Speed of Gravitational Waves from Strongly Lensed Gravitational Waves and Electromagnetic Signals

Understand

We propose a new model-independent measurement strategy for the propagation speed of gravitational waves (GWs) based on strongly lensed GWs and their electromagnetic (EM) counterparts.

• This can be done in two ways: by comparing arrival times of GWs and their EM counterparts and by comparing the time delays between images seen in GWs and their EM counterparts.
• The lensed GW-EM event is perhaps the best way to identify an EM counterpart.
• Conceptually, this method does not rely on any specific theory of massive gravitons or modified gravity.