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Transmission photometry of WASP-12b: simultaneous measurement of the planetary radius in three bands

Copperwheat, CM, Wheatley, PJ, Southworth, J, Bento, J, Marsh, TR, Dhillon, VS, Fortney, JJ, Littlefair, SP and Hickman, R (2013) Transmission photometry of WASP-12b: simultaneous measurement of the planetary radius in three bands. Monthly Notices of the Royal Astronomical Society, 434 (1). pp. 661-670. ISSN 0035-8711

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Transmission spectroscopy has been successfully used from both the ground and in space to characterize the atmospheres of transiting exoplanets. This technique is challenging from the ground because ground-based spectrographs tend not to be designed to be photometrically stable, and effects such as variable slit losses cause significant systematic uncertainties. An alternative approach is to use simultaneous photometric observations in multiple wavebands to determine wavelength-dependent transit depth differences. We report an application of this technique to one of the hottest known exoplanets, WASP-12b, using the triple-beam camera ULTRACAM. We obtained simultaneous light curves in Sloan u′, and two narrow-band filters centred on 4169 and 6010 Å, with full widths at half-maximum 52 and 118 Å, respectively. We fit these light curves with a photometric model and determine the planetary radius in the three different bands. Our data show no evidence for a difference in planetary radius over the wavelength range we study, and are consistent with an atmosphere that is dominated by Rayleigh scattering from a high-altitude haze, as well as more complicated atmosphere models which include the effects of molecules such as TiO. Our planetary radius measurements have an average precision of 2.6 per cent, compared to the ∼1.4–2.4 per cent radius differences predicted by the models over this wavelength range. We also find a consistent time of ingress and egress across our three wavebands, in contrast to the early ingress which has been reported for this system at shorter wavelengths.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 0201 Astronomical and Space Sciences
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Related URLs:
Date Deposited: 16 Jul 2019 09:52
Last Modified: 04 Sep 2021 09:09
DOI or ID number: 10.1093/mnras/stt1056
URI: https://researchonline.ljmu.ac.uk/id/eprint/11036
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