Program: GS-2015A-Q-104

A new discovery space for short period binary white dwarfs has been opened up with the availability of SDSS Data Release 10 spectroscopy. The Extremely Low-Mass (ELM) Survey takes advantage of the SDSS photometry and spectroscopy to identify compact systems with 1 hour or shorter orbital periods. We recently fit all of the SDSS DR10 stellar spectra to identify ELM white dwarfs with M < 0.3 Msun, all of these objects should be in binary systems. Here we propose to obtain follow-up Gemini-South Poor-Weather spectroscopic observations of 29 relatively bright ELM white dwarfs. Our two major science goals are to discover detached gravitational wave sources for fundamental tests of general relativity, and to constrain the formation rate and space density of merging white dwarfs. The latter is important for constraining the contribution of double degenerates to Type Ia and underluminous supernovae.