Estimating 5-year rotation stability of PSR B1937+21 using NICER observations

Abstract

Using observations of millisecond pulsars (MSPs) can construct a time scale that is independent of terrestrial time standards. We investigate the 5-year rotation stability of PSR B1937 + 21 (PSR J1939 + 2134) using the Neutron Star Interior Composition Explorer (NICER) observations and compare it with that of the radio data from North American Nanohertz Observatory for Gravitational Waves (NANOGrav). We implement a data screening method to improve the accuracy of X-ray pulse times of arrival (TOAs), and develop a data-analysis framework based on an iterative least square technique for the X-ray timing parameter fitting. Finally, we carefully consider the main factors affecting the pulsar rotation stability. We find that the root mean square error (RMS) of the timing residuals of PSR B1937 + 21 based on NICER observations is 4.7 μs (1σ), and the 5-year rotation stability is 1.7 × 10−14 the accuracy of which is comparable to that of NANOGrav data. In order to ensure less than 10−14 of the main factors influencing the rotation stability on 5-year time scale, the errors of R.A. and Dec shall be no more than 2 mas and 6 mas respectively, while the amplitudes of the white noise and red noise must be less than 5 μs and 1 μs, respectively.