Late-time Observations of Calcium-rich Transient SN 2019ehk Reveal a Pure Radioactive Decay Power Source
Late-time Observations of Calcium-rich Transient SN 2019ehk Reveal a Pure Radioactive Decay Power Source
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DOI：
10.3847/2041-8213/abdebc
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发表时间：
2020-10
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通讯作者：
W. Jacobson-Galán;R. Margutti;C. Kilpatrick;J. Raymond;E. Berger;P. Blanchard;A. Bobrick;R. Foley;S. Gomez;G. Hosseinzadeh;D. Milisavljevic;H. Perets;G. Terreran;Y. Zenati
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作者：
W. Jacobson-Galán;R. Margutti;C. Kilpatrick;J. Raymond;E. Berger;P. Blanchard;A. Bobrick;R. Foley;S. Gomez;G. Hosseinzadeh;D. Milisavljevic;H. Perets;G. Terreran;Y. Zenati
我们展示了富钙超新星（SN） SN 2019ehk在爆炸后276-389天的多波段哈勃太空望远镜成像。这些观测结果代表了迄今为止最新的富钙瞬变天体的b波段至近红外光度测量结果，并首次有机会分析这类观测SN天体的后期辐射演化。我们发现SN 2019ehk的晚时间热光度曲线可以主要通过56Co的放射性衰变来描述，我们推导出M（56Co）的质量=（2.8±0.1）× 10−2 M⊙。此外，辐射光度的下降速率需要γ射线在时间尺度上的泄漏（tγ = 53.9±1.30天），但我们没有发现SN喷发中不完全正电子捕获的统计证据。虽然我们的观测结果不能约束SN 2019ehk中合成的其他放射性同位素的确切质量，但我们估计质量比极限为M(57Co)/M(56Co)≤0.030。这一极限与低质量白矮星合并时产生的爆炸性核合成相一致，这是SN 2019ehk早期研究中最受欢迎的祖情景之一。
We present multiband Hubble Space Telescope imaging of the calcium-rich supernova (SN) SN 2019ehk at 276-389 days after explosion. These observations represent the latest B-band to near-IR photometric measurements of a calcium-rich transient to date and allow for the first opportunity to analyze the late-time bolometric evolution of an object in this observational SN class. We find that the late-time bolometric light curve of SN 2019ehk can be described predominantly through the radioactive decay of 56Co for which we derive a mass of M(56Co) = (2.8 ± 0.1) × 10−2 M⊙. Furthermore, the rate of decline in bolometric luminosity requires the leakage of γ-rays on timescale tγ = 53.9 ± 1.30 days, but we find no statistical evidence for incomplete positron trapping in the SN ejecta. While our observations cannot constrain the exact masses of other radioactive isotopes synthesized in SN 2019ehk, we estimate a mass ratio limit of M(57Co)/M(56Co) ≤ 0.030. This limit is consistent with the explosive nucleosynthesis produced in the merger of low-mass white dwarfs, which is one of the favored progenitor scenarios in early-time studies of SN 2019ehk.