Observational signatures of past mass-exchange episodes in massive binaries

Mass and momentum exchanges in massive binaries can produce several observational signatures, such as asynchronous rotation and altered chemical compositions, which remain once the stars detach again. We have started to investigate these effects for a sample of detached massive O-star binaries that are thought to have previously experienced a Case A Roche lobe overflow. Using phase-resolved spectroscopy, we perform the disentangling of the spectra of the two stars. The reconstructed primary and secondary spectra are then analyzed to determine a range of stellar effective temperatures and gravity, as well as rotational velocities. Using model atmosphere codes we also constrain the chemical composition of the components. In this contribution, we present the first results of our analyses of HD149404 (O7.5If + ON9.5I, P = 9.81 days).