FAINT POPULATION III SUPERNOVAE AS THE ORIGIN OF THE MOST IRON-POOR STARS

The most iron-poor stars in the Milky Way provide important observational clues to the astrophysical objects that enriched the primordial gas with heavy elements. Among them, the recently discovered iron-deficient star SMSS J031300.36-670839.3 shows a remarkable chemical composition with a non-detection of iron ([Fe/H] < -7.1) and large enhancement of carbon and magnesium relative to calcium. We investigate supernova yields of metal-free ( Population III) stars to interpret the abundance pattern observed in this star. We report that the high [C/Ca] and [C/Mg] ratios and upper limits of other elemental abundances are well reproduced with the yields of core-collapse supernovae ( which have normal kinetic energies of explosion E of E-51 = E/10(51) erg = 1) and hypernovae ( E-51 >= 10) of Population III 25 M-circle dot or 40 M-circle dot stars. The best-fit models assume that the explosions undergo extensive matter mixing and fallback, leaving behind a black hole remnant. In these models, Ca is produced by static/explosive O burning and incomplete Si burning in the Population III supernova/hypernova, in contrast to the suggestion that Ca is originated from the hot-CNO cycle during pre-supernova evolution. Chemical abundances of four carbon-rich iron-poor stars with [Fe/H] < -4.5, including SMSS J031300.36-670839.3, are consistently explained by faint supernova models with ejected masses of Ni-56 less than 10(-3) M-circle dot