A NON-ISOTHERMAL THEORY FOR INTERPRETING SODIUM LINES IN TRANSMISSION SPECTRA OF EXOPLANETS
- University of Bern, Physics Institute, Center for Space and Habitability, Sidlerstrasse 5, CH-3012 Bern (Switzerland)
- Observatoire de l’Université de Genève, 51 chemin des Maillettes, CH-1290 Sauverny (Switzerland)
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 ± 0.0154 K km{sup −1}, and find densities ∼1–10{sup 4} cm{sup −3}.
- OSTI ID:
- 22518697
- Journal Information:
- Astrophysical Journal Letters, Vol. 803, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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