4.6 Article

CHEOPS geometric albedo of the hot Jupiter HD 209458 b

Journal

ASTRONOMY & ASTROPHYSICS
Volume 659, Issue -, Pages -

Publisher

EDP SCIENCES S A
DOI: 10.1051/0004-6361/202243082

Keywords

techniques: photometric; planetary systems; planets and satellites: atmospheres; planets and satellites: individual: HD 209458 b

Funding

  1. Spanish MINECO [AYA2017-84089]
  2. SNSA
  3. STFC [ST/M001040/1]
  4. FCT -Fundacao para a Ciancia e a Tecnologia
  5. FEDER through COMPETE2020 -Programa Operacional Competitividade e Internacionalizacao [UID/FIS/04434/2019, UIDB/04434/2020, UIDP/04434/2020, PTDC/FIS-AST/32113/2017, POCI01-0145-FEDER-032113, PTDC/FIS-AST/28953/2017, POCI-01-0145FEDER-028953, PTDC/FIS-AST/28987/2017, POCI-01-0145-FEDER028987]
  6. FCT [DL 57/2016/CP1364/CT0004, IF/01312/2014/CP1215/CT0004, CEECIND/00826/2018]
  7. Belgian Federal Science Policy O ffice (BELSPO)
  8. University of Liege through an ARC grant for Concerted Research Actions - WalloniaBrussels Federation
  9. Swiss National Science Foundation [PP00P2-190080, 200021_200726]
  10. Swiss National Fund [200020_172746]
  11. Spanish Ministry of Science and Innovation
  12. European Regional Development Fund [ESP2016-80435-C2-1-R, ESP2016-80435-C2-2-R, PGC2018-098153-B-C33, PGC2018-098153-B-C31, ESP2017-87676-C5-1-R, MDM-2017-0737]
  13. Generalitat de Catalunya/CERCA programme
  14. ESA [4000124370]
  15. CNES
  16. European Research Council (ERC) under the European Union [724427]
  17. Swiss National Science Foundation (SNSF)
  18. SNSA [DNR 65/19, 174/18]
  19. CRT foundation [2018.2323]
  20. CNES [837319]
  21. Region Ile de France
  22. project Equip@Meso of the programme Investissements d'Avenir [ANR-10-EQPX-29-01]
  23. Simons Foundation [327127]
  24. Hungarian National Research, Development and Innovation O ffice (NKFIH) [GINOP-2.3.2-15-201600003, K-119517, K-125015]
  25. City of Szombathely [67.177-21/2016]
  26. Swiss National Science Foundation (SNF) [200020_172746, 200021_200726] Funding Source: Swiss National Science Foundation (SNF)

Ask authors/readers for more resources

This article reports the detection of the secondary eclipse of the hot Jupiter HD 209458 b in optical/visible light using the CHEOPS space telescope. The measurement of the geometric albedo is considered one of the most robust measurements of A(g) for any exoplanet and indicates a cloud-free atmosphere where starlight is reflected via Rayleigh scattering by hydrogen molecules.
We report the detection of the secondary eclipse of the hot Jupiter HD 209458 b in optical/visible light using the CHEOPS space telescope. Our measurement of 20.4(-3.3)(+3.2) parts per million 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 bandpassintegrated 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 209458 b observed by CHEOPS would have a distinct shape associated with Rayleigh scattering if the atmosphere is indeed cloud free.

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