The Discovery of a Companion to the Lowest Mass White Dwarf

@article{Kilic2007TheDO,
  title={The Discovery of a Companion to the Lowest Mass White Dwarf},
  author={Mukremin Kilic and Warren R. Brown and Carlos Allende Prieto and Marc H. Pinsonneault and Scott J. Kenyon},
  journal={The Astrophysical Journal},
  year={2007},
  volume={664},
  pages={1088 - 1092}
}
We report the detection of a radial velocity companion to SDSS J091709.55+463821.8, the lowest mass white dwarf currently known, with M ~ 0.17 M☉. The radial velocity of the white dwarf shows variations with a semi-amplitude of 148.8 ± 6.9 km s-1 and a period of 7.5936 ± 0.0024 hr, which implies a companion mass of M ≥ 0.28 M☉. The lack of evidence of a companion in the optical photometry forces any main-sequence companion to be smaller than 0.1 M☉, hence a low-mass main-sequence star companion… 

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