arXiv 2108.083402021-08-18astro-ph.SRastro-ph.GA

银河系早型O超巨星的经验质量损失率和聚团性质

Empirical mass-loss rates and clumping properties of Galactic early-type O supergiants

C. Hawcroft, H. Sana, L. Mahy, J. O. Sundqvist, M. Abdul-Masih, J. C. Bouret, S. A. Brands, A. de Koter, F. A. Driessen, J. Puls

备注：: Accepted for publication in A&A; 35 pages, 20 figures
发表信息：: A&A 655, A67 (2021)
DOI：: 10.1051/0004-6361/202140603

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摘要：

我们调查的影响，光学厚聚集在O超巨星恒星风诊断和约束风参数与速度空间中的孔隙度。这是第一次光学厚聚集的影响已经调查了大质量的热恒星的样本，使用模型，包括一个完整的光学厚聚集的描述。我们重新分析光谱观测的样本8 O超巨星。使用遗传算法包装周围的NLTE大气代码FASTWIND，我们获得同时适合光学和紫外光谱，并确定光球和风的属性和表面丰度。我们提供了一些风参数的经验约束，包括聚集因子，质量损失率和终端风速。此外，我们建立了第一个系统的经验约束速度填充因子和interclump密度。这些参数分别描述了团块在速度空间中的分布和团块间介质在物理空间中的密度。我们观察到，与Vink等人（2000）的理论预测相比，质量损失率降低了3.6倍，而Björklund等人（2021）的预测值为1.4倍。我们确认，包括光学厚结块允许同时拟合的重组线和共振线，包括不饱和的UV磷线（PV 1118-1128），而不减少磷的丰度。我们发现，平均而言，风速场的一半被密集的团块所覆盖。我们还发现，这些团块的密度是平均风的25倍，而团块间介质的密度是平均风的3-10倍。前者的结果与理论预测吻合得很好，后者表明，径向压缩气体的横向填充可能是确定稀薄的团间物质的规模的关键。

英文摘要：

We investigate the impact of optically thick clumping on stellar wind diagnostics in O supergiants and constrain wind parameters associated with porosity in velocity space. This is the first time the effects of optically thick clumping have been investigated for a sample of massive hot stars, using models including a full optically thick clumping description. We re-analyse spectroscopic observations of a sample of eight O supergiants. Using a genetic algorithm wrapper around the NLTE atmosphere code FASTWIND we obtain simultaneous fits to optical and UV spectra and determine photospheric and wind properties and surface abundances. We provide empirical constraints on a number of wind parameters including the clumping factors, mass-loss rates and terminal wind velocities. Additionally, we establish the first systematic empirical constraints on velocity filling factors and interclump densities. These parameters describe clump distribution in velocity-space and density of the interclump medium in physical-space, respectively. We observe a mass-loss rate reduction of a factor of 3.6 compared to theoretical predictions from Vink et al. (2000), and mass-loss rates within a factor 1.4 of predictions from Björklund et al. (2021). We confirm that including optically thick clumping allows simultaneous fitting of recombination lines and resonance lines, including the unsaturated UV phosphorus lines (Pv 1118-1128), without reducing the phosphorus abundance. We find that, on average, half of the wind velocity field is covered by dense clumps. We also find that these clumps are 25 times denser than the average wind, and that the interclump medium is 3-10 times less dense than the mean wind. The former result agrees well with theoretical predictions, the latter suggests that lateral filling-in of radially compressed gas might be critical for setting the scale of the rarefied interclump matter.

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