Evidence for a merger of binary white dwarfs: the case of GD 362

Abstract

GD 362 is a massive white dwarf with a spectrum suggesting a H-rich atmosphere which also shows very high abundances of Ca, Mg, Fe and other metals. However, for pure H-atmospheres the diffusion timescales are so short that very extreme assumptions have to be made to account for the observed abundances of metals. The most favored hypothesis is that the metals are accreted from either a dusty disk or from an asteroid belt. Here we propose that the envelope of GD 362 is dominated by He, which at these effective temperatures is almost completely invisible in the spectrum. This assumption strongly alleviates the problem, since the diffusion timescales are much larger for He-dominated atmospheres. We also propose that the He-dominated atmosphere of GD 362 is likely to be the result of the merger of a binary white dwarf.

arXiv comment4 pages, 3 figures. Accepted for publication in Astrophysical Journal Letters

References in corpus (12)

• Spectral Energy Distributions of T Tauri Stars With Passive Circumstellar Disks
• A Tidally-Disrupted Asteroid Around the White Dwarf G29-38
• The Formation Rate, Mass and Luminosity Functions of DA White Dwarfs from the Palomar Green Survey
• A Dusty Disk Around GD 362, a White Dwarf With a Uniquely High Photospheric Metal Abundance
• Magnetic braking of T Tauri stars
• The ages of very cool hydrogen-rich white dwarfs
• The accretion-diffusion scenario for metals in cool white dwarfs
• Excess Infrared Radiation from a Massive DAZ White Dwarf: GD362 - a Debris Disk?
• Infrared Emission from the Dusty Disk Orbiting GD 362, An Externally-Polluted White Dwarf
• Discovery of a Cool, Massive, and Metal-Rich DAZ White Dwarf
• Disks and Planets Around Massive White Dwarfs
• Gravitational Radiation from Pulsating White Dwarfs

Cited by in corpus (11)

• The Evolution of Compact Binary Star Systems
• The Chemical Composition of an Extrasolar Minor Planet
• Double degenerate mergers as progenitors of high-field magnetic white dwarfs
• Nuclear astrophysics: the unfinished quest for the origin of the elements
• Twins: The Two Shortest Period Non-Interacting Double Degenerate White Dwarf Stars
• A white dwarf merger as progenitor of the anomalous X-ray pulsar 4U 0142+61?
• Single magnetic white dwarfs with Balmer emission lines: A small class with consistent physical characteristics as possible signposts for close-in planetary companions
• Magnetic white dwarfs with debris discs
• Direct Distance Measurement to the Dusty White Dwarf GD 362
• Magnetic White Dwarfs: Observations, Theory, and Future Prospects
• Constraining the Surface Inhomogeneity and Settling Times of Metals on Accreting White Dwarfs