The Helium Abundance in the Ejecta of U Scorpii

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U Scorpii is a recurrent nova which has been observed in outburst on 10 occasions, most recently in 2010. We present near-infrared and optical spectroscopy of the 2010 outburst of U Sco. The reddening of U Sco is found to be E(B-V) = 0.14±0.12, consistent with previous determinations, from simultaneous optical and near-IR observations. The spectra show the evolution of the line widths and profiles to be consistent with previous outbursts. Velocities are found to be up to 14000kms⁻¹ in broad components and up to 1800kms⁻¹ in narrow line components, which become visible around day 8 due to changes in the optical depth. From the spectra we derive a helium abundance of N(He)/N(H) = 0.073±0.031 from the most reliable lines available; this is lower than most other estimates and indicates that the secondary is not helium-rich, as previous studies have suggested.