RSAA Colloquia / Seminars / Feast-of-Facts: Friday, 30 January 2015, 14:25-14:45; Duffield Lecture Theatre

Mike Bessell

"The C/O ratio in the ejecta of a primordial supernova"

Discovered initially by SkyMapper, SMSS J031300.36-670839.3, is a sub-giant halo star, found from a high resolution blue MIKE spectrum to have an undetectable Fe abundance and overabundances of C, Mg, and Ca, relative to Fe. We recently obtained 29 UVES spectra extending to 3060 Angstroms which has enabled us to measure the oxygen abundance from the OH lines, and lower the 1D, LTE Fe abundance limit to [Fe/H]<-7.7. We believe that the star formed from the iron-poor ejecta of a single low-energy supernova and the observed C/O ratio points to the primordial SN precursor having a mass of about 20 solar masses.