It is now recognized that long-duration gamma-ray Bursts (GRBs) are linked to the collapse of massive stars, based on the association between (low redshift) GRBs and (Type Ic) core-collapse supernovae (SNe). The census of massive stars and GRBs reveals, however, that not all massive stars produce a GRB. Only-1% of corecollapse SNe are able to produce a highly relativistic collimated outflow, and hence a GRB. The extra crucial parameter has long been suspected to be metallicity and/or rotation. We find observational evidence strongly supporting that both ingredients are necessary in order to make a GRB out of a core-collapsing star. A detailed study of the absorption pattern in the X-ray spectrum of GRB 060218 reveals evidence of material highly enriched in low-atomic-number metals ejected before the SN/GRB explosion. We find that, within the current scenarios of stellar evolution, only a progenitor star characterized by a fast stellar rotation and subsolar initial metallicity could produce such a metal enrichment in its close surrounding. © 2008. The American Astronomical Society. All rights reserved. Printed in U.S.A.
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Campana, S., Panagia, N., Lazzati, D., Beardmore, A. P., Cusumano, G., Godet, O., … Tagliaferri, G. (2008). Outliers from the Mainstream: How a Massive Star Can Produce a Gamma-Ray Burst. The Astrophysical Journal, 683(1), L9–L12. https://doi.org/10.1086/591421