Super-solar metallicity at the position of the ultra-long GRB130925A

摘要: Over the last decade there has been immense progress in follow-up of short and long GRBs, resulting a significant rise detection rate X-ray optical afterglows, determination GRB redshifts, identification underlying host galaxies. Nevertheless, our theoretical understanding on progenitors central engines powering these vast explosions is lagging behind, newly identified class `ultra-long' GRBs fuelled speculation existence new channel formation. In this paper we present high signal-to-noise X-shooter observations galaxy GRB130925A, which fourth unambiguously ultra-long GRB, with prompt gamma-ray emission detected for ~20ks. The line sight was close to nucleus, spectroscopic cover both region along bulge/disk galaxy, addition bright star-forming within outskirts galaxy. From broad wavelength coverage obtain accurate metallicity dust-extinction measurements at an outer region, measure super-solar locations, placing 10-20% most metal-rich Such metal enrichment implications progenitor models although edge-on orientation does not allow us rule out large variation sight. spatially resolved data presented offer important insight into variations dust abundance They also illustrate need IFU larger sample galaxies varies metallicities provide more quantitative view relation between circumburst galaxy-whole properties.