D. Weßmayer, M. A. Urbaneja, K. Butler, N. Przybilla
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引用次数: 0
摘要
我们对位于中银河纬度的极氮增强超巨星HD 93840(BN1 Ib)进行了光谱定量分析。除了盖亚数据之外,我们还根据光学高分辨率光谱和补充紫外线和红外线(光谱)测光数据,对这颗恒星的特性进行了全面描述。我们使用了静水模型大气和统一(光层+风)模型大气,以考虑偏离局部热力学平衡的情况。非常不寻常的表面 CNO 混合特征和与质量相比明显的恒星过光度意味着这颗恒星过去的演化是双星通道。运动学显示,它是作为一颗失控恒星到达银河系平面上方的,很可能是被其前伴星的超新星爆炸喷射出来的。它目前的主要成分是核心氦和外壳氢燃烧,平均分子量显著增加,这表明它处于高级演化阶段。它很快就会产生一颗罕见的蓝超巨星核心坍缩超新星,该超新星位于银河系盘面上方约十个 OB 星群尺度高度处,有助于环银河介质的金属富集。
Runaway BN supergiant star HD 93840: Progenitor of an imminent core-collapse supernova above the Galactic plane
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.
期刊介绍:
Astronomy & Astrophysics is an international Journal that publishes papers on all aspects of astronomy and astrophysics (theoretical, observational, and instrumental) independently of the techniques used to obtain the results.