Program: GN-2010B-Q-54

Observations over the past 15 years have uncovered evidence for a large population of low mass, helium-core white dwarfs formed from binary evolution, many of which reside in binaries with white dwarf companions today. Helium white dwarfs form when stars lose their envelopes on the red giant branch. Their evolution is uncertain because at masses $< 0.2 M_\odot$ it is thought that their cooling may be greatly slowed by residual hydrogen burning. This is now testable because of our recent discovery of the first known detached eclipsing double white dwarf binary which contains a carbon-oxygen white dwarf in a 5.6 hour orbit with a helium white dwarf. We request Gemini/NIRI observations of multiple primary and secondary eclipses in $J$- and $K_{\rm s}$-bands to acquire multi-color lightcurves in the near-IR. This will help: (1) constrain the temperature and hence age of the secondary, (2) establish the shape of the primary eclipse to probe the primary's atmosphere, (3) constrain the eccentricity of the system, and (4) try to measure the semi-major axis through accurate timing. Overall, these observations will help establish the reference data for future timing measurements of this unique object, and aid in determining the eventual fate of the system.