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The light curve of SN 1987A revisited: constraining production masses of radioactive nuclides  2014
In this paper, We revisit the evidence for the contribution of the longlived radioactive nuclides ^{44}Ti, ^{55}Fe, ^{56}Co, ^{57}Co, and ^{60}Co to the UVOIR light curve of SN~1987A. We show that the Vband luminosity constitutes a roughly constant fraction of the bolometric luminosity between 900 and 1900 days, and we obtain an approximate bolometric light curve out to 4334 days by scaling the late time Vband data by a constant factor where no bolometric light curve data is available. Considering the five most relevant decay chains starting at ^{44}Ti, ^{55}Co, ^{56}Ni, ^{57}Ni, and ^{60}Co, we perform a least squares fit to the constructed composite bolometric light curve. For the nickel isotopes, we obtain best fit values of M(^{56}Ni) = (7.1 ± 0.3) × 10^{2} M_{⊙} and M(^{57}Ni) = (4.1 ± 1.8) × 10^{3} M_{⊙}. Our best fit ^{44}Ti mass is M(^{44}Ti) = (0.55 ± 0.17) × 10^{4} M_{⊙}. which is in disagreement with the much higher (3.1 ± 0.8) × 10^{4} M_{⊙} recently derived from INTEGRAL observations. The halflives of ^{60}Co and ^{55}Fe are quite similar, which introduces a degeneracy for the fitting algorithm. As a result, we can only give upper limits on the relevant production masses of M(^{55}Co) < 7.2 × 10^{3} M_{⊙} and M(^{60}Co) < 1.7 × 10^{4} M_{⊙}. Furthermore, we find that the leptonic channels in the decay of ^{57}Co (internal conversion and Auger electrons) are a significant contribution and constitute up to 15.5% of the total luminosity. Consideration of the kinetic energy of these electrons is essential in lowering our best fit nickel isotope production ratio to [^{57}Ni/^{56}Ni] = 2.5±1.1 which is still somewhat high but in agreement with gammaray observations and model predictions.



