Discovery of a Redshifted Iron K Line in the X-Ray Afterglow of GRB 000214

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Abstract
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 ≥ 3 × 1015 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.
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