2000ApJ...545L..39A

We report the detection (3 σ 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 Kα emission from hydrogen-like iron, corresponds to a redshift of z=0.47. The intensity (EW∼2 keV) and duration (tens of hours) of the line give information on the distance, from the burst region, of the emitting material (R≥3x10¹⁵ cm) and its mass (M≥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 (~10¹⁶ cm) and at Newtonian speeds.