A non-isothermal theory for interpreting sodium lines in transmission spectra of exoplanets
Heng, Kevin; Wyttenbach, Aurélien; Lavie, Baptiste; et al.Sing, David K.; Ehrenreich, D.; Lovis, C.
Date: 8 April 2015
Article
Journal
Astrophysical Journal Letters
Publisher
American Astronomical Society
Publisher DOI
Abstract
We present a theory for interpreting the sodium lines detected in transmission spectra of exoplanetary atmospheres. Previous analyses employed the isothermal approximation and dealt only with the transit radius. By recognizing the absorption depth and the transit radius as being independent observables, we develop a theory for jointly ...
We present a theory for interpreting the sodium lines detected in transmission spectra of exoplanetary atmospheres. Previous analyses employed the isothermal approximation and dealt only with the transit radius. By recognizing the absorption depth and the transit radius as being independent observables, we develop a theory for jointly interpreting both quantities, which allows us to infer the temperatures and number densities associated with the sodium lines. We are able to treat a non-isothermal situation with a constant temperature gradient. Our novel diagnostics take the form of simple-to-use algebraic formulae and require measurements of the transit radii (and their corresponding absorption depths) at line center and in the line wing for both sodium lines. We apply our diagnostics to the HARPS data of HD 189733b, confirm the upper atmospheric heating reported by Huitson et al., derive a temperature gradient of 0.4376±0.0154Kkm−1, and find densities ∼1–104 cm−3.
Physics and Astronomy
Faculty of Environment, Science and Economy
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