Re-crowning The Queen: Membership, Age and Rotation Periods for the Open Cluster Coma Berenices

TL;DR

This study refines the membership, age, and rotation periods of the Coma Berenices open cluster using Gaia, LAMOST, TESS, and ZTF data, establishing it as a key benchmark for stellar evolution studies.

Contribution

It provides the first comprehensive membership list, metallicity, reddening, age, and rotation periods for Coma Berenices, enhancing its utility for age-rotation-activity research.

Findings

Confirmed Coma Berenices is coeval with Hyades and Praesepe.

Derived new membership list based on Gaia DR2 astrometry.

Measured rotation periods for low-mass members using TESS and ZTF.

Abstract

Coma Berenices (Coma Ber), an open cluster about the same age as Praesepe and the Hyades (700-800 Myr) is, despite being only 85 pc away, less well studied than its famous cousins. This is due principally to its sparseness and low proper motion, which together made Coma Ber's membership challenging to establish pre-Gaia. We have curated a new list of its members based on Gaia DR2 astrometry, derived its metallicity and interstellar reddening using LAMOST data, and inferred the cluster's age by fitting PARSEC isochrones to its color$-$magnitude diagram. We then measured rotation periods for Coma Ber's low-mass members using TESS and ZTF photometry. Our isochrone fitting and the TESS- and ZTF-derived rotation periods confirm that Coma Ber is coeval with the Hyades and Praesepe. This work is the first step toward re-establishing Coma Ber as another valuable benchmark cluster for age$-$rotation$-$activity studies.