We report the imaging and spectroscopic localization of GRB 060218 to a low-metallicity dwarf starburst galaxy at z = 0.03345 ± 0.00006. In addition to making it the second nearest gamma-ray burst known, optical spectroscopy reveals the earliest detection of weak, supernova-like Si II near 5720 Å (∼0.1c), starting 1.95 days after the burst trigger. UBVRI photometry obtained between 1 and 26 days postburst confirms the early rise of supernova light, and suggests a short time delay between the gamma-ray burst and the onset of SN 2006aj if the early appearance of a soft component in the X-ray spectrum is understood as a "shock breakout." Together, these results verify the long-hypothesized origin of soft gamma-ray bursts in the deaths of massive stars.
Bibliographical noteFunding Information:
5 IRAF is distributed by the National Optical Astronomy Observatories, which are operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.
This work was supported by the National Science Foundation under grant 0206051.
- Gamma rays: bursts
- Supernovae: general
- Supernovae: individual (SN 2006aj)