Long gamma-ray bursts and core-collapse supernovae have different environments.
Fruchter AS, Levan AJ, Strolger L, Vreeswijk PM, Thorsett SE, Bersier D, Burud I, Castro Cerón JM, Castro-Tirado AJ, Conselice C, Dahlen T, Ferguson HC, Fynbo JP, Garnavich PM, Gibbons RA, Gorosabel J, Gull TR, Hjorth J, Holland ST, Kouveliotou C, Levay Z, Livio M, Metzger MR, Nugent PE, Petro L, Pian E, Rhoads JE, Riess AG, Sahu KC, Smette A, Tanvir NR, Wijers RA, Woosley SE.
Fruchter AS, et al. Among authors: thorsett se.
Nature. 2006 May 25;441(7092):463-8. doi: 10.1038/nature04787. Epub 2006 May 10.
Nature. 2006.
PMID: 16688183