The dominant radioactive energy source powering SNIa light curves is expected to switch from the decay of ⁵⁶Co to ⁵⁷Co at very late epochs. We use archival Hubble Space Telescope images of SN1992A obtained more than 900days after explosion to constrain its cobalt isotopic abundance ratio and compare it to the well-studied event SN2011fe. We confirm the ⁵⁷Co/⁵⁶Co ratio for SN2011fe of 0.0260.004 found by Shappee et al., consistent with a “double degenerate” progenitor scenario. For SN1992A, we find a ratio of 0.0340.010, but the large uncertainty does not allow us to differentiate between progenitor models.

为 SNIa 光变曲线提供动力的主要放射性能源预计会在很晚的时期从⁵⁶ Co 的衰变转变为^{57 Co。}我们使用 SN1992A 爆炸后 900 多天获得的哈勃太空望远镜档案图像来限制其钴同位素丰度比，并将其与经过充分研究的事件 SN2011fe 进行比较。我们确认了Shappee 等人发现的 SN2011fe 的⁵⁷ Co/ ⁵⁶ Co 比率为 0.0260.004，与“双简并”祖先情景一致。对于 SN1992A，我们发现比率为 0.0340.010，但较大的不确定性不允许我们区分祖模型。