In our previous work [H.-S. Cho, Phys. Rev. D 105. 124022 (2022)], we studied the impact of eccentricity on gravitational-wave parameter estimation for a nonspinning binary neutron star (BNS) system. We here extend the work to a general binary system by including the spin parameter. As in the previous work, we employ the analytic Fisher-Cutler-Vallisneri method to calculate the systematic bias that can be produced by using noneccentric waveforms in parameter estimation, and we verify the reliability of the method by comparing it with numerical Bayesian parameter estimation results. We generate ${10}^4$ BNS sources randomly distributed in the parameter space $m_1–m_2–{\chi }_{\mathrm{eff}}–e_0$, where the neutron star mass is in the range of $1M_{\odot }\le m_{1,2}\le 2M_{\odot }(m_2\le m_1)$, the effective spin is $-0.2\le {\chi }_{\mathrm{eff}}\le 0.2$, and the eccentricity (at the reference frequency 10 Hz) is $0\le e_0\le 0.024$. For the true value of the tidal deformability ($\lambda$) of neutron stars, we assume the equation of state model APR4. For all gravitational-wave signals emitted from the sources, we calculate the systematic biases ($\mathrm{\Delta }\theta$) for the chirp mass ($M_c$), symmetric mass ratio ($\eta$), effective spin (${\chi }_{\mathrm{eff}}$), and effective tidal deformability ($\tilde{\lambda }$), and obtain generalized distributions of the biases. The distribution of biases in $M_c,\eta$, and ${\chi }_{\mathrm{eff}}$ shows narrow bands, and the median value of the bias increases or decreases quadratically with increasing $e_0$, indicating a weak dependence of biases on the three parameters. On the other hand, the biases of $\tilde{\lambda }$ are widely distributed depending on the values of the mass and spin parameters at a given $e_0$. We investigate the implications of biased parameters for the inference of neutron star properties by performing Bayesian parameter estimation for specific cases. We find that a BNS signal consisting of two neutron stars within the typical mass range $[1,2]M_{\odot }$ can be estimated to be a BNS signal whose component mass is much smaller or much larger than the typical mass range. In particular, by showing concrete examples, we demonstrate that parameter estimation using noneccentric waveforms for eccentric BNS signals can yield false predictions for the neutron star equation of state.

Close

PrevNext

View figure in article

• Gravitational waves