The IACOB project: IV. New predictions for high-degree non-radial mode instability domains in massive stars and connection with macroturbulent broadening
M. Godart, S. Simón-Díaz, A. Herrero, M. A. Dupret, A. Grötsch-Noels, S. J. A. J. Salmon, P. Ventura
备注：
14 pages, 8 figures, Reproduced with permission from Astronomy & Astrophysics, \c{opyright} ESO
Asteroseismology is a powerful tool to access the internal structure of stars. Apart from the important impact of theoretical developments, progress in this field has been commonly associated with the analysis of time-resolved observations. Recently, the so-called macroturbulent broadening has been proposed to be a complementary and less expensive way -- in terms of observational time -- to investigate pulsations in massive stars. We assess to what extent this ubiquitous non-rotational broadening component shaping the line profiles of O stars and B supergiants is a spectroscopic signature of pulsation modes driven by a heat mechanism. We compute stellar main sequence and post-main sequence models from 3 to 70Msun with the ATON stellar evolution code and determine the instability domains for heat-driven modes for degrees l=1-20 using the adiabatic and non-adiabatic codes LOSC and MAD. We use the observational material presented in Simón-Díaz et al. (2016) to investigate possible correlations between the single snapshot line-broadening properties of a sample of ~260 O and B-type stars and their location inside/outside the various predicted instability domains. We present an homogeneous prediction for the non-radial instability domains of massive stars for degree l up to 20. We provide a global picture of what to expect from an observational point of view in terms of frequency range of excited modes, and investigate the behavior of the instabilities with stellar evolution and increasing degree of the mode. Furthermore, our pulsational stability analysis, once compared to the empirical results of Simón-Díaz et al. (2016), indicates that stellar oscillations originated by a heat mechanism can not explain alone the occurrence of the large non-rotational line-broadening component commonly detected in the O star and B supergiant domain.
Is macroturbulent broadening in OB Supergiants related to pulsations?
O型和B型超巨星的光谱被认为会受到一种重要的额外谱线增宽（通常称为宏观湍流）的影响，这种增宽会增加恒星的自转。最近对高分辨率光谱的分析表明，将这种谱线展宽解释为大尺度湍流运动的结果将意味着高度超音速的速度场，使得这种情况非常不可能。恒星振荡被认为是一种可能的替代解释。我们首先介绍了一个旨在研究O和B超巨星中的$macroturbulent$增宽及其与光谱变率现象和恒星振荡的可能联系的观测项目的令人鼓舞的结果：a）所有研究的B超巨星都显示出谱线轮廓的变化，通过< v >谱线的一阶（）和三阶速度（< v^3 >）矩来量化; b）谱线和< v^3 >变率的峰-峰幅度与额外增宽的大小之间存在很强的相关性< v >。
Large-scale variability in macroturbulence driven by pulsations in the rapidly rotating massive star Zeta Oph from high-cadence ESPRESSO spectroscopy and TESS photometry
Newcastle University（纽卡斯尔大学）；KU Leuven（荷语鲁汶大学）；Universidad de La Laguna（拉古纳大学）
Constraining general massive-star physics by exploring the unique properties of magnetic O-stars: Rotation, macroturbulence, and sub-surface convection
