Volume 658, February 2022
|Number of page(s)||26|
|Section||Planets and planetary systems|
|Published online||02 February 2022|
Spi-OPS: Spitzer and CHEOPS confirm the near-polar orbit of MASCARA-1 b and reveal a hint of dayside reflection★
Physikalisches Institut, University of Bern,
2 Aix Marseille Univ, CNRS, CNES, LAM, 38 rue Frédéric Joliot-Curie, 13388 Marseille, France
3 Center for Space and Habitability, Gesellsschaftstrasse 6, 3012 Bern, Switzerland
4 Institute of Planetary Research, German Aerospace Center (DLR), Rutherfordstrasse 2, 12489 Berlin, Germany
5 Centre for Exoplanet Science, SUPA School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
6 Observatoire Astronomique de l’Université de Genève, Chemin Pegasi 51, Versoix, Switzerland
7 Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
8 Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, UK
9 Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
10 Instituto de Astrofisica de Canarias, 38200 La Laguna, Tenerife, Spain
11 Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, A-8042 Graz, Austria
12 Department of Astronomy, Stockholm University, AlbaNova University Center, 10691 Stockholm, Sweden
13 Instituto de Astrofisica e Ciencias do Espaco, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
14 Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
15 Department of Space, Earth and Environment, Onsala Space Observatory, Chalmers University of Technology, 439 92 Onsala, Sweden
16 INAF, Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
17 Departamento de Astrofisica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
18 Institut de Ciencies de l’Espai (ICE, CSIC), Campus UAB, Can Magrans s/n, 08193 Bellaterra, Spain
19 Institut d’Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain
20 Admatis, 5. Kandó Kálmán Street, 3534 Miskolc, Hungary
21 Depto. de Astrofisica, Centro de Astrobiologia (CSIC-INTA), ESAC campus, 28692 Villanueva de la Cañada (Madrid), Spain
22 Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
23 Université de Paris, Institut de physique du globe de Paris, CNRS, 75005 Paris, France
24 Centre for Mathematical Sciences, Lund University, Box 118, 22100 Lund, Sweden
25 Astrobiology Research Unit, Université de Liège, Allée du 6 Août 19C, 4000 Liège, Belgium
26 Space sciences, Technologies and Astrophysics Research (STAR) Institute, Université de Liège, Allée du 6 Août 19C, 4000 Liège, Belgium
27 INAF, Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
28 Leiden Observatory, University of Leiden, PO Box 9513, 2300 RA Leiden, The Netherlands
29 Department of Space, Earth and Environment, Onsala space observatory, Chalmers University of Technology, 439 92 Onsala, Sweden
30 Dipartimento di Fisica, Universita degli Studi di Torino, via Pietro Giuria 1, 10125, Torino, Italy
31 University of Vienna, Department of Astrophysics, Türkenschanzstrasse 17, 1180 Vienna, Austria
32 Science and Operations Department – Science Division (SCI-SC), Directorate of Science, European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Keplerlaan 1, 2201-AZ Noordwijk, The Netherlands
33 Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, 1121 Budapest, Konkoly Thege Miklós út 15–17, Hungary
34 ELTE Eötvös Loránd University, Institute of Physics, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary
35 Sydney Institute for Astronomy, School of Physics A29, University of Sydney, NSW 2006, Australia
36 IMCCE, UMR8028 CNRS, Observatoire de Paris, PSL Univ., Sorbonne Univ., 77 av. Denfert-Rochereau, 75014 Paris, France
37 Institut d’astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, 98bis bvd. Arago, 75014 Paris, France
38 Department of Astrophysics, University of Vienna, Tuerkenschanzstrasse 17, 1180 Vienna, Austria
39 INAF, Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
40 Institute of Optical Sensor Systems, German Aerospace Center (DLR), Rutherfordstrasse 2, 12489 Berlin, Germany
41 Dipartimento di Fisica e Astronomia “Galileo Galilei”, Universita degli Studi di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
42 ESTEC, European Space Agency, 2201AZ Noordwijk, The Netherlands
43 Center for Astronomy and Astrophysics, Technical University Berlin, Hardenberstrasse 36, 10623 Berlin, Germany
44 Institut für Geologische Wissenschaften, Freie Universität Berlin, 12249 Berlin, Germany
45 ELTE Eötvös Loránd University, Gothard Astrophysical Observatory, 9700 Szombathely, Szent Imre h. u. 112, Hungary
46 MTA-ELTE Exoplanet Research Group, 9700 Szombathely, Szent Imre h. u. 112, Hungary
47 Ingenieurbüro Ulmer, Im Technologiepark 1, 15236 Frankfurt/Oder, Germany
48 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
Accepted: 10 September 2021
Context. The light curves of tidally locked hot Jupiters transiting fast-rotating, early-type stars are a rich source of information about both the planet and star, with full-phase coverage enabling a detailed atmospheric characterisation of the planet. Although it is possible to determine the true spin–orbit angle Ψ – a notoriously difficult parameter to measure – from any transit asymmetry resulting from gravity darkening induced by the stellar rotation, the correlations that exist between the transit parameters have led to large disagreements in published values of Ψ for some systems.
Aims. We aimed to study these phenomena in the light curves of the ultra-hot Jupiter MASCARA-1 b, which is characteristically similar to well-studied contemporaries such as KELT-9 b and WASP-33 b.
Methods. We obtained optical CHaracterising ExOPlanet Satellite (CHEOPS) transit and occultation light curves of MASCARA-1 b, and analysed them jointly with a Spitzer/IRAC 4.5 μm full-phase curve to model the asymmetric transits, occultations, and phase-dependent flux modulation. For the latter, we employed a novel physics-driven approach to jointly fit the phase modulation by generating a single 2D temperature map and integrating it over the two bandpasses as a function of phase to account for the differing planet–star flux contrasts. The reflected light component was modelled using the general ab initio solution for a semi-infinite atmosphere.
Results. When fitting the CHEOPS and Spitzer transits together, the degeneracies are greatly diminished and return results consistent with previously published Doppler tomography. Placing priors informed by the tomography achieves even better precision, allowing a determination of Ψ = 72.1−2.4+2.5 deg. From the occultations and phase variations, we derived dayside and nightside temperatures of 3062−68+66 K and 1720 ± 330 K, respectively.Our retrieval suggests that the dayside emission spectrum closely follows that of a blackbody. As the CHEOPS occultation is too deep to be attributed to blackbody flux alone, we could separately derive geometric albedo Ag = 0.171−0.068+0.066 and spherical albedo As = 0.266−0.100+0.097 from the CHEOPS data, and Bond albedoAB = 0.057−0.101+0.083 from the Spitzer phase curve.Although small, the Ag and As indicate that MASCARA-1 b is more reflective than most other ultra-hot Jupiters, where H− absorption is expected to dominate.
Conclusions. Where possible, priors informed by Doppler tomography should be used when fitting transits of fast-rotating stars, though multi-colour photometry may also unlock an accurate measurement of Ψ. Our approach to modelling the phase variations at different wavelengths provides a template for how to separate thermal emission from reflected light in spectrally resolved James Webb Space Telescope phase curve data.
Key words: techniques: photometric / planets and satellites: atmospheres / planets and satellites: physical evolution / planets and satellites: individual: MASCARA-1 b
The photometric time series data are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/658/A75
© ESO 2022
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