AI 中文总结
研究超致密白矮星中磁压各向异性，通过求解TOV方程各向异性扩展获恒星平衡结构，对比不同成分俘获前后序列，发现强磁场减小低质量白矮星半径，为观测评估磁压各向异性作用提供参考。
AI 中文摘要
强磁场通过将简并电子的横向运动量子化到朗道能级，并将压力分为平行和垂直于磁场的分量，从而改变白矮星物质的热力学。我们研究了在状态方程中一致处理库仑晶格贡献、电子俘获阈值、中子滴极限和核组成时，这种微观压力各向异性如何影响超致密白矮星序列。通过求解托尔曼 - 奥本海默 - 沃尔科夫（TOV）方程的各向异性扩展来获得恒星平衡结构。我们比较了纯\(^{12}\rm{C}\)、\(^{16}\rm{O}\)、\(^{20}\rm{Ne}\)和\(^{24}\rm{Mg}\)组成以及固定的50/50 C/O、Ne/O和Mg/Ne混合物的电子俘获后分支与其相应的俘获前序列。状态方程预测在仅占据少数朗道能级的密度范围内\(P_\perp < P_\parallel\)。因此，压力各向异性使恒星序列向较小半径移动，最大质量变化较小。我们还发现，仅从质量 - 半径平面无法解释俘获后构型，因为相应的\(M(\rho_c)\)曲线在达到最大质量后显示出不稳定部分。我们的结果表明，强磁场显著减小了低质量白矮星的半径，与蒙特利尔白矮星数据库中的观测数据更好地吻合，并表明未来对大质量磁性白矮星的高精度观测有助于评估磁压各向异性在确定其质量和半径方面的作用。
英文摘要
Strong magnetic fields modify the thermodynamics of white dwarf (WD) matter by quantizing the transverse motion of degenerate electrons into Landau levels and splitting the pressure into components parallel and perpendicular to the magnetic field. We investigate how this microscopic pressure anisotropy affects ultra-dense WD sequences when Coulomb lattice contributions, electron capture thresholds, neutron drip limits, and nuclear composition are treated consistently in the equation of state (EoS). The stellar equilibrium structure is obtained by solving an anisotropic extension of the Tolman--Oppenheimer--Volkoff (TOV) equations, where $P_r = P_\parallel$ and $P_t = P_\perp$ denote the radial and tangential pressures, respectively. We compare the post-electron-capture branches with their corresponding pre-capture sequences for pure $^{12}\rm{C}$, $^{16}\rm{O}$, $^{20}\rm{Ne}$, and $^{24}\rm{Mg}$ compositions, as well as for fixed 50/50 C/O, Ne/O, and Mg/Ne mixtures. The EoS predicts $P_\perp < P_\parallel$ in density ranges where only a few Landau levels are occupied. Consequently, pressure anisotropy shifts the stellar sequences toward smaller radii, with only minor changes in the maximum masses. We also find that post-capture configurations cannot be interpreted from the mass--radius plane alone, since the corresponding $M(ρ_c)$ curves reveal unstable portions after the maximum mass is reached. Our results show that strong magnetic fields significantly reduce the radii of low-mass WDs, yielding better agreement with the observational data available in the Montreal White Dwarf Database and suggesting that future high-precision observations of massive magnetic WDs could help assess the role of magnetic pressure anisotropy in determining their masses and radii.
Comments13 pages, 6 figures and 2 tables
