TiO opacity in grain-free environment

[gary]

TiO is the dominant opacity in the atmosphere of a cool star. It is never considered in the ISM due to the high depletion of Ti. In environments where dust is not present, TiO will be a major opacity in the optical / IR. We do not include it.

this paper does an approximate treatment of TiO in a disk: http://adsabs.harvard.edu/abs/1994A%26A...290...34H we might follow that treatment