The ELM Survey. VIII. 98 Double White Dwarf Binaries. (arXiv:2002.00064v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Brown_W/0/1/0/all/0/1">Warren R. Brown</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kilic_M/0/1/0/all/0/1">Mukremin Kilic</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kosakowski_A/0/1/0/all/0/1">Alekzander Kosakowski</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Andrews_J/0/1/0/all/0/1">Jeff J. Andrews</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Heinke_C/0/1/0/all/0/1">Craig O. Heinke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Agueros_M/0/1/0/all/0/1">Marcel A. Agueros</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Camilo_F/0/1/0/all/0/1">Fernando Camilo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gianninas_A/0/1/0/all/0/1">A. Gianninas</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hermes_J/0/1/0/all/0/1">J.J. Hermes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kenyon_S/0/1/0/all/0/1">Scott J. Kenyon</a>
We present the final sample of 98 detached double white dwarf (WD) binaries
found in the Extremely Low Mass (ELM) Survey, a spectroscopic survey targeting
<0.3 Msun He-core WDs completed in the Sloan Digital Sky Survey footprint. Over
the course of the survey we observed ancillary low mass WD candidates like
GD278, which we show is a P=0.19 d double WD binary, as well as candidates that
turn out to be field blue straggler/subdwarf A-type stars with luminosities too
large to be WDs given their Gaia parallaxes. Here, we define a clean sample of
ELM WDs that is complete within our target selection and magnitude range
15<g_0<20 mag. The measurements are consistent with 100% of ELM WDs being
0.0089 < P < 1.5 d double WD binaries, 35% of which belong to the Galactic
halo. We infer these are mostly He+CO WD binaries given the measurement
constraints. The merger rate of the observed He+CO WD binaries exceeds the
formation rate of stable mass transfer AM CVn binaries by a factor of 25, and
so the majority of He+CO WD binaries must experience unstable mass transfer and
merge. The shortest-period systems like J0651+2844 are signature {it LISA}
verification binaries that can be studied with gravitational waves and light.
We present the final sample of 98 detached double white dwarf (WD) binaries
found in the Extremely Low Mass (ELM) Survey, a spectroscopic survey targeting
<0.3 Msun He-core WDs completed in the Sloan Digital Sky Survey footprint. Over
the course of the survey we observed ancillary low mass WD candidates like
GD278, which we show is a P=0.19 d double WD binary, as well as candidates that
turn out to be field blue straggler/subdwarf A-type stars with luminosities too
large to be WDs given their Gaia parallaxes. Here, we define a clean sample of
ELM WDs that is complete within our target selection and magnitude range
15<g_0<20 mag. The measurements are consistent with 100% of ELM WDs being
0.0089 < P < 1.5 d double WD binaries, 35% of which belong to the Galactic
halo. We infer these are mostly He+CO WD binaries given the measurement
constraints. The merger rate of the observed He+CO WD binaries exceeds the
formation rate of stable mass transfer AM CVn binaries by a factor of 25, and
so the majority of He+CO WD binaries must experience unstable mass transfer and
merge. The shortest-period systems like J0651+2844 are signature {it LISA}
verification binaries that can be studied with gravitational waves and light.
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