The Relativistic Spin Precession in the Compact Double Neutron Star System PSR~J1946+2052

Abstract

We observe systematic profile changes in the visible pulsar of the compact double neutron star system PSR~J1946+2052 using observations with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The interpulse of PSR~J1946+2052 changed from single-peak to double-peak shape from 2018 to 2021. We attribute this evolution as the result of the relativistic spin precession of the pulsar. With the high sensitivity of FAST, we also measure significant polarization for the first time, allowing us to model this with the precessional rotating vector model. Assuming, to the first order, a circular hollow-cone-like emission beam pattern and taking the validity of general relativity, we derive the binary's orbital inclination angle (${63^{\circ }}_{-3^{\circ }}^{+5^{\circ }}$) and pulsar's spin geometry. Pulsar's spin vector and the orbital angular momentum vector are found to be only slightly misaligned (${0.21^{\circ }}_{-0.10^{\circ }}^{+0.28^{\circ }}$).The quoted uncertainties do not reflect the systematic uncertainties introduced by our model assumptions. By simulating future observations of profile and polarization evolution, we estimate that we could constrain the precession rate within a $43\%$ uncertainty in 9 years. Hence, we suggest that the system's profile evolution could be combined with precise pulsar timing to test general relativity in the future.

12 pages, 9 figures, accepted for publication in ApJ

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• The double neutron star PSR J1946+2052 I. Masses and tests of general relativity
• Constraining the origin of the long term periodicity of FRB 20180916B with Polarization Position Angle
• Search for Periodic Radio Signals from Double Neutron Star System Companions Using the Fast Folding Algorithm