Bounding the Speed of Gravity with Gravitational Wave Observations

Area of Science:

• Astrophysics
• Cosmology
• Gravitational Wave Astronomy

Background:

• Gravitational waves (GWs) offer a new window into the universe.
• The propagation speed of GWs is a fundamental prediction of Einstein's theory of general relativity.
• Measuring GW speed can test alternative theories of gravity.

Purpose of the Study:

• To constrain the propagation speed of gravitational waves (GWs) using existing detection data.
• To establish a framework for improving these constraints with future GW observations.
• To test fundamental physics by comparing GW speed to the speed of light.

Main Methods:

• Utilized a Bayesian inference approach.
• Combined data from the first three confirmed GW detections by the LIGO Scientific Collaboration and Virgo Collaboration.
• Analyzed the time-of-arrival differences of GW signals at different detectors.

Main Results:

• Constrained the GW propagation speed (c_gw) to a 90% credible interval of 0.55c < c_gw < 1.42c, where c is the speed of light.
• Demonstrated that GW speed is consistent with the speed of light within current uncertainties.
• Projected significant improvements in precision with increased detection rates and network size.

Conclusions:

• Current GW data are consistent with GWs traveling at the speed of light.
• The precision of GW speed measurements will dramatically improve with more detections and expanded detector networks (e.g., LIGO-Virgo-Kagra).
• Future GW observations will provide increasingly stringent tests of general relativity and alternative gravity theories.