GCN Circular 329
G. Marconi and G.L. Israel (Observ. of Rome, Italy), D. Lazzati, S. Covino and G. Ghisellini (Observ. of Brera, Milan, Italy) report: A 30 min exposure taken at ESO-NTT-SUSI2 1999, May 16.10984, with a seeing of 1.8" shows the OT of GRB990510 at the magnitude R=23.0+-0.1 (assuming R=16.5 for the USNO star at RA = 13:38:00.82, DEC=-80:29:11.7). The faintest detected objects in the field have R=24.5. No candidate host galaxy can be seen. We have collected all available photometric data in V, R and I. The light curve in the three bands can be fitted by the following 4 parameters formula (similar to that given by Bloom et al. in GCN 323): F_nu(t) = k t^(-al1) / [1+ (t/t_*)^(al2-al1)] where k is a normalization constant, such that the magnitude is given by m(t)=-2.5*log(F_nu). This formula fits very well the light curve in the 3 bands varying only k. We find: al1 = 0.85, al2 = 2.6, t_* = 1.8e5 sec = 2.08 days. The collection of data together with the above fit and the NTT image are posted at: http://www.merate.mi.astro.it/~gabriele/990510/ This message is citeable.