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Asymmetry in the atmosphere of the ultra-hot Jupiter WASP-76 b

Demangeon, O. D. S.; Cubillos, P. E.; Singh, V.; Wilson, T. G.; Carone, L.; Bekkelien, A.; Deline, A.; Ehrenreich, D.; Maxted, P. F. L.; Demory, B.-O.; Zingales, T.; Lendl, M.; Bonfanti, A.; Sousa, S. G.; Brandeker, A.; Alibert, Y.; Alonso, R.; Asquier, J.; Bárczy, T.; Navascues, D. Barrado; Barros, S. C. C.; Baumjohann, W.; Beck, M.; Beck, T.; Benz, W.; Billot, N.; Biondi, F.; Borsato, L.; Broeg, Ch.; Buder, M.; Cameron, A. Collier; Csizmadia, Sz.; Davies, M. B.; Deleuil, M.; Delrez, L.; Erikson, A.; Fortier, A.; Fossati, L.; Fridlund, M.; Gandolfi, D.; Gillon, M.; Güdel, M.; Günther, M. N.; Heitzmann, A.; Helling, Ch.; Hoyer, S.; Isaak, K. G.; Kiss, L. L.; Lam, K. W. F.; Laskar, J.; des Etangs, A. Lecavelier; Magrin, D.; Mecina, M.; Mordasini, Ch.; Nascimbeni, V.; Olofsson, G.; Ottensamer, R.; Pagano, I.; Pallé, E.; Peter, G.; Piotto, G.; Pollacco, D.; Queloz, D.; Ragazzoni, R.; Rando, N.; Rauer, H.; Ribas, I.; Rieder, M.; Salmon, S.; Santos, N. C.; Scandariato, G.; Ségransan, D.; Si...

Authors

O. D. S. Demangeon

P. E. Cubillos

V. Singh

T. G. Wilson

L. Carone

A. Bekkelien

A. Deline

D. Ehrenreich

B.-O. Demory

T. Zingales

M. Lendl

A. Bonfanti

S. G. Sousa

A. Brandeker

Y. Alibert

R. Alonso

J. Asquier

T. Bárczy

D. Barrado Navascues

S. C. C. Barros

W. Baumjohann

M. Beck

T. Beck

W. Benz

N. Billot

F. Biondi

L. Borsato

Ch. Broeg

M. Buder

A. Collier Cameron

Sz. Csizmadia

M. B. Davies

M. Deleuil

L. Delrez

A. Erikson

A. Fortier

L. Fossati

M. Fridlund

D. Gandolfi

M. Gillon

M. Güdel

M. N. Günther

A. Heitzmann

Ch. Helling

S. Hoyer

K. G. Isaak

L. L. Kiss

K. W. F. Lam

J. Laskar

A. Lecavelier des Etangs

D. Magrin

M. Mecina

Ch. Mordasini

V. Nascimbeni

G. Olofsson

R. Ottensamer

I. Pagano

E. Pallé

G. Peter

G. Piotto

D. Pollacco

D. Queloz

R. Ragazzoni

N. Rando

H. Rauer

I. Ribas

M. Rieder

S. Salmon

N. C. Santos

G. Scandariato

D. Ségransan

A. E. Simon

A. M. S. Smith

M. Stalport

Gy. M. Szabó

N. Thomas

S. Udry

V. Van Grootel

J. Venturini

E. Villaver

N. A. Walton



Abstract

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 ~20º. 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.

Citation

Demangeon, O. D. S., Cubillos, P. E., Singh, V., Wilson, T. G., Carone, L., Bekkelien, A., …Walton, N. A. (2024). Asymmetry in the atmosphere of the ultra-hot Jupiter WASP-76 b. Astronomy & Astrophysics, 684, Article A27. https://doi.org/10.1051/0004-6361/202348270

Journal Article Type Article
Acceptance Date Jan 16, 2024
Online Publication Date Apr 5, 2024
Publication Date 2024-04
Deposit Date Jun 3, 2024
Journal Astronomy & Astrophysics
Print ISSN 0004-6361
Electronic ISSN 1432-0746
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 684
Article Number A27
DOI https://doi.org/10.1051/0004-6361/202348270
Public URL https://keele-repository.worktribe.com/output/845256