학술논문
The tidal deformation and atmosphere of WASP-12b from its phase curve
Document Type
Working Paper
Author
Akinsanmi, B.; Barros, S. C. C.; Lendl, M.; Carone, L.; Cubillos, P. E.; Bekkelien, A.; Fortier, A.; Florén, H. -G.; Cameron, A. Collier; Boué, G.; Bruno, G.; Demory, B. -O.; Brandeker, A.; Sousa, S. G.; Wilson, T. G.; Deline, A.; Bonfanti, A.; Scandariato, G.; Hooton, M. J.; Correia, A. C. M.; Demangeon, O. D. S.; Smith, A. M. S.; Singh, V.; Alibert, Y.; Alonso, R.; Asquier, J.; Bárczy, T.; Navascues, D. Barrado; Baumjohann, W.; Beck, M.; Beck, T.; Benz, W.; Billot, N.; Bonfils, X.; Borsato, L.; Broeg, Ch.; Buder, M.; Charnoz, S.; Csizmadia, Sz.; Davies, M. B.; Deleuil, M.; Delrez, L.; Ehrenreich, D.; Erikson, A.; Farinato, J.; 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.; Etangs, A. Lecavelier des; Magrin, D.; Maxted, P. F. L.; Mecina, M.; Mordasini, Ch.; Nascimbeni, V.; Olofsson, G.; Ottensamer, R.; Pagano, I.; Pallé, E.; Peter, G.; Piazza, D.; Piotto, G.; Pollacco, D.; Queloz, D.; Ragazzoni, R.; Rando, N.; Rauer, H.; Ribas, I.; Santos, N. C.; Ségransan, D.; Simon, A. E.; Stalport, M.; Szabó, Gy. M.; Thomas, N.; Udry, S.; Van Grootel, V.; Venturini, J.; Villaver, E.; Walton, N. A.
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Subject
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Abstract
Ultra-hot Jupiters present a unique opportunity to understand the physics and chemistry of planets at extreme conditions. WASP-12b stands out as an archetype of this class of exoplanets. We performed comprehensive analyses of the transits, occultations, and phase curves of WASP-12b by combining new CHEOPS observations with previous TESS and Spitzer data to measure the planet's tidal deformation, atmospheric properties, and orbital decay rate. The planet was modeled as a triaxial ellipsoid parameterized by the second-order fluid Love number, $h_2$, which quantifies its radial deformation and provides insight into the interior structure. We measured the tidal deformation of WASP-12b and estimated a Love number of $h_2=1.55_{-0.49}^{+0.45}$ (at 3.2$\sigma$) from its phase curve. We measured occultation depths of $333\pm24$ppm and $493\pm29$ppm in the CHEOPS and TESS bands, respectively, while the dayside emission spectrum indicates that CHEOPS and TESS probe similar pressure levels in the atmosphere at a temperature of 2900K. We also estimated low geometric albedos of $0.086\pm0.017$ and $0.01\pm0.023$ in the CHEOPS and TESS passbands, respectively, suggesting the absence of reflective clouds in the dayside of the WASP-12b. The CHEOPS occultations do not show strong evidence for variability in the dayside atmosphere of the planet. Finally, we refine the orbital decay rate by 12% to a value of -30.23$\pm$0.82 ms/yr. WASP-12b becomes the second exoplanet, after WASP-103b, for which the Love number has been measured (at 3$sigma$) from the effect of tidal deformation in the light curve. However, constraining the core mass fraction of the planet requires measuring $h_2$ with a higher precision. This can be achieved with high signal-to-noise observations with JWST since the phase curve amplitude, and consequently the induced tidal deformation effect, is higher in the infrared.
Comment: accepted for publication in A&A
Comment: accepted for publication in A&A