标题： 恒星碰撞期间低质量恒星中的磁场增强 显示英文标题

标题： Magnetic Field Amplification during Stellar Collisions between Low-Mass Stars

摘要： 蓝星在星团中是比其他星团成员更蓝且看起来更年轻的恒星子集，似乎在演化过程中落后了。 它们为理解宿主中的恒星动力学和恒星种群提供了独特的机会。 在碰撞形成情景中，一个持续的挑战是碰撞产物中角动量过多。 过渡到稳定状态期间随之而来的显著质量损失会导致一颗质量过低而无法成为蓝星的恒星，除非它能有效减速。 虽然许多提出的减速机制涉及通过碰撞产物内的磁制动增强角动量损失，但这些磁场的存在或强度尚未得到证实。 在这里，我们报告了两颗低质量主序星碰撞的三维磁流体动力学模拟，并研究了磁场的增强。 磁场能量被放大了 $10^{8}-10^{10}$倍，在碰撞产物核心处的磁场强度达到 $10^{7}-10^{8}$G，与碰撞参数无关。 表面磁场强度已增加到高达 $10-10^{4}$ G。此外，在非轴对称碰撞中，碰撞产物周围出现了一个明显扁平、旋转的气体结构，这可能是可能的盘状结构形成的迹象。 这种显著的磁场增强和潜在的盘状结构形成表明，通过磁制动和磁盘锁定有效减速碰撞产物的可能性，这可能导致它们表现为蓝星。 显示英文摘要

摘要： Blue straggler stars in stellar clusters are a subset of stars that are bluer and appear younger than other cluster members, seemingly straggling behind in their evolution. They offer a unique opportunity to understand the stellar dynamics and populations within their hosts. In the collisional formation scenario, a persistent challenge is the excessive angular momentum in the collision product. The consequent significant mass loss during transition to a stable state leads to a star with too low a mass to be a blue straggler, unless it spins down efficiently. While many proposed spin-down mechanisms involve boosted angular momentum loss via magnetic braking within the collision product, the existence or strength of these magnetic fields has not been confirmed. Here, we report three-dimensional magnetohydrodynamical simulations of collisions between two low-mass main-sequence stars and investigate magnetic field amplification. Magnetic field energy is amplified by a factor of $10^{8}-10^{10}$, resulting in the magnetic field strength of $10^{7}-10^{8}$G at the core of the collision product, independent of collision parameters. The surface magnetic field strengths have increased up to $10-10^{4}$ G. In addition, a distinctly flattened, rotating gas structure appears around the collision products in off-axis collisions, which may be a hint of possible disk formation. Such significant magnetic amplification and potential disk formation suggest the possibility of efficient spin-down of collision products via magnetic braking and magnetic disk locking, which can result in their appearance as blue stragglers.