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arXiv 2108.12436astro-ph.HEgr-qc
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广义相对论中强磁化中子星和奇异夸克星的各向异性效应

Effects of anisotropy on strongly magnetized neutron and strange quark stars in general relativity

Debabrata Deb, Banibrata Mukhopadhyay, Fridolin Weber

摘要:

我们研究了由强磁化物质组成的各向异性球对称致密星,特别是中子星和奇异夸克星的性质。中子星用SLy状态方程描述,奇异夸克星用基于MIT Bag模型的状态方程描述。恒星模型是基于一个先验假设的密度依赖的磁场,从而各向异性。我们的研究表明,不仅强磁场和各向异性的存在,而且磁场本身的方向,对恒星的物理性质有重要影响。考虑两种可能的磁场取向,径向取向,其中局部磁场指向径向方向,以及横向取向,其中局部磁场垂直于径向方向。有趣的是,我们发现,对于磁场的横向取向,随着各向异性和磁场强度的增加以及尺寸的增加,恒星变得更大,因为在这种情况下,排斥力,有效的各向异性力增加。然而,在径向磁场的情况下,恒星的质量和半径随着磁场强度的增加而减小,因为有效的各向异性力减小。重要的是,我们还表明,为了实现流体静力学平衡配置的磁化物质,它是必不可少的占当地的各向异性效应以及由强磁场引起的各向异性效应。否则,流体静力学平衡是没有达到磁化恒星模型。

英文摘要:

We investigate the properties of anisotropic, spherically symmetric compact stars, especially neutron stars and strange quark stars, made of strongly magnetized matter. The neutron stars are described by SLy equation of state, the strange quark stars by an equation of state based on the MIT Bag model. The stellar models are based on an a priori assumed density dependence of the magnetic field and thus anisotropy. Our study shows that not only the presence of a strong magnetic field and anisotropy, but also the orientation of the magnetic field itself, have an important influence on the physical properties of stars. Two possible magnetic field orientations are considered, a radial orientation, where the local magnetic fields point in the radial direction, and a transverse orientation, where the local magnetic fields are perpendicular to the radial direction. Interestingly, we find that for a transverse orientation of the magnetic field, the stars become more massive with increasing anisotropy and magnetic field strength and increase in size, since the repulsive, effective anisotropic force increases in this case. In the case of a radially orientated magnetic field, however, the masses and radii of the stars decrease with increasing magnetic field strength, because of the decreasing effective anisotropic force. Importantly, we also show that in order to achieve hydrostatic equilibrium configurations of magnetized matter, it is essential to account for both the local anisotropy effects as well as the anisotropy effects caused by a strong magnetic field. Otherwise, hydrostatic equilibrium is not achieved for magnetized stellar models.

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