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 observed 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>3x10^15 cm) and its mass (M>1.4 solar mass). These results are not easily reconciled with the binary merger and hypernova models for gamma ray bursts. 
L.A. Antonelli, L. Piro, M. Vietri, E. Costa, P. Soffitta, M. Feroci,   L. Amati, F. Frontera, E. Pian, J.J.M. in 't Zand, J...