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

TL;DR

This study empirically measures the total mass loss of stars in omega Centauri during red giant and horizontal branch phases, providing insights into stellar evolution and validating models of horizontal branch stars.

Contribution

It introduces an empirical method to determine integrated stellar mass loss in globular cluster stars, focusing on omega Centauri, and compares results with theoretical models.

Findings

Average mass loss on RGB is 0.21 solar masses.

Average mass loss on AGB is 0.09 solar masses.

Implied HB star mass is 0.62 solar masses.

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.