The Interferometric Binary Epsilon Cancri in Praesepe: Precise Masses and Age

TL;DR

This study precisely measures the masses of a binary star system in Praesepe, using interferometry and spectroscopy, to refine the cluster's age and test stellar evolution models with detailed observational data.

Contribution

The paper provides new precise mass measurements of Epsilon Cancri in Praesepe and uses these to estimate the cluster's age, offering insights into stellar evolution models.

Findings

Masses of the stars are M_1 = 2.420 ± 0.008 M_sun and M_2 = 2.226 ± 0.004 M_sun.

Cluster age is estimated at 637 ± 19 million years.

Results support models with standard convective core overshooting.

Abstract

We observe the brightest member of the Praesepe cluster, Epsilon Cancri, to precisely measure the characteristics of the stars in this binary system, en route to a new measurement of the cluster's age. We present spectroscopic radial velocity measurements and interferometric observations of the sky-projected orbit to derive the masses, which we find to be M_1/M_sun = 2.420 +/- 0.008 and M_2/M_sun = 2.226 +/- 0.004. We place limits on the color-magnitude positions of the stars by using spectroscopic and interferometric luminosity ratios while trying to reproduce the spectral energy distribution of Epsilon Cancri. We re-examine the cluster membership of stars at the bright end of the color-magnitude diagram using Gaia data and literature radial velocity information. The binary star data are consistent with an age of 637 +/- 19 Myr, as determined from MIST model isochrones. The masses and luminosities of the stars appear to select models with the most commonly used amount of convective core overshooting.