Issue |
A&A
Volume 545, September 2012
|
|
---|---|---|
Article Number | A93 | |
Number of page(s) | 7 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/201219294 | |
Published online | 12 September 2012 |
Thermal emission from WASP-24b at 3.6 and 4.5 μm
1
Astrophysics Group, Lennard-Jones LaboratoriesKeele
University, Keele,
Staffordshire,
ST5 5BG,
UK
e-mail: a.m.s.smith@keele.ac.uk
2
Department of Physics, and Department of Astronomy, Yale
University, New
Haven, CT
06511,
USA
3
SUPA, School of Physics and Astronomy, University of St.
Andrews, North Haugh, St.
Andrews, Fife,
KY16 9SS,
UK
4
Planetary Sciences Group, Department of Physics, University of
Central Florida, Orlando, FL
32816-2385,
USA
5
Astrophysics Research Centre, Physics Building, Queen’s
University, Belfast, County
Antrim, BT7
1NN, UK
6
Observatoire de Genève, Université de Genève,
51 Chemin des Maillettes,
1290
Sauverny,
Switzerland
7
Department of Physics, University of Warwick,
Coventry
CV4 7AL,
UK
Received: 23 March 2012
Accepted: 17 August 2012
Aims. We observe occultations of WASP-24b to measure brightness temperatures and to determine whether or not its atmosphere exhibits a thermal inversion (stratosphere).
Methods. We observed occultations of WASP-24b at 3.6 and 4.5 μm using the Spitzer Space Telescope. It has been suggested that there is a correlation between stellar activity and the presence of inversions, so we analysed existing HARPS spectra in order to calculate log R′HK for WASP-24 and thus determine whether or not the star is chromospherically active. We also observed a transit of WASP-24b in the Strömgren u and y bands, with the CAHA 2.2-m telescope.
Results. We measure occultation depths of 0.159 ± 0.013 per cent at 3.6 μm and 0.202 ± 0.018 per cent at 4.5 μm. The corresponding planetary brightness temperatures are 1974 ± 71 K and 1944 ± 85 K respectively. Atmosphere models with and without a thermal inversion fit the data equally well; we are unable to constrain the presence of an inversion without additional occultation measurements in the near-IR. We find log R′HK = −4.98 ± 0.12, indicating that WASP-24 is not a chromospherically active star. Our global analysis of new and previously-published data has refined the system parameters, and we find no evidence that the orbit of WASP-24b is non-circular.
Conclusions. These results emphasise the importance of complementing Spitzer measurements with observations at shorter wavelengths to gain a full understanding of hot Jupiter atmospheres.
Key words: planetary systems / planets and satellites: atmospheres / stars: individual: WASP-24 / planets and satellites: individual: WASP-24b / infrared: planetary systems
© ESO, 2012
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.