Simulation Study on Constraining GW Propagation Speed by GW and GRB Joint Observation on Binary Neutron Star Mergers

TL;DR

This study simulates joint GW and gamma-ray burst observations from neutron star mergers to improve constraints on GW propagation speed, graviton mass, and Lorentz violation, surpassing previous limits.

Contribution

It introduces a simulation framework for joint GW-EM observations to tighten bounds on GW speed, graviton mass, and Lorentz violation parameters.

Findings

Constraint on GW speed deviation: ~10^{-17} (aLIGO) and ~10^{-18} (ET).

Upper bound on graviton mass: 7.1×10^{-20} eV (aLIGO) and 3.2×10^{-20} eV (ET).

Constraints on Lorentz violation coefficients: -1×10^{-15} to 9×10^{-17} (aLIGO), -4×10^{-16} to 8×10^{-18} (ET).

Abstract

Theories of modified gravity suggest that the propagation speed of gravitational wave (GW) $v_g$ may deviate from the speed of light $c$. A constraint can be placed on the difference between $c$ and $v_g$ with a simple method that uses the arrival time delay between GW and electromagnetic (EM) wave simultaneously emitted from a burst event. We simulated the joint observation of GW and short Gamma-Ray burst (sGRB) signals from Binary Neutron Star (BNS) merger events in different observation campaigns, involving advanced LIGO (aLIGO) in design sensitivity and Einstein Telescope (ET) joint-detected with \textit{Fermi}/GBM. As a result, the relative precision of constraint on $v_g$ can reach $\sim 10^{-17}$ (aLIGO) and $\sim 10^{-18}$ (ET), which are one and two orders of magnitude better than that from GW170817, respectively. We continue to obtain the bound of graviton mass $m_g \leq 7.1(3.2)\times 10^{-20}\,$eV with aLIGO (ET). Applying the Standard-Model Extension (SME) test framework, the constraint on $v_g$ allows us to study the Lorentz violation in the nondispersive, nonbirefringent limit of the gravitational sector. We obtain the constraints of the dimensionless isotropic coefficients $\bar{s}_{00}^{(4)}$ at mass dimension $d = 4$, which are $-1\times 10^{-15}< \bar{s}_{00}^{(4)}<9\times 10^{-17}$ for aLIGO and $-4\times 10^{-16}< \bar{s}_{00}^{(4)}<8\times 10^{-18}$ for ET.