Carbon monoxide in supernova 1987A

The identification of carbon monoxide (CO) in the infrared spectra of SN 1987A and of CO+ represents the first ever detection of a molecule in a supernova. In IR spectra obtained with the Anglo-Australian Telescope (AAT), first overtone emission from CO was observed near 2.3 μm as early as day 112 after the explosion, and was clearly detectable in all subsequent spectra. Spectra of the CO fundamental at 4.6 μm support this identification. We argue that the CO forms part of the supernova ejecta, and present a preliminary analysis of the first overtone band using Boltzmann population statistics. The model reproduces well the spectra obtained on days 192 and 255 and implies the presence of about 5X10-5 solar mass of CO by day 255. By day 284 the fit is less good, due to increasingly prominent emission from other species, possibly in combination with the breakdown of the Boltzmann distribution