tokens: ACKNOWLEDGEMENTS This paper uses observations made at the South African Astronomical Observatory; is based partly upon work supported financially by the University of the Western Cape and the National Research Foundation of South Africa; and has made use of the SIMBAD data base operated at the Centre de Données astronomiques de Strasbourg (CDS) in Strasbourg, France. We are grateful to the referee, Prof. M.D. Reed, for comments which have enabled the authors to improve this paper.
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