학술논문
CHEOPS geometric albedo of the hot Jupiter HD 209458b
Document Type
Working Paper
Author
Brandeker, A.; Heng, K.; Lendl, M.; Patel, J. A.; Morris, B. M.; Broeg, C.; Guterman, P.; Beck, M.; Maxted, P. F. L.; Demangeon, O.; Delrez, L.; Demory, B. -O.; Kitzmann, D.; Santos, N. C.; Singh, V.; Alibert, Y.; Alonso, R.; Anglada, G.; Bárczy, T.; Navascues, D. Barrado y; Barros, S. C. C.; Baumjohann, W.; Beck, T.; Benz, W.; Billot, N.; Bonfils, X.; Bruno, G.; Cabrera, J.; Charnoz, S.; Cameron, A. Collier; van Damme, C. Corral; Csizmadia, Sz.; Davies, M. B.; Deleuil, M.; Deline, A.; Ehrenreich, D.; Erikson, A.; Farinato, J.; Fortier, A.; Fossati, L.; Fridlund, M.; Gandolfi, D.; Gillon, M.; Güdel, M.; Hoyer, S.; Isaak, K. G.; Kiss, L.; Laskar, J.; Etangs, A. Lecavelier des; Lovis, C.; Luntzer, A.; Magrin, D.; 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.; Scandariato, G.; Ségransan, D.; Simon, A. E.; Smith, A. M. S.; Sousa, S. G.; Steller, M.; Szabó, Gy. M.; Thomas, N.; Udry, S.; Van Grootel, V.; Walton, N.; Wolter, D.
Source
Subject
Language
Abstract
We report the detection of the secondary eclipse of the hot Jupiter HD 209458b in optical/visible light using the CHEOPS space telescope. Our measurement of 20.4 +/- 3.3 ppm translates into a geometric albedo of A_g = 0.096 +/- 0.016. The previously estimated dayside temperature of about 1500 K implies that our geometric albedo measurement consists predominantly of reflected starlight and is largely uncontaminated by thermal emission. This makes the present result one of the most robust measurements of A_g for any exoplanet. Our calculations of the bandpass-integrated geometric albedo demonstrate that the measured value of A_g is consistent with a cloud-free atmosphere, where starlight is reflected via Rayleigh scattering by hydrogen molecules, and the water and sodium abundances are consistent with stellar metallicity. We predict that the bandpass-integrated TESS geometric albedo is too faint to detect and that a phase curve of HD 209458b observed by CHEOPS would have a distinct shape associated with Rayleigh scattering if the atmosphere is indeed cloud free.
Comment: 9 pages, accepted by A&A Letters
Comment: 9 pages, accepted by A&A Letters