Obtaining normalised component spectra with FDBinary

We discuss the problem of the normalisation of stellar spectra obtained through spectral disentangling of a time series of spectra of a double-lined spectroscopic binary and describe our disentangling code FDBinary. We consider in detail the case of component stars with a time-independent flux ratio. The component spectra are then uniquely determined only up to a constant term. Additionally, due to deviations between the data and the model assumptions, the component spectra may be distorted and present undulations in the continua.