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[30.03] Discovery of a redshifted Iron K-feature in the X-ray afterglow of GRB 000214.

L.A. Antonelli (Osservatorio Astronomico di Roma), L. Piro (Istituto di Astrofisica Spaziale, C.N.R.), M. Vietri (Universita' degli Studi "Roma Tre"), E. Costa, P. Soffita, M. Feroci (Istituto di Astrofisica Spaziale, C.N.R.), L. Amati, F. Frontera, E. Pian (Istituto Tecnologie e Studio delle Radiazioni Extraterrestri, C.N.R.), J.J.M. in 't Zand, J. Heise, E. Kuulkers (Space Research Organization Netherlands), L. Nicastro (Istituto di Fisica Cosmica e Applicazioni Calcolo Informatico, C.N.R.), L. Stella (Osservatorio Astronomico di Roma), R.C. Butler (Agenzia Spaziale Italiana), G.C. Perola (Universita' degli Studi "Roma Tre")

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±.2 keV which, if interpreted as K\alpha 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\geq3\times10¹⁵ cm) and its mass (M\geq0.7M_\odot). We show that these results are not easily reconciled with the binary merger and hypernova models for gamma ray bursts.

The author(s) of this abstract have provided an email address for comments about the abstract: angelo@coma.mporzio.astro.it