1994A&A...284..839H

We present here the results of the analysis of the error box of the gamma ray bursts source GRB 910219 carried out on 9104 photographic plates representing 2.06 years of exposure (the most extended archival search for any particular GRBS position so far). One probable optical flashing candidate has been found and analysed in detail to avoid any misinterpretation. This analysis has confirmed that the image detected on May 10, 1905, is a real object, reaching for≤35 min the brightness of≤5.8 mag. The image was not caused by a plate defect (brightness more than 5 mag above plate limit, presence of coma and halo like bright stars) or by a double exposure (negative blinktest). Further, the object cannot be explained as a satellite glint or aircraft flash (the plate was taken in 1905), an asteroid or comet (very bright object with lack of trailing at high ecliptic latitude, no image on adjacent plate),a novae (not found on adjacent plates),a dwarf novae (light amplitude ≥15 mag, absent on adjacent plates) and/or a flare star (too large amplitude). The image was found to show lack of trailing and inside of the error box of GRB 910219 as provided by the WATCH experiment onboard of the GRANAT satellite. The parameters and the consequences of this optical transient candidate are presented and discussed.