An optical transmission spectrum of the giant planet WASP-36 b

• Published in: Monthly notices of the Royal Astronomical Society Vol. 459; no. 2; pp. 1393 - 1402
• Main Authors: Mancini, L., Kemmer, J., Southworth, J., Bott, K., Mollière, P., Ciceri, S., Chen, G., Henning, Th
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 21.06.2016
• Subjects: Confidence intervals; Light; Optical properties; Photometry; Physical properties; Planets; Rayleigh scattering; Scale height; Scattering; Space telescopes; Spectrum analysis; Transits; Wavelengths; stars: fundamental parameters; stars: individual: WASP-36; planetary systems; techniques: photometric
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stw659

We present broad-band photometry of five transits in the planetary system WASP-36, totalling 17 high-precision light curves. Four of the transits were simultaneously observed in four passbands (g′, r′, i′, z′), using the telescope-defocusing technique, and achieving scatters of less than 1 mmag per observation. We used these data to improve the measured orbital and physical properties of the system, and obtain an optical transmission spectrum of the planet. We measured a decreasing radius from bluer to redder passbands with a confidence level of more than 5σ. The radius variation is roughly 11 pressure scale heights between the g′ and the z′ bands. This is too strong to be Rayleigh scattering in the planetary atmosphere, and implies the presence of a species which absorbs strongly at bluer wavelengths.