A Carbon-rich Mira variable in a globular cluster: A stellar merger

TL;DR

This paper reports the discovery of the first known carbon-rich Mira variable in a globular cluster, suggesting it is a stellar merger product with an unexpected age and mass.

Contribution

It provides evidence for a stellar merger origin of a carbon-rich Mira in a globular cluster, challenging previous assumptions about such stars' ages.

Findings

Confirmed cluster membership via radial velocities

Identified the star as a stellar merger product

First C-Mira discovered in a globular cluster

Abstract

The membership of Matsunaga's variable 1, a carbon-rich, mass-losing, Mira variable, in the globular cluster Lynga 7 is discussed on the basis of radial velocities. We conclude that it is a member, the first known C-Mira in a globular cluster. Since such a variable is expected to have an age of $\sim 1-2$ Gyr and an initial mass of $\sim 1.5$ solar masses, we conclude that this star must be the product of a stellar merger.