The Cluster AgeS Experiment (CASE). Analysis of the Detached Eclipsing Binary V15 in the Metal-Rich Open Cluster NGC 6253

TL;DR

This study provides a detailed analysis of the detached eclipsing binary V15 in NGC 6253, deriving precise stellar parameters and a higher age estimate for the cluster than previous studies, highlighting challenges in modeling and measurement.

Contribution

First detailed analysis of V15 in NGC 6253, providing new stellar parameters and a revised, higher age estimate for the cluster using mass-radius and CMD fitting methods.

Findings

Estimated cluster age: 3.8-4.6 Gyr

Derived stellar parameters with high precision

Model atmospheres do not fully match observed CMD

Abstract

We present the first detailed analysis of the detached eclipsing binary V15 in the super-metal rich open cluster NGC 6253. We obtain the following absolute parameters: M_p=1.303+-0.006 Msun, R_p=1.71+-0.03 Rsun, L_p=2.98+-0.10 Lsun for the primary, and M_s=1.225+-0.006 Msun, R_s=1.44+-0.02 Rsun, L_s=2.13+-0.06 Lsun for the secondary. Based on Dartmouth isochrones, the age of NGC 6253 is estimated to be 3.80 - 4.25 Gyr from the mass-radius diagram and 3.9 - 4.6 Gyr from color-magnitude diagram (CMD) fitting. Both of these estimates are significantly higher than those reported so far. The derived apparent distance modulus of 11.65 mag agrees well with the range of 10.9 - 12.2 mag derived by other authors; however our estimated reddening (0.113 mag) is lower than the lowest published value (0.15 mag). We confirm earlier observations that model atmospheres are not accurate enough to account for the whole CMD of the cluster, with the largest discrepancies appearing on the subgiant and giant branches. Although age estimation from the mass-radius diagram is a relatively safe, distance- and reddening-independent procedure, our results should be verified by photometric and spectroscopic observations of additional detached eclipsing binaries which we have discovered, at least two of which are proper-motion members of NGC 6253.