The Interferometric Binary ϵ Cnc in Praesepe: Precise Masses and Age
Klement, Robert; Monnier, John D.; Schaefer, Gail H.; Lanthermann, Cyprien; Anugu, Narsireddy; Kraus, Stefan; Gardner, Tyler; Le Bouquin, Jean-Baptiste; Bedin, Luigi R.; Libralato, Mattia; Nardiello, Domenico; Orosz, Jerome A.; ten Brummelaar, Theo; Farrington, Christopher D.; Davies, Claire L.; Ennis, Jacob; Sandquist, Eric L.; Malavolta, Luca; Morales, Leslie M.
United States, Italy, France, United Kingdom
Abstract
We observe the brightest member of the Praesepe cluster, ϵ Cnc, 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 ⊙ = 2.420 ± 0.008 and M 2/M ⊙ = 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 ϵ Cnc. We reexamine 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.