We present infrared spectroscopy of the recurrent nova RS Ophiuchi , obtained 11.81 , 20.75 and 55.71 days following its 2006 eruption .
The spectra are dominated by hydrogen recombination lines , together with He i , O i and O ii lines ; the electron temperature of \sim 10 ^ { 4 } K implied by the recombination spectrum suggests that we are seeing primarily the wind of the red giant , ionized by the ultraviolet flash when RS Oph erupted .
However , strong coronal emission lines ( i.e .
emission from fine structure transitions in ions having high ionization potential ) are present in the last spectrum .
These imply a temperature of 930 000 K for the coronal gas ; this is in line with x-ray observations of the 2006 eruption .
The emission line widths decrease with time in a way that is consistent with the shock model for the x-ray emission .