When do stars in 47 Tucanae lose their mass?

TL;DR

This study uses white dwarf diffusion in 47 Tucanae to pinpoint when stars lose most of their mass, finding it occurs near the asymptotic giant branch phase and not on the red-giant branch.

Contribution

It provides new constraints on the timing of stellar mass loss in globular cluster stars, challenging previous assumptions about red-giant branch mass loss.

Findings

Mass loss occurs around the AGB phase, not on the red-giant branch.

Mass loss epoch is approximately 3 million years before the AGB tip.

Red-giant branch mass loss exceeding 0.2 solar masses is statistically excluded.

Abstract

By examining the diffusion of young white dwarfs through the core of the globular cluster 47 Tucanae, we estimate the time when the progenitor star lost the bulk of its mass to become a white dwarf. According to stellar evolution models of the white-dwarf progenitors in 47 Tucanae, we find this epoch to coincide approximately with the star ascending the asymptotic giant branch ($3.0 \pm 8.1$ Myr before the tip of the AGB) and more than ninety million years after the helium flash (with ninety-percent confidence). From the diffusion of the young white dwarfs we can exclude the hypothesis that the bulk of the mass loss occurs on the red-giant branch at the four-sigma level. Furthermore, we find that the radial distribution of horizontal branch stars is consistent with that of the red-giant stars and upper-main-sequence stars and inconsistent with the loss of more than 0.2 solar masses on the red-giant branch at the six-sigma level.