March with depth of molecular abundances in the outer layers of K and M stars

Abstract

A programme has been developed for computing the equilibrium concentration of one hundred molecules, atoms, positive, negative ions, formed out of fifteen elements. This programme, coupled with the programmes for computing mean opacities and for model atmospheres, has been used to determine the abundances of various molecules as a function of optical depth in K and M spectral type stars. We have found several new compounds, which may play not insignificant roles in late-type stars. A careful comparison of the march of molecular abundances in different spectral types reveals why certain molecules, even though sufficiently abundant in a certain layer of a given star, may be observed only in earlier or later spectral type stars than that of the given star.