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On the Structure and Properties of Differentially Rotating, Main-Sequence Stars in the 1-2 M☉ Range

机译:1-2M☉范围内差序旋转主序星的结构和性质

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摘要

We present models for chemically homogeneous, differentially rotating, main-sequence stars with masses in the range 1-2 M☉. The models were constructed using a code based on a reformulation of the self-consistent field method of computing the equilibrium stellar structure for a specified conservative internal rotation law. Relative to nonrotating stars of the same mass, these models all have reduced luminosities and effective temperatures, and flattened photospheric shapes (i.e., decreased polar radii) with equatorial radii that can be larger or smaller, depending on the degree of differential rotation. For a fixed ratio of the axial rotation rate to the surface equatorial rotation rate, increasingly rapid rotation generally deepens convective envelopes, shrinks convective cores, and can lead to the presence of a convective core (envelope) in a 1 (2) M☉ model, a feature that is absent in a nonrotating star of the same mass. The positions of differentially rotating models for a given mass in the H-R diagram can be shifted in such a way as to approximate the nonrotating ZAMS for lower mass stars. Implications of these results include (1) possible ambiguities arising from similarities between the properties of rotating and nonrotating models of different masses, (2) a reduced radiative luminosity for a young, rapidly rotating Sun, (3) modified rates of lithium destruction by nuclear processes in the layers beneath an outer convective envelope, and (4) the excitation of solar-like oscillations and the operation of a solar-like hydromagnetic dynamo in some 1.5-2 M☉ stars.
机译:我们提出了质量在1-2M☉范围内的化学均质,差速旋转主序列恒星的模型。这些模型是使用一种代码构建的,该代码基于重新计算自洽场方法的公式,该方法用于为指定的保守内旋律计算平衡恒星结构。相对于相同质量的非自转恒星,这些模型都具有降低的亮度和有效温度,并且具有平坦的光球形状(即减小的极半径),且赤道半径可以更大或更小,具体取决于微分旋转的程度。对于轴向旋转速度与赤道表面旋转速度的固定比率,越来越快的旋转通常会加深对流包络,使对流芯收缩,并可能导致1(2)M☉模型中存在对流芯(包络) ,是质量不变的非旋转恒星中所没有的特征。 H-R图中给定质量的差分旋转模型的位置可以以近似低质量恒星的非旋转ZAMS的方式移动。这些结果的含义包括:(1)不同质量的旋转模型和非旋转模型的性质之间的相似性可能引起的歧义;(2)快速旋转的年轻太阳的辐射光度降低;(3)核对锂的破坏率提高了在外对流包层下面的各层中的过程,以及(4)在大约1.5-2M☉的恒星中激发太阳状振荡和使太阳状水磁发电机运转。

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