1994A&A...284..499H

We have analysed in detail the image of optical transient OT 1928 suggested to be an optical flashing counterpart of the gamma ray burst source GRBS 781119. Different investigations of this image have however yielded very different and controversial results. We have therefore analysed the image in detail together with a number of comparison stars from the discovery plate and comparison plates taken under analogous conditions. We have found by means of image distortion analysis that the image was caused by a real optical flash. The image was also found not to have obviously different density of developed grains on the glass/emulsion boundary if compared with the stars with similar total density of developed grains. All observed parameters and properties of the OT image can be explained by the fact that the event was caused by extremely colored light. For other two Schaefer's OT candidates, no similar conclusions could be obtained due to the faintness of these images.