Self-consistent atmospheric models of very massive stars and their early evolution in dense stellar systems

大质量星爆星团致密核心的演化受到n体相互作用诱导的动力学过程的影响。通过合并形成的质量高达1000个太阳质量的大质量恒星，可能对星系的演化至关重要，对此类星团的演化具有决定性作用。例如，已经收集到的证据表明，银河系凸起的年轻致密星团中存在质量高达1000个太阳质量的中等质量黑洞（IMBHs）；这些天体可以为理解银河系中心超大质量黑洞（SMBHs）的形成提供重要线索。超大质量恒星（vss）的演化受到其明显的恒星风的显著影响，合并产物的进一步演化关键取决于它们的质量损失率。然而，质量损失率的测定需要对流出气体的物理状态以及膨胀的大气中的流体动力学和辐射过程进行高度一致的处理。在先前的初步工作中，我们已经将膨胀大气的一致模型与vss的恒星演化计算相结合，目的是模拟致密星团的演化。正如所怀疑的那样，计算出的质量损失率、终端风速和光谱能量分布揭示了恒星演化计算的重要意义。例如，太阳金属丰度恒星被证明具有很高的质量损失率，但可能不会高到排除在密集星团中由动态过程形成的vss的可能性，因为它们的生命结束时质量足以形成IMBHs。本建议的主要目标是发展一种先进的o型恒星大气诊断方法，包括通过对观测结果的详细解释来评估丰度、恒星和风参数测定的准确性；作为一项中心任务，不同组成的vms的质量损失率将以更高的一致性计算。从这些计算中推断出的基本参数将用于与目前超大质量恒星演化的预测进行比较，我们将重点关注改善质量损失率对IMBHs形成的重要性。

The evolution of the dense cores of massive starburst clusters is affected by dynamical processes induced by N-body interactions. The resultant formation, via mergers, of very massive stars with masses up to several 1000 solar masses may be essential for the evolution of galaxies and decisive for the evolution of such clusters. For example, evidence has been collected that young dense clusters in galactic bulges harbor intermediate-mass black holes (IMBHs) with masses up to several 1000 solar masses; these objects could provide important clues for understanding the formation of supermassive black holes (SMBHs) in galactic centers.The evolution of such very massive stars (VMSs) is significantly influenced by their pronounced stellar winds, and the further evolution of merger products depends critically on their mass loss rates. The determination of the mass loss rates, however, requires a highly consistent treatment of the physical state of the outflowing gas and of the hydrodynamic and radiative processes in the expanding atmospheres.In preliminary prior work we have already combined consistent models of expanding atmospheres with stellar evolutionary calculations of VMSs for the purpose of modelling the evolution of dense stellar clusters. As suspected, the computed mass loss rates, terminal wind velocities, and spectral energy distributions revealed important implications for stellar evolutionary calculations. Solar-metallicity stars, for instance, were shown to have high mass-loss rates, but presumably not so high as to exclude VMSs, formed by dynamical processes in dense clusters, from ending their life massive enough to form IMBHs.The primary objective of the present proposal is to develop an advanced diagnostic method of O-type stellar atmospheres, including an assessment of the accuracy of the determinations of abundances, stellar and wind parameters by means of detailed interpretations of observational results; as a central task, mass loss rates of VMSs for different compositions will be computed with an improved level of consistency. The basic parameters deduced from these computations will be used for comparisons with present predictions from the evolution of very massive stars, and we will focus on the importance of the improved mass loss rates for the formation of IMBHs.