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

Bixel, Alex; Rackham, Benjamin V.; Apai, Dániel; Espinoza, Néstor; López-Morales, Mercedes; Osip, David; Jordán, Andrés; McGruder, Chima; Weaver, Ian

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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;

External Ressource

https://ui.adsabs.harvard.edu/abs/2019AJ....157...68B
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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.