Evolution of Accretor Stars in Massive Binaries: Broader Implications from Modeling ζ Ophiuchi
Evolution of Accretor Stars in Massive Binaries: Broader Implications from Modeling ζ Ophiuchi
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DOI：
10.3847/1538-4357/ac29c5
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发表时间：
2021-07
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影响因子：
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通讯作者：
M. Renzo;Y. Götberg
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作者：
M. Renzo;Y. Götberg
大多数大质量恒星诞生于距离足够近以进行质量转移的双星中。这些改变了两颗恒星的外观、结构和未来的演化。我们计算了一个 100 天周期的双星的演化，该双星最初由一颗 25 M ⊙ 恒星和一颗 17 M ⊙ 恒星组成，经历稳定的质量传递。我们重点关注质量吸积对吸积体表面成分、内部旋转和结构的影响。为了锚定我们的模型，我们证明了我们的吸积因子广泛地再现了蛇夫座 δ 的特性，长期以来，人们一直认为，当伴星爆炸时，它在作为失控恒星被弹射出去之前具有吸积质量。我们将我们的吸积体与单个旋转恒星的模型进行比较，发现质量吸积提供的更晚且更强的自旋产生了显着差异。具体来说，吸积子的核心在主序列结束时保持较高的自旋，并且对流层的发展改变了其密度分布。此外，吸积星的表面还受到伴星捐赠的碳氮氧化物处理过的物质的污染。我们的模型显示了双星中质量吸积的影响，而这些影响在单个旋转恒星模型中并未捕获。这可能会影响进一步的演化（无论是双星还是单星）、最终的塌缩以及由此产生的致密天体的旋转。
Most massive stars are born in binaries close enough for mass transfer episodes. These modify the appearance, structure, and future evolution of both stars. We compute the evolution of a 100-day-period binary, consisting initially of a 25 M ⊙ star and a 17 M ⊙ star, which experiences stable mass transfer. We focus on the impact of mass accretion on the surface composition, internal rotation, and structure of the accretor. To anchor our models, we show that our accretor broadly reproduces the properties of ζ Ophiuchi, which has long been proposed to have accreted mass before being ejected as a runaway star when the companion exploded. We compare our accretor to models of single rotating stars and find that the later and stronger spin-up provided by mass accretion produces significant differences. Specifically, the core of the accretor retains higher spin at the end of the main sequence, and a convective layer develops that changes its density profile. Moreover, the surface of the accretor star is polluted by CNO-processed material donated by the companion. Our models show effects of mass accretion in binaries that are not captured in single rotating stellar models. This possibly impacts the further evolution (either in a binary or as single stars), the final collapse, and the resulting spin of the compact object.