Volume 624, April 2019
|Number of page(s)||9|
|Section||Planets and planetary systems|
|Published online||10 April 2019|
Low albedos of hot to ultra-hot Jupiters in the optical to near-infrared transition regime★,★★
Leibniz-Institut für Astrophysik Potsdam,
An der Sternwarte 16,
2 Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
Accepted: 20 February 2019
The depth of a secondary eclipse contains information of both the thermally emitted light component of a hot Jupiter and the reflected light component. If the day side atmosphere of the planet is assumed to be isothermal, it is possible to disentangle both. In this work, we analyzed 11 eclipse light curves of the hot Jupiter HAT-P-32 b obtained at 0.89 μm in the z′ band. We obtained a null detection for the eclipse depth with state-of-the-art precision, −0.01 ± 0.10 ppt. We confirm previous studies showing that a non-inverted atmosphere model is in disagreement to the measured emission spectrum of HAT-P-32 b. We derive an upper limit on the reflected light component, and thus, on the planetary geometric albedo Ag. The 97.5% confidence upper limit is Ag < 0.2. This is the first albedo constraint for HAT-P-32 b, and the first z′ band albedo value for any exoplanet. This finding disfavors the influence of large-sized silicate condensates on the planetary day side. We inferred z′ band geometric albedo limits from published eclipse measurements also for the ultra-hot Jupiters WASP-12 b, WASP-19 b, WASP-103 b, and WASP-121 b, applying the same method. These values consistently point to a low reflectivity in the optical to near-infrared transition regime for hot to ultra-hot Jupiters.
Key words: methods: observational / techniques: photometric / planets and satellites: fundamental parameters
Based on data obtained with the STELLA robotic telescopes in Tenerife, an AIP facility jointly operated by AIP and IAC.
Lightcurves are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A62
© ESO 2019
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