|
Molecules in cool stars and circumstellar regions
Peter Sarre (Nottingham)
This project is making use of recent laboratory and theoretical
advances in the molecular electronic spectroscopy of SiC2
and TiO to probe stellar and circumstellar material and processes.
The aims include improvement in our understanding of the
molecule-grain transition, and the outflow of material from stars into
the interstellar medium. Moderate and high resolution spectra of
carbon and oxygen-rich stars have been obtained using the WHT and 1.9-m
Radcliffe (SAAO) telescopes. In general N and J-type carbon stars
show the Merrill-Sanford bands of SiC2 in absorption. A unique
object, IRAS 12311-3509, which is possibly of J-silicate type, has
cool circumstellar SiC2 in emission. Photospheric TiO is seen in
absorption in M stars, but IRAS 08182-6000 has unusually cool TiO
which is also seen in absorption. We describe rotational contour and
radiative transfer modelling calculations that yield molecular
rotational and other internal temperatures, and outline evidence for
non-LTE effects and molecular outflows.
|