Low albedos of hot to ultra-hot Jupiters in the optical to near-infrared transition regime
Abstract
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.
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 http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A62- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- April 2019
- DOI:
- 10.1051/0004-6361/201935079
- arXiv:
- arXiv:1902.07944
- Bibcode:
- 2019A&A...624A..62M
- Keywords:
-
- methods: observational;
- techniques: photometric;
- planets and satellites: fundamental parameters;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- accepted for publication in A&