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Title: A NON-ISOTHERMAL THEORY FOR INTERPRETING SODIUM LINES IN TRANSMISSION SPECTRA OF EXOPLANETS

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}.
Authors:
;  [1] ; ; ;  [2] ;  [3]
  1. University of Bern, Physics Institute, Center for Space and Habitability, Sidlerstrasse 5, CH-3012 Bern (Switzerland)
  2. Observatoire de l’Université de Genève, 51 chemin des Maillettes, CH-1290 Sauverny (Switzerland)
  3. Astrophysics Group, School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom)
Publication Date:
OSTI Identifier:
22518697
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 803; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION SPECTRA; ABSORPTION SPECTROSCOPY; DENSITY; HEATING; PLANETARY ATMOSPHERES; PLANETS; RADIANT HEAT TRANSFER; SATELLITE ATMOSPHERES; SODIUM; TEMPERATURE GRADIENTS