067, with a 99.7% confidence level. This result contradicts earlier proposed scenarios aimed at explaining the asymmetry observed in high-resolution transit spectroscopy.
Conclusions.
In light of these findings, we hypothesise that WASP-76 b could have night-side clouds that extend predominantly towards its eastern limb. At this limb, the clouds would be associated with spherical droplets or spherically shaped aerosols of an unknown species, which would be responsible for a glory effect in the visible phase curves.
WASP-76 b has been a recurrent subject of study since the detection of a signature in high-resolution transit spectroscopy data indicating an asymmetry between the two limbs of the planet. The existence of this asymmetric signature has been confirmed by multiple studies, but its physical origin is still under debate. In addition, it contrasts with the absence of asymmetry reported in the infrared (IR) phase curve.
Aims.
We provide a more comprehensive dataset of WASP-76 b with the goal of drawing a complete view of the physical processes at work in this atmosphere. In particular, we attempt to reconcile visible high-resolution transit spectroscopy data and IR broadband phase curves. Methods. We gathered 3 phase curves, 20 occultations, and 6 transits for WASP-76 b in the visible with the CHEOPS space telescope. We also report the analysis of three unpublished sectors observed by the TESS space telescope (also in the visible), which represents 34 phase curves.
Results.
WASP-76 b displays an occultation of 260 ± 11 and 152 ± 10 ppm in TESS and CHEOPS bandpasses respectively. Depending on the composition assumed for the atmosphere and the data reduction used for the IR data, we derived geometric albedo estimates that range from 0.05 ± 0.023 to 0.146 ± 0.013 and from <0.13 to 0.189 ± 0.017 in the CHEOPS and TESS bandpasses, respectively. As expected from the IR phase curves, a low-order model of the phase curves does not yield any detectable asymmetry in the visible either. However, an empirical model allowing for sharper phase curve variations offers a hint of a flux excess before the occultation, with an amplitude of ∼40 ppm, an orbital offset of ∼−30◦, and a width of ∼20◦. We also constrained the orbital eccentricity of WASP-76 b to a value lower than 0.0067, with a 99.7% confidence level. This result contradicts earlier proposed scenarios aimed at explaining the asymmetry observed in high-resolution transit spectroscopy.
Conclusions.
In light of these findings, we hypothesise that WASP-76 b could have night-side clouds that extend predominantly towards its eastern limb. At this limb, the clouds would be associated with spherical droplets or spherically shaped aerosols of an unknown species, which would be responsible for a glory effect in the visible phase curves.
planets and satellites: atmospheres
planets
satellites: composition
techniques: photometric
Författare
O. Demangeon
Universidade do Porto
P. E. Cubillos
Istituto nazionale di astrofisica (INAF)
Institut fur Weltraumforschung
V. Singh
Istituto nazionale di astrofisica (INAF)
T.G. Wilson
The University of Warwick
L. Carone
Institut fur Weltraumforschung
A. Bekkelien
Université de Genève
A. Deline
Université de Genève
D. Ehrenreich
Université de Genève
P. Maxted
Keele University
B.O. Demory
Universität Bern
Tiziano Zingales
Istituto nazionale di astrofisica (INAF)
Università di Padova
M. Lendl
Université de Genève
A. Bonfanti
Institut fur Weltraumforschung
S. G. Sousa
Universidade do Porto
A. Brandeker
Stockholms universitet
Y. Alibert
Universität Bern
R. Alonso
Universidad de la Laguna
Instituto de Astrofísica de Canarias
J. Asquier
European Space Research and Technology Centre (ESA ESTEC)
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
F. Biondi
Istituto nazionale di astrofisica (INAF)
Max-Planck-Gesellschaft
L. Borsato
Istituto nazionale di astrofisica (INAF)
C. Broeg
Universität Bern
M. Buder
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
A. Collier Cameron
University of St Andrews
Szilard Csizmadia
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
M. B. Davies
Lunds universitet
M. Deleuil
Laboratoire d'Astrophysique de Marseille
L. Delrez
Universite de Liège
Anders Erikson
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
A. Fortier
Universität Bern
L. Fossati
Institut fur Weltraumforschung
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
Maximilian N. Günther
European Space Research and Technology Centre (ESA ESTEC)
A. Heitzmann
Université de Genève
Ch. Helling
Institut fur Weltraumforschung
Technische Universität Graz
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
K. W.F. Lam
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
J. Laskar
Observatoire de Paris
A. L. des Etangs
Institut d 'Astrophysique de Paris
D. Magrin
Istituto nazionale di astrofisica (INAF)
M. Mecina
Universität Wien
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)
Enric Palle
Universidad de la Laguna
Instituto de Astrofísica de Canarias
G. Peter
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
Giampaolo P. Piotto
Istituto nazionale di astrofisica (INAF)
Università di Padova
D. Pollacco
The University of Warwick
D. Queloz
Eidgenössische Technische Hochschule Zürich (ETH)
University of Cambridge
R. Ragazzoni
Istituto nazionale di astrofisica (INAF)
Università di Padova
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
Institut d'Estudis Espacials de Catalunya (IEEC)
Institut de Ciències de l'Espai (ICE) - CSIC
M. Rieder
Universität Bern
S. Salmon
Université de Genève
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)
M. Stalport
Universite de Liège
G.M. Szabó
HUN-REN-ELTE Exoplanet Research Group
Eötvös Loránd University (ELTE)
Nicolas Thomas
Universität Bern
S. Udry
Université de Genève
V. Van Grootel
Universite de Liège
J. Venturini
Université de Genève
E. Villaver
Instituto de Astrofísica de Canarias
Universidad de la Laguna
N. A. Walton
University of Cambridge
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 684 A27Ämneskategorier
Astronomi, astrofysik och kosmologi
Infrastruktur
Onsala rymdobservatorium
DOI
10.1051/0004-6361/202348270