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The triple degenerate star WD1704+481

P. F. L. Maxted·T. R. Marsh·C. K. J. Moran·Z. Han
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Abstract

WD1704+481 is a visual binary in which both components are white dwarfs. We present spectra of the H-alpha line of both stars which show that one component (WD1704+481.2 = Sanduleak B = GR 577) is a close binary with two white dwarf components. Thus, WD1704+481 is the first known triple degenerate star. From radial velocity measurements of the close binary we find an orbital period of 0.1448d, a mass ratio, q=Mbright/Mfaint of q=0.70+-0.03 and a difference in the gravitational redshifts of 11.5+-2.3km/s. The masses of the close pair of white dwarfs predicted by the mass ratio and gravitational redshift difference combined with theoretical cooling curves are 0.39+-0.05 solar mass and 0.56+-0.07 solar masses. WD1704+481 is therefore also likely to be the first example of a double degenerate in which the less massive white dwarf is composed of helium and the other white dwarf is composed of carbon and oxygen.

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P. F. L. Maxted, T. R. Marsh, C. K. J. Moran, Z. Han. 2000-05-23. The triple degenerate star WD1704+481. https://doi.org/10.1046/j.1365-8711.2000.03343.x

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