Spitzer Space Telescope evidence in NGC 6791: no super-mass-loss at super-solar metallicity to explain helium white dwarfs?

TL;DR

This study uses Spitzer data to investigate mass loss in super-solar metallicity red giants in NGC 6791, finding no evidence of enhanced mass loss or circumstellar dust production, challenging previous assumptions.

Contribution

It provides observational evidence that super-solar metallicity red giants do not experience significant mass loss to prevent helium flash, contrary to prior hypotheses.

Findings

No evidence of circumstellar dust indicative of high mass loss.

Luminosity functions match theoretical models.

Red giants at super-solar metallicity do not avoid helium flash.

Abstract

We use archival Spitzer Space Telescope photometry of the old, super-solar metallicity massive open cluster NGC 6791 to look for evidence of enhanced mass loss, which has been postulated to explain the optical luminosity function and low white dwarf masses in this benchmark cluster. We find a conspicuous lack of evidence for prolificacy of circumstellar dust production that would have been expected to accompany such mass loss. We also construct the optical and infrared luminosity functions, and demonstrate that these fully agree with theoretical expectations. We thus conclude that there is no evidence for the mass loss of super-solar metallicity red giants to be sufficiently high that they can avoid the helium flash at the tip of the red giant branch.