A massive white dwarf member of the Coma Berenices Open Cluster

TL;DR

This study identifies a massive white dwarf in the Coma Berenices cluster, analyzing its properties, potential companions, and progenitor star to inform stellar evolution models.

Contribution

It provides detailed characterization of a white dwarf in a nearby open cluster, including mass, temperature, cooling age, and progenitor mass, contributing to understanding the initial-final mass relation.

Findings

White dwarf mass is 0.90 ± 0.04 M_sun.

Cooling time is approximately 363 Myrs.

Progenitor star mass estimated at 4.77 M_sun.

Abstract

We report the identification, from a photometric, astrometric and spectroscopic study, of a massive white dwarf member of the nearby, approximately solar metalicity, Coma Berenices open star cluster (Melotte 111). We find the optical to near-IR energy distribution of WD1216+260 to be entirely consistent with that of an isolated DA and determine the effective temperature and surface gravity of this object to be $T_{\rm eff}$=$15739^{+197}_{-196}$K and log $g$=$8.46^{+0.03}_{-0.02}$. We set tight limits on the mass of a putative cool companion, M$\simgreat$0.036M$_{\odot}$ (spatially unresolved) and M$\simgreat$0.034M$_{\odot}$, (spatially resolved and a$\simless$2500AU). Based on the predictions of CO core, thick-H layer evolutionary models we determine the mass and cooling time of WD1216+260 to be M$_{\rm WD}$=$0.90 \pm0.04$M$_{\odot}$ and $\tau$$_{\rm cool}$=$363^{+46}_{-41}$Myrs respectively. For an adopted cluster age of $\tau$=500$\pm$100Myrs we infer the mass of its progenitor star to be M$_{\rm init}$=$4.77^{+5.37}_{-0.97}$M$_{\odot}$. We briefly discuss this result in the context of the form of the stellar initial mass-final mass relation.