The following document lists the file abstract/MBARLOW_WATER.abs
from catalogue VI/111.
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This proposal requests time to extend the LWS Guaranteed Time proposal MBARLOW.HIRES in order to recover the original science goals. Following the launch of ISO, we have made the first detection from a cool star wind of the long-sought rotational lines of H2O that occur in the 45-181um region, in a Guaranteed Time LWS grating spectrum of the M8e semi-regular variable star W Hya, an oxygen-rich AGB star that is a well-known H2O and OH maser source. Our modelling of the spectrum confirms that these collisionally excited thermal H2O lines are the dominant coolants in the wind, with an H2O/H2 abundance ratio of 4E-4 and a mass loss rate of 6E-7 Msun/yr being estimated. Many of the H2O lines in our low-resolution LWS grating spectrum are heavily blended with other H2O lines, and the steeply rising continuum to shorter wavelengths also makes the higher-excitation lines that occur there hard to measure. This confirms our pre-launch conclusion that high resolution observations are needed to accurately determine the abundances of ortho- and para-H2O (which are effectively independent species), to investigate whether the H2O abundance varies as a function of radius (for which there is some evidence in our W Hya grating data) and to derive the kinetic temperature profile in the wind as a function of radius. The LWS Consortium had allocated sufficient GT time to obtain such high-resolution Fabry-Perot (FP) observations of H2O lines from the 12 brightest oxygen-rich cool stars, given pre-launch sensitivity estimates. However, with the factor of three decrease in sensitivities due to the higher than expected in-orbit particle hit-rate, the allocated GT time is only sufficient to obtain FP H2O-line observations of 1-2 stars. We therefore request sufficient time to obtain such observations for a further five O-rich cool stars, all of them famous archetype sources. Due to the unobservability of the H2O cooling lines from the ground or from airborne observatories, ISO will provide the only opportunity to obtain such observations for some considerable time in the future.