Possible tidal dissipation in millisecond pulsar binaries

Department of Physics, Huazhong University of Science and Technology, Wuhan 430074, PR China
e-mail: bpgong@hust.edu.cn

Received: 25 December 2019
Accepted: 2 April 2022

Abstract

Aims. The post-Keplerian(PK) parameters inferred from pulsar timing provide a convenient way to test Einstein’s general theory of relativity. However, before obtaining a pure orbital decay Ṗ_b induced by gravitational wave radiation, which is one of the PK parameters, a number of factors need to be accounted for carefully. The effect of tidal dissipation on Ṗ_b has been thought of as negligible. Here, we investigate the data for possible effects of tidal dissipation on Ṗ_b.

Methods. The possibility of the tidal dissipation as a contributor to Ṗ_b in a large sample of millisecond pulsar binaries is investigated in detail.

Results. We collected a large sample of pulsar binaries with measured Ṗ_b. All of the systems are millisecond pulsars. The residual Ṗ_b^Res of these systems was obtained by subtracting the three normal effects, that is to say the effect of Shklovskii, line-of-sight acceleration, and gravitational radiation. Assuming that tidal dissipation is responsible for such a residual Ṗ_b^Resa, the tidal parameters of these systems can be calculated and compared with the tidal models.

Conclusions. The residual Ṗ_b^Resa is distributed over the half positive and half negative. The dynamical tidal model can explain the residual Ṗ_b of millisecond pulsar-white dwarf binaries. And the Love number of the main-sequence companion of PSR J1227-4853 can be derived as a reasonable value k₂ = 0.177_−0.058^+0.098 with the equilibrium tidal model. Those results are compatible with the scenario of tidal dissipation. Additionally, a weak correlation between the tidal parameter and orbital period is revealed, likely originating in the tidal process of the recycled stage which is worthy of further investigation.