Similar CM Draconis, Struve 2398, Draco Dwarf | ||
SDSSJ1240+6710 or SDSS J124043.01+671034.68, nicknamed Dox, is a white dwarf with an atmosphere of almost pure oxygen discovered by Kepler de Souza Oliveira, Detlev Koester and Gustavo Ourique. The atmosphere also has a detectable amount of magnesium, neon (under 4%) and silicon, but no hydrogen, helium or carbon. A possible explanation for the unusual composition would be if its mass were close to the limit for collapsing to a neutron star. But its mass is only 0.56 solar masses, below the mass expected for a star that could convert carbon to oxygen, neon and magnesium.
The star was originally catalogued in the catalogue of new white dwarf stars from the Data Release 12 of the Sloan Digital Sky Survey. Gustavo Ourique, an undergraduate in Physics at Universidade Federal do Rio Grande do Sul, identified the star's unique spectrum, working under the advice of Dr. Kepler Oliveira (S.O. Kepler). The star's spectrum was modeled by Dr. Detlev Koester, characterizing its composition, temperature and mass.