August 11-15, 2014


Hot DQ White Dwarf Stars as Failed Type Ia Supernovae

Bart Dunlap (University of North Carolina at Chapel Hill)

Chris Clemens (University of North Carolina at Chapel Hill)

Of the two hundred or so white dwarf stars showing spectroscopic signatures of carbon (the DQs), the hottest dozen are unique in having atmospheres actually dominated by carbon and oxygen. Furthermore, many of these hot DQ white dwarfs are photometrically variable, and a large fraction show Zeeman splitting in their spectral lines, revealing the presence of magnetic fields. Based on theoretical pulsational stability studies, pulsations have been proposed to explain the observed brightness variations. However, based on our observations of the hot DQs with the SOAR telescope and using archival data, I will present evidence that the hot DQs are the result of CO-core white dwarf mergers that were not massive enough to explode as Type Ia supernovae. In this scenario, the variable hot DQs are magnetic rotators whose magnetic fields, fast rotation rates, and atmospheric composition are all explained by the merger. As such the masses of the hot DQs will place lower limits on the mass of the proposed channel of sub-Chandrasekhar double-degenerate Type Ia SNe. And their field strengths and spin periods will provide observational constraints for models of double-degenerate mergers and magnetic field generation.

Mode of presentation: oral