# The Helium Abundance of NGC 6791 from Modeling of Stellar Oscillations

## TL;DR

This study uses detailed asteroseismology of Kepler data to precisely determine the helium abundance and age of the old, metal-rich open cluster NGC 6791, providing new insights into stellar evolution.

## Contribution

It introduces a method to constrain helium abundance and age of cluster stars using individual mode frequencies from Kepler data, improving upon previous global parameter approaches.

## Key findings

- Helium abundance of Y0=0.297±0.003 for NGC 6791
- Cluster age determined to be 8.2±0.3 Gyr
- Enhanced precision in stellar parameter estimation

## Abstract

The helium abundance of stars is a strong driver of evolutionary timescales, however it is difficult to measure in cool stars. We conduct an asteroseismic analysis of NGC 6791, an old, metal rich open cluster that previous studies have indicated also has a high helium abundance. The cluster was observed by Kepler and has unprecedented lightcurves for many of the red giant branch stars in the cluster. Previous asteroseismic studies with Kepler data have constrained the age through grid based modeling of the global asteroseismic parameters ($\Delta\nu$ and $\nu_{\mathrm{max}}$). However, with the precision of Kepler data, it is possible to do detailed asteroseismology of individual mode frequencies to better constrain the stellar parameters, something that has not been done for these cluster stars as yet. In this work, we use the observed mode frequencies in 27 hydrogen shell burning red giants to better constrain initial helium abundance ($Y_0$) and age of the cluster. The distributions of helium abundance and age for each individual red giant are combined to create a final probability distribution for age and helium abundance of the entire cluster. We find a helium abundance of $Y_0=0.297\pm0.003$ and a corresponding age of $8.2\pm0.3$ Gyr.