The model of magnetic braking of solar rotation considered by Charbonneau & MacGregor (1993) has been modified so that it is able to reproduce for the first time the rotational evolution of both the fastest and slowest rotators among solar-type stars in open clusters of different ages, without coming into conflict with other observational constraints, such as the time evolution of the atmospheric Li abundance in solar twins and the thinness of the solar tachocline. This new model assumes that rotation-driven turbulent diffusion, which is thought to amplify the viscosity and magnetic diffusivity in stellar radiative zones, is strongly anisotropic with the horizontal components of the transport coefficients strongly dominating over those in the vertical direction. Also taken into account is the poloidal field decay that helps to confine the width of the tachocline at the solar age. The model's properties are investigated by numerically solving the azimuthal components of the coupled momentum and magnetic induction equations in two dimensions using a finite element method
Rotational evolution of slow-rotator sequence stars. II. Modeling the wind braking and the rotational coupling in the entire mass range of solar-like stars
Università di Catania(卡塔尼亚大学);INAF-Osservatorio Astrofisico di Catania(意大利国家天体物理研究所卡塔尼亚天文台)
Constraining Progenitors of Observed LMXBs Using CARB Magnetic Braking
提出了一种新的方法来约束低质量X射线双星(LMXBs)的质量传递演化-反向布居合成技术。这是使用详细的1D恒星演化代码MESA(恒星天体物理学实验模块)来完成的,以演化出一个高分辨率的双星系统网格,该网格涵盖了初始施主质量和轨道周期的全面范围。我们使用最近开发的对流和旋转助推(CARB)磁制动计划。CARB磁制动方案是唯一的磁制动处方,能够再现整个样本的充分研究持久的LMXB-那些与他们的质量比,周期和质量传递速率,已被观测确定。使用反向人口合成技术,其中我们遵循任何模拟系统,成功地再现了所观察到的LMXB向后,我们已经约束了可能的祖先,为每个观察到的良好的研究持久的LMXB。我们还确定,如果我们排除天鹅座X-2,银河系中LMXB形成的最小数量是每Gyr 1500个。对于天鹅座X-2来说,最有可能的形成率是9000 LMXB/Gyr。我们所描述的技术可以应用于任何观察到的LMXB具有良好的约束质量比,周期和传质速率。随着即将到来的GAIA DR 3包含有关双星系统的信息,这种技术可以应用于数据发布,以搜索观测到的持久性LMXB的祖先。
The effects of surface fossil magnetic fields on massive star evolution: IV. Grids of models at Solar, LMC, and SMC metallicities
磁场可以通过质量损失淬火,磁制动和有效的角动量传输,我们的目标是在这项工作中量化的大质量恒星的演化模型的预测急剧变化。我们使用MESA软件工具来计算恒星结构和演化模型的广泛的主序星网格,以及等时线,考虑到归因于表面化石磁场的影响。该网格在初始质量(3-60 M $_\odot$)、表面赤道磁场强度(0-50 kG)和金属丰度(代表太阳邻域和麦哲伦云)方面密集分布。我们使用两个磁制动和两个化学混合方案,并比较模型预测的缓慢旋转,富氮(“组2”)恒星与观测的大麦云云。我们量化了一系列的初始场强,允许生产组2星,并发现典型的值(高达几公斤)导致的解决方案。在子网格之间,我们发现表面丰度和演化路径有显着的偏离。在我们的磁性模型中,由于快速自旋下降,与非磁性模型相比,化学混合总是效率较低。我们确定,准化学均匀的主序列演化的有效混合可以防止化石磁场。我们建议将这个演化模型网格与分光偏振和光谱观测进行比较,目的是i)重新审视已知磁星的恒星参数,ii)观测上限制不确定的磁制动和化学混合方案。
Ion-Scale Waves Regulated by Plasma Beta and Cross Helicity: Observational Evidence for the Helicity Barrier in Imbalanced Solar Wind Turbulence
Institute of Space Physics, Luoyang Normal University(洛阳理工学院空间物理研究所);Henan Key Laboratory of Electromagnetic Transformation and Detection(河南省电磁转换与探测重点实验室);Space Science Center and Department of Physics and Astronomy, University of New Hampshire(新罕布什尔大学空间科学中心及物理与天文学系);Department of Physics, University of Otago(奥塔哥大学物理系);Research Center for Novel Solar-Blind Ultraviolet and Infrared Photoelectronic Detectors of Henan province(河南省新型日盲紫外红外光电探测器研究中心)
Observational constraints on the origin of the elements. III. Evidence for the dominant role of sub-Chandrasekhar SN Ia in the chemical evolution of Mn and Fe in the Galaxy