Optical/IR follow-up observations of Gamma-Ray Bursts detected by RXTE

Optical/IR follow-up observations have been performed for GRB 970616, GRB 970815, GRB 970828 and GRB 980703. With the exception on GRB 980703, no optical/IR counterparts have been found. In the case of GRB 970828, the absence of the optical/IR afterglow, together with the rather high hydrogen column density towards the source, at a high galactic latitude, indicates an intrinsic absorption. For GRB 980703, a fading optical/IR object was detected, and further imagery revealed the GRB host galaxy, the brightest so far detected. These results would support the existence of a dense and rich-gas medium in which the GRBs occurred, thus linking these events to star forming regions, favouring the hypernova model scenarios. © 1999 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint.