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tokens: We warmly thank the Swift PI Neil Gehrels and his team for approving our observations and scheduling them. We acknowledge with thanks the variable star observations from the AAVSO International Database contributed by observers worldwide and used in this research. We also thank François Teyssier for altering us to the many amateur spectroscopic observations which have been made and we acknowledge and thank François Teyssier, Umberto Sollecchia, Joan Guarro Flo, Jacques Montier, Peter Somogyi, Keith Graham and V Bouttard for use of their spectra. Armagh Observatory is supported by the Northern Ireland Government through the Dept of Culture, Arts and Leisure. GJML and NEN acknowledge support from Argentina grant ANPCYT-PICT 0478/14. GJML and NEN are members of the ‘Carrera del Investigador Cientifico (CIC)’ of CONICET. We thank the referee for a helpful and constructive report.