Wednesday 05 Mar 2014Three years of ExoMol: New molecular line lists for exoplanets and other atmospheres (3PM)

Dr Sergey Yurchenko - UCL

Physics, 4th floor 15:00-16:00

Spectral characterization of astrophysical objects cool enough to form molecules in their atmospheres (cool stars, extrasolar planets and planetary discs) requires considerable amounts of fundamental molecular data. In my talk I will demonstrate that experimental molecular line lists are not sufficiently complete. The ExoMol project aims at providing comprehensive line lists for all molecules likely to be observable in exoplanet atmospheres in the foreseeable future. This is a huge undertaking which will mean providing in excess of tens of billions of spectral lines for a large variety of molecular species [Tennyson and Yurchenko, MNRAS, 425, 21 (2012)].

The physics of molecular absorptions is complex and varies between different classes of absorbers, which are therefore divided into following topics (a) diatomic, (b) triatomics, (c) tetratomics, (d) methane and (e) larger molecules. Special techniques are being developed to treat each case. The line lists for a number of key atmospheric species currently available from ExoMol ( ammonia, methane, CaH, MgH, BeH, SiO, HCN/HNC, formaldehyde, phosphine, SO3, KCl, NaCl.
The line lists in progress are for KCl, NaCl, PN, SiH, SO, ScH, TiH, C2, AlH, MgH, HNO3 and C2H4.
As an example I will present our main result so far, a new methane line
list generated using high level of theory [Yurchenko and Tennyson, MNRAS (2014), arXiv:1307.5450v1], called 10to10, which contains just under 10 billion transitions. This 10to10 line list has the potential to revolutionise the accuracy of T-dwarf models.

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