ISO LWS Observations of Evolved Stars and Nebulae

Abstract

This review reports, on behalf of the LWS Consortium1, some of the spectroscopic results on evolved stars and nebulae that have been obtained at far-infrared wavelengths by the Infrared Space Observatory (ISO) since its launch in November 1995. The results reported have been obtained mainly using ISO’s Long Wavelength Spectrometer (LWS; Clegg et al. 1996), but for some objects complementary spectra have also been obtained with the Short Wavelength Spectrometer (SWS; de Graauw et al. 1996). In this review I present some of the results that have been obtained (a) for oxygen-rich cool stars and (b) for carbon stars and carbon-rich post-AGB objects and planetary nebulae. Highlights from the first area include the first detection of the far-infrared rotational lines of water vapour, the dominant coolant in their outflows, and the detailed confirmation of the proposed radiative pump mechanism for circumstellar OH masers. Highlights from the second area include the detection of a rich HCN and CO far-infrared line spectrum from the carbon star IRC+10°216, with HCN found to be the dominant coolant, the detection of very strong shock-excited CO rotational lines from the post-AGB object AFGL 2688, and the first detection of the far-infared rotational lines of CH+ (from the the PDR of the carbon-rich planetary nebula NGC 7027), as well as the first detection in emission of the far-IR rotational lines of CH (also from NGC 7027).