一颗具有类似沃尔夫-拉叶星风的银河系中等质量剥离恒星
A Galactic intermediate-mass stripped star with a Wolf-Rayet-like wind
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中文总结 AI 辅助
研究在SDSS-V调查中发现一颗银河系中等质量剥离恒星，其质量损失率符合经典沃尔夫-拉叶星特征，为相关双星演化等模型提供关键基准。
中文摘要 AI 辅助
大质量恒星的双星相互作用预计会产生大量中等质量（2-8 M☉）的包层剥离恒星，但这类天体在银河系中一直难以被发现。我们报告在SDSS-V银河系测绘调查中发现的一个短周期（P=5.94天）双谱线分光双星中，明确识别出一个银河系中的此类天体。该系统由一颗快速旋转的O型星和一颗更热、质量更小的伴星组成，伴星呈现He II和N IV发射线，且具有大的径向速度变化，揭示了其双星性质。结合轨道约束以及光谱和测光联合建模表明，该伴星是一颗温度（T*≈60 kK）高、富含氦的恒星，质量为3.2-5.8 M☉，正好处于中等质量范围，且低于经典沃尔夫-拉叶星（WR）的典型质量值。该系统的短周期、可忽略的偏心率以及快速旋转的O型星，表明其是经历了高效质量转移和吸积星自旋加速后的相互作用后构型。与双星演化模型的比较表明，这颗剥离恒星在质量转移后处于短暂的膨胀阶段，这增加了它的光通量贡献并促进了其被探测到。推断的质量损失率log Ṁ = -6.3 ± 0.1，与银河系中经典WR星观测到的质量损失率一致，且超过了麦哲伦云中测量的中等质量剥离恒星的质量损失率，需要注意的是，我们的目标选择偏向于具有更强发射特征的系统。作为一颗明确且特征良好的中等质量剥离恒星，该系统为太阳金属丰度下的双星演化模型、包层剥离超新星前身星以及致密天体双星的形成提供了关键基准。
英文摘要
Binary interaction in massive stars is expected to produce a large population of intermediate-mass ($2$-$8$ M$_\odot$) envelope-stripped stars, yet such objects have remained elusive in the Milky Way. We report the identification of an unambiguous Galactic example in a short-period ($P=5.94$ d), double-lined spectroscopic binary, discovered in the SDSS-V Milky Way Mapper survey. The system consists of a rapidly rotating O-type star and a hotter, lower-mass companion, which shows He II and N IV emission lines with large radial velocity variations, revealing its binary nature. Combined orbital constraints and joint spectroscopic and photometric modelling show that the companion is a hot ($T_\ast \approx 60$ kK), helium-rich star with a mass of $3.2$-$5.8$ M$_\odot$, placing it squarely in the intermediate-mass regime and below values typically inferred for classical Wolf-Rayet (WR) stars. The system's short period, negligible eccentricity, and rapidly rotating O-star point to a post-interaction configuration following efficient mass transfer and spin-up of the accretor. Comparison with binary evolution models suggests that the stripped star is observed in a brief inflated phase following mass transfer, which increases its optical flux contribution and facilitates its detection. The inferred mass-loss rate $\log \dot{M} = -6.3 \pm 0.1$ is in line with mass-loss rates observed for classical WR stars in the Milky Way and exceeds those measured for intermediate-mass stripped stars in the Magellanic Clouds, with the caveat that our target selection is biased towards systems with stronger emission features. As an unambiguous and well-characterised intermediate-mass stripped star, this system provides a key benchmark for models of binary evolution at solar metallicity, stripped-envelope supernova progenitors, and the formation of compact-object binaries.
