A more stringent constraint on the mass ratio of binary neutron star merger GW170817

He Gao; Zhoujian Cao; Shunke Ai; Bing Zhang

doi:10.3847/2041-8213/aaa0c6

paper

A more stringent constraint on the mass ratio of binary neutron star merger GW170817

arXiv:1711.08577 · doi:10.3847/2041-8213/aaa0c6

Abstract

Recently, the LIGO-Virgo collaboration reported their first detection of gravitational wave (GW) signals from a low mass compact binary merger GW170817, which is most likely due to a double neutron star (NS) merger. With the GW signals only, the chirp mass of the binary is precisely constrained to $1.18 8_{- 0.002}^{+ 0.004} M_{⊙}$ , but the mass ratio is loosely constrained in the range $0.4 - 1$ , so that a very rough estimation of the individual NS masses ( $0.86 M_{⊙} < M_{1} < 1.36 M_{⊙}$ and $1.36 M_{⊙} < M_{2} < 2.26 M_{⊙}$ ) was obtained. Here we propose that if one can constrain the dynamical ejecta mass through performing kilonova modeling of the optical/IR data, by utilizing an empirical relation between the dynamical ejecta mass and the mass ratio of NS binaries, one may place a more stringent constraint on the mass ratio of the system. For instance, considering that the red "kilonova" component is powered by the dynamical ejecta, we reach a tight constraint on the mass ratio in the range of $0.46 - 0.59$ . Alternatively, if the blue "kilonova" component is powered by the dynamical ejecta, the mass ratio would be constrained in the range of $0.53 - 0.67$ . Overall, such a multi-messenger approach could narrow down the mass ratio of GW170817 system to the range of $0.46 - 0.67$ , which gives a more precise estimation of the individual NS mass than pure GW signal analysis, i.e. $0.90 M_{⊙} < M_{1} < 1.16 M_{⊙}$ and $1.61 M_{⊙} < M_{2} < 2.11 M_{⊙}$ .

Published in 2017, ApJL, 851, L45

A more stringent constraint on the mass ratio of binary neutron star merger GW170817

Abstract

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