The frequency by mass of Galactic carbon stars inferred from Gaia measurements of star cluster members

TL;DR

This study uses Gaia data to analyze the occurrence of Galactic carbon stars across different progenitor masses, revealing similarities with Magellanic Clouds and identifying a potential high-mass candidate.

Contribution

It provides the first mass-dependent frequency analysis of Galactic carbon stars using Gaia cluster data, highlighting differences and similarities with other galaxies.

Findings

C star frequency matches Magellanic Clouds at certain masses

Frequency increases at around 1.38 solar masses due to cluster distribution

No C stars observed below 1.24 solar masses, indicating older stellar populations

Abstract

We investigate the frequency of occurrence of Galactic carbon stars as a function of progenitor mass using Gaia data. Small number statistics limit fidelity, but C star frequency agrees with that observed in the Magellanic Clouds (MCs) down to $m \approx1.67$ M$_\odot$. At $m \approx 1.38$ M$_\odot$, the frequency rises by a factor of three even though the frequency appears to drop to zero for the MCs. In fact this is due to a lack of clusters at the key age range in the MCs. At $m \approx 1.24$ M$_\odot$ and below, no C stars are observed, corresponding to ages older than 4 Gyr. Within uncertainties, C~star frequency in M 31 is consistent with that of the Galaxy and the MCs. We find an ambiguous C-star candidate at $\sim$7 M$_\odot$.