Oxygen yield of the explosion of massive stars of various main sequence masses (Nomoto et al. 1997: red; Rauscher et al. 2002: light blue; Limongi & Chieffi 2003: orange). The horizontal line indicates the estimated oxygen mass for iPTF13bvn assuming T = 3200 K, with uncertainty represented by the shaded region. Dashed horizontal lines denote the oxygen mass values for different temperature assumptions. The estimated oxygen mass if 50% of oxygen was unseen is indicated with a dash-dotted line.