Limits on the anomalous speed of gravitational waves from binary pulsars

Understand

A large class of modified theories of gravity used as models for dark energy predict a propagation speed for gravitational waves which can differ from the speed of light.

• This difference of propagations speeds for photons and gravitons has an impact in the emission of gravitational waves by binary systems.
• Thus, we revisit the usual quadrupolar emission of binary system for an arbitrary propagation speed of gravitational waves and obtain the corresponding period decay formula.
• We then use timing data from the Hulse-Taylor binary pulsar and obtain that the speed of gravitational waves can only differ from the speed of light at the percentage level.