Radial velocities of HR 4049

The radial velocities suggest that the H{alpha} emission moves in phase with the primary, but with a slightly lower velocity amplitude. From this we infer that the H{alpha} emission comes from outside the orbit of the primary, but still gravitationally bound to the primary. H{alpha} also shows a weak emission feature at -21.3+/-3.5km/s, which originates from the circumbinary disc and a weak absorption feature at -7.5+/-1.6km/s due to absorption by the circumbinary disc.

We propose two competing models that could account for the observed velocity and intensity variations of the H{alpha} profile. Model I: light from the primary reflects on a localized spot near the inner radius of the circumbinary disc which is closest to the primary. Model II: H{alpha} emission originates in the outer layers of the extended atmosphere of the primary due to activity.

These activities are locked to the position of the primary in its orbit. We discuss the similarities of variability and shape of the H{alpha} emission of HR 4049 with those of early type T-Tauri stars (e.g SU Aur).