Exploring Binary-Neutron-Star-Merger Scenario of Short-Gamma-Ray Bursts by Gravitational-Wave Observation

We elucidate the feature of gravitational waves (GWs) from a binary-neutron-star merger collapsing to a black hole by general relativistic simulation. We show that GW spectrum imprints the coalescence dynamics, formation process of disk, equation of state for neutron stars, total masses, and mass ratio. A formation mechanism of the central engine of short-$\gamma$-ray bursts, which are likely to be composed of a black hole and surrounding disk, therefore could be constrained by GW observation.

Figure 1

$+$ modes of GWs for (a) A2.9-0.8, (b) S2.8-1, and (c) F2.6-0.8. $D$ is the distance from the source to the observer, who is located along the axis perpendicular to the orbital plane. $t_{\mathrm{merge}}$ denotes approximate time at the onset of the merger.

Figure 2

Effective amplitude for models A2.9-1, A2.9-0.8, S2.8-1, F2.6-1, and F2.6-0.8. The filled circles denote the QNM frequency of the formed BHs. The small panel shows a schematic figure of the GW spectrum.

Figure 3

$G{f}_{\mathrm{cut}}{m}_1/c^3$ as a function of compactness of a less massive binary component for all the models. Sequence A(1) represents the models A2.9-0.8, A3-0.8, and A3.1-0.8 from left to right. In a similar way, A(2) is a sequence of A2.9-0.9, A3-0.9, and A3.1-0.9, A(3) is A2.9-1, A3-1, and A3.1-1, S(1) is S2.8-1, S2.9-1, and S3-1, and F(1) is F2.6-1, F2.7-1, and F2.8-1. The models below the horizontal line of $G{f}_{\mathrm{cut}}{m}_1/c^3=0.02$ can produce disks of mass $\ge 0.01M_{\odot }$.

Figure 4

Disk mass as a function of $\sigma /f_{\mathrm{peak}}$ for all the models.