Contents of: VI/111/./abstract/MBARLOW_FASTWIND.abs

The following document lists the file abstract/MBARLOW_FASTWIND.abs from catalogue VI/111.
A plain copy of the file (without headers/trailers) may be downloaded.


SCIENTIFIC ABSTRACT
(A) We propose to derive the C, N and O abundances in the outer winds of  WR
stars and O and B-type stars by measuring, in LWS grating mode, the fluxes in
the fine structure lines of [C II], [N II], [N III] and [O III]. Such
abundances cannot easily be derived from optical or ultraviolet spectra. The
WC9 stars and some of the extreme supergiants  show strong circumstellar dust
emission, whose far-IR spectral characteristics will be simultaneously
measured. Three of the extreme B supergiants have been found to show 2.3um CO
emission by McGregor et al. (1988), so CO rotational line emission may be
detectable in their LWS spectra.

B) The shells of old novae are interesting in several respects, most notably
because they are often highly enriched in heavy elements of the oxygen group
and beyond. The most  important objective of ISO for novae is determining the
elemental abundances in the ejecta, from observations of fine structure lines.
IR observations are essential because, due to the enrichment, the gas easily
cools to very low temperatures, so that the optical and UV forbidden lines
eventually become very weak.

(C)  Novae occurring during the ISO mission are likely to be targets of
opportunity. However, young novae that have occurred in the year or so before
launch and during the ISO mission could also be profitably observed,
particularly in order to follow the rise in excitation of the fine structure
lines as the central remnant evolves to higher temperatures. Such observations
would also help to determine whether the dramatic fall in [O III] 5007A
emission in some evolving nova shells is due to strong evolution and fading of
the ionization source, or is instead due to the temperature drop caused by the
increased efficiency of IR fine structure line cooling as the density of the
expanding shell drops below the critical density for collisional de-excitation
of the upper levels of the various lines. In addition, ISO observations  with
both LWS and SWS can for the first time provide a complete study of the
recently discovered infrared coronal emission line phase of young classical
nova outbursts, resulting in new constraints on heavy element abundances in
both their ejecta and the cores of their precursor stars.

A LaTex file containing fuller details of this proposal is available from


OBSERVATION SUMMARY
For either a Spring or Autumn launch, 8.95 hours (535.1 minutes) of LWS
Guaranteed (spacecraft) time are allocated to this programme. For a Spring
launch (Orion-hole observable), 474.5 minutes will be used for full LWS01
43-196.7um grating scans of 17 early-type stars, 5 old novae and 2 young nova,
using 4 sample points per resolution element and an integration time of 2
seconds per sample point, along with 60.6 minutes for full SWS01 2.43-45um
low-resolution (R/8) grating scans of the 2 young novae. For an Autumn launch
(Orion-hole observable) 474.5 minutes will be used for full LWS01 43-196.7um
grating scans of 16 early-type stars, 6 old novae and 2 new nova, along with
60.6 minutes for full SWS01 2.43-45um R/8 grating scans  of the 2 new novae.
The Priority 1 LWS Guaranteed spacecraft time allocated to this programme is
3.55 hours for the case of either a  Spring or an Autumn launch.



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