Sounding open clusters: asteroseismic constraints from Kepler on the properties of NGC 6791 and NGC 6819

TL;DR

This study uses asteroseismic data from NASA's Kepler mission to determine fundamental properties such as mass, radius, distance, and age of stars in open clusters NGC 6791 and NGC 6819, providing new insights into their characteristics.

Contribution

It presents the first asteroseismic constraints on the properties of these clusters, including model-independent distance estimates and average stellar masses.

Findings

Distance modulus for NGC 6791 is 13.11±0.06

Distance modulus for NGC 6819 is 11.85±0.05

Ages are approximately 7 Gyr for NGC 6791 and 2-2.4 Gyr for NGC 6819

Abstract

We present initial results on some of the properties of open clusters NGC 6791 and NGC 6819 derived from asteroseismic data obtained by NASA's Kepler mission. In addition to estimating the mass, radius and log g of stars on the red-giant branch of these clusters, we estimate the distance to the clusters and their ages. Our model-independent estimate of the distance modulus of NGC 6791 is (m-M)_0= 13.11\pm 0.06. We find (m-M)_0= 11.85\pm 0.05 for NGC 6819. The average mass of stars on the red-giant branch of NGC 6791 is 1.20 \pm 0.01 M_sun, while that of NGC 6819 is 1.68\pm 0.03M_sun. It should be noted that we do not have data that cover the entire red-giant branch and the actual mass will be somewhat lower. We have determined model-dependent estimates of ages of these clusters. We find ages between 6.8 and 8.6 Gyr for NGC 6791, however, most sets of models give ages around 7Gyr. We obtain ages between 2 and 2.4 Gyr for NGC 6819.