Interferometric Observations of RS Ophiuchi and the Origin of the Near-Infrared Emission

We report observations of the recurrent nova RS Oph using long-baseline near-IR interferometry. We are able to resolve emission from the nova for several weeks after the 2006 February outburst. The near-IR source initially expands to a size of ~5 mas. However, beginning around day 10, the IR source appears to begin to shrink, reaching ~2 mas by day 100. We combine our measured angular diameters with previously available interferometric and photometric data to derive an emission measure for the source, and hence are able to determine the mass-loss rate of the nova in the days following the outburst.