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Progress in pulsar timing studies at Nanshan
2020-12-07| 【A A A【Print】【Close】

Using the pulsar timing data of the 26-m radio telescope (NSRT) at Nanshan, the researchers of pulsar group of Xinjiang Astronomical Observatory have obtained more accurate rotation parameters, braking indices and glitches for 87 pulsars. The researchers using Cholesky transform to reduce the coupling error, and further determined the positions and proper motions for 48 pulsars. The pulsar rotation irregularities revealed in this work will help us to understand the rotation properties of neutron stars. 

Because the rotation energy of pulsar is continuously converted into high-energy particles and electromagnetic radiation, the rotation frequency of pulsar gradually slows down with time. The rotation parameters, positions and proper motions of pulsars can be obtained by the long-term timing observations. Long term observations have shown that the spin-down of most of pulsars is affected by the timing noise and glitches. These two phenomena are considered to be driven by the activities of the internal superfluid of pulsars, so they can be used to probe the internal physics of pulsars.

Using the NSRT, the researchers have detected glitches in PSRs J1722-3632, J1852-0635 and J1957 + 2831. This is the first time to report glitches in the first two pulsars. PSR J1722-3632 is the second old pulsar which shows large glitches. It is found that there is a strong correlation between the absolute value of the braking index and the characteristic age for the middle-age pulsars in which the numbers of positive and negative values of the braking index are almost equal. However, there is no correlation between the braking index and the characteristic age for young pulsars in which the braking index is almost always positive. The results provide an important samples for the study of pulsar spin evolution and  internal physics. 

The results have been published in the  Astrophysical journal (ApJ, 2020, 896, 140). The researchers will continue to use the NSRT to monitor these pulsars to analyze their timing characteristics, which will help to understand the mechanism of the timing noise and internal physics of neutron stars. 
Figure 1: The glitches of PSRs J1722-3632, J1852-0635, and J1957+2831. The dashed line in each panel indicates the glitch epoch

Figure 2: Absolute value of braking index |n| with a significance > 3σ vs. 

Contact: DANG Shijun, YAN Wenming

Xinjiang Astronomical Observatory, Chinese Academy of Sciences



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