Supernova 1987A: analysis of ultraviolet absorption spectra obtained with the ASTRON station

Absorption spectra of SN 1987A in the near UV region, obtained with ASTRON in the period from 9 to 394 days after the explosion, are investigated. Using the measurements of the λ 3230A blend shifts, the radial velocity V, is determined. It is shown that in the Supernova envelope the ionization of Fe I atoms and probably of other elements of the iron group is considerably higher than the equilibrium one, and such over-ionization leads to a strong weakening of lines of neutral atoms. The synthetic spectra computations enable to conclude that absorption blends at the wave lengths 3350, 3230 and 3080A, which are the most pronounced features in the observed spectra, are formed by the lines of the first Ti II multiples. A sharp strengthening of the blends for t>>120d as compared to the period t=9-17d is noticed; one of possible explanations if that the envelope, starting from t=120d, the titanium synthesized in the Supernova explosion is observed