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arXiv 2407.01037astro-ph.SRastro-ph.GAastro-ph.HE
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失控的BN超巨星HD 93840:银河平面上方即将发生核心坍缩超新星的前身星

Runaway BN supergiant star HD 93840: Progenitor of an imminent core-collapse supernova above the Galactic plane

D. Weßmayer, M. A. Urbaneja, K. Butler, N. Przybilla

AI总结:

本文对银河平面上方的极端氮增强超巨星HD 93840进行定量光谱分析,揭示其异常的CNO混合、超光度及失控运动学特征,表明其经双星演化被超新星抛射,即将成为罕见的蓝超巨星核心坍缩超新星。

摘要:

我们对位于中等银纬的极端氮增强超巨星HD 93840(BN1 Ib)进行了定量光谱分析。基于光学高分辨率光谱、互补的紫外和红外(光谱)测光数据以及Gaia数据,我们对这颗恒星的性质进行了全面表征。我们同时使用了流体静力学和统一(光球+星风)模型大气,这些模型考虑了偏离局部热力学平衡的效应。极为罕见的表面CNO混合特征以及相对于其质量而言显著的恒星超光度,表明该恒星过去的演化经历了一个双星通道。运动学分析显示,它作为一颗 runaway star(失控星)到达了当前位于银河平面上方的位置,很可能是被其前伴星的超新星爆发抛射出来的。它目前的整体化学成分——由于核心He燃烧和进行的壳层H燃烧导致平均分子量显著增加——表明其处于晚期演化阶段。它即将在相对较近的时间内,在银河盘上方约十个OB星族标高之处,产生一颗罕见的蓝超巨星核心坍缩超新星,从而为环银河系介质的金属增丰做出贡献。

英文摘要:

We present a quantitative spectral analysis of the extreme nitrogen-enhanced supergiant HD 93840 (BN1 Ib) at an intermediate galactic latitude. Based on an optical high-resolution spectrum and complementary ultraviolet and infrared (spectro-)photometry, in addition to Gaia data, we carried out a full characterisation of the star's properties. We used both hydrostatic and unified (photosphere+wind) model atmospheres that account for deviations from local thermodynamic equilibrium. A highly unusual surface CNO-mixing signature and a marked stellar overluminosity compared to the mass imply a binary channel for the star's past evolution. The kinematics shows that it has reached its current position above the Galactic plane as a runaway star, likely ejected by the supernova explosion of its former companion star. Its current bulk composition, with a notably increased mean molecular weight due to core He- and progressed shell H-burning, suggests an advanced evolutionary stage. It is poised to yield a rare core-collapse supernova of a blue supergiant about ten OB star population scale heights above the Galactic disk relatively soon, contributing to the metal enrichment of the circumgalactic medium.

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