HST DATA SUGGEST PROPER MOTION FOR THE OPTICAL COUNTERPART OF GRB-970228

After a quarter of a century of gamma-ray burst (GRB) astronomy, the I talian-Dutch satellite BeppoSAX on Feb 28(th), 1997 detected a soft X- ray afterglow from GRB 970228 and positioned it accurately. This made possible the successful detection of an optical transient. Two public Hubble Space Telescope (HST) images of the GRB/optical transient regio n were taken on March 26(th) and April 7(th), 1997. They are analyzed here, with the purpose of understanding the nature of GRB 970228. We f ind that the position of the faint point-like object (m(v) similar to 26) seen at the transient location changed by 0.40 +/- 0.10 pixels in 12 days, corresponding to a proper motion of similar to 550 mas/year. By comparison, four adjacent sources in the same field do not show any significant displacement, with astrometric residuals close to zero an d average absolute displacements less than 0.09 pixels. If confirmed, this result would strongly support the galactic nature of GRB 970228.