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We report the identification, from a photometric, astrometric and spectroscopic study, of a massive white dwarf member of the nearby, approximately solar metallicity, Coma Berenices open star cluster (Melotte 111). We find the optical to near‐infrared energy distribution of WD 1216+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  eff = 15 739 +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 ≳ 0.036 M ⊙   (spatially unresolved) and   M ≳ 0.034 M ⊙   (spatially resolved and   a ≲ 2500 au ). Based on the predictions of CO core, thick H layer evolutionary models we determine the mass and cooling time of WD 1216+260 to be   M  WD = 0.90 ± 0.04 M ⊙   and  τ cool = 363 +46  −41  Myr , respectively. For an adopted cluster age of  τ= 500 ± 100 Myr  we infer the mass of its progenitor star to be   M  init = 4.77 +5.37  −0.97  M ⊙  . We briefly discuss this result in the context of the form of the stellar initial mass–final mass relation.

A massive white dwarf member of the Coma Berenices open cluster