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arXiv · 1108.0335

Discovery of a Bright, Extremely Low-Mass White Dwarf in a Close Double Degenerate System

S. Vennes·J. R. Thorstensen·A. Kawka·P. Nemeth·J. N. Skinner·A. Pigulski·M. Steslicki·Z. Kolaczkowski·P. Srodka
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Abstract

We report the discovery of a bright (V ~ 13.7), extremely low-mass white dwarf in a close double degenerate system. We originally selected GALEX J171708.5+675712 for spectroscopic follow-up among a group of white dwarf candidates in an ultraviolet-optical reduced proper-motion diagram. The new white dwarf has a mass of 0.18 M_solar and is the primary component of a close double degenerate system (P=0.246137 d, K_1 = 288 km/s) comprising a fainter white dwarf secondary with M_2 ~ 0.9 M_solar. Light curves phased with the orbital ephemeris show evidence of relativistic beaming and weaker ellipsoidal variations. The light curves also reveal secondary eclipses (depth ~ 8 mmag) while the primary eclipses appear partially compensated by the secondary gravitational deflection and are below detection limits. Photospheric abundance measurements show a nearly solar composition of Si, Ca, and Fe (0.1-1 solar), while the normal kinematics suggest a relatively recent formation history. Close binary evolutionary scenarios suggest that extremely low mass white dwarfs form via a common-envelope phase and possible Roche-lobe overflow.

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S. Vennes, J. R. Thorstensen, A. Kawka, P. Nemeth, J. N. Skinner, A. Pigulski, M. Steslicki, Z. Kolaczkowski, P. Srodka. 2011-08-01. Discovery of a Bright, Extremely Low-Mass White Dwarf in a Close Double Degenerate System. https://doi.org/10.1088/2041-8205%2F737%2F1%2Fl16

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