SCYON Abstract

Received on June 7 2011

Empirical determination of the integrated red giant and horizontal branch stellar mass loss in omega Centauri

AuthorsIain McDonald (1), Christian Johnson (2,3), and Albert Zijlstra (1)
Affiliation(1) Jodrell Bank Centre for Astrophysics, Alan Turing Building, Manchester, M13 9PL, UK
(2)Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547, USA
(3)National Science Foundation Astronomy and Astrophysics Postdoctoral Fellow
Accepted byMonthly Notices of the Royal Astronomical Society
Contactmcdonald@jb.man.ac.uk
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Abstract

We herein determine the average integrated mass loss from stars stars belonging to the dominant metal-poor population ([Fe/H] ~ -1.7) of the Galactic globular cluster omega Centauri (NGC 5139) during their red giant and horizontal branch evolution. Masses are empirically calculated from spectroscopic measurements of surface gravity and photometric measurements of temperature and luminosity. Systematic uncertainties prevent an absolute measurement of masses at a phase of evolution. However, the relative masses of early asymptotic giant branch stars and central red giant branch stars can be measured, and used to derive the mass loss between these two phases. This can then be used as a physical check of models of horizontal branch (HB) stars. For omega Cen, the average difference is found to be 26 +/- 4%. Assuming initial and final masses of 0.83 and 0.53 solar masses, we determine that 0.21 +/- 0.03 solar masses is lost on the RGB and 0.09 +/- ~0.05 solar masses is lost on the AGB. The implied HB stellar mass of 0.62 +/- 0.04 solar masses is commensurate with literature determinations of the masses of the cluster's HB stars. The accuracy of this measurement can be improved through better selection of stars and spectral coverage, and applied to other clusters where horizontal branch models do not currently agree.