Volume 620, December 2018
|Number of page(s)||20|
|Section||Planets and planetary systems|
|Published online||10 December 2018|
Deciphering the atmosphere of HAT-P-12b: solving discrepant results★
Leibniz-Institut für Astrophysik Potsdam (AIP),
An der Sternwarte 16,
2 Stellar Astrophysics Centre (SAC), Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
3 Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA
4 Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
5 Dipartimento di Fisica, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy
6 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
7 INAF - Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese, Italy
8 Department of Astronomy, Stockholm University, Alba Nova University Center, 106 91 Stockholm, Sweden
Accepted: 3 October 2018
Context. Two independent investigations of the atmosphere of the hot Jupiter HAT-P-12b by two different groups resulted in discrepant solutions. Using broad-band photometry from the ground, one study found a flat and featureless transmission spectrum that was interpreted as gray absorption by dense cloud coverage. The second study made use of Hubble Space Telescope (HST) observations and found Rayleigh scattering at optical wavelengths caused by haze.
Aims. The main purpose of this work is to determine the source of this inconsistency and provide feedback to prevent similar discrepancies in future analyses of other exoplanetary atmospheres.
Methods. We studied the observed discrepancy via two methods. With further broad-band observations in the optical wavelength regions, we strengthened the previous measurements in precision, and with a homogeneous reanalysis of the published data, we were able to assess the systematic errors and the independent analyses of the two different groups.
Results. Repeating the analysis steps of both works, we found that deviating values for the orbital parameters are the reason for the aforementioned discrepancy. Our work showed a degeneracy of the planetary spectral slope with these parameters. In a homogeneous reanalysis of all data, the two literature data sets and the new observations converge to a consistent transmission spectrum, showing a low-amplitude spectral slope and a tentative detection of potassium absorption.
Key words: planets and satellites: gaseous planets / planets and satellites: atmospheres / stars: individual: HAT-P-12
The transit light curves of HAT-P-12b are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (184.108.40.206) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/620/A142
© ESO 2018
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