Abstract

By now the resonance lines of the isotope \({}^{7}\)Be have been detected in five novae. The known estimates of the relative abundance of this isotope from the equivalent widths of \({}^{7}\)Be II and Ca II lines lead to the conclusion that the \({}^{7}\)Be abundance is considerably higher than the predictions of thermonuclear burning models during a nova outburst. In an attempt to understand the reason for the discrepancy, we have investigated the possibility of an increase in the \({}^{7}\)Be yield during nova outbursts based on nuclear burning kinetics within the framework of a two-zone model and shown that the mass fraction of this isotope does not exceed \(3\times 10^{-5}\) even for the most favorable set of parameters. This agrees with the known theoretical results and leaves the contradiction between the theory and observations unresolved. The reason for the contradiction is shown to be the assumption that the relative fractions of the ions Be II/Be and Ca II/Ca are equal, which was made when determining the \({}^{7}\)Be abundance. For Nova V5668 Sgr the relative fraction of the Be II ions in the ejecta turns out to be higher than the relative fraction of the Ca II ions at least by an order of magnitude because of the difference between the ionization potentials. Our new estimate of the \({}^{7}\)Be mass fraction is consistent with the theory. The calculated gamma-ray flux at 478 keV from the \({}^{7}\)Be decay agrees with the upper limit from INTEGRAL satellite observations.

中文翻译：

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Nova V5668 Sgr中的$$ {} ^ {\ mathbf {7}} $$ Be Abundance与理论相符

摘要

到现在为止，已经在五个新星中发现了同位素\（{} ^ {7} \） Be的共振线。根据\（{} ^ {7} \） Be II和Ca II线的等效宽度对该同位素的相对丰度的已知估计得出以下结论：\（{} ^ {7} \） Be丰度为远高于新星爆发期间热核燃烧模型的预测。为了理解差异的原因，我们根据两区模型的框架内的核燃烧动力学，研究了新星爆发期间\（{} ^ {7} \） Be产量增加的可能性。并且表明该同位素的质量分数不超过\（3 \乘以10 ^ {-5} \）即使是最有利的参数集。这与已知的理论结果是一致的，并且使得理论和观察之间的矛盾尚未解决。证明矛盾的原因是假设离子Be II / Be和Ca II / Ca的相对分数相等，这是在确定\（{} ^ {7} \） Be丰度时得出的。对于Nova V5668 Sgr，由于电离电位之间的差异，喷射器中Be II离子的相对分数至少比Ca II离子的相对分数高一个数量级。我们对\（{} ^ {7} \） Be质量分数的新估计与该理论是一致的。从\（{} ^ {7} \）计算得出的478 keV的伽马射线通量衰减与INTEGRAL卫星观测的上限一致。