Instituto de Física, Universidade Federal do Rio Grande do Sul, 91501-900 Porto Alegre, RS, Brazil.
Institut für Theoretische Physik und Astrophysik, Universität Kiel, 24098 Kiel, Germany.
Science. 2016 Apr 1;352(6281):67-9. doi: 10.1126/science.aad6705.
Stars born with masses below around 10 solar masses end their lives as white dwarf stars. Their atmospheres are dominated by the lightest elements because gravitational diffusion brings the lightest element to the surface. We report the discovery of a white dwarf with an atmosphere completely dominated by oxygen, SDSS J124043.01+671034.68. After oxygen, the next most abundant elements in its atmosphere are neon and magnesium, but these are lower by a factor of ≥25 by number. The fact that no hydrogen or helium are observed is surprising. Oxygen, neon, and magnesium are the products of carbon burning, which occurs in stars at the high-mass end of pre-white dwarf formation. This star, a possible oxygen-neon white dwarf, will provide a rare observational test of the evolutionary paths toward white dwarfs.
质量小于约 10 个太阳质量的恒星最终会成为白矮星。它们的大气主要由最轻的元素组成，因为引力扩散会将最轻的元素带到表面。我们报告了一颗白矮星的发现，其大气完全由氧主导，这颗白矮星名为 SDSS J124043.01+671034.68。在氧之后，其大气中含量第二丰富的元素是氖和镁，但按数量计算，这两种元素的丰度低了≥25 倍。实际上，没有观测到氢或氦，这令人惊讶。氧、氖和镁是碳燃烧的产物，而碳燃烧发生在预白矮星形成的高质量端的恒星中。这颗可能的氧氖白矮星将为研究白矮星形成的演化路径提供一个难得的观测测试机会。
