孪生喷流和密近双星的形成
Twin Jets and Close Binary Formation
摘要：
利用三维电阻磁流体动力学模拟研究了密近双星系统的形成。从星前云开始，计算了直到原恒星形成后约400年的云演化。碎片发生在引力坍缩的云和两个碎片演变成原恒星。原恒星相互环绕，形成原双星系统。一个广角的低速外流出现从环绕双星流，包围两个原恒星，而每个原恒星的情节驱动高速喷流。因此，这两个高速射流被低速环双星外流所包围。喷射速度超过$\gtrsim 100 km s^{-1}$。虽然喷流具有准直结构，但由于双星轨道运动，它们在小尺度上向后摆动，在大尺度上纠缠。在每颗原恒星周围也会出现一个拱星盘。在主吸积相早期，双星轨道复杂，双星分离在$<30$ au范围内。第一次，最近用大型望远镜观察到的原双星系统的所有特征都在数值模拟中重现。
英文摘要：
The formation of a close binary system is investigated using a three-dimensional resistive magnetohydrodynamics simulation. Starting from a prestellar cloud, the cloud evolution is calculated until about 400 yr after protostar formation. Fragmentation occurs in the gravitationally collapsing cloud and two fragments evolve into protostars. The protostars orbit each other and a protobinary system appears. A wide-angle low-velocity outflow emerges from the circumbinary streams that encloses two protostars, while each protostar episodically drives high-velocity jets. Thus, the two high-velocity jets are surrounded by the low-velocity circumbinary outflow. The speed of the jets exceeds $\gtrsim 100 km s^{-1}$. Although the jets have a collimated structure, they are swung back on the small scale and are tangled at the large scale due to the binary orbital motion. A circumstellar disk also appears around each protostar. In the early main accretion phase, the binary orbit is complicated, while the binary separation is within $<30$ au. For the first time, all the characteristics of protobinary systems recently observed with large telescopes are reproduced in a numerical simulation.
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