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

The following document lists the file abstract/NTRAMS_LMCSICA.abs from catalogue VI/111.
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The recent discovery of one high luminosity carbon star in the SMC
by Whitelock et al (1989) indicates that the formation of C stars at
sub solar metallicities may be discouraged but is not excluded as was
predicted by stellar evolution theory including hot bottom burning, and
observed in optically selected samples of asymptotic giant branch stars.
In our extensive programme using ground based observatories
and ISO we found one high luminosity carbon star in the LMC. The 3 micron
spectrum of this object (IRAS04496-6958, LI-LMC57) shows a strong 3.1 micron
absorption, typical for carbon stars, and also the optical spectrum confirms
the carbon rich nature. In our ISO project we obtained a 10 micron spectrum
of this source using the ISOCAM-CVF. This spectrum shows an emission at
10 micron, indicative of silicates, and thus oxygen rich dust. If this
feature is confirmed it would make this object the first and only known
carbon star with oxygen rich dust in the LMC and the only one with a known
distance. Unfortunately the spectral
range covered in our CVF spectrum is not enough to unambiguously identify
the feature. Some galactic carbon stars show in their (SWS) spectra
absorptions at about 7 and 15 micron. We can at this moment not exclude the
possibility that a similar absorption is present in IRAS04496-6958. The
identification of the feature is important since it put strong constraints
on evolutionary models (requiring either a very rapid and recent evolution
from oxygen to carbon rich, or a stationary oxygen rich dust component,
possibly in a disk). We therefore propose to reobserve
the object with the CAM CVF to extend the wavelength range of the CVF
spectrum. Furthermore we propose to obtain a 60 micron photometric measurement
using ISOPHOT in mapping mode to be able to better constrain models of
the spectral energy distribution of this object. Preliminary modelling indicates
that a long wavelength point is essential to properly define the models.

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