An optical study of the GRB 970111 field beginning 19 hours after the gamma-ray burst ?;??;???

We present the results of the monitoring of the GRB 970111 field that started 19 hours after the event. This obser- vation represents the fastest ground-based follow-up performed for GRB 970111 in all wavelengths. As soon as the detection of the possible GRB 970111 X-ray afterglow was reported by Feroci et al. (1998) we reanalyzed the optical data collected for the GRB 970111 field. Although we detect small magnitude variability in some objects, no convincing optical counterpart is found inside the WFC error box. Any change in brightness 19 hours after the GRB is less than 0.2 mag for objects with B < 21 and R < 20.8. The bluest object found in the field is coincident with 1SAX J1528.8+1937. Spectroscopic observations revealed that this object is a Seyfert-1 galaxy with redshift z =0 :657, which we propose as the optical counterpart of the X-ray source. Further observations allowed to perform multicolour pho- tometry for objects in the GRB 970111 error box. The colour- colour diagrams do not show any object with unusual colours. We applied a photometric classification method to the objects inside the GRB error box, that can distinguish stars from galax- ies and estimate redshifts. We were able to estimate photometric