arXivDaily arXiv每日学术速递 周一至周五更新
arXiv周末暂无论文更新,休息一下吧,周末愉快~~
arXiv 2204.06408astro-ph.HE
收藏

Her X-1中子星三轴自由进动的Fermi/GBM脉冲周期测量证据

Evidence for neutron star triaxial free precession in Her X-1 from Fermi/GBM pulse period measurements

Dmitry Kolesnikov, Nikolai Shakura, Konstantin Postnov

摘要:

Her X-1/HZ Her是研究得最好的吸积X射线天体之一。除了脉动和轨道周期,X射线和光学的光变曲线的源表现出几乎周期性的35天的变化所造成的进动吸积盘。观察到的35天周期的长期稳定性的性质是有争议的。Fermi/GBM测量的Her X-1的X射线脉冲频率显示出在源的Main-on态下随X射线通量的周期性变化。我们解释所观察到的周期性亚微秒脉冲频率的变化由一个三轴中子星的自由进动与参数推断从一个独立的分析的X射线脉冲演化超过35天的周期。在Fermi/GBM数据中,我们确定了几个持续时间为半年或更长的时间间隔,其中描述脉冲频率变化的中子星岁差周期没有变化。我们发现,NS岁差周期在不同的时间间隔内变化在百分之一以内。这种在一年时间尺度上的自由岁差周期的变化可以用三轴中子星的转动惯量之间小于1%的变化来解释,这是由于中子星壳与核的吸积质量重新调整或可变的内部耦合造成的。

英文摘要:

Her X-1/HZ Her is one of the best studied accreting X-ray pulsars. In addition to the pulsating and orbital periods, the X-ray and optical light curves of the source exhibit an almost periodic 35-day variability caused by a precessing accretion disk. The nature of the observed long-term stability of the 35-day cycle has been debatable. The X-ray pulse frequency of Her X-1 measured by the Fermi/GBM demonstrates periodical variations with X-ray flux at the Main-on state of the source. We explain the observed periodic sub-microsecond pulse frequency changes by the free precession of a triaxial neutron star with parameters previously inferred from an independent analysis of the X-ray pulse evolution over the 35-day cycle. In the Fermi/GBM data, we identified several time intervals with a duration of half a year or longer where the neutron star precession period describing the pulse frequency variations does not change. We found that the NS precession period varies within one per cent in different intervals. Such variations in the free precession period on a year time scale can be explained by <1% changes in the fractional difference between the triaxial neutron star's moments of inertia due to the accreted mass readjustment or variable internal coupling of the neutron star crust with the core.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑