The early chemical evolution of nova outflows

ABSTRACT

The chemistry of the early stages of the evolution of a nova wind is examined. The new models include an extended chemistry and, in the light of current model atmosphere calculations, a careful treatment of the photoreactions. The results indicate that the chemistry may be somewhat richer than previously determined and, contrary to the findings of previous studies, is essentially not photon-dominated. The abundance of species such as CN and CO match observations well and the ratio of their abundances may be a useful density diagnostic. However, except at very early times, CO formation does not saturate; this has important implications for the subsequent dust-formation epoch. In particular it provides theoretical backing for those observations which suggest that carbon-rich and silicate dusts can be formed concurrently.