Comments on Graviton Propagation in Light of GW150914
  The observation of gravitational waves from the Laser Interferometer Gravitational-Wave Observatory (LIGO) event GW150914 may be used to constrain the possibility of Lorentz violation in graviton propagation, and the observation by the Fermi Gamma-Ray Burst Monitor of a transient source in apparent coincidence may be used to constrain the difference between the velocities of light and gravitational waves: $c_g - c_\gamma < 10^{-17}$. 
John Ellis, Nick E. Mavromatos, Dimitri V. Nanopoulos
gr-qc astro-ph.CO astro-ph.HE hep-ph hep-th