Discovery of a Redshifted Iron K Line in the X-Ray Afterglow of GRB 000214
The Astrophysical Journal2000Vol. 545(1), pp. L39–L42
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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. Heise, E. Kuulkers, L. Nicastro, R. C. Butler, L. Stella, G. C. Perola
Abstract
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.