We report the discovery of SDSS J 131326.89 - 001941.4 , an ultra iron-poor red giant star ( [ Fe/H ] \simeq - 4.3 ) with a very large carbon abundance ( [ C/Fe ] \simeq + 2.5 ) .
This object is the fifth star in this rare class , and the combination of a fairly low effective temperature ( T _ { eff } \simeq 5300 K ) , which enhances line absorption , with its brightness ( g = 16.9 ) , makes it possible to measure the abundances of calcium , carbon and iron using a low-resolution spectrum from the Sloan Digital Sky Survey .
We examine the carbon and iron abundance ratios in this star and other similar objects in the light of predicted yields from metal-free massive stars , and conclude that they are consistent .
By way of comparison , stars with similarly low iron abundances but lower carbon-to-iron ratios deviate from the theoretical predictions .