Asteroseismology of overmassive, undermassive, and potential past members of the open cluster NGC6791

TL;DR

This study uses asteroseismology, Gaia, and Kepler data to identify overmassive and undermassive giant stars in NGC 6791, revealing complex stellar evolution and potential past cluster membership.

Contribution

It provides the first detailed asteroseismic analysis of atypical giants in NGC 6791, highlighting the presence of stars with non-standard evolution due to mass transfer or mergers.

Findings

Approximately 10% of red giants show evidence of mass transfer or mergers.

Identification of non-members with potential past cluster membership.

Potential for spectroscopic follow-up to confirm evolutionary histories.

Abstract

We perform an asteroseismic investigation of giant stars in the field of NGC 6791 with previous indications of atypical evolution. The analysis makes use of observations from Kepler and Gaia in combination with ground-based photometry, a literature radial-velocity study, and measurements of eclipsing binaries in the cluster. We derive mass, radius, effective temperature, evolutionary stage and apparent distance modulus of each target. Among the investigated cluster giants we find clear evidence of overmassive and undermassive members, and non-members with strong hints of potential past membership. Our results indicate that about 10% of the red giants in the cluster have experienced mass-transfer or a merger. High resolution, high-S/N spectroscopic follow-up could confirm potential past membership of the non-members, and reveal whether certain element abundances might expose the non-standard evolution of overmassive and undermassive stars. If so, field stars of similar type could be identified as what they are, i.e. over- or undermassive stars, and not mistakenly classified as younger or older than they are.