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Abstract
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 albedo AB = 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.
Original language | English |
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Article number | A75 |
Number of pages | 26 |
Journal | Astronomy and Astrophysics |
Volume | 658 |
Early online date | 2 Feb 2022 |
DOIs | |
Publication status | Published - 2 Feb 2022 |
Keywords
- Planets and satellites: atmospheres
- Planets and satellites: individual: MASCARA-1 b
- Planets and satellites: physical evolution
- Techniques: photometric
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Dive into the research topics of 'Spi-OPS: Spitzer and CHEOPS confirm the near-polar orbit of MASCARA-1 b and reveal a hint of dayside reflection'. Together they form a unique fingerprint.Projects
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Astronomy at St Andrews 2018-2021: Astronomy at St Andrews 2018-2021
Jardine, M. M. (PI), Bonnell, I. A. (CoI), Cameron, A. C. (CoI), Cyganowski, C. J. (CoI), Dominik, M. (CoI), Helling, C. (CoI), Horne, K. D. (CoI), Scholz, A. (CoI), Tojeiro, R. (CoI), Weijmans, A.-M. (CoI), Wild, V. (CoI), Woitke, P. (CoI), Wood, K. (CoI) & Zhao, H. (CoI)
1/04/18 → 31/03/22
Project: Standard