标题： Swift J0243.6+6124 脉冲星热辐射的建模与广义相对论辐射磁流体动力学模拟 显示英文标题

标题： Modeling of Thermal Emission from ULX Pulsar Swift J0243.6+6124 with General Relativistic Radiation MHD simulations

摘要： 我们对具有偶极磁场的中子星周围的超爱丁顿吸积流进行了广义相对论辐射磁流体动力学（MHD）模拟，以建模表现出X射线脉动的银河系超亮X射线源（ULX）Swift J0243.6+6124。我们的模拟显示了靠近磁极的吸积柱、磁层外的吸积盘以及来自盘的外流。结果显示，如果质量吸积率远高于爱丁顿率$\dot{M}_{\rm Edd}$，并且磁层半径小于球化半径，则会产生有效光学厚度较大的外流，这与观测到的在$\sim10^7$ K处的热辐射一致。为了在不与报告的自转周期（$9.8~{\rm s}$）和自转加速率（$\dot{P}=-2.22\times10^{-8}~{\rm s~s^{-1}}$）矛盾的情况下解释黑体半径（$\sim 100-500$ km），需要质量吸积率为$(200-1200)\dot{M}_{\rm Edd}$。 由于热辐射在两次观测中检测到$\dot{P}$的$-2.22\times10^{-8}~{\rm s~s^{-1}}$和$-1.75\times10^{-8}~{\rm s~s^{-1}}$，但在另一次观测中未检测到$\dot{P}=-6.8 \times10^{-9}~{\rm s~s^{-1}}$，因此估计 Swift J0243.6+6124 中中子星的表面磁场强度在$3\times10^{11}~{\rm G}$和$4\times10^{12}~{\rm G}$之间。 从这个受限的磁场强度范围内，当热辐射出现时，吸积率将是$(200-500)\dot{M}_{\rm Edd}$，而当未被检测到时，吸积率将是$(60-100)\dot{M}_{\rm Edd}$。我们的结果支持这样的假设，即Swift J0243.6+6124在2017-2018年巨大爆发中的超爱丁顿阶段是由磁化中子星上的高度超爱丁顿吸积流提供的。 显示英文摘要

摘要： We perform general relativistic radiation magnetohydrodynamics (MHD) simulations of super-Eddington accretion flows around a neutron star with a dipole magnetic field for modeling the galactic ultra-luminous X-ray source (ULX) exhibiting X-ray pulsations, Swift J0243.6+6124. Our simulations show the accretion columns near the magnetic poles, the accretion disk outside the magnetosphere, and the outflows from the disk. It is revealed that the effectively optically thick outflows, consistent with the observed thermal emission at $\sim10^7$ K, are generated if the mass accretion rate is much higher than the Eddington rate $\dot{M}_{\rm Edd}$ and the magnetospheric radius is smaller than the spherization radius. In order to explain the blackbody radius ($\sim 100-500$ km) without contradicting the reported spin period ($9.8~{\rm s}$) and spin-up rate ($\dot{P}=-2.22\times10^{-8}~{\rm s~s^{-1}}$), the mass accretion rate of $(200-1200)\dot{M}_{\rm Edd}$ is required. Since the thermal emission was detected in two observations with $\dot{P}$ of $-2.22\times10^{-8}~{\rm s~s^{-1}}$ and $-1.75\times10^{-8}~{\rm s~s^{-1}}$ but not in another with $\dot{P}=-6.8 \times10^{-9}~{\rm s~s^{-1}}$, the surface magnetic field strength of the neutron star in Swift J0243.6+6124 is estimated to be between $3\times10^{11}~{\rm G}$ and $4\times10^{12}~{\rm G}$. From this restricted range of magnetic field strength, the accretion rate would be $(200-500)\dot{M}_{\rm Edd}$ when the thermal emission appears and $(60-100)\dot{M}_{\rm Edd}$ when it is not detected. Our results support the hypothesis that the super-Eddington phase in the 2017-2018 giant outburst of Swift J0243.6+6124 is powered by highly super-Eddington accretion flows onto a magnetized neutron star.