Spectroscopy of the growing circumstellar disk in the δ Scorpii Be binary

We present the results of a spectroscopic monitoring program of the binary system delta Scorpii, whose primary became a Be star after the last periastron encounter in the Summer of 2000. The observations cover a period of 2 years ( March 2001 June 2003) and are a continuation of our previous campaign reported in Miroshnichenko et al. ( 2001). We found that the emission-line spectrum was gradually strengthening over the whole monitoring period. Several short-term increases of the line emission, possibly due to outbursts of matter ejected from the stellar surface, were detected. The outbursts seem to be responsible for the brightness fadings, seen afterwards. We attempt to explain the overall observed line and continuum behaviour in terms of a circumstellar disk, growing in density and size. The disk is most likely Keplerian with an outer radius of similar to 10 R-* and a mean expansion speed of similar to 0.4 km s(-1).