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Molecular line lists

When spectra of exoplanets are retrieved, we must compare the observations to the output of models in order to understand what we are seeing. To do this, we first use the Quantemol programme suite (developed here at UCL) to generate the 'line lists', which tell us how various molecules absorb light at different wavelengths and temperatures.

The generation of these molecular line lists is led by Prof. Jonathan Tennyson and the ExoMol group - their comprehensive line list of water, BT2, was used in the detection of water in exoplanet HD 189733b and is being used widely in a number of astronomical and non-astronomical studies. 



Comparison of the completeness of BYTe (Exomol) and HITRAN line lists
Simulated transmission spectra of HD189733b

















FIGURES. (from left) 1. A comparison of the completeness of BYTe (Exomol) and HITRAN line lists. 2. Simulated transmission spectra of HD189733b, from Tinetti et al. (2007).

Jonathan’s group has also calculated a number of other line lists, in particular their HCN/HNC linelist will be used to search for these species in exoplanets. As already demonstrated for cool stars, the HCN/HNC ratio provides a useful temperature diagnostic. In work supported by the Leverhulme Trust, the ExoMol team are currently computing comprehensive lists for species such as methane, ammonia and phosphene too. This work was originally intended for the detection and characterisation of Y-dwarf stars, but has become of great significance for exoplanet studies, especially at high temperatures.



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Page last modified on 04 nov 13 17:18 by Morgan D Hollis