techniques: photometric; planets and satellites: atmospheres; planets; and satellites: composition
Abstract :
[en] 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. <BR /> 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. <BR /> 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 We also report the analysis of three unpublished sectors observed by the TESS space telescope (also in the visible), which represents 34 phase curves. <BR /> 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. <BR /> 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. <P />The CHEOPS raw and detrended photometric time-series data used in this paper are available at the CDS via anonymous ftp to <A href="https://cdsarc.cds.unistra.fr">cdsarc.cds.unistra.fr</A> (ftp://130.79.128.5) or via <A href="https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/684/A27">https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/684/A27</A> <P />This study uses CHEOPS data observed as part of the Guaranteed Time Observation (GTO) programmes CH_PR00009, CH_PR00016 and CH_PR00036.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Demangeon, O. D. S.; University of Porto, Center for Astrophysics, University of Porto, Center for Astrophysics
Cubillos, P. E.; Astronomical Observatory of Turin, Austrian Institute of Space Science Research
Singh, V.; Astronomical Observatory of Catania
Wilson, T. G.; University of Warwick, Department of Physics
Carone, L.; Austrian Institute of Space Science Research
Bekkelien, A.; University of Geneva, Astronomical Observatory
Deline, A.; University of Geneva, Astronomical Observatory
Ehrenreich, D.; University of Geneva, Astronomical Observatory, University of Geneva, Switzerland
Maxted, P. F. L.; Keele University, Department of Physics and Astrophysics
Demory, B. -O.; University of Bern, Switzerland, -
Zingales, T.; Astronomical Observatory of Padua, Astronomical Observatory of Padua
Lendl, M.; University of Geneva, Astronomical Observatory
Bonfanti, A.; Austrian Institute of Space Science Research
Sousa, S. G.; University of Porto, Center for Astrophysics
Brandeker, A.; AlbaNova University Center
Alibert, Y.; University of Bern, Switzerland, -
Alonso, R.; Astrophysical Institute of the Canaries, -
Asquier, J.; European Space Research and Technology Centre
Bárczy, T.; Admatis, 5. Kandó Kálmán Street, 3534, Miskolc, Hungary
Navascues, D. Barrado; Depto. de Astrofisica, Centro de Astrobiologia (CSIC-INTA), ESAC campus, 28692, Villanueva de la Cañada (Madrid), Spain
Barros, S. C. C.; University of Porto, Center for Astrophysics, University of Porto, Center for Astrophysics
Baumjohann, W.; Austrian Institute of Space Science Research
Beck, M.; University of Geneva, Astronomical Observatory
Beck, T.; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland
Benz, W.; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland, Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland
Billot, N.; University of Geneva, Astronomical Observatory
Biondi, F.; Astronomical Observatory of Padua, Max-Planck-Institute for Extraterrestrial Physics, Garching
Borsato, L.; Astronomical Observatory of Padua
Broeg, Ch.; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland, Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland
Buder, M.; German Aerospace Center, Berlin
Cameron, A. Collier; Scottish Universities Physics Alliance
Csizmadia, Sz.; Helmholtz Institute for Planetary Research, Berlin
Davies, M. B.; University of Lund, Sweden
Deleuil, M.; Aix-Marseille Universite, Laboratoire d'Astrophysique
Delrez, Laetitia ; Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO) > Exoplanets in Transit: Identification and Characterization
Erikson, A.; Helmholtz Institute for Planetary Research, Berlin
Fortier, A.; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland, Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland
Fossati, L.; Austrian Institute of Space Science Research
Fridlund, M.; Leiden Observatory, Onsala Space Observatory
Gandolfi, D.; University of Turin, Department of Physics
Gillon, Michaël ; Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO)
Güdel, M.; University of Vienna, Department of Astronomy
Günther, M. N.; European Space Research and Technology Centre
Heitzmann, A.; University of Geneva, Astronomical Observatory
Helling, Ch.; Austrian Institute of Space Science Research, Technical University of Graz, Austria
Isaak, K. G.; European Space Research and Technology Centre
Kiss, L. L.; Konkoly Observatory, Eotvos Lorand University, Hungary
Lam, K. W. F.; Helmholtz Institute for Planetary Research, Berlin
Laskar, J.; Observatoire de Paris, Institut de Mecanique Celeste et de Calcul des Ephemerides
des Etangs, A. Lecavelier; Institut d'Astrophysique de Paris
Magrin, D.; Astronomical Observatory of Padua
Mecina, M.; University of Vienna, Department of Astronomy
Mordasini, Ch.; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland, Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland
Nascimbeni, V.; Astronomical Observatory of Padua
Olofsson, G.; AlbaNova University Center
Ottensamer, R.; University of Vienna, Department of Astronomy
Pagano, I.; Astronomical Observatory of Catania
Pallé, E.; Astrophysical Institute of the Canaries, -
Peter, G.; German Aerospace Center, Berlin
Piotto, G.; Astronomical Observatory of Padua, University of Padua, Department of Physics and Astronomy
Pollacco, D.; University of Warwick, Department of Physics
Queloz, D.; ETH Zurich, Department of Physics, Wolfgang-Pauli-Strasse 2, 8093, Zurich, Switzerland, Cavendish Laboratory, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
Ragazzoni, R.; Astronomical Observatory of Padua, University of Padua, Department of Physics and Astronomy
Rando, N.; European Space Research and Technology Centre
Rauer, H.; Helmholtz Institute for Planetary Research, Berlin, Technical University of Berlin, Center for Astronomy and Astrophysics, -
Ribas, I.; Institute of Space Studies, Catalona, Institute of Space Studies, Catalona
Rieder, M.; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland, Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland
Salmon, S.; University of Geneva, Astronomical Observatory
Santos, N. C.; University of Porto, Center for Astrophysics, University of Porto, Center for Astrophysics
Scandariato, G.; Astronomical Observatory of Catania
Ségransan, D.; University of Geneva, Astronomical Observatory
Simon, A. E.; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland, Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland
Smith, A. M. S.; Helmholtz Institute for Planetary Research, Berlin
Stalport, Manu ; Université de Liège - ULiège > Unités de recherche interfacultaires > Space sciences, Technologies and Astrophysics Research (STAR)
Szabó, Gy. M.; Eotvos Lorand University, Hungary, -
Thomas, N.; Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland
Udry, S.; University of Geneva, Astronomical Observatory
Van Grootel, Valérie ; Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Venturini, J.; University of Geneva, Astronomical Observatory
Villaver, E.; Astrophysical Institute of the Canaries, -
Walton, N. A.; University of Cambridge, Institute of Astronomy
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