The 1999 outburst of the eclipsing and recurrent nova U Scorpii

The spectroscopic and photometric evolution of the 1999 outburst of the ecl ipsing and recurrent nova U Sco is presented. The photometric evolution clo sely matches that of the previous events. The FWZI = 10,000 km sec(-1) for emission lines at maximum has decreased to 4000 km sec(-1) by day +23, with continuous and dramatic changes in the line profiles. No nebular line has become visible and the ionization degree has increased during the brightnes s decline. A not previously reported and quite puzzling splitting of the em ission lines into three components after the first two weeks is outstanding in our spectra. The radiated luminosity is found to be a tiny fraction of that of classical novae for any reasonable distance to U Sco.