The double neutron star PSR J1946+2052. I Masses and tests of general relativity

Aims. Double neutron star (DNS) systems are superb laboratories for testing theories of gravity and constraining the equation of state of ultra-dense matter. PSR J1946+2052 is a particularly intriguing DNS system due to its orbital period (1h 53 m), as it is the shortest among all DNS systems known in our Galaxy.
Methods. We aim to conduct high-precision timing of PSR J1946+2052 to determine the masses of the two neutron stars in the system, test general relativity (GR), and assess the system’s potential for future measurement of the moment of inertia of the pulsar.
Results. We analysed seven years of timing data from the Arecibo 305-m radio telescope, the Green Bank Telescope, and the Five-hundred-meter Aperture Spherical radio Telescope. The data processing accounted for dispersion measure variations and relativistic spin precession-induced profile evolution. We employed both theory-independent (DDFWHE) and GR-dependent (DDGR) binary models to measure the spin parameters, kinematic parameters, and orbital parameters.
Results. The timing campaign resulted in the precise measurement of five post-Keplerian parameters, which yield very precise masses for the system (total mass M = 2.531858(60) M_⊙, companion mass M_c = 1.2480(21) M_⊙, and pulsar mass M_p = 1.2838(21) M_⊙), and three tests of GR. One of these tests is the second-most precise test of the radiative properties of gravity to date. The intrinsic orbital decay, Ṗ_b,int = −1.8288(16) × 10⁻¹², s s⁻¹, represents 1.00005(91) of the GR prediction, indicating that the theory has passed this stringent test. The other two tests of the Shapiro delay parameters have precisions of 6% and 5%, respectively. This is caused by the moderate orbital inclination of the system, ∼74°. The measurements of the Shapiro delay parameters also agree with the GR predictions. Additionally, we analysed the higher-order contributions of ω˙, including the Lense-Thirring contribution. Both the second post-Newtonian and the Lense-Thirring contributions are larger than the current uncertainty of ω˙ (δω˙ = 4 × 10⁻⁴ deg yr⁻¹), leading to the higher-order correction for the total mass.