Discovery of a redshifted iron K line in the X-ray afterglow of GRB 000214

We report the detection (3 sigma significance level) of a strong iron emission line in the X-ray spectrum of the afterglow of GRB 000214 ("Valentine's Day Burst") observed by BeppoSAX. An emission-line feature was observed with a centroid energy of 4.7 +/- 0.2 keV, which, if interpreted as K alpha emission from hydrogen-like iron, corresponds to a redshift of z = 0.47. The intensity (EW similar to 2 keV) and duration (tens of hours) of the line give information on the distance, from the burst region, of the emitting material (R greater than or equal to 3 x 10(15) cm) and its mass (M greater than or equal to 1.4 M.). These results are not easily reconciled with the binary merger and hypernova models for gamma-ray bursts because they require large amounts of mass (about 1 M.) at large distances (approximate to 10(16) cm) and at Newtonian speeds.