The VLT Interferometer - ESO

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CHAPTER 2. SCIENTIFIC ASPECTS
the array will considerably widen the spatial volume to explore, and
consequently it will improve the statistics markedly.
Stars in the Magellanic Clouds,' measuring the third dimension of
the SMC: Imaging spectroscopic binaries in the Magellanic Clouds
will provide both the masses of the components and their distance.
This is highly interesting since most of the candidates are very luminous
stars (e.g.: Wolf-Rayet stars or supergiants) of which the mass
is little known, particularly in the case of the Magellanic Clouds:
this parameter is critical in the models of the chemical evolution
of the Clouds and, more generally, of galaxies. Furthermore, the
accurate determination of the distance of stars in the Small Magellanic
Cloud, independently of any questionable calibration, will
bring new light on its structure, which is a subject of great controversy
: its depth along the line of sight would be as large as 47 kpc
[Mathewson et al 1986]. The morphology of the Small Magellanic
Cloud is directly related to the formation process of the Clouds.
Figure 2.2 shows the typical range in the log (period) versus log
(semi-major axis) diagram for which the masses and the distances
could be derived within a reasonable time interval
• Final stage of stellar evolution:
Our view of the potential contribution of the VLT Interferometer in the
field of the ultimate stages of stellar evolution increased considerably after
the campaign of observations of the LMC supernova SN 1987a.
The physical parameters of the ejection
From regularly spaced observations either in spectral features (e.g.:
[01] or Ha and in the continuum in the visible and in the infrared,
the VLT Interferometer will provide unique information about the
chronology and the dynamics of the ejecta from supernovae, about
the fragmentation as a function of age. The Crab nebula shows a very
complex structure: it will be highly interesting to study the growth
of such a fine structure in the ejecta from SN1987a, and to relate it
to the magnetic field and to the surrounding remnant of the wind
expelled by the progenitor of SN1987a. The detection and the survey
of the infrared echo as that associated to SN1987a [Chalabaev 1989]
is a unique tool to probe the circumstellar material resulting from
the high mass loss from the progenitor, from which comes the history
of the presupernova evolutionary phase [Chevalier et al 1989],
as well as the luminosity of the UV flash. This will provide totally
new observational constraints on the theoretical evolutionary t.racks