A New Merging Double Degenerate Binary in the Solar Neighborhood

Abstract

Characterizing the local space density of double degenerate binary systems is a complementary approach to broad sky surveys of double degenerates to determine the expected rates of white dwarf binary mergers, in particular those that may evolve into other observable phenomena such as extreme helium stars, Am CVn systems, and supernovae Ia. However, there have been few such systems detected in local space. We report here the discovery that WD 1242$-$105, a nearby bright WD, is a double-line spectroscopic binary consisting of two degenerate DA white dwarfs of similar mass and temperature, despite it previously having been spectroscopically characterized as a single degenerate. Follow-up photometry, spectroscopy, and trigonometric parallax have been obtained in an effort to determine the fundamental parameters of each component of this system. The binary has a mass ratio of 0.7 and a trigonometric parallax of 25.5 mas, placing it at a distance of 39 pc. The system's total mass is 0.95 M${}_{\odot }$ and has an orbital period of 2.85 hours, making it the strongest known gravitational wave source ($\log h=-20.78$) in the mHz regime. Because of its orbital period and total mass, WD 1242$-$105 is predicted to merge via gravitational radiation on a timescale of 740 Myr, which will most likely not result in a catastrophic explosion.

22 pages, 5 figures, 2 tables; to appear in Astronomical Journal

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Cited by in corpus (8)

• Measurements of Physical Parameters of White Dwarfs: A Test of the Mass-Radius Relation
• The Solar Neighborhood. XXXIX. Parallax Results from the CTIOPI and NOFS Programs: 50 New Members of the 25 Parsec White Dwarf Sample
• A Catalogue of Potential Post Common Envelope Binaries
• Convection and Spin-Up During Common Envelope Evolution: The Formation of Short-Period Double White Dwarfs
• Influence of a mass transfer stability criterion on double white dwarf populations
• Two new Double-lined Spectroscopic Binary White Dwarfs
• A Gemini Snapshot Survey for Double Degenerates
• The evolution of relative frequencies of ONe and CO SNe Ia