Methane line opacities in very cool stellar objects

Aims. We investigate the effects of different line data for methane ¹²CH₄ on the structures of model atmospheres and low resolution synthetic spectra for ultra-cool substellar objects.

Methods. For each set of methane line data we compare the resulting model atmospheres and spectra computed with the general purpose model atmosphere code PHOENIX.

Results. The new HGW methane line data compares well to the HITRAN2004 data. We find the the HITRAN2004 methane lines are in some bands stronger than the HGW lines, resulting in deeper absorption bands in the synthetic spectra.

Conclusions.