Model-independent Exoplanet Transit Spectroscopy

Journal Article · Tue May 01 04:00:00 EDT 2018 · The Astronomical Journal (Online)

DOI:https://doi.org/10.3847/1538-3881/AAA3FE· OSTI ID:22897473

Aronson, Erik; Piskunov, Nikolai ^[1]

---

1. Observational Astronomy, Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala (Sweden)

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.

• OSTI ID: 22897473
• Journal Information: The Astronomical Journal (Online), Journal Name: The Astronomical Journal (Online) Journal Issue: 5 Vol. 155; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
ABSORPTION SPECTRA
BRIGHTNESS
COMPARATIVE EVALUATIONS
DATA ANALYSIS
EQUATIONS
FILTERS
PLANETS
RESOLUTION
SATELLITE ATMOSPHERES
SIGNAL-TO-NOISE RATIO
SPECTROSCOPY
STARS