A precessing Be disc as a possible model for occultation events in GX 304−1

MK acknowledges support by the Bundesministerium fur Wirtschaft und Technologie under Deutsches Zentrum fur Luft- und Raumfahrt grants 50OR1113 and 50OR1207 and by the European Space Agency under contract number C4000115860/15/NL/IB. SMN acknowledges support by research project ESP2016-76683-C3-1-R. JMT acknowledges research grant ESP2014-53672-C3-3P. We thank the Deutscher Akademischer Austauschdienst (DAAD) for funding JC through the Research Internships in Science and Engineering (RISE).