Differential rotation of giants and fast-rotating dwarf stars

巨星和快速旋转矮星的差分旋转

• 批准号: 50602300
• 负责人: Professor Dr. Günther Rüdiger
• 金额: --
• 依托单位: Leibniz-Institut für Astrophysik Potsdam (AIP)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2007
• 资助国家: 德国
• 起止时间: 2006-12-31 至 2010-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/50602300?language=en
• 关键词: Differential; rotation; giants; fast; rotating

In recent models of the solar dynamo both differential rotation and meridional flow play important parts. Understanding these phenomena is therefore essential for the theory of stellar activity. A numerical study of the differential rotation of giants and rapidly rotating MS stars by means of a new MHD code for parallel computers is thus proposed.Based on a successful model of the solar rotation (see the coverplot) we have developed a code that predicts the rotation and meridional flow pattern of stellar convection zones. So far our computations have been restricted to solar-type stars of slow and intermediate rotation. Models for these stars always produce solar-type rotation laws with the equator rotating faster than the poles where the equator-pole difference of the rotation rate Q hardly depends on the rotation period. The theory for such stars is supported by recent satellite-based observations of young solar-type stars with about 10 days rotation period.Doppler imaging of HD 31993 finds, however, an anti-solar rotation law for this K2-giant with decelerated equator. The angular momentum conservation law predicts such a pattern in case of very fast meridional flow which is indeed observed. We therefore propose to compute the rotation of HD 31993 and other giant stars. Another class of stars with intense meridional circulation are very young fast-rotating MS stars.As there is also an increasing amount of observations of F-type stars with rotation periods as short as ≈ 1d we plan to apply the model also to these objects with their rather thin convection zones. Such completely new results can only be derived with a code which fulfills highest constraints for resolution and numerical stability.

在最近的太阳能发电机模型中，差动自转和子午线流动都起到了重要作用。因此，理解这些现象对于恒星活动理论至关重要。利用一种新的MHD并行计算机程序，对巨星和快速自转的MS恒星的差动自转进行了数值研究。在一个成功的太阳自转模型的基础上，我们开发了一个预测恒星对流区自转和经向流态的程序。到目前为止，我们的计算仅限于慢自转和中等自转的太阳型恒星。这些恒星的模型总是产生太阳类型的自转规律，赤道自转速度比两极自转速度快，其中自转速度Q的赤道极差几乎不依赖于自转周期。这类恒星的理论得到了最近对大约10天自转周期的年轻太阳型恒星的卫星观测的支持。然而，HD 31993的多普勒成像发现了这颗赤道减速的K2巨星的反太阳自转规律。角动量守恒定律预测了在非常快的经向流动的情况下，确实观察到了这样的模式。因此，我们建议计算HD 31993和其他巨星的自转。另一类具有强烈经向环流的恒星是非常年轻的快速旋转的MS恒星。由于也有越来越多的观测到自转周期短至≈1D的F型恒星，我们计划将该模型也应用于这些具有相当薄的对流区的天体。这种全新的结果只能用满足分辨率和数值稳定性最高约束的代码来推导。