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Context. Mass loss of ~0.1-0.3 M$_{\odot}$ from Population II red giant stars(RGB) is a requirement of stellar evolution theory in order to account forseveral observational evidences in globular clusters. Aims. The aim of thisstudy is to detect the presence of outward velocity fields, which areindicative of mass outflow, in six luminous red giant stars of the stellarcluster {\omega} Cen. Methods. We compare synthetic line profiles computedusing relevant model chromospheres to observed profiles of the H{\alpha} and CaII K lines. The spectra were taken with UVES (R=45,000) and the stars wereselected so that three of them belong to the metal-rich population and three tothe metal-poor population, and sample as far down as 1 to 2.5 magnitudesfainter than the respective RGB tips. Results. We do indeed reveal the presenceof low-velocity outward motions in four of our six targets, without anyapparent correlation with astrophysical parameters. Conclusions. This providesdirect evidence that outward velocity fields and mass motions exist in RGBstars as much as 2.5 mag fainter than the tip. On the assumption that the massoutflow may eventually lead to mass loss from the star, we estimate mass-lossrates of some 10^{-9}-10^{-10} M$_{\odot}$ yr^{-1} that are compatible with thestellar evolution requirements. These rates seem to be correlated withluminosity rather than metallicity.

Modelling chromospheric line profiles as diagnostics of velocity fields in {\omega} Centauri red giant stars