The Evolutionary Status of the Frosty Leo Nebula

We present new observational data for IRAS 09371+1212, the Frosty Leo Nebula, in the form of infrared spectra from 2.2-2.5μm which reveal photospheric bands of CO. The ¹²CO/¹³CO band ratio determined is similar to those exhibited by evolved K giant stars, and supports the proposal that the object is highly evolved. The equivalent width of the CO bands implies, however, that the spectral type lies in the range G5III to K0III, somewhat earlier than K7III, as derived from colours and optical spectra. The smaller equivalent widths of the CO bands may reflect a low metal abundance which could fit well with the considerable height of the source above the galactic plane (>0.9kpc).