  The H$\alpha$ profile varies with the orbital period. The two strong shell
type emission peaks are identified as from one single broad emission feature
with an absorption centered around -7.5~\kms. The intensity variations are
largely attributed to a differential amount of reddening towards the H$\alpha$
emitting region and the stellar continuum. The radial velocities suggest that
the H$\alpha$ emission moves in phase with the primary, but with a slightly
lower velocity amplitude.
  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).
