GCN Circular 9054
Adria Updike (Clemson University), Sylvio Klose (Tautenburg Obs.), Christian Clemens and Jochen Greiner (MPE Garching) report on behalf of the GROND team: We observed the field of GRB 090328 (Fermi trigger 259925808; McEnergy et al., GCN 9044) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m ESO/MPI telescope at La Silla Observatory (Chile). Observations started at 23:24 UT on date, about 1.6 days after the GRB trigger, and are continuing. They were performed at an average seeing of 1.8" and at an average airmass of 1.06. We detect the afterglow reported by Kennea et al. (GCN 9045) in all bands. Based on the first 8 min of total exposures in g'r'i'z' JHK, we estimate preliminary magnitudes (all in AB system) of g' = 20.97 +/- 0.05 mag, r' = 20.23 +/- 0.03 mag, i' = 19.89 +/- 0.04 mag, z' = 19.54 +/- 0.03 mag, J = 19.54 +/- 0.06 mag, H = 19.02 +/- 0.06 mag and K = 18.52 +/- 0.08 mag Given magnitudes are calibrated against USNO as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.06 mag in the direction of the burst (Schlegel et al. 1998).