Accretion of magnetized stellar winds in the Galactic centre: implications for Sgr A* and PSR J1745−2900
Accretion of magnetized stellar winds in the Galactic centre: implications for Sgr A* and PSR J1745−2900
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DOI：
10.1093/mnrasl/sly201
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发表时间：
2018-10
影响因子：
--
通讯作者：
S. Ressler;E. Quataert;J. Stone
中科院分区：
文献类型：
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作者：
S. Ressler;E. Quataert;J. Stone
观测到的朝向银河中心磁星和人马座A*的自转测量(RMS)对银河中心吸积流的MHD模型提供了很强的约束，探测到与黑洞相距许多数量级的距离。通过对绕黑洞运行的Wolf-Rayet恒星磁化恒星风吸积的三维模拟，我们发现脉冲星PSR J1745-2900观测到的大的、时变的Rm可以用顺时针方向恒星盘中附近恒星的磁化风速冲击来解释。在同一模拟中，总的X射线光度积分超过2-10$‘’，磁星的色散测量的时间变异性，以及Rm指向人马座A*都与观测一致。我们认为(为了让脉冲星的大Rm不是先天不可能的)，脉冲星应该在一个轨道上，使它保持在顺时针方向的恒星圆盘附近。我们给出了一张银河系中心1/2秒中心的2D RM图，可以用来测试我们的模型。我们的模拟预测，SgrA*典型地吸积了一个明显有序的磁场，最终可能导致一个强烈的磁化流，磁通在磁滞极限的$\sim$10$\$处穿过地平线。
The observed rotation measures (RMs) towards the galactic centre magnetar and towards Sagittarius A* provide a strong constraint on MHD models of the galactic centre accretion flow, probing distances from the black hole separated by many orders of magnitude. We show, using 3D simulations of accretion via magnetized stellar winds of the Wolf-Rayet stars orbiting the black hole, that the large, time-variable RM observed for the pulsar PSR J1745-2900 can be explained by magnetized wind-wind shocks of nearby stars in the clockwise stellar disc. In the same simulation, both the total X-ray luminosity integrated over 2-10$''$, the time variability of the magnetar's dispersion measure, and the RM towards Sagittarius A* are consistent with observations. We argue that (in order for the large RM of the pulsar to not be a priori unlikely) the pulsar should be on an orbit that keeps it near the clockwise disc of stars. We present a 2D RM map of the central 1/2 parsec of the galactic centre that can be used to test our models. Our simulations predict that Sgr A* is typically accreting a significantly ordered magnetic field that ultimately could result in a strongly magnetized flow with flux threading the horizon at $\sim$ 10$\%$ of the magnetically arrested limit.