SIMBAD references

An optical spectrum covering the range ll4300-6900 Å of the recurrent nova U Sco in outburst was taken on February 26th 1999, only 16 hours after maximum. Broad emission lines of H I, He I, N II, N III were seen on the spectrum, while the emission line of He II l4686 was not yet seen. The FWHM of the emission component of Hα was 8000km/s and the FWZI was roughly 12000km/s. The emission line of Hα had blue (-3250km/s), central (+30km/s), and red (+2770km/s) peaks, among which the red one was the most prominent. A narrow absorption component of Hα blue-shifted by -4850km/s was seen. The other prominent lines had a main emission peak red-shifted by 2000-3000km/s and a weak secondary peak blue-shifted by (-2000)-(-3000)km/s. Most of He I and N II lines were flanked by a narrow absorption component blue-shifted by about -4300km/s which was a good clue for the detailed identification of these lines. These absorption components and some emission lines of N II faded very rapidly and nearly disappeared one day after our observation. The widths of the emission lines decreased with time. The radial velocities of three emission peaks of Hα were -1560km/s, +60km/s and +1800km/s on March 14th, 17 days after maximum, when the blue one became stronger than the others. The helium abundance by the number of atom of the ejecta is estimated as N(He)/N(H)=0.16±0.02 which is much lower than those found in previous works, and is not different from those of normal classical novae. Adopting the distance 6kpc, the mass of the ejecta is estimated as 3-9x10^–7M_☉.