We use axisymmetric magnetohydrodynamic (MHD) simulations to investigate the launching and collimation of jets emerging from the disk-magnetosphere boundary of accreting magnetized stars. Our analysis shows that the matter flows into the jet from the inner edge of the accretion disk. It is magnetically accelerated along field lines extending up from the disk and simultaneously collimated by the magnetic pinch force. In the reference run which we use for analysis, the matter in the jet crosses the Alfvén surface a few R_* above the disk and the fast magnetosonic surface ~13 R_* above the disk. At larger distances, the magnetic pressure is a few times smaller than the total matter pressure but the magnetic force continues to accelerate and collimate the jet. In steady state, we observe a matter ejection-to-accretion ratio of ~0.2. Across different simulation runs, we measure a range of half-opening angles between Θ \approx 4° and 20° at the top of the simulation region, depending on the degree of magnetization in the outflow. We consider the case of stars undergoing epochs of high accretion (such as EXors, FUORs, and CTTSs) where the stellar magnetosphere is strongly compressed by the incoming accretion disk. For a typical EXor (mass 0.8 M_sun, radius 2 R_sun) accreting at ~10^-5 M_sun/yr, we measure poloidal velocities in the jet ranging from 30 km/s on the outer edge of the jet to more than 260 km/s on the inner edge. In general, the models can be applied to a variety of magnetized stars--white dwarfs, neutron stars, and brown dwarfs--which exhibit periods of high accretion.
On the collimation properties of jets with finite Poynting flux launched from Keplerian accretion discs
University of Cambridge（剑桥大学）；Univ. Grenoble Alpes, CNRS, IPAG（格勒诺布尔阿尔卑斯大学，法国国家科学研究中心，天体物理学与行星学研究所）；INAF - Osservatorio Astrofisico di Torino（意大利国家天体物理研究所都灵天文台）
Modeling YSO Jets in 3D II: Accretion-Fed, Star-Anchored Poynting Jets in the Low-Density Polar Cavity Powered by Disk-Magnetosphere Interaction
University of Virginia（弗吉尼亚大学）；Virginia Institute of Theoretical Astronomy, University of Virginia（弗吉尼亚大学理论天体物理研究所）；University of Nevada, Las Vegas（内华达大学拉斯维加斯分校）；Nevada Center for Astrophysics, University of Nevada, Las Vegas（内华达大学拉斯维加斯分校内华达天体物理学中心）；University of Florida（佛罗里达大学）
Sub-arcsecond high sensitivity measurements of the DG~Tau jet with e-MERLIN
我们提出了非常高的空间分辨率深射电连续观测5 GHz（6厘米）与e-MERLIN的年轻恒星DG Tau A和B。假设它是从非常接近（~=1天文单位）的恒星发射，我们的研究结果表明，DG Tau A流出最初开始作为一个不良集中的风，并经历了显着的准直进一步沿喷流（~=50天文单位）。我们推导出了DG Tau A的喷流参数，发现在距离源2天文单位的范围内，初始喷流张开角为86度，喷流电离成分的质量损失率为1.5 × 10 ^-8太阳质量/年，总的喷射/吸积比在0.06 ~ 0.3之间。这些结果与磁流体喷气发射理论的预测是一致的。
Jet from the enigmatic high-latitude star BP Psc and evolutionary status of its driving source
BP Psc是一颗位于高银纬$b=-57^{\circ}$、演化状态不明的活动晚型（sp：G9）恒星。它也是准直良好的双极射流的来源。我们目前的自行和径向速度研究BP Psc流出的基础上档案$Hα$成像与GMOS相机在8.1米双子北望远镜，以及最近的成像和长缝光谱与SCORPIO多模缩焦器在6米BTA望远镜的SAO RAS。喷流的三维运动学揭示了$\sim$ 140 km $\cdot$ s $^{-1}$的全空间速度，并允许我们估计到BP Psc系统的距离为$D=135\pm40$ pc。这个距离导致了中心源光度$L_*\approx1.2L_{\odot}$的估计，表明它是$\approx$ 1.3 $M_{\odot}$ T金牛座恒星，年龄为$t\lesssim$ 7百万年。我们测量了喷流结内的$N_e\sim10^2$ cm $^{-3}$量级的电子密度和平均电离分数$f\approx0.04$，并估算了NE瓣质量损失率的上限为$\dot{M}_{out}\approx1.2\cdot10^{-8}M_{\odot}\cdot yr^{-1}$。外流的物理特性是典型的低激发YSO喷流，其发射和准直的磁离心机制一致。$Hα$影像中所显示的显著摆动模式，使我们得以假设在非共面轨道上存在第二颗亚恒星伴星，并估计其最合理的质量为$M_p\approx 30M_{Jup}$。我们的结…
