论文标题

X射线脉冲星的两个亚群的运动学区别

Kinematic distinction of the two subpopulations of X-ray pulsars

论文作者

Prišegen, M.

论文摘要

BE/X射线二进制体的种群显示出强烈的双峰性证据,尤其是在中子恒星的自旋时期。几种物理机制可能会产生这种双峰性。最喜欢的候选机制是BE/X射线二进制中的两个不同的超新星通道或中子星的不同积聚模式。研究这些系统的运动学可能会为这种双峰性的物理学提供一些更多的见解。如果两种是/X射线二进制亚群来自两种不同的超新星类型,则两个亚群应该具有不同的特殊(全身)速度。可以直接通过测量系统在其出生地中测量系统的位置来直接测量系统的速度,或间接测量这一点。使用最新的Gaia数据集和小型麦哲伦云(SMC)星形群的最新目录,我们分析了银河系中BE/X射线二进制文件的切向特殊速度以及SMC中BE/X射线二进制的位置。我们将系统从最近的年轻恒星簇的距离用作系统的切向速度的代理。我们应用统计测试来研究两个被中子星的自旋分割的亚群在运动学上也不同。有证据表明,这两个亚群确实在运动学上是不同的。然而,两个亚群的切向特殊速度与不同的超新元通道假设的期望相反。我们发现一些边际证据($ p \ $ 〜0.005)表明,来自短自旋亚群中的银河系BE/X射线二进制组的系统速度比长旋转亚群的系统具有更高的特殊速度。对于所有考虑的群集目录的SMC BE/X射线二进制文件也恢复了相同的效果,但也较弱。

The population of Be/X-ray binaries shows strong evidence of bimodality, especially in the spin period of neutron stars. Several physical mechanisms may produce this bimodality. The most favored candidate mechanisms are two distinct supernova channels or different accretion modes of the neutron stars in Be/X-ray binaries. Investigating the kinematics of these systems may provide some additional insight into the physics of this bimodality. If the two Be/X-ray binary subpopulations arise from two distinct supernova types, then the two subpopulations should have different peculiar (systemic) velocities. This can be tested either directly, by measuring the velocity of the system, or indirectly, by measuring the position of the system with respect to its birthplace. Using the most recent Gaia dataset and the newest catalogs of Small Magellanic Cloud (SMC) star clusters, we analyzed the tangential peculiar velocities of Be/X-ray binaries in the Galaxy and the positions of Be/X-ray binaries in the SMC. We used the distance of the system from the nearest young star cluster as a proxy to the tangential velocity of the system. We applied statistical testing to investigate whether the two subpopulations that are divided by the spin of the neutron star are also kinematically distinct. There is evidence that the two subpopulations are indeed kinematically distinct. However, the tangential peculiar velocities of the two subpopulations are the reverse from what is expected from the distinct supernova channel hypothesis. We find some marginal evidence ($p \approx$~0.005) that the Galactic Be/X-ray binaries from the short-spin subpopulation have systematically higher peculiar velocities than the systems from the long-spin subpopulation. The same effect, but weaker, is also recovered for the SMC Be/X-ray binaries for all considered cluster catalogs.

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