Discovery of a Cool, Massive, and Metal-Rich DAZ White Dwarf

Abstract

We report the discovery of a new metal-rich DAZ white dwarf, GD 362. High signal-to-noise optical spectroscopy reveals the presence of spectral lines from hydrogen as well as CaI, CaII, MgI, and FeI. A detailed model atmosphere analysis of this star yields an effective temperature of Teff = 9740 +/- 50 K, a surface gravity of log g = 9.12 +/- 0.07, and photospheric abundances of log Ca/H = -5.2 +/- 0.1, log Mg/H = -4.8 +/- 0.1, and log Fe/H = -4.5 +/- 0.1. White dwarf cooling models are used to derive a mass of 1.24 Mo for GD 362, making it the most massive and metal-rich DAZ uncovered to date. The problems related to the presence of such large metal abundances in a nearby (d ~ 25 pc) white dwarf in terms of an accretion scenario are briefly discussed.