Based on data collected at the European Southern Observatory, La Silla, Chile.

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Tables, Figures and the complete data set are available in electronic form at the CDS via anonymous ftp to
cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/397/987

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