LATE-TIME PHOTOMETRY OF TYPE IA SUPERNOVA SN 2012cg REVEALS THE RADIOACTIVE DECAY OF 57Co
LATE-TIME PHOTOMETRY OF TYPE IA SUPERNOVA SN 2012cg REVEALS THE RADIOACTIVE DECAY OF 57Co
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DOI：
10.3847/0004-637x/819/1/31
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发表时间：
2015-05
期刊：
影响因子：
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通讯作者：
O. Graur;D. Zurek;M. Shara;A. Riess;I. Seitenzahl;A. Rest
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文献类型：
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作者：
O. Graur;D. Zurek;M. Shara;A. Riess;I. Seitenzahl;A. Rest
塞滕扎尔等人。预测在爆炸大约三年后，我们从 Ia 型超新星 (SN Ia) 接收到的光将主要来自放射性衰变链 57Co → 57Fe 发射的电子和 X 射线的再处理，而不是来自早期主导 SN 光的衰变链 56Co → 56Fe 的正电子。使用哈勃太空望远镜，我们跟踪了 SN Ia SN 2012cg 的光变曲线，直至最大光照后 1055 天。我们的测量结果与 57Co 衰变发射的电子再处理和 X 射线能量贡献所预测的光变曲线一致，这提供了 57Co 是在 SN Ia 爆炸中产生的证据。然而，数据也与峰值时比 SN 2012cg 弱约 14 星等的光回波一致。假设没有光回波污染，爆炸产生的 57Ni 和 56Ni 的质量比（对任何 SN Ia 爆炸模型的强烈约束）为 0.043 − 0.011 + 0.012 ?> ，大约是 Solar 的两倍。在当前爆炸模型的背景下，这个值有利于质量接近钱德拉塞卡极限的前身白矮星。
Seitenzahl et al. have predicted that roughly three years after its explosion, the light we receive from a Type Ia supernova (SN Ia) will come mostly from reprocessing of electrons and X-rays emitted by the radioactive decay chain 57Co → 57Fe, instead of positrons from the decay chain 56Co → 56Fe that dominates the SN light at earlier times. Using the Hubble Space Telescope, we followed the light curve of the SN Ia SN 2012cg out to 1055 days after maximum light. Our measurements are consistent with the light curves predicted by the contribution of energy from the reprocessing of electrons and X-rays emitted by the decay of 57Co, offering evidence that 57Co is produced in SN Ia explosions. However, the data are also consistent with a light echo ∼14 mag fainter than SN 2012cg at peak. Assuming no light-echo contamination, the mass ratio of 57Ni and 56Ni produced by the explosion, a strong constraint on any SN Ia explosion models, is 0.043 − 0.011 + 0.012 ?> , roughly twice Solar. In the context of current explosion models, this value favors a progenitor white dwarf with a mass near the Chandrasekhar limit.