Keck Infrared Spectroscopy of WZ Sagittae: Detection of Molecular Emission from the Accretion Disk

Abstract

Time-resolved IR spectroscopy of WZ Sge was obtained using NIRSPEC on Keck II. We detect CO and Hrm 2 emission from the accretion disk placing WZ Sge into a rarefied class of astronomical objects including YSOs and high luminosity early-type stars. During the eclipse phase, the molecular emission greatly weakens but no firm evidence for the secondary star is seen allowing new limits on its luminosity to be determined. The detection of molecular emission provides physical properties within the outer disk of T=3000K and NH>10 10 cm -3. Such a cool, dense region, not associated with areas of H I and He I emission, provides the first observational confirmation of predictions made by accretion disk models.