2012A&A...544A.149M

We present optical and near-infrared (NIR) spectroscopic observations of U Sco 2010 outburst. From the analysis of lines profiles we identify a broad and a narrow component and show that the latter originates from the reforming accretion disk. We show that the accretion resumes shortly after the outburst, on day +8, roughly when the super-soft (SSS) X-ray phase starts. Consequently U Sco SSS phase is fueled (in part or fully) by accretion and should not be used to estimate m_rem, the mass of accreted material which has not been ejected during the outburst. In addition, most of the He emission lines, and the Heii lies in particular, form in the accretion flow/disk within the binary and are optically thick, thus preventing an accurate abundance determination. A late spectrum taken in quiescence and during eclipse shows CaiiH&K, the G-band and Mgib absorption from the secondary star. However, no other significant secondary star features have been observed at longer wavelengths and in the NIR band.