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Journal Article

ACCESS: Ground-based Optical Transmission Spectroscopy of the Hot Jupiter WASP-4b

MPS-Authors

Bixel,  Alex
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Rackham,  Benjamin V.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Apai,  Dániel
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Espinoza,  Néstor
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

López-Morales,  Mercedes
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Osip,  David
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Jordán,  Andrés
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

McGruder,  Chima
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Weaver,  Ian
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

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Citation

Bixel, A., Rackham, B. V., Apai, D., Espinoza, N., López-Morales, M., Osip, D., et al. (2019). ACCESS: Ground-based Optical Transmission Spectroscopy of the Hot Jupiter WASP-4b. The Astronomical Journal, 157.


Cite as: http://hdl.handle.net/21.11116/0000-0005-D40F-C
Abstract
We present an optical transmission spectrum of the atmosphere of WASP-4b obtained through observations of four transits with Magellan/IMACS, as part of the Arizona-CfA-Católica-Carnegie Exoplanet Spectroscopy Survey (ACCESS). Using a Bayesian approach to atmospheric retrieval, we find no evidence for scattering or absorption features in our transit spectrum. Our models include a component to model the transit light source effect (spectral contamination from unocculted spots on the stellar photosphere), which we show can have a marked impact on the observed transmission spectrum for reasonable spot-covering fractions (<5%) this is the first such analysis for WASP-4b. We are also able to fit for the size and temperature contrast of spots observed during the second and third transits, finding evidence for both small, cool and large, warm spot-like features on the photosphere. Finally, we compare our results to those published by Huitson et al. using Gemini/GMOS and May et al. using IMACS, and we find that our data are in agreement.