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Model-independent Exoplanet Transit Spectroscopy
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
2018 (English)In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 155, no 5, article id 208Article in journal (Refereed) Published
Abstract [en]

We propose a new data analysis method for obtaining transmission spectra of exoplanet atmospheres and brightness variation across the stellar disk from transit observations. The new method is capable of recovering exoplanet atmosphere absorption spectra and stellar specific intensities without relying on theoretical models of stars and planets. We simultaneously fit both stellar specific intensity and planetary radius directly to transit light curves. This allows stellar models to be removed from the data analysis. Furthermore, we use a data quality weighted filtering technique to achieve an optimal trade-off between spectral resolution and reconstruction fidelity homogenizing the signal-to-noise ratio across the wavelength range. Such an approach is more efficient than conventional data binning onto a low-resolution wavelength grid. We demonstrate that our analysis is capable of reproducing results achieved by using an explicit quadratic limb-darkening equation and that the filtering technique helps eliminate spurious spectral features in regions with strong telluric absorption. The method is applied to the VLT FORS2 observations of the exoplanets GJ 1214 b and WASP-49 b, and our results are in agreement with previous studies. Comparisons between obtained stellar specific intensity and numerical models indicates that the method is capable of accurately reconstructing the specific intensity. The proposed method enables more robust characterization of exoplanetary atmospheres by separating derivation of planetary transmission and stellar specific intensity spectra (that is model-independent) from chemical and physical interpretation.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD , 2018. Vol. 155, no 5, article id 208
Keywords [en]
methods: data analysis, planets and satellites: atmospheres, techniques: spectroscopic
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-356193DOI: 10.3847/1538-3881/aaa3feISI: 000430925000001OAI: oai:DiVA.org:uu-356193DiVA, id: diva2:1236030
Available from: 2018-07-30 Created: 2018-07-30 Last updated: 2018-07-30Bibliographically approved

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Aronson, ErikPiskunov, Nikolai

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