Extremely precise age and metallicity of the open cluster NGC 2506 using detached eclipsing binaries

TL;DR

This study precisely determines the age and metallicity of open cluster NGC 2506 using detached eclipsing binaries and red giant stars, providing key constraints for stellar evolution models.

Contribution

It introduces a method combining eclipsing binary analysis and red giant parameters to accurately measure cluster age and metallicity, emphasizing the importance of convective core-overshooting in models.

Findings

Cluster age estimated at 2.01 ± 0.10 Gyr.

Cluster metallicity determined as -0.36 ± 0.10 dex.

Detected oscillation signals in cluster members from TESS data.

Abstract

Accurate stellar parameters of stars in open clusters can help constrain models of stellar structure and evolution. Here we wish to determine the age and metallicity content of the open cluster NGC 2506. To this end we investigated three detached eclipsing binaries (DEBs; V2032, V4, and V5) for which we determined their masses and radii, as well as four red giant branch stars for which we determined their effective temperatures, surface gravities, and metallicities. Three of the stars in the DEBs have masses close to the cluster turn-off mass, allowing for extremely precise age determination. Comparing the values for the masses and radii of the binaries to BaSTI isochrones we estimated a cluster age of $2.01 \pm 0.10$ Gyr. This does depend on the models used in the comparison, where we have found that the inclusion of convective core-overshooting is necessary to properly model the cluster. From red giant branch stars we determined values for the effective temperatures, the surface gravities, and the metallicities. From these we find a cluster metallicity of $-0.36 \pm 0.10$ dex. Using this value and the values for the effective temperatures we determine the reddening to be E$(b - y) = 0.057 \pm 0.004$ mag. Furthermore, we derived the distance to the cluster from Gaia parallaxes and found $3.101 \pm 0.017$ kpc, and we have performed a radial velocity membership determination for stars in the field of the cluster. Finally, we report on the detection of oscillation signals in $\gamma$ Dor and $\delta$ Scuti members in data from the TESS mission, including the possible detection of solar-like oscillations in two of the red giants.