A Framework to Combine Low- and High-resolution Spectroscopy for the Atmospheres of Transiting Exoplanets

Current observations of the atmospheres of close-in exoplanets are predominantly obtained with two techniques: low-resolution spectroscopy with space telescopes and high-resolution spectroscopy from the ground.

Although the observables delivered by the two methods are in principle highly complementary, no attempt has ever been made to combine them, perhaps due to the different modeling approaches that are typically used in their interpretation. Here we present the first combined analysis of previously-published dayside spectra of the exoplanet HD 209458b obtained at low resolution with HST/WFC3 and Spitzer/IRAC, and at high resolution with VLT/CRIRES. By utilizing a novel retrieval algorithm capable of computing the joint probability distribution of low- and high-resolution spectra, we obtain tight constraints on the chemical composition of the planet’s atmosphere.

We measure a metallicity 0.1-3.7x the stellar value (1 sigma) and our analysis strongly favors an oxygen-rich atmosphere (C/O = 0.43+0.04−0.06). While the abundance of H2O is consistent with the expectations for a solar-composition atmosphere in chemical equilibrium, CO is found slightly under-abundant (1.9 sigma) and CO2 over-abundant (2.2 sigma). This study opens the way to coordinated exoplanet surveys between the flagship ground- and space-based facilities, which ultimately will be crucial for characterizing potentially-habitable planets.

M. Brogi, M. Line, J. Bean, J.-M. Désert, H. Schwarz
(Submitted on 21 Dec 2016)

Comments: 6 pages, 5 figures, submitted to ApJ Letters
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1612.07008 [astro-ph.EP] (or arXiv:1612.07008v1 [astro-ph.EP] for this version)
Submission history
From: Matteo Brogi
[v1] Wed, 21 Dec 2016 08:25:55 GMT (1287kb,D)
https://arxiv.org/abs/1612.07008