The helium abundance in the ejecta of U Scorpii

U Scorpii (U Sco) is a recurrent nova which has been observed in outburst on 10 occasions, most recently in 2010. We present near-infrared (near-IR) 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 linewidths and profiles to be consistent with previous outbursts. Velocities are found to be up to 14 000 km s−1 in broad components and up to 1800 km s−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.