Early detection of the optical counterpart to GRB 980329

J. Gorosabel, A. J. Castro-Tirado, A. Pedrosa, M. R. Zapatero-Osorio, A. J. L. Fernades, M. Feroci, E. Costa, F. Frontera

Published 1999-06-11Version 1

We report optical observations of the GRB 980329 error box which represent the second earliest detection of the GRB 980329 optical transient. We determine R = 23.7 $\pm$ 0.5 mag on 29.89 March, which is consistent with R = 23.6 $\pm$ 0.2 mag as reported by Palazzi et al. (1998) on 29.99 March. Based on extrapolations of the light curve we claim that the R-band magnitude of the GRB 980329 host galaxy should lie in the range 26.8 mag $<$ R $<$ 29 mag. We also discuss the similarities with GRB 970111.