Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Heidelberg, Germany.
Heidelberger Institut für Theoretische Studien, Heidelberg, Germany.
Nature. 2019 Oct;574(7777):211-214. doi: 10.1038/s41586-019-1621-5. Epub 2019 Oct 9.
About ten per cent of 'massive' stars (those of more than 1.5 solar masses) have strong, large-scale surface magnetic fields. It has been suggested that merging of main-sequence and pre-main-sequence stars could produce such strong fields, and the predicted fraction of merged massive stars is also about ten per cent. The merger hypothesis is further supported by a lack of magnetic stars in close binaries, which is as expected if mergers produce magnetic stars. Here we report three-dimensional magnetohydrodynamical simulations of the coalescence of two massive stars and follow the evolution of the merged product. Strong magnetic fields are produced in the simulations, and the merged star rejuvenates such that it appears younger and bluer than other coeval stars. This can explain the properties of the magnetic 'blue straggler' star τ Sco in the Upper Scorpius association that has an observationally inferred, apparent age of less than five million years, which is less than half the age of its birth association. Such massive blue straggler stars seem likely to be progenitors of magnetars, perhaps giving rise to some of the enigmatic fast radio bursts observed, and their supernovae may be affected by their strong magnetic fields.
大约 10%的“大质量”恒星（质量超过 1.5 个太阳质量）具有较强的、大规模的表面磁场。有人提出，主序星和前主序星的合并可能会产生如此强的磁场，而预测的合并大质量恒星的比例也约为 10%。合并假说还得到了一个事实的支持，即在紧密双星中没有磁性恒星，如果合并会产生磁性恒星，那么这是可以预期的。在这里，我们报告了两个大质量恒星合并的三维磁流体动力学模拟，并跟踪了合并产物的演化。在模拟中产生了强磁场，合并后的恒星恢复了活力，使其看起来比其他同一年龄的恒星更年轻、更蓝。这可以解释天蝎座上部星协中磁性“蓝离散星”τ Sco 的性质，它的观测到的表观年龄小于 500 万年，不到其诞生星协年龄的一半。这种大质量蓝离散星似乎很可能是磁星的前身，也许会产生一些观察到的神秘的快速射电暴，而它们的超新星可能会受到强磁场的影响。
